Survey on Network Virtualization Hypervisors for Software Defined Networking
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paper_title: FlowVisor: A Network Virtualization Layer

paper_content:

Network virtualization has long been a goal of of the network research community. With it, multiple isolated logical networks each with potentially different addressing and forwarding mechanisms can share the same physical infrastructure. Typically this is achieved by taking advantage of the flexibility of software (e.g. [20, 23]) or by duplicating components in (often specialized) hardware[19]. In this paper we present a new approach to switch virtualization in which the same hardware forwarding plane can be shared among multiple logical networks, each with distinct forwarding logic. We use this switch-level virtualization to build a research platform which allows multiple network experiments to run side-by-side with production traffic while still providing isolation and hardware forwarding speeds. We also show that this approach is compatible with commodity switching chipsets and does not require the use of programmable hardware such as FPGAs or network processors. We build and deploy this virtualization platform on our own production network and demonstrate its use in practice by running five experiments simultaneously within a campus network. Further, we quantify the overhead of our approach and evaluate the completeness of the isolation between virtual slices.
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paper_title: Memory resource management in VMware ESX server

paper_content:

VMware ESX Server is a thin software layer designed to multiplex hardware resources efficiently among virtual machines running unmodified commodity operating systems. This paper introduces several novel ESX Server mechanisms and policies for managing memory. A ballooning technique reclaims the pages considered least valuable by the operating system running in a virtual machine. An idle memory tax achieves efficient memory utilization while maintaining performance isolation guarantees. Content-based page sharing and hot I/O page remapping exploit transparent page remapping to eliminate redundancy and reduce copying overheads. These techniques are combined to efficiently support virtual machine workloads that overcommit memory.
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paper_title: Virtual machine monitors: current technology and future trends

paper_content:

Developed more than 30 years ago to address mainframe computing problems, virtual machine monitors have resurfaced on commodity platforms, offering novel solutions to challenges in security, reliability, and administration. Stanford University researchers began to look at the potential of virtual machines to overcome difficulties that hardware and operating system limitations imposed: This time the problems stemmed from massively parallel processing (MPP) machines that were difficult to program and could not run existing operating systems. With virtual machines, researchers found they could make these unwieldy architectures look sufficiently similar to existing platforms to leverage the current operating systems. From this project came the people and ideas that underpinned VMware Inc., the original supplier of VMMs for commodity computing hardware. The implications of having a VMM for commodity platforms intrigued both researchers and entrepreneurs.
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paper_title: OpenFlow: enabling innovation in campus networks

paper_content:

This whitepaper proposes OpenFlow: a way for researchers to run experimental protocols in the networks they use every day. OpenFlow is based on an Ethernet switch, with an internal flow-table, and a standardized interface to add and remove flow entries. Our goal is to encourage networking vendors to add OpenFlow to their switch products for deployment in college campus backbones and wiring closets. We believe that OpenFlow is a pragmatic compromise: on one hand, it allows researchers to run experiments on heterogeneous switches in a uniform way at line-rate and with high port-density; while on the other hand, vendors do not need to expose the internal workings of their switches. In addition to allowing researchers to evaluate their ideas in real-world traffic settings, OpenFlow could serve as a useful campus component in proposed large-scale testbeds like GENI. Two buildings at Stanford University will soon run OpenFlow networks, using commercial Ethernet switches and routers. We will work to encourage deployment at other schools; and We encourage you to consider deploying OpenFlow in your university network too
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paper_title: Survey of virtual machine research

paper_content:

The complete instruction-by-instruction simulation of one computer system on a different system is a well-known computing technique. It is often used for software development when a hardware base is being altered. For example, if a programmer is developing software for some new special purpose (e.g., aerospace) computer X which is under construction and as yet unavailable, he will likely begin by writing a simulator for that computer on some available general-purpose machine G. The simulator will provide a detailed simulation of the special-purpose environment X, including its processor, memory, and I/O devices. Except for possible timing dependencies, programs which run on the “simulated machine X” can later run on the “real machine X” (when it is finally built and checked out) with identical effect. The programs running on X can be arbitrary — including code to exercise simulated I/O devices, move data and instructions anywhere in simulated memory, or execute any instruction of the simulated machine. The simulator provides a layer of software filtering which protects the resources of the machine G from being misused by programs on X.
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paper_title: Overcoming the Internet impasse through virtualization

paper_content:

The Internet architecture has proven its worth by the vast array of applications it now supports and the wide variety of network technologies over which it currently runs. Most current Internet research involves either empirical measurement studies or incremental modifications that can be deployed without major architectural changes. Easy access to virtual testbeds could foster a renaissance in applied architectural research that extends beyond these incrementally deployable designs.
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paper_title: GENI: A federated testbed for innovative network experiments

paper_content:

GENI, the Global Environment for Networking Innovation, is a distributed virtual laboratory for transformative, at-scale experiments in network science, services, and security. Designed in response to concerns over Internet ossification, GENI is enabling a wide variety of experiments in a range of areas, including clean-slate networking, protocol design and evaluation, distributed service offerings, social network integration, content management, and in-network service deployment. Recently, GENI has been leading an effort to explore the potential of its underlying technologies, SDN and GENI racks, in support of university campus network management and applications. With the concurrent deployment of these technologies on regional and national R&E backbones, this will result in a revolutionary new national-scale distributed architecture, bringing to the entire network the shared, deeply programmable environment that the cloud has brought to the datacenter. This deeply programmable environment will support the GENI research mission and as well as enabling research in a wide variety of application areas.
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paper_title: VMThunder: Fast Provisioning of Large-Scale Virtual Machine Clusters

paper_content:

Infrastructure as a service (IaaS) allows users to rent resources from cloud to meet their various computing requirements. The pay-as-you-use model, however, poses a non-trivial technical challenge to the IaaS cloud service providers: how to fast provision a large number of virtual machines (VMs) to meet users' dynamic computing requests? We address this challenge with VMThunder, a new VM provisioning tool, which downloads data blocks on demand during the VM booting process and speeds up VM image streaming by strategically integrating peer-to-peer (P2P) streaming techniques with enhanced optimization schemes such as transfer on demand (ToD), cache on read (CoR), snapshot on local (SoL), and relay on cache (RoC). In particular, VMThunder stores the original images in a share storage and in the meantime it adopts a tree-based P2P streaming scheme so that common image blocks are cached and re-used across the nodes in the cluster. We implement VMThunder in CentOS Linux and thoroughly test its performance. Comprehensive experimental results show that VMThunder outperforms the state-of-the-art VM provisioning methods, with respect to scalability, latency, and VM runtime I/O performance.
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paper_title: Traffic pattern based virtual network embedding

paper_content:

Virtual Network Embedding (VNE) algorithms are used to find the best embedding of multiple Virtual Networks (VNs) with respect to a performance metric such as network utilization. However, most algorithms assume that the demands of the VNs are static over time. We focus on VNE algorithms for VNs whose demands are changing according to traffic patterns of their provided services. In order to always guarantee high performance and network resource efficiency, the embedding of the VNs has to change, i.e., the VNs have to be re-embedded. By considering traffic patterns of different services, we propose an algorithm that looks ahead and minimize the impact of reconfigurations that are the result of a re-embedding. First simulation results show the potential of VNE algorithms that consider the behavior of evolving service demands.
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paper_title: Data Center Network Virtualization: A Survey

paper_content:

With the growth of data volumes and variety of Internet applications, data centers (DCs) have become an efficient and promising infrastructure for supporting data storage, and providing the platform for the deployment of diversified network services and applications (e.g., video streaming, cloud computing). These applications and services often impose multifarious resource demands (storage, compute power, bandwidth, latency) on the underlying infrastructure. Existing data center architectures lack the flexibility to effectively support these applications, which results in poor support of QoS, deployability, manageability, and defence against security attacks. Data center network virtualization is a promising solution to address these problems. Virtualized data centers are envisioned to provide better management flexibility, lower cost, scalability, better resources utilization, and energy efficiency. In this paper, we present a survey of the current state-of-the-art in data center networks virtualization, and provide a detailed comparison of the surveyed proposals. We discuss the key research challenges for future research and point out some potential directions for tackling the problems related to data center design.
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paper_title: A Survey of Virtual Machine System: Current Technology and Future Trends

paper_content:

With the development of the computer technology, the virtual machine has been become the main research topic. Understanding of the current technology and future trends of virtual machine system greatly help to improve the service performance of system. Therefore, we describe the current technology and present the future trends of virtual machine system in the paper. In the current technology of virtual machine system, we mainly describe the virtualization technology, the resource scheduling technology, the migration technology, the security technology and the performance evaluation technology. In the future trends of virtual machine system, we mainly present an overview of the future CPU architecture, the management mode of future memory and resource, the future maintaining method of system security and the performance evaluation method of future multiple virtual machine system.
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paper_title: Towards flexible, scalable and autonomic virtual tenant slices

paper_content:

Multi-tenant flexible, scalable and autonomic virtual networks isolation has long been a goal of the network research and industrial community. For today's Software-Defined Networking (SDN) platforms, providing cloud tenants requirements for scalability, elasticity, and transparency is far from straightforward. SDN programmers typically enforce strict and inflexible traffic isolation resorting to low-level encapsulations mechanisms which help and facilitate network programmer reasoning about their complex slices behavior. In this paper, we propose SD-NMS, a novel software-defined architecture overcoming SDN and encapsulation techniques limitations. SD-NMS lifts several network virtualization roadblocks by combining these two separate approaches into an unified design. SD-NMS design leverages the benefits of SDN to provide Layer 2 (L2) isolation coupled with network overlay protocols with simple and flexible virtual tenant slices abstractions. This yields a network virtualization architecture that is both flexible, scalable and secure on one side, and self-manageable on the other. The experiment results showed that the proposed design offers negligible overhead and guarantees the network performance while achieving the desired isolation goals.
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paper_title: Traffic engineering with mpls in the internet

paper_content:

This article discusses traffic engineering with multiprotocol label switching (MPLS) in an Internet service provider's network. We first review MPLS, constraint-based routing, and enhanced link state interior gateway protocols to provide a background for traffic engineering. We then discuss the general issues of designing an MPLS system for traffic engineering. The design of GlobalCenter's MPLS system is presented. Based on our experiences, a generic procedure for deploying an MPLS system is proposed. We also discuss how to provide QoS in a network with MPLS. Putting these together, we present to readers the practical issues of traffic engineering and a working solution for traffic engineering with MPLS in the Internet.
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paper_title: Network virtualization: a hypervisor for the Internet?

paper_content:

Network virtualization is a relatively new research topic. A number of articles propose that certain benefits can be realized by virtualizing links between network elements as well as adding virtualization on intermediate network elements. In this article we argue that network virtualization may bring nothing new in terms of technical capabilities and theoretical performance, but it provides a way of organizing networks such that it is possible to overcome some of the practical issues in today?s Internet. We strengthen our case by an analogy between the concept of network virtualization as it is currently presented in research, and machine virtualization as proven useful in deployments in recent years. First we make an analogy between the functionality of an operating system and that of a network, and identify similar concepts and elements. Then we emphasize the practical benefits realized by machine virtualization, and we exploit the analogy to derive potential benefits brought by network virtualization. We map the established applications for machine virtualization to network virtualization, thus identifying possible use cases for network virtualization. We also use this analogy to structure the design space for network virtualization.
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paper_title: Overcoming the Internet impasse through virtualization

paper_content:

The Internet architecture has proven its worth by the vast array of applications it now supports and the wide variety of network technologies over which it currently runs. Most current Internet research involves either empirical measurement studies or incremental modifications that can be deployed without major architectural changes. Easy access to virtual testbeds could foster a renaissance in applied architectural research that extends beyond these incrementally deployable designs.
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paper_title: An instrumentation and analytics framework for optimal and robust NFV deployment

paper_content:

This article details a novel approach to the fine-tuning of carrier-grade virtualized network function deployments for both performance optimization and diagnostic purposes, using embedded instrumentation with an analytics framework. The work presented in this article is the output of a co-lab established between BT and Intel Labs Europe to investigate network-function-virtualization-related problems faced by traditional telecom operators. Results from comprehensive testing of virtual CDN and WAN acceleration use cases are presented. These results led to the development of a number of insights that will help network operators optimize the deployment of NFV on standard high volume servers. Significantly, it was found that the default configuration for some use cases resulted in suboptimal resource allocation and consumption. Consequently, opportunities exist for carriers to fine-tune their NFV deployments from both the technical and economic perspectives using approaches such as embedded instrumentation.
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paper_title: Resource Discovery and Allocation in Network Virtualization

paper_content:

Network virtualization is considered an important potential solution to the gradual ossification of the Internet. In a network virtualization environment, a set of virtual networks share the resources of a common physical network although each virtual network is isolated from others. Benefits include increased flexibility, diversity, security and manageability. Resource discovery and allocation are fundamental steps in the process of creating new virtual networks. This paper surveys previous work on, and the present status of, resource discovery and allocation in network virtualization. We also describe challenges and suggest future directions for this area of research.
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paper_title: GENI: A federated testbed for innovative network experiments

paper_content:

GENI, the Global Environment for Networking Innovation, is a distributed virtual laboratory for transformative, at-scale experiments in network science, services, and security. Designed in response to concerns over Internet ossification, GENI is enabling a wide variety of experiments in a range of areas, including clean-slate networking, protocol design and evaluation, distributed service offerings, social network integration, content management, and in-network service deployment. Recently, GENI has been leading an effort to explore the potential of its underlying technologies, SDN and GENI racks, in support of university campus network management and applications. With the concurrent deployment of these technologies on regional and national R&E backbones, this will result in a revolutionary new national-scale distributed architecture, bringing to the entire network the shared, deeply programmable environment that the cloud has brought to the datacenter. This deeply programmable environment will support the GENI research mission and as well as enabling research in a wide variety of application areas.
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paper_title: A Survey on Service-Oriented Network Virtualization Toward Convergence of Networking and Cloud Computing

paper_content:

The crucial role that networking plays in Cloud computing calls for a holistic vision that allows combined control, management, and optimization of both networking and computing resources in a Cloud environment, which leads to a convergence of networking and Cloud computing. Network virtualization is being adopted in both telecommunications and the Internet as a key attribute for the next generation networking. Virtualization, as a potential enabler of profound changes in both communications and computing domains, is expected to bridge the gap between these two fields. Service-Oriented Architecture (SOA), when applied in network virtualization, enables a Network-as-a-Service (NaaS) paradigm that may greatly facilitate the convergence of networking and Cloud computing. Recently the application of SOA in network virtualization has attracted extensive interest from both academia and industry. Although numerous relevant research works have been published, they are currently scattered across multiple fields in the literature, including telecommunications, computer networking, Web services, and Cloud computing. In this article we present a comprehensive survey on the latest developments in service-oriented network virtualization for supporting Cloud computing, particularly from a perspective of network and Cloud convergence through NaaS. Specifically, we first introduce the SOA principle and review recent research progress on applying SOA to support network virtualization in both telecommunications and the Internet. Then we present a framework of network-Cloud convergence based on service-oriented network virtualization and give a survey on key technologies for realizing NaaS, mainly focusing on state of the art of network service description, discovery, and composition. We also discuss the challenges brought in by network-Cloud convergence to these technologies and research opportunities available in these areas, with a hope to arouse the research community's interest in this emerging interdisciplinary field.
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paper_title: A Survey of Network Virtualization

paper_content:

Due to the existence of multiple stakeholders with conflicting goals and policies, alterations to the existing Internet architecture are now limited to simple incremental updates; deployment of any new, radically different technology is next to impossible. To fend off this ossification, network virtualization has been propounded as a diversifying attribute of the future inter-networking paradigm. By introducing a plurality of heterogeneous network architectures cohabiting on a shared physical substrate, network virtualization promotes innovations and diversified applications. In this paper, we survey the existing technologies and a wide array of past and state-of-the-art projects on network virtualization followed by a discussion of major challenges in this area.
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paper_title: Virtual Network Embedding: A Survey

paper_content:

Network virtualization is recognized as an enabling technology for the future Internet. It aims to overcome the resistance of the current Internet to architectural change. Application of this technology relies on algorithms that can instantiate virtualized networks on a substrate infrastructure, optimizing the layout for service-relevant metrics. This class of algorithms is commonly known as "Virtual Network Embedding (VNE)" algorithms. This paper presents a survey of current research in the VNE area. Based upon a novel classification scheme for VNE algorithms a taxonomy of current approaches to the VNE problem is provided and opportunities for further research are discussed.
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paper_title: A survey on security issues in service delivery models of cloud computing

paper_content:

Cloud computing is a way to increase the capacity or add capabilities dynamically without investing in new infrastructure, training new personnel, or licensing new software. It extends Information Technology's (IT) existing capabilities. In the last few years, cloud computing has grown from being a promising business concept to one of the fast growing segments of the IT industry. But as more and more information on individuals and companies are placed in the cloud, concerns are beginning to grow about just how safe an environment it is. Despite of all the hype surrounding the cloud, enterprise customers are still reluctant to deploy their business in the cloud. Security is one of the major issues which reduces the growth of cloud computing and complications with data privacy and data protection continue to plague the market. The advent of an advanced model should not negotiate with the required functionalities and capabilities present in the current model. A new model targeting at improving features of an existing model must not risk or threaten other important features of the current model. The architecture of cloud poses such a threat to the security of the existing technologies when deployed in a cloud environment. Cloud service users need to be vigilant in understanding the risks of data breaches in this new environment. In this paper, a survey of the different security risks that pose a threat to the cloud is presented. This paper is a survey more specific to the different security issues that has emanated due to the nature of the service delivery models of a cloud computing system.
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paper_title: Survey of virtual machine research

paper_content:

The complete instruction-by-instruction simulation of one computer system on a different system is a well-known computing technique. It is often used for software development when a hardware base is being altered. For example, if a programmer is developing software for some new special purpose (e.g., aerospace) computer X which is under construction and as yet unavailable, he will likely begin by writing a simulator for that computer on some available general-purpose machine G. The simulator will provide a detailed simulation of the special-purpose environment X, including its processor, memory, and I/O devices. Except for possible timing dependencies, programs which run on the “simulated machine X” can later run on the “real machine X” (when it is finally built and checked out) with identical effect. The programs running on X can be arbitrary — including code to exercise simulated I/O devices, move data and instructions anywhere in simulated memory, or execute any instruction of the simulated machine. The simulator provides a layer of software filtering which protects the resources of the machine G from being misused by programs on X.
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paper_title: Review and status of wavelength-division-multiplexing technology and its application

paper_content:

Wavelength-division-multiplexing (WDM) technology is now recognized as one of the key technologies in optical communications systems. This is because it has great potential to enhance system design and flexibility. This paper reviews state-of-the-art optical multi/demultiplexers (MUX/DEMUX) and WDM system design. Various system applications are also summarized.
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paper_title: vConductor: An enabler for achieving virtual network integration as a service

paper_content:

Network function virtualization is regarded as a promising candidate for future networks. Although many advantages are expected, there is still a lack of services that directly link to increased revenue for telecom operators. Therefore, we propose a new NFV-based service, virtual network integration as a service (VNIaaS). The service allows enterprise network administrators to construct and monitor virtual enterprise networks as necessary. As a key enabler, we further propose vConductor, an innovative technology due to its automatic network provisioning, multi-objective resource scheduling, and NFV-oriented inventory management characteristics. Finally, we show the feasibility through implementation of a prototype system. We believe that this contribution will be a catalyst to accelerate the industrialization of NFV.
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paper_title: Comparing delta, open stack and Xen Cloud Platforms: A survey on open source IaaS

paper_content:

In the next five years to come people around the globe would choose open source deployment not just because they cut down cost but also helps avoid vendor lock-in. Our research paper gives you an insight to use open source IaaS to set your own public, private or hybrid cloud. The reason behind it is that it delivers value to your enterprise. Comparing these three open clouds will help researcher and other users to decide which one would be a better option for their enterprise.
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paper_title: NFV: State of the Art, Challenges and Implementation in Next Generation Mobile Networks (vEPC)

paper_content:

As mobile network users look forward to the connectivity speeds of 5G networks, service providers are facing challenges in complying with connectivity demands without substantial financial investments. Network function virtualization (NFV) is introduced as a new methodology that offers a way out of this bottleneck. NFV is poised to change the core structure of telecommunications infrastructure to be more cost-efficient. In this article, we introduce an NFV framework, and discuss the challenges and requirements of its use in mobile networks. In particular, an NFV framework in the virtual environment is proposed. Moreover, in order to reduce signaling traffic and achieve better performance, this article proposes a criterion to bundle multiple functions of a virtualized evolved packet core in a single physical device or a group of adjacent devices. The analysis shows that the proposed grouping can reduce the network control traffic by 70 percent.
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paper_title: Virtuosity: Programmable resource management for spawning networks

paper_content:

Abstract The creation, deployment and management of network architecture is manual, time consuming and costly. To the network architect the creation process is ad hoc in nature, based on hand crafting small-scale network prototypes that evolve toward wide scale deployment. We envision a different paradigm where `spawning networks' are capable of profiling, spawning, architecting and managing distinct virtual network architectures. This paper provides an overview of the Genesis Kernel framework and its life cycle of spawning virtual networks, and focuses on the design, implementation and evaluation of virtuosity, a plug-in module for the Genesis framework that supports programmable resource management of spawned virtual networks. The design goal of virtuosity is to minimize the complexity of handling multiple spawned virtual networks that potentially operate over multiple resource management timescales. We present a spawning network emulation environment and a virtuosity simulation system. Both of these components are implemented as virtual network extensions to ns. Through simulation we evaluate programmability, signaling, timescales, measurement-based estimation and traffic metering of virtual networks using virtuosity.
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paper_title: Beehive: Towards a Simple Abstraction for Scalable Software-Defined Networking

paper_content:

Simplicity is a prominent advantage of Software-Defined Networking (SDN), and is often exemplified by implementing a complicated control logic as a simple control application on a centralized controller. In practice, however, SDN controllers turn into distributed systems due to performance and reliability limitations, and the supposedly simple control applications transform into complex logics that demand significant effort to design and optimize. In this paper, we present Beehive, a distributed control platform aiming at simplifying this process. Our proposal is built around a programming abstraction which is almost identical to a centralized controller yet enables the platform to automatically infer how applications maintain their state and depend on one another. Using this abstraction, the platform automatically generates the distributed version of each control application, while preserving its behavior. With runtime instrumentation, the platform dynamically migrates applications among controllers aiming to optimize the control plane as a whole. Beehive also provides feedback to identify design bottlenecks in control applications, helping developers enhance the performance of the control plane. Our prototype shows that Beehive significantly simplifies the process of realizing distributed control applications.
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paper_title: SDN-based cloud computing networking

paper_content:

Software Defined Networking (SDN) is a concept which provides the network operators and data centres to flexibly manage their networking equipment using software running on external servers. According to the SDN framework, the control and management of the networks, which is usually implemented in software, is decoupled from the data plane. On the other hand cloud computing materializes the vision of utility computing. Tenants can benefit from on-demand provisioning of networking, storage and compute resources according to a pay-per-use business model. In this work we present the networking issues in IaaS and networking and federation challenges that are currently addressed with existing technologies. We also present innovative software-define networking proposals, which are applied to some of the challenges and could be used in future deployments as efficient solutions. cloud computing networking and the potential contribution of software-defined networking along with some performance evaluation results are presented in this paper.
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paper_title: Orion: A Hybrid Hierarchical Control Plane of Software-Defined Networking for Large-Scale Networks

paper_content:

The decoupled architecture and the fine-grained flow control feature of SDN limit the scalability of SDN network. In order to address this problem, some studies construct the flat control plane architecture, other studies build the hierarchical control plane architecture to improve the scalability of SDN. However, the two kinds of structure still have unresolved issues: the flat control plane structure can not solve the super-linear computational complexity growth of the control plane when SDN network scales to large size, the centralized abstracted hierarchical control plane structure brings path stretch problem. To address the two issues, we propose Orion, a hybrid hierarchical control plane for large-scale networks. Orion can effectively reduce the computational complexity growth of SDN control plane from super-linear to linear. Meanwhile, we design an abstracted hierarchical routing method to solve the path stretch problem. Further, Orion is implemented to verify the feasibility of the hybrid hierarchical approach. Finally, we verify the effectiveness of Orion both from the theoretical and experimental aspects.
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paper_title: OpenFlow: The Next Generation of the Network?

paper_content:

Software-defined-network technologies like OpenFlow could change how datacenters, cloud systems, and perhaps even the Internet handle tomorrow's heavy network loads.
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paper_title: Software-Defined Networking (SDN) and Distributed Denial of Service (DDoS) Attacks in Cloud Computing Environments: A Survey, Some Research Issues, and Challenges

paper_content:

Distributed denial of service (DDoS) attacks in cloud computing environments are growing due to the essential characteristics of cloud computing. With recent advances in software-defined networking (SDN), SDN-based cloud brings us new chances to defeat DDoS attacks in cloud computing environments. Nevertheless, there is a contradictory relationship between SDN and DDoS attacks. On one hand, the capabilities of SDN, including software-based traffic analysis, centralized control, global view of the network, dynamic updating of forwarding rules, make it easier to detect and react to DDoS attacks. On the other hand, the security of SDN itself remains to be addressed, and potential DDoS vulnerabilities exist across SDN platforms. In this paper, we discuss the new trends and characteristics of DDoS attacks in cloud computing, and provide a comprehensive survey of defense mechanisms against DDoS attacks using SDN. In addition, we review the studies about launching DDoS attacks on SDN, as well as the methods against DDoS attacks in SDN. To the best of our knowledge, the contradictory relationship between SDN and DDoS attacks has not been well addressed in previous works. This work can help to understand how to make full use of SDN's advantages to defeat DDoS attacks in cloud computing environments and how to prevent SDN itself from becoming a victim of DDoS attacks, which are important for the smooth evolution of SDN-based cloud without the distraction of DDoS attacks.
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paper_title: Software-Defined and Virtualized Future Mobile and Wireless Networks: A Survey

paper_content:

With the proliferation of mobile demands and increasingly multifarious services and applications, mobile Internet has been an irreversible trend. Unfortunately, the current mobile and wireless network (MWN) faces a series of pressing challenges caused by the inherent design. In this paper, we extend two latest and promising innovations of Internet, software-defined networking and network virtualization, to mobile and wireless scenarios. We first describe the challenges and expectations of MWN, and analyze the opportunities provided by the software-defined wireless network (SDWN) and wireless network virtualization (WNV). Then, this paper focuses on SDWN and WNV by presenting the main ideas, advantages, ongoing researches and key technologies, and open issues respectively. Moreover, we interpret that these two technologies highly complement each other, and further investigate efficient joint design between them. This paper confirms that SDWN and WNV may efficiently address the crucial challenges of MWN and significantly benefit the future mobile and wireless network.
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paper_title: The beacon openflow controller

paper_content:

Beacon is a Java-based open source OpenFlow controller created in 2010. It has been widely used for teaching, research, and as the basis of Floodlight. This paper describes the architectural decisions and implementation that achieves three of Beacon's goals: to improve developer productivity, to provide the runtime ability to start and stop existing and new applications, and to be high performance.
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paper_title: Security in Software Defined Networks: A Survey

paper_content:

Software defined networking (SDN) decouples the network control and data planes. The network intelligence and state are logically centralized and the underlying network infrastructure is abstracted from applications. SDN enhances network security by means of global visibility of the network state where a conflict can be easily resolved from the logically centralized control plane. Hence, the SDN architecture empowers networks to actively monitor traffic and diagnose threats to facilitates network forensics, security policy alteration, and security service insertion. The separation of the control and data planes, however, opens security challenges, such as man-in-the middle attacks, denial of service (DoS) attacks, and saturation attacks. In this paper, we analyze security threats to application, control, and data planes of SDN. The security platforms that secure each of the planes are described followed by various security approaches for network-wide security in SDN. SDN security is analyzed according to security dimensions of the ITU-T recommendation, as well as, by the costs of security solutions. In a nutshell, this paper highlights the present and future security challenges in SDN and future directions for secure SDN.
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paper_title: Opportunities and research challenges of hybrid software defined networks

paper_content:

Software Defined Networking (SDN) promises to ease design, operation and management of communication networks. However, SDN comes with its own set of challenges, including incremental deployability, robustness, and scalability. Those challenges make a full SDN deployment difficult in the short-term and possibly inconvenient in the longer-term. In this paper, we explore hybrid SDN models that combine SDN with a more traditional networking approach based on distributed protocols. We show a number of use cases in which hybrid models can mitigate the respective limitations of traditional and SDN approaches, providing incentives to (partially) transition to SDN. Further, we expose the qualitatively diverse tradeoffs that are naturally achieved in hybrid models, making them convenient for different transition strategies and long-term network designs. For those reasons, we argue that hybrid SDN architectures deserve more attention from the scientific community.
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paper_title: Network Innovation using OpenFlow: A Survey

paper_content:

OpenFlow is currently the most commonly deployed Software Defined Networking (SDN) technology. SDN consists of decoupling the control and data planes of a network. A software-based controller is responsible for managing the forwarding information of one or more switches; the hardware only handles the forwarding of traffic according to the rules set by the controller. OpenFlow is an SDN technology proposed to standardize the way that a controller communicates with network devices in an SDN architecture. It was proposed to enable researchers to test new ideas in a production environment. OpenFlow provides a specification to migrate the control logic from a switch into the controller. It also defines a protocol for the communication between the controller and the switches. As discussed in this survey paper, OpenFlow-based architectures have specific capabilities that can be exploited by researchers to experiment with new ideas and test novel applications. These capabilities include software-based traffic analysis, centralized control, dynamic updating of forwarding rules and flow abstraction. OpenFlow-based applications have been proposed to ease the configuration of a network, to simplify network management and to add security features, to virtualize networks and data centers and to deploy mobile systems. These applications run on top of networking operating systems such as Nox, Beacon, Maestro, Floodlight, Trema or Node.Flow. Larger scale OpenFlow infrastructures have been deployed to allow the research community to run experiments and test their applications in more realistic scenarios. Also, studies have measured the performance of OpenFlow networks through modelling and experimentation. We describe the challenges facing the large scale deployment of OpenFlow-based networks and we discuss future research directions of this technology.
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paper_title: On Controller Performance in Software-Defined Networks

paper_content:

Network architectures in which the control plane is decoupled from the data plane have been growing in popularity. Among the main arguments for this approach is that it provides a more structured software environment for developing network-wide abstractions while potentially simplifying the data plane. As has been adopted elsewhere [11], we refer to this split architecture as Software-Defined Networking (SDN). While it has been argued that SDN is suitable for some deployment environments (such as homes [17, 13], data centers [1], and the enterprise [5]), delegating control to a remote system has raised a number of questions on control-plane scaling implications of such an approach. Two of the most often voiced concerns are: (a) how fast can the controller respond to data path requests?; and (b) how many data path requests can it handle per second? There are some references to the performance of SDN systems in the literature [16, 5, 3]. For example, an oft-cited study shows that a popular network controller (NOX) handles around 30k flow initiation events1 per second while maintaining a sub-10ms flow install time [14]. Unfortunately, recent measurements of some deployment environments suggests that these numbers are far from sufficient. For example, Kandula et al. [9] found that a 1500-server cluster has a median flow arrival rate of 100k flows per second. Also, Benson et al. [2] show that a network with 100 switches can have spikes of 10M flows arrivals per second in the worst case. In addition, the 10ms flow setup delay of an SDN controller would add a 10% delay to the majority of flows (short-lived) in such a network. This disconnect between relatively poor controller performance and high network demands has motivated a
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paper_title: Leveraging SDN layering to systematically troubleshoot networks

paper_content:

Today's networks are maintained by "masters of complexity": network admins who have accumulated the wisdom to troubleshoot complex problems, despite a limiting toolset. This position paper advocates a more structured troubleshooting approach that leverages architectural layering in Software-Defined Networks (SDNs). In all networks, high-level intent (policy) must correctly map to low-level forwarding behavior (hardware configuration). In SDNs, intent is explicitly expressed, forwarding semantics are explicitly defined, and each architectural layer fully specifies the behavior of the network. Building on these observations, we show how recently-developed troubleshooting tools fit into a coherent workflow that detects mistranslations between layers to precisely localize sources of errant control logic. Our goals are to explain the overall picture, show how the pieces fit together to enable a systematic workflow, and highlight the questions that remain. Once this workflow is realized, network admins can formally verify that their network is operating correctly, automatically troubleshoot bugs, and systematically track down their root cause -- freeing admins to fix problems, rather than diagnose their symptoms.
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paper_title: Interfaces, attributes, and use cases: A compass for SDN

paper_content:

The term Software Defined Networking (SDN) is prevalent in today's discussion about future communication networks. As with any new term or paradigm, however, no consistent definition regarding this technology has formed. The fragmented view on SDN results in legacy products being passed off by equipment vendors as SDN, academics mixing up the attributes of SDN with those of network virtualization, and users not fully understanding the benefits. Therefore, establishing SDN as a widely adopted technology beyond laboratories and insular deployments requires a compass to navigate the multitude of ideas and concepts that make up SDN today. The contribution of this article represents an important step toward such an instrument. It gives a thorough definition of SDN and its interfaces as well as a list of its key attributes. Furthermore, a mapping of interfaces and attributes to SDN use cases is provided, highlighting the relevance of the interfaces and attributes for each scenario. This compass gives guidance to a potential adopter of SDN on whether SDN is in fact the right technology for a specific use case.
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paper_title: OpenFlow: enabling innovation in campus networks

paper_content:

This whitepaper proposes OpenFlow: a way for researchers to run experimental protocols in the networks they use every day. OpenFlow is based on an Ethernet switch, with an internal flow-table, and a standardized interface to add and remove flow entries. Our goal is to encourage networking vendors to add OpenFlow to their switch products for deployment in college campus backbones and wiring closets. We believe that OpenFlow is a pragmatic compromise: on one hand, it allows researchers to run experiments on heterogeneous switches in a uniform way at line-rate and with high port-density; while on the other hand, vendors do not need to expose the internal workings of their switches. In addition to allowing researchers to evaluate their ideas in real-world traffic settings, OpenFlow could serve as a useful campus component in proposed large-scale testbeds like GENI. Two buildings at Stanford University will soon run OpenFlow networks, using commercial Ethernet switches and routers. We will work to encourage deployment at other schools; and We encourage you to consider deploying OpenFlow in your university network too
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paper_title: Network Programmability With ForCES

paper_content:

Network programmability has re-emerged as a top item of the networking research agenda since Software Defined Networking (SDN) gained wide acceptance simultaneously in vendor product line plans and operator expectations for future deployments. Key ingredients for the successful deployment of SDN technologies are standardized models, mechanisms, and protocols for the separation of the control and forwarding planes. The Internet Engineering Task Force (IETF) standardization effort on Forwarding and Control Element Separation (ForCES) has published a set of standards track documents which specify in detail a comprehensive architectural framework and the respective standard protocols which can be employed to implement the separation of these two planes in a flexible, scalable, and vendor-agnostic yet fully interoperable manner. The IETF standards on ForCES define how to achieve said separation through a complete and modular system model of the forwarding plane elements. In the ForCES model every network element is composed of numerous logically separate and well-defined functional entities that cooperate to provide the desired overall functionality, such as a routing or IP switching. The elegance of the model lies in the fact that a ForCES-based implementation of a network element is indistinguishable from a traditional (“closed-box”) network element and therefore can be deployed in the field without any need for migration to a new architecture. Conversely, ForCES allows for rapid prototyping and agile deployment of new architectures as emphasis is placed on software-defined functionality and full programmability. The difference of ForCES from other SDN approaches that depend on logically centralized controllers and the deployment of solely simple or “dumb” switches is that ForCES standards provide a complete toolbox to design, implement, and interoperate ForCES-based network elements with both previously deployed infrastructures as well as in experimental or early-deployment phase endeavors. An example of the former is the implementation of 3GPP-standardized network elements such as a packet gateway (PGW). Examples of the latter include the use of ForCES for network function virtualization (NFV) proofs-of-concepts. This paper surveys the programmable networks and SDN area and provides a comprehensive tutorial on ForCES by summarizing numerous standards documents and thus making the technology easily understood by the wider research community. We present the design goals, choices, and tradeoffs for this standardized approach for network programmability and provide a thorough primer on the ForCES model and protocol. This paper also surveys recent independent interoperable implementations that showcase the full spectrum of ForCES applications in the era of NFV and SDN.
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paper_title: Software-defined networking: management requirements and challenges

paper_content:

SDN is an emerging paradigm currently evidenced as a new driving force in the general area of computer networks. Many investigations have been carried out in the last few years about the benefits and drawbacks in adopting SDN. However, there are few discussions on how to manage networks based on this new paradigm. This article contributes to this discussion by identifying some of the main management requirements of SDN. Moreover, we describe current proposals and highlight major challenges that need to be addressed to allow wide adoption of the paradigm and related technology.
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paper_title: Scalability and Resilience of Software-Defined Networking: An Overview

paper_content:

Software-Defined Networking (SDN) allows to control the available network resources by an intelligent and centralized authority in order to optimize traffic flows in a flexible manner. However, centralized control may face scalability issues when the network size or the number of traffic flows increases. Also, a centralized controller may form a single point of failure, thereby affecting the network resilience. ::: This article provides an overview of SDN that focuses on (1) scalability concerning the increased control overhead faced by a central controller, and (2) resiliency in terms of protection against controller failure, network topology failure and security in terms of malicious attacks.
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paper_title: HyperFlow: A Distributed Control Plane for OpenFlow

paper_content:

OpenFlow assumes a logically centralized controller, which ideally can be physically distributed. However, current deployments rely on a single controller which has major drawbacks including lack of scalability. We present HyperFlow, a distributed event-based control plane for OpenFlow. HyperFlow is logically centralized but physically distributed: it provides scalability while keeping the benefits of network control centralization. By passively synchronizing network-wide views of OpenFlow controllers, HyperFlow localizes decision making to individual controllers, thus minimizing the control plane response time to data plane requests. HyperFlow is resilient to network partitioning and component failures. It also enables interconnecting independently managed OpenFlow networks, an essential feature missing in current OpenFlow deployments. We have implemented HyperFlow as an application for NOX. Our implementation requires minimal changes to NOX, and allows reuse of existing NOX applications with minor modifications. Our preliminary evaluation shows that, assuming sufficient control bandwidth, to bound the window of inconsistency among controllers by a factor of the delay between the farthest controllers, the network changes must occur at a rate lower than 1000 events per second across the network.
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paper_title: SDN and NFV benchmarking for performance and reliability

paper_content:

With dynamic networking environment demands from internet applications and services, network operators are adopting software-based infrastructure and functions. Software-Defined Networking (SDN) and Network Function Virtualization (NFV) promise increased flexibility and agility for their networks. Accordingly, the SDN and NFV performance benchmarking methodologies are under discussion in standardization bodies. SDN and NFV combine Information Technology (IT) with Communication Technology (CT). As the benchmarking metrics are different between IT and CT, new benchmarking metrics are highly necessary. This paper introduces benchmarking test metrics presented in standardization bodies and proposes SDN and NFV benchmarking metrics for performance and reliability from the perspective of operators. Moreover, benchmarking influence elements are also considered. In conclusion, the paper discusses benchmarking issues to put SDN and NFV into practical uses.
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paper_title: API Design Challenges for Open Router Platforms on Proprietary Hardware

paper_content:

Most switch vendors have launched “open” platform designs for routers and switches, allowing code from customers or third-party vendors to run on their proprietary hardware. An open platform needs a programming interface, to provide switchlets sufficient access to platform features without exposing too much detail. We discuss the design of an abstraction layer and API designed to support portability between vendor platforms, isolation between switchlets and both the platform and other switchlets, high performance, and programming simplicity. The API would also support resource-management abstractions; for example, to allow policy-based allocation of TCAM entries among multiple switchlets.
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paper_title: Taming SDN Controllers in Heterogeneous Hardware Environments

paper_content:

The ability to deploy applications which control network resources using a global view is a major benefit of the SDN paradigm. The SDN dataplane is comprised of a topology of forwarding elements programmed by a centralized controller over a common, well-defined interface. We believe that the heterogeneity of forwarding devices is an inherent property of software defined networks rather than a side effect. Therefore it is vital to design SDN frameworks in manner which explicitly takes variable hardware capabilities into account. In this work we argue that the concurrent operation of switches with diverse capacities for control message processing leads to unpredictable delays in SDN applications. To address this issue, we use a queuing model to characterize the service of a switch's control interface. Furthermore, we outline a measurement based-approach to derive the corresponding parameters. We propose a simple interface extension for controller frameworks which enables operators to configure delay bounds for transmitted control messages. As a result, developers can create SDN applications which exhibit consistent and predicable behavior.
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paper_title: SDN Issues – A Survey

paper_content:

SDN separates the control plane and data plane. SDN needs to be equipped with complex and proprietary networking devices as it needs to separate the infrastructure layer (network device) from the control layer (network OS, which provides a central view and control over the network and network services) and the application layer (software/business application)[1][6][8]. When a single controller is given the job of controlling multiple devices (switches/routers) these changes in network structure brought about by SDN will inevitably impact on network security. In this paper we studied issues and security challenges in SDN and current status.
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paper_title: RAON: A recursive abstraction of SDN control-plane for large-scale production networks

paper_content:

In this invited paper, we introduce RAON: a recursive abstraction of SDN control-plane for large-scale production networks. RAON leverages a recursion, where the solution to a problem depends on solutions to smaller instances of the same problem, and organizes them in hierarchical domains. To this end, RAON abstracts the details of the underlying network as a big virtual switch, then the switch is recursively connected to other controllers like normal openflow switch. We have implemented and deployed RAON in our lab-scale testbed.
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paper_title: NOX: towards an operating system for networks

paper_content:

As anyone who has operated a large network can attest, enterprise networks are difficult to manage. That they have remained so despite significant commercial and academic efforts suggests the need for a different network management paradigm. Here we turn to operating systems as an instructive example in taming management complexity. In the early days of computing, programs were written in machine languages that had no common abstractions for the underlying physical resources. This made programs hard to write, port, reason about, and debug. Modern operating systems facilitate program development by providing controlled access to high-level abstractions for resources (e.g., memory, storage, communication) and information (e.g., files, directories). These abstractions enable programs to carry out complicated tasks safely and efficiently on a wide variety of computing hardware. In contrast, networks are managed through low-level configuration of individual components. Moreover, these configurations often depend on the underlying network; for example, blocking a user’s access with an ACL entry requires knowing the user’s current IP address. More complicated tasks require more extensive network knowledge; forcing guest users’ port 80 traffic to traverse an HTTP proxy requires knowing the current network topology and the location of each guest. In this way, an enterprise network resembles a computer without an operating system, with network-dependent component configuration playing the role of hardware-dependent machine-language programming. What we clearly need is an “operating system” for networks, one that provides a uniform and centralized programmatic interface to the entire network. Analogous to the read and write access to various resources provided by computer operating systems, a network operating system provides the ability to observe and control a network. A network operating system does not manage the network itself; it merely provides a programmatic interface. Applications implemented on top of the network operating system perform the actual management tasks. The programmatic interface should be general enough to support a broad spectrum of network management applications. Such a network operating system represents two major conceptual departures from the status quo. First, the network operating system presents programs with a centralized programming model; programs are written as if the entire network were present on a single machine (i.e., one would use Dijkstra to compute shortest paths, not Bellman-Ford). This requires (as in [3, 8, 14] and elsewhere) centralizing network state. Second, programs are written in terms of high-level abstractions (e.g., user and host names), not low-level configuration parameters (e.g., IP and MAC addresses). This allows management directives to be enforced independent of the underlying network topology, but it requires that the network operating system carefully maintain the bindings (i.e., mappings) between these abstractions and the low-level configurations. Thus, a network operating system allows management applications to be written as centralized programs over highlevel names as opposed to the distributed algorithms over low-level addresses we are forced to use today. While clearly a desirable goal, achieving this transformation from distributed algorithms to centralized programming presents significant technical challenges, and the question we pose here is: Can one build a network operating system at significant scale?
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paper_title: Towards correct network virtualization

paper_content:

In SDN, the underlying infrastructure is usually abstracted for applications that can treat the network as a logical or virtual entity. Commonly, the ``mappings" between virtual abstractions and their actual physical implementations are not one-to-one, e.g., a single "big switch" abstract object might be implemented using a distributed set of physical devices. A key question is, what abstractions could be mapped to multiple physical elements while faithfully preserving their native semantics? E.g., can an application developer always expect her abstract "big switch" to act exactly as a physical big switch, despite being implemented using multiple physical switches in reality? We show that the answer to that question is "no" for existing virtual-to-physical mapping techniques: behavior can differ between the virtual "big switch" and the physical network, providing incorrect application-level behavior. We also show that that those incorrect behaviors occur despite the fact that the most pervasive and commonly-used correctness invariants, such as per-packet consistency, are preserved throughout. These examples demonstrate that for practical notions of correctness, new systems and a new analytical framework are needed. We take the first steps by defining end-to-end correctness, a correctness condition that focuses on applications only, and outline a research vision to obtain virtualization systems with correct virtual to physical mappings.
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paper_title: Network virtualization and software defined networking for cloud computing: a survey

paper_content:

Network virtualization is the key to the current and future success of cloud computing. In this article, we explain key reasons for virtualization and briefly explain several of the networking technologies that have been developed recently or are being developed in various standards bodies. In particular, we explain software defined networking, which is the key to network programmability. We also illustrate SDN?s applicability with our own research on OpenADN - application delivery in a multi-cloud environment.
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paper_title: Can the Production Network Be the Testbed?

paper_content:

A persistent problem in computer network research is validation. When deciding how to evaluate a new feature or bug fix, a researcher or operator must trade-off realism (in terms of scale, actual user traffic, real equipment) and cost (larger scale costs more money, real user traffic likely requires downtime, and real equipment requires vendor adoption which can take years). Building a realistic testbed is hard because "real" networking takes place on closed, commercial switches and routers with special purpose hardware. But if we build our testbed from software switches, they run several orders of magnitude slower. Even if we build a realistic network testbed, it is hard to scale, because it is special purpose and is in addition to the regular network. It needs its own location, support and dedicated links. For a testbed to have global reach takes investment beyond the reach of most researchers. ::: ::: In this paper, we describe a way to build a testbed that is embedded in--and thus grows with--the network. The technique--embodied in our first prototype, FlowVisor--slices the network hardware by placing a layer between the control plane and the data plane. We demonstrate that FlowVisor slices our own production network, with legacy protocols running in their own protected slice, alongside experiments created by researchers. The basic idea is that if unmodified hardware supports some basic primitives (in our prototype, Open-Flow, but others are possible), then a worldwide testbed can ride on the coat-tails of deployments, at no extra expense. Further, we evaluate the performance impact and describe how FlowVisor is deployed at seven other campuses as part of a wider evaluation platform.
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paper_title: Characterizing hypervisor vulnerabilities in cloud computing servers

paper_content:

The rise of the Cloud Computing paradigm has led to security concerns, taking into account that resources are shared and mediated by a Hypervisor which may be targeted by rogue guest VMs and remote attackers. In order to better define the threats to which a cloud server's Hypervisor is exposed, we conducted a thorough analysis of the codebase of two popular open-source Hypervisors, Xen and KVM, followed by an extensive study of the vulnerability reports associated with them. Based on our findings, we propose a characterization of Hypervisor Vulnerabilities comprised of three dimensions: the trigger source (i.e. where the attacker is located), the attack vector (i.e. the Hypervisor functionality that enables the security breach), and the attack target (i.e. the runtime domain that is compromised). This can be used to understand potential paths different attacks can take, and which vulnerabilities enable them. Moreover, most common paths can be discovered to learn where the defenses should be focused, or conversely, least common paths can be used to find yet-unexplored ways attackers may use to get into the system.
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paper_title: The Dictionary of Psychology

paper_content:

Contents: How To Use This Dictionary. Appendices: Prefixes, Suffixes, and Affixes DSM-IV Terms The Greek Alphabet Medical Prescription Terms Systems of Treatment Measuring Instruments Symbols Learning Theory Symbols Rorschach Descriptions Biographies. Index.
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paper_title: Reducing TCAM power consumption and increasing throughput

paper_content:

TCAMs have been an emerging technology for packet forwarding in the networking industry. They are fast and easy to use. However, due to their inherent parallel structure they consume high power - much higher than SRAMs or DRAMs. A system using four TCAMs could consume upto 60 watts. The power issue is one of the chief disadvantages of TCAMs over RAM based methods for forwarding. For a system using multiple TCAMs we present methods to significantly reduce TCAM power consumption for forwarding, making it comparable to RAM based forwarding solutions. Using our techniques one can use a TCAM for forwarding at 3 to 4 watts worst case. Our techniques also have an interesting connotation to TCAM forwarding rates. For a static distribution of requests we present methods that make the forwarding rate of a system proportional to the number of TCAMs. So if a system has four TCAMs, one could achieve a four fold performance of that of a single TCAM for a static distribution of requests.
---
paper_title: Towards correct network virtualization

paper_content:

In SDN, the underlying infrastructure is usually abstracted for applications that can treat the network as a logical or virtual entity. Commonly, the ``mappings" between virtual abstractions and their actual physical implementations are not one-to-one, e.g., a single "big switch" abstract object might be implemented using a distributed set of physical devices. A key question is, what abstractions could be mapped to multiple physical elements while faithfully preserving their native semantics? E.g., can an application developer always expect her abstract "big switch" to act exactly as a physical big switch, despite being implemented using multiple physical switches in reality? We show that the answer to that question is "no" for existing virtual-to-physical mapping techniques: behavior can differ between the virtual "big switch" and the physical network, providing incorrect application-level behavior. We also show that that those incorrect behaviors occur despite the fact that the most pervasive and commonly-used correctness invariants, such as per-packet consistency, are preserved throughout. These examples demonstrate that for practical notions of correctness, new systems and a new analytical framework are needed. We take the first steps by defining end-to-end correctness, a correctness condition that focuses on applications only, and outline a research vision to obtain virtualization systems with correct virtual to physical mappings.
---
paper_title: Composing software-defined networks

paper_content:

Managing a network requires support for multiple concurrent tasks, from routing and traffic monitoring, to access control and server load balancing. Software-Defined Networking (SDN) allows applications to realize these tasks directly, by installing packet-processing rules on switches. However, today's SDN platforms provide limited support for creating modular applications. This paper introduces new abstractions for building applications out of multiple, independent modules that jointly manage network traffic. First, we define composition operators and a library of policies for forwarding and querying traffic. Our parallel composition operator allows multiple policies to operate on the same set of packets, while a novel sequential composition operator allows one policy to process packets after another. Second, we enable each policy to operate on an abstract topology that implicitly constrains what the module can see and do. Finally, we define a new abstract packet model that allows programmers to extend packets with virtual fields that may be used to associate packets with high-level meta-data. We realize these abstractions in Pyretic, an imperative, domain-specific language embedded in Python.
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paper_title: Virtualizing the network forwarding plane

paper_content:

Modern system design often employs virtualization to decouple the system service model from its physical realization. Two common examples are the virtualization of computing resources through the use of virtual machines and the virtualization of disks by presenting logical volumes as the storage interface. The insertion of these abstraction layers allows operators great flexibility to achieve operational goals divorced from the underlying physical infrastructure. Today, workloads can be instantiated dynamically, expanded at runtime, migrated between physical servers (or geographic locations), and suspended if needed. Both computation and data can be replicated in real time across multiple physical hosts for purposes of high-availability within a single site, or disaster recovery across multiple sites.
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paper_title: Content-addressable memory (CAM) circuits and architectures: a tutorial and survey

paper_content:

We survey recent developments in the design of large-capacity content-addressable memory (CAM). A CAM is a memory that implements the lookup-table function in a single clock cycle using dedicated comparison circuitry. CAMs are especially popular in network routers for packet forwarding and packet classification, but they are also beneficial in a variety of other applications that require high-speed table lookup. The main CAM-design challenge is to reduce power consumption associated with the large amount of parallel active circuitry, without sacrificing speed or memory density. In this paper, we review CAM-design techniques at the circuit level and at the architectural level. At the circuit level, we review low-power matchline sensing techniques and searchline driving approaches. At the architectural level we review three methods for reducing power consumption.
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paper_title: A Survey of Network Virtualization

paper_content:

Due to the existence of multiple stakeholders with conflicting goals and policies, alterations to the existing Internet architecture are now limited to simple incremental updates; deployment of any new, radically different technology is next to impossible. To fend off this ossification, network virtualization has been propounded as a diversifying attribute of the future inter-networking paradigm. By introducing a plurality of heterogeneous network architectures cohabiting on a shared physical substrate, network virtualization promotes innovations and diversified applications. In this paper, we survey the existing technologies and a wide array of past and state-of-the-art projects on network virtualization followed by a discussion of major challenges in this area.
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paper_title: What you need to know about SDN control and data planes

paper_content:

SDN and OpenFlow are actively being standardized and deployed. These deployments rely on switches that come from various vendors and differ in terms of their performance and available features. Understanding these differences and basic performance characteristics is essential for ensuring efficient deployments. In this paper we measure, report, and explain the performance characteristics of the controland data-planes in three hardware OpenFlow switches. Our results can help controller developers to make their programs efficient. Further, we also highlight differences between the OpenFlow specification and its implementations, that if ignored, pose a serious threat to network security and correctness.
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paper_title: On Controller Performance in Software-Defined Networks

paper_content:

Network architectures in which the control plane is decoupled from the data plane have been growing in popularity. Among the main arguments for this approach is that it provides a more structured software environment for developing network-wide abstractions while potentially simplifying the data plane. As has been adopted elsewhere [11], we refer to this split architecture as Software-Defined Networking (SDN). While it has been argued that SDN is suitable for some deployment environments (such as homes [17, 13], data centers [1], and the enterprise [5]), delegating control to a remote system has raised a number of questions on control-plane scaling implications of such an approach. Two of the most often voiced concerns are: (a) how fast can the controller respond to data path requests?; and (b) how many data path requests can it handle per second? There are some references to the performance of SDN systems in the literature [16, 5, 3]. For example, an oft-cited study shows that a popular network controller (NOX) handles around 30k flow initiation events1 per second while maintaining a sub-10ms flow install time [14]. Unfortunately, recent measurements of some deployment environments suggests that these numbers are far from sufficient. For example, Kandula et al. [9] found that a 1500-server cluster has a median flow arrival rate of 100k flows per second. Also, Benson et al. [2] show that a network with 100 switches can have spikes of 10M flows arrivals per second in the worst case. In addition, the 10ms flow setup delay of an SDN controller would add a 10% delay to the majority of flows (short-lived) in such a network. This disconnect between relatively poor controller performance and high network demands has motivated a
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paper_title: OFLOPS: An Open Framework for OpenFlow Switch Evaluation

paper_content:

Recent efforts in software-defined networks, such as OpenFlow, give unprecedented access into the forwarding plane of networking equipment. When building a network based on OpenFlow however, one must take into account the performance characteristics of particular OpenFlow switch implementations. In this paper, we present OFLOPS, an open and generic software framework that permits the development of tests for OpenFlow-enabled switches, that measure the capabilities and bottlenecks between the forwarding engine of the switch and the remote control application. OFLOPS combines hardware instrumentation with an extensible software framework. ::: ::: We use OFLOPS to evaluate current OpenFlow switch implementations and make the following observations: (i) The switching performance of flows depends on applied actions and firmware. (ii) Current OpenFlow implementations differ substantially in flow updating rates as well as traffic monitoring capabilities. (iii) Accurate OpenFlow command completion can be observed only through the data plane. These observations are crucial for understanding the applicability of Open- Flow in the context of specific use-cases, which have requirements in terms of forwarding table consistency, flow setup latency, flow space granularity, packet modification types, and/or traffic monitoring abilities.
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paper_title: HyperFlow: A Distributed Control Plane for OpenFlow

paper_content:

OpenFlow assumes a logically centralized controller, which ideally can be physically distributed. However, current deployments rely on a single controller which has major drawbacks including lack of scalability. We present HyperFlow, a distributed event-based control plane for OpenFlow. HyperFlow is logically centralized but physically distributed: it provides scalability while keeping the benefits of network control centralization. By passively synchronizing network-wide views of OpenFlow controllers, HyperFlow localizes decision making to individual controllers, thus minimizing the control plane response time to data plane requests. HyperFlow is resilient to network partitioning and component failures. It also enables interconnecting independently managed OpenFlow networks, an essential feature missing in current OpenFlow deployments. We have implemented HyperFlow as an application for NOX. Our implementation requires minimal changes to NOX, and allows reuse of existing NOX applications with minor modifications. Our preliminary evaluation shows that, assuming sufficient control bandwidth, to bound the window of inconsistency among controllers by a factor of the delay between the farthest controllers, the network changes must occur at a rate lower than 1000 events per second across the network.
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paper_title: Efficient Fair Queueing Algorithms for Packet-Switched Networks

paper_content:

Although weighted fair queueing (WFQ) has been regarded as an ideal scheduling algorithm in terms of its combined delay bound and proportional fairness properties, its asymptotic time complexity increases linearly with the number of sessions serviced by the scheduler, thus limiting its use in high-speed networks. An algorithm that combines the delay and fairness bounds of WFQ with O(1) timestamp computations had remained elusive so far. In this paper we present two novel scheduling algorithms that have O(1) complexity for timestamp computations and provide the same bounds on end-to-end delay and buffer requirements as those of WFQ. The first algorithm, frame-based fair queueing (FFQ), uses a framing mechanism to periodically recalibrate a global variable tracking the progress of work in the system, limiting any short-term unfairness to within a frame period. The second algorithm, starting potential based fair queueing (SPFQ), performs the recalibration at packet boundaries, resulting in improved fairness while still maintaining the O(1) timestamp computations. Both algorithms are based on the general framework of rate-proportional servers (RPSs) introduced by Stiliadis and Varma (see ibid., vol.6, no.2, p.164-74, 1998). The algorithms may be used in both general packet networks with variable packet sizes and in asynchronous transfer mode (ATM) networks.
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paper_title: Hierarchical packet fair queueing algorithms

paper_content:

We propose to use the idealized hierarchical generalized processor sharing (H-GPS) model to simultaneously support guaranteed real-time, rate-adaptive best-effort, and controlled link-sharing services. We design hierarchical packet fair queueing (H-PFQ) algorithms to approximate H-GPS by using one-level variable-rate PFQ servers as basic building blocks. By computing the system virtual time and per packet virtual start/finish times in unit of bits instead of seconds, most of the PFQ algorithms in the literature can be properly defined as variable-rate servers. We develop techniques to analyze delay and fairness properties of variable-rate and hierarchical PFQ servers. We demonstrate that in order to provide tight delay bounds with an H-PFQ server, it is essential for the one-level PFQ servers to have small worst-case fair indices (WFI). We propose a new PFQ algorithm called WF/sup 2/Q+ that is the first to have all the following three properties: (1) providing the tightest delay bound among all PFQ algorithms; (2) having the smallest WFI among all PFQ algorithms; and (3) having a relatively low asymptotic complexity of O(log N). Simulation results are presented to evaluate the delay and link-sharing properties of H-WF/sup 2/Q+, H-WFQ, H-SFQ, and H-SCFQ.
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paper_title: Scalable Network Virtualization in Software-Defined Networks

paper_content:

Network virtualization gives each "tenant" in a data center its own network topology and control over its traffic flow. Software-defined networking offers a standard interface between controller applications and switch-forwarding tables, and is thus a natural platform for network virtualization. Yet, supporting numerous tenants with different topologies and controller applications raises scalability challenges. The FlowN architecture gives each tenant the illusion of its own address space, topology, and controller, and leverages database technology to efficiently store and manipulate mappings between virtual networks and physical switches.
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paper_title: Slicing the next mobile packet core network

paper_content:

The mobile network plays an important role in the evolution of humanity and society. However, due to the increase of users as well as of mobile applications, the current mobile network architecture faces many challenges. In this paper we describe V-Core, a new architecture for the mobile packet core network which is based on Software Defined Networking and Network Function Virtualization. Then, we introduce a MobileVisor which is a machine to slice the above mobile packet core network into different control platforms according to either different mobile operators or different technologies (e.g. 3G or 4G). With our architecture, the mobile network operators can reduce their costs for deployment and operation as well as use network resources efficiently.
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paper_title: Optical FlowVisor: An OpenFlow-based optical network virtualization approach

paper_content:

A novel impairment aware optical network virtualization mechanism (Optical FlowVisor) based on software defined networking (OpenFlow-based) paradigm is experimentally demonstrated. End-to-end flow setup time and the performance of virtual switches and OpenFlow controller are reported.
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paper_title: OpenSlice: An OpenFlow-based control plane for spectrum sliced elastic optical path networks

paper_content:

A control plane is a key enabling technique for dynamic and intelligent end-to-end path provisioning in optical networks. In this paper, we present an OpenFlow-based control plane for spectrum sliced elastic optical path networks, called OpenSlice, for dynamic end-to-end path provisioning and IP traffic offloading. Experimental demonstration and numerical evaluation show its overall feasibility and efficiency.
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paper_title: CoVisor: a compositional hypervisor for software-defined networks

paper_content:

We present CoVisor, a new kind of network hypervisor that enables, in a single network, the deployment of multiple control applications written in different programming languages and operating on different controller platforms. Unlike past hypervisors, which focused on slicing the network into disjoint parts for separate control by separate entities, CoVisor allows multiple controllers to cooperate on managing the same shared traffic. Consequently, network administrators can use CoVisor to assemble a collection of independently-developed "best of breed" applications--a firewall, a load balancer, a gateway, a router, a traffic monitor--and can apply those applications in combination, or separately, to the desired traffic. CoVisor also abstracts concrete topologies, providing custom virtual topologies in their place, and allows administrators to specify access controls that regulate the packets a given controller may see, modify, monitor, or reroute. The central technical contribution of the work is a new set of efficient algorithms for composing controller policies, for compiling virtual networks into concrete OpenFlow rules, and for efficiently processing controller rule updates. We have built a CoVisor prototype, and shown that it is several orders of magnitude faster than a naive implementation.
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paper_title: Toward Software-Defined Cellular Networks

paper_content:

Existing cellular networks suffer from inflexible and expensive equipment, complex control-plane protocols, and vendor-specific configuration interfaces. In this position paper, we argue that software defined networking (SDN) can simplify the design and management of cellular data networks, while enabling new services. However, supporting many subscribers, frequent mobility, fine-grained measurement and control, and real-time adaptation introduces new scalability challenges that future SDN architectures should address. As a first step, we propose extensions to controller platforms, switches, and base stations to enable controller applications to (i) express high-level policies based on subscriber attributes, rather than addresses and locations, (ii) apply real-time, fine-grained control through local agents on the switches, (iii)perform deep packet inspection and header compression on packets, and (iv)remotely manage shares of base-station resources.
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paper_title: Network Virtualization in Multi-tenant Datacenters

paper_content:

Multi-tenant datacenters represent an extremely challenging networking environment. Tenants want the ability to migrate unmodified workloads from their enterprise networks to service provider datacenters, retaining the same networking configurations of their home network. The service providers must meet these needs without operator intervention while preserving their own operational flexibility and efficiency. Traditional networking approaches have failed to meet these tenant and provider requirements. Responding to this need, we present the design and implementation of a network virtualization solution for multi-tenant datacenters.
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paper_title: HyperFlex: An SDN virtualization architecture with flexible hypervisor function allocation

paper_content:

Network Virtualization (NV) and Software-Defined Networking (SDN) are both expected to increase the flexibility and programmability of today's communication networks. Combining both approaches may even be a further step towards increasing the efficiency of network resource utilization. Multiple solutions for virtualizing SDN networks have already been proposed, however, they are either implemented in software or they require special network hardware. We propose HyperFlex, an SDN hypervisor architecture that relies on the decomposition of the hypervisor into functions that are essential for virtualizing SDN networks. The hypervisor functions can be flexibly executed in software or hosted on SDN network elements. Furthermore, existing hypervisor solutions focus on data-plane virtualization mechanisms and neglect the virtualization of the control-plane of SDN networks. HyperFlex provides control-plane virtualization by adding a control-plane isolation function, either in software or on network elements. The isolation function ensures that the resources of the control-plane are shared correctly between each virtual SDN network while it also protects the hypervisor resources from resource exhaustion.
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paper_title: RadioVisor: a slicing plane for radio access networks

paper_content:

To cope with the exponential traffic growth, increasingly diverse traffic mix including voice, video, machine-tomachine(M2M), and the spectrum shortage, wireless networks have to get densely deployed and dynamically adapt to meet the distinct requirements of diverse traffic classes. However, current network architectures are ill-equipped to support a dense and dynamic wireless infrastructure. First, since it will be impossible to obtain regularly placed cell sites for an infrastructure with higher density, basestations will be deployed wherever possible in a chaotic fashion. However, a chaotic and dense wireless deployment will be very complex to manage, since it will experience highly variable loads and unpredictable inter-cell interference among other things. Further since spectrum is limited, very likely all the basestations will be operating on the same frequency (referred to as frequency reuse factor of one). This leads to a tremendous amount of inter-cell interference, and that becomes the limiting factor for network capacity. Second, a dense infrastructure is very expensive to deploy and operate. Current deployments are unaffordable except to the largest operators, so a deployment with significantly higher density will likely be enormously expensive even for the largest operators, preventing smaller operators from expanding and offering consumers the choices they need. Rather than looking at the radio access layer as a collection of independent base stations, SoftRAN [1] proposes that all base stations deployed in a geographical area should be abstracted as a virtual big-base station which is made up of radio elements (the individual physical base stations). A logically centralized control plane makes all decisions regarding handovers and interference management, while the radio elements are simpler devices with minimal control logic. Since all neighboring base stations are allocating from a fixed set of shared resources, SoftRAN abstracts the radio resources as a 3D resource grid of space, time, and frequency slots; and program them in a software defined fashion through a logically centralized radio access control plane. Rather than having a single entity controlling radio access networks which limits sharing as standardized by 3GPP on LTE [2], we build on SoftRAN and argue that the 3D resource grid should be dynamically sliced based on traffic among virtual operators. This will enable virtual operators to innovate in scheduling, interference management and even in physical layer (PHY). Operators should be able to flexibly define slices based on subscriber attributes and application types (e.g. voice, video) to support a wide range of application requirements. Such architecture raises unique challenges compared to data-center and enterprise networks. Indeed, radio resources are inherently coupled due to the shared nature of wireless media. Unlike FlowVisor [3] which slices the flow space and easily isolates the disjoint subspaces. Slicing radio resources would need to consider interference.
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paper_title: OpenVirteX: A Network Hypervisor.

paper_content:

Virtualized environments have been around for a long time, but until recently these have focused solely on compute virtualization and left the network behind. Network virtualization enables multiple tenants to share the same physical infrastructure by decoupling the physical network from the virtual network. In this paper, we introduce OpenVirteX, a Network Virtualization Platform which provides virtual Software Defined Networks (vSDNs). Each vSDN is customizable in terms of topology as well as addressing scheme. Introduction. Techniques for virtualizing network infrastructure have lagged behind that of compute resource virtualization. This has hampered the ability of operators to provide full virtualization that extends down to the network. In the ideal case, operators would be able to provide networks whose topologies, management schemes, and use cases are under the full control of their tenants. Realization of this scheme requires the ability to construct virtual networks that are not only logically isolated, but also have fully configurable topologies and properties akin to virtual machines, e.g., can be created, destroyed, snapshotted, and migrated on demand. Such a mechanism would provide operators with the ability to give a tenant the illusion that they have full control of topology, addressing, and management of the infrastructure despite sharing it with other tenants. Here we present OpenVirteX, a network hypervisor that enables operators to provide this form of network virtualization to their customers. We leverage the growing focus on Software Defined Networks (SDN) amongst infrastructure providers aiming to simplify and add flexibility to the process of provisioning networks. In specific, OpenVirteX builds on OpenFlow [1] as the SDN medium, and our experiences with FlowVisor [2] for design. Like FlowVisor, OpenVirteX functions as a proxy within the control channel, presenting OpenFlow networks to tenants, while controlling the underlying physical infrastructure via the southbound OpenFlow interface. Figure 1 depicts this architecture. By exposing OpenFlow networks, OpenVirteX allows tenants to use their own network OS (NOS) to control the network resources corresponding to their virtual network. In other words, OpenVirteX creates multiple virtual software defined networks out of one. Unlike FlowVisor, which simply slices the entire flowspace amongst the tenants, OpenVirteX provides each tenant with a fully virtualized network featuring a tenant-specified topology and a full header space. Motivation. OpenVirteX offers a pragmatic approach to meeting the requirements of both operators and tenants in increasingly common computing situations: • Cloud: OVX facilitates the migration of an enterprise to a Cloud Infrastructure. Each customer can request an exact copy of his/her physical network, with the same address scheme and topology of the current network. The level of abstraction offered by OpenVirteX creates the illusion that the Cloud physical infrastructure fits exactly the client requirements, in terms of isolation, topology and addressing scheme. • Provider: Similarly, in a WAN scenario, virtualization is essential, e.g. to allow multiple enterprises to connect their remote sites. With OVX, this could be done easily, spawning virtual networks that provide inherited traffic isolation, security, and flexibility. Moreover, with OpenVirteX, the tenant can still control how traffic is forwarded inside his network through a NOS and can apply policies (e.g. firewall, load balancer) that in a standard network are completely managed by the ISP. The remainder of this abstract describes the virtualization approach taken by OpenVirteX, and its current state. Topology Virtualization. OpenVirteX maintains internal representations of the physical and virtual networks as a collection of software switches, links, and end hosts. The physical topology representation is the basis upon which virtual networks are mapped. Tenants can request a topology by supplying a mapping between the elements in the physical topology and their desired virtual network. Virtual topologies can range from an exact copy or subset of the physical network, over a giant virtual switch that abstracts away all physical switches and links, to any custom topology as described by the tenant. The ability to control topology abstraction allows tenants to simplify their NOS, or operators to implement policies in the network. For example, a tenant may forego loop resolution in their NOS by requesting a loop-free topology, or an operator can require traffic to pass through chosen nodes by modifying the connecting path of a virtual link or between the ports of a giant switch. The mapping between virtual and physical elements are stored in a global map, but otherwise kept separate. This allows tenant networks to be reconfigured, halted, and re-initialized by simply modifying this mapping, i.e. pointing keys to different values. Finally, since virtual topologies need not correspond to the physical network, resilience can be enabled in the former Fig. 1: Network virtualization with OpenVirteX. Fig. 2: The address virtualization process. by allowing tenants to specify multiple backup paths for any virtual links between switches, or within giant switches, between ports. Address Virtualization. OpenVirteX grants tenants the ability to choose address assignments for their end hosts, allowing multiple, potentially-overlapping IP address blocks to exist in the same physical network. To differentiate hosts, OpenVirteX generates globally unique tenant IDs for each tenant, and for each host, a physical IP addresses that encodes the host’s membership using the tenant ID. Collisions of addresses are avoided by installing flow rules to rewrite addresses at the edge switches of the network, from tenant-assigned address to physical IP address at the ingress edge, and vice-versa at the egress edge. The translation process is illustrated in Figure 2. Importantly, this procedure is invisible to a tenant’s NOS or hosts, implying that a NOS used to control a virtual network created by OpenVirteX doesn’t need to be modified in any way to properly function. In addition to preventing address aliasing in a transparent way, the mapping created by the procedure is used by OpenVirteX to demultiplex northbound control messages so that they reach the correct tenant networks. Control Function Virtualization. Each virtual network may run its own NOS to program the virtual switches. OpenVirteX makes this possible by mapping various control functions for the virtual network on to the corresponding physical network resources. The translations can get complex, since an operation for one virtual switch may map onto multiple switches and links in the physical network. OpenVirteX leverages its position as proxy that allows it to intercept and manipulate the control packets before they reach their intended destination, which OpenVirteX also determines based on its virtual-physical mapping. Implementation. We have implemented a preliminary version of OpenVirteX in Java. This version currently supports OpenFlow 1.0, and supports the creation of custom topologies under overlapping IP address spaces, the ability to start and stop virtual networks and their components, and persistent storage using Mongo DB. Backup paths for resilient links and giant switches can be manually configured, or automatically generated with a simple SPF algorithm. A JSONRPC API is provided to enable configuration and monitoring of both tenant and infrastructure networks. This API has been used for an implementation of a GUI, as well as a topology embedder that generates virtual-physical mappings as configurations to OpenVirteX. Currently on-going work includes the addition of features such as virtual network snapshotting and migration, dynamic configuration of virtual networks, and external and inter-tenant connectivity. In the future topics such as HA and scalability may be explored.
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paper_title: AutoSlice: automated and scalable slicing for software-defined networks

paper_content:

We present AutoSlice, a virtualization layer that automates the deployment and operation of software-defined network (SDN) slices on top of shared network infrastructures. AutoSlice enables substrate providers to resell their SDN to multiple tenants while minimizing operator intervention. At the same time, tenants are given the means to lease programmable network slices enabling the deployment of arbitrary services based on SDN principles. We outline the control plane architecture of AutoSlice and discuss the most challenging aspects of the forwarding plane design with emphasis on scalability.
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paper_title: ONOS: towards an open, distributed SDN OS

paper_content:

We present our experiences to date building ONOS (Open Network Operating System), an experimental distributed SDN control platform motivated by the performance, scalability, and availability requirements of large operator networks. We describe and evaluate two ONOS prototypes. The first version implemented core features: a distributed, but logically centralized, global network view; scale-out; and fault tolerance. The second version focused on improving performance. Based on experience with these prototypes, we identify additional steps that will be required for ONOS to support use cases such as core network traffic engineering and scheduling, and to become a usable open source, distributed network OS platform that the SDN community can build upon.
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paper_title: OpenFlow Virtualization Framework with Advanced Capabilities

paper_content:

Due to its simplicity, transparency and performance, Flow Visor takes it all in today's virtualization tools for OpenFlow networks. We argue that this effectiveness comes at the price of intolerance towards diverse OpenFlow versions used simultaneously and also limited switch functionality. What is more Flow Visor based management frameworks cannot run and configure the network controllers. In this paper we present an integrated OpenFlow virtualization framework, that is capable of (i) running and managing multiple instances of OpenFlow switches with different forwarding capabilities and OpenFlow versions, (ii) running and configuring full controllers or network applications designed for controlling a virtual network under the management of the proposed framework, and (iii) configuring QoS in the network. Besides introducing the architecture we share implementation and deployment details in our prototype system.
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paper_title: Taming SDN Controllers in Heterogeneous Hardware Environments

paper_content:

The ability to deploy applications which control network resources using a global view is a major benefit of the SDN paradigm. The SDN dataplane is comprised of a topology of forwarding elements programmed by a centralized controller over a common, well-defined interface. We believe that the heterogeneity of forwarding devices is an inherent property of software defined networks rather than a side effect. Therefore it is vital to design SDN frameworks in manner which explicitly takes variable hardware capabilities into account. In this work we argue that the concurrent operation of switches with diverse capacities for control message processing leads to unpredictable delays in SDN applications. To address this issue, we use a queuing model to characterize the service of a switch's control interface. Furthermore, we outline a measurement based-approach to derive the corresponding parameters. We propose a simple interface extension for controller frameworks which enables operators to configure delay bounds for transmitted control messages. As a result, developers can create SDN applications which exhibit consistent and predicable behavior.
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paper_title: FlowVisor: A Network Virtualization Layer

paper_content:

Network virtualization has long been a goal of of the network research community. With it, multiple isolated logical networks each with potentially different addressing and forwarding mechanisms can share the same physical infrastructure. Typically this is achieved by taking advantage of the flexibility of software (e.g. [20, 23]) or by duplicating components in (often specialized) hardware[19]. In this paper we present a new approach to switch virtualization in which the same hardware forwarding plane can be shared among multiple logical networks, each with distinct forwarding logic. We use this switch-level virtualization to build a research platform which allows multiple network experiments to run side-by-side with production traffic while still providing isolation and hardware forwarding speeds. We also show that this approach is compatible with commodity switching chipsets and does not require the use of programmable hardware such as FPGAs or network processors. We build and deploy this virtualization platform on our own production network and demonstrate its use in practice by running five experiments simultaneously within a campus network. Further, we quantify the overhead of our approach and evaluate the completeness of the isolation between virtual slices.
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paper_title: A survey of advanced ethernet forwarding approaches

paper_content:

The higher transmission rates currently supported by Ethernet lead to the possibility of expanding Ethernet beyond the local area network scope, bringing it into the core of large scale networks, of which a metropolitan area network (MAN) is a significant example. However, originally Ethernet was not devised to scale in such environments: its design does not contemplate essential requirements of larger and more complex networks, such as the need for resilience, scalability, or even integrated control features. Furthermore, its spanning-tree based forwarding results in slow convergence and weak resource efficiency. Specifically focusing on Ethernet's forwarding behaviour, this survey covers solutions that enhance the Ethernet's path computation, allowing it to scale in larger, more complex environments. General notions concerning the application of Ethernet in Metro areas are also provided, as a specific example of Ethernet's application in large scale networks.
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paper_title: Control-plane slicing methods in multi-tenant software defined networks

paper_content:

In this paper, we focused on two prevailing architectural approaches for control-plane virtualization in multi-tenant OpenFlow-ready SDN domains: The first permits the delegation of a specific, non-overlapping part of the overall flowspace to each tenant OpenFlow controller, exposing him/her the entire substrate topology; the second conceals the substrate topology to tenants by abstracting resources and exposing user-controlled (tenant) Virtual Networks (VNs). For both cases, we propose and analyze three control-plane slicing methods (domain, switch and port-wide), enforced by the management plane, that safeguard control-plane isolation among tenant VNs. Their effectiveness is assessed in terms of control-plane resources (number of flowspace policy rule entries, table lookup times and memory consumption) via measurements on a prototype implementation. To that end, we introduced and prototyped the Flowspace Slicing Policy (FSP) rule engine, an automated mechanism translating substrate management-plane policies into VN mapping control-plane rules. Our experiments, involving thousands of tenants VN requests over a variety of WAN-scale network topologies (e.g. Internet2/OSE3 and GEANT), demonstrate that the port-wide slicing method is the most efficient in terms of tenant request acceptance ratio, within acceptable control-plane delays and memory consumption.
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paper_title: Implementation of an OpenFlow network virtualization for multi-controller environment

paper_content:

To share Future Internet OpenFlow testbed with multi-users using multi-controllers without each other's intervention, network virtualization based on FlowVisor should be implemented. For network resource virtualization, bandwidth isolation at allocated switches on a given slice and admission control are required. In this paper, we implemented admission control and minimum bandwidth guaranteeing scheme at the FlowVisor and tested the transmission performance of QoS-video streams on this testbed. Using our enhanced FlowVisor, we show that each user's bandwidth requirement can be guaranteed irrespective of other users' flow traffic.
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paper_title: FlowVisor: A Network Virtualization Layer

paper_content:

Network virtualization has long been a goal of of the network research community. With it, multiple isolated logical networks each with potentially different addressing and forwarding mechanisms can share the same physical infrastructure. Typically this is achieved by taking advantage of the flexibility of software (e.g. [20, 23]) or by duplicating components in (often specialized) hardware[19]. In this paper we present a new approach to switch virtualization in which the same hardware forwarding plane can be shared among multiple logical networks, each with distinct forwarding logic. We use this switch-level virtualization to build a research platform which allows multiple network experiments to run side-by-side with production traffic while still providing isolation and hardware forwarding speeds. We also show that this approach is compatible with commodity switching chipsets and does not require the use of programmable hardware such as FPGAs or network processors. We build and deploy this virtualization platform on our own production network and demonstrate its use in practice by running five experiments simultaneously within a campus network. Further, we quantify the overhead of our approach and evaluate the completeness of the isolation between virtual slices.
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paper_title: Generalizing Virtual Network Topologies in OpenFlow-Based Networks

paper_content:

Network Virtualization (NV) is one of the most promising technique to enable innovation in today's network. A recent approach toward NV has been proposed through FlowVisor, whose aim is to leverage on the specific features of an OpenFlow-controlled network to share the same hardware forwarding plane among multiple logical networks. However, FlowVisor lacks some features to enable a full implementation of a NV architecture: the virtual topologies that can be established are restricted to subsets of the physical topology and it has no way for two slices to share flowspace and simultaneously prevent them from interfering with each other's traffic. In this work, an innovative system called ADVisor (ADvanced FlowVisor) which enhances FlowVisor while overcoming its major constraints is presented and a set of experimental results discussed to demonstrate its capability to provide an effective support toward a Network Virtualization architecture.
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paper_title: VeRTIGO: Network Virtualization and Beyond

paper_content:

In this paper we present Vertigo (Virtual Topologies Generalization in OpenFlow networks), a Software-defined networking platform designed for network virtualization. Based on the OpenFlow original network slicing system Flow Visor, the Vertigo platform aims at covering all flavors of network virtualization: in particular, it is able to expose a simple abstract node on one extreme, and to deliver a logically fully connected network at the very opposite end. In this work, we first introduce the Vertigo system architecture and its design choices, then we report on a prototypical implementation deployed over an OpenFlow-enabled test bed. Experimental results show that Vertigo can deliver flexible and reliable network virtualization services to a wide range of use cases in spite of failure and/or congestion at the underlying physical network.
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paper_title: Traffic engineering with mpls in the internet

paper_content:

This article discusses traffic engineering with multiprotocol label switching (MPLS) in an Internet service provider's network. We first review MPLS, constraint-based routing, and enhanced link state interior gateway protocols to provide a background for traffic engineering. We then discuss the general issues of designing an MPLS system for traffic engineering. The design of GlobalCenter's MPLS system is presented. Based on our experiences, a generic procedure for deploying an MPLS system is proposed. We also discuss how to provide QoS in a network with MPLS. Putting these together, we present to readers the practical issues of traffic engineering and a working solution for traffic engineering with MPLS in the Internet.
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paper_title: Slices Isolator for a Virtualized Openflow Node

paper_content:

Virtualization is emerging as a key mechanism of scaling the infrastructure and facilitating service deployment for future Internet. Network virtualization provides the ability to slice larger, underutilized physical nodes into smaller, virtual ones. To ensure deterministic performance, guaranteed QoS, and independent behavior, virtual nodes have to be properly isolated. However, a high isolation can have an important impact on the node performance and configuration flexibility. This paper investigates the problem of isolation between the slices of a virtualized switch. Our approach consists on adapting isolation to the desired performance and flexibility while ensuring fairness between the slice. Based on that approach, we developed a model that provide the choice between several levels of isolation. Each level corresponds to one or more resources. We implemented this model for a virtualized Open Flow 1.1 switch. We propose a utility-based evaluation balancing performance and flexibility that provide the adapted isolation level to the required demand. This model gives preference to the user to have isolation with a higher flexibility or lower overhead. Our analysis also shows that the overhead and the resource consumption of the isolation is reduced while remaining flexible and dynamic.
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paper_title: A survey of advanced ethernet forwarding approaches

paper_content:

The higher transmission rates currently supported by Ethernet lead to the possibility of expanding Ethernet beyond the local area network scope, bringing it into the core of large scale networks, of which a metropolitan area network (MAN) is a significant example. However, originally Ethernet was not devised to scale in such environments: its design does not contemplate essential requirements of larger and more complex networks, such as the need for resilience, scalability, or even integrated control features. Furthermore, its spanning-tree based forwarding results in slow convergence and weak resource efficiency. Specifically focusing on Ethernet's forwarding behaviour, this survey covers solutions that enhance the Ethernet's path computation, allowing it to scale in larger, more complex environments. General notions concerning the application of Ethernet in Metro areas are also provided, as a specific example of Ethernet's application in large scale networks.
---
paper_title: Implementation of an OpenFlow network virtualization for multi-controller environment

paper_content:

To share Future Internet OpenFlow testbed with multi-users using multi-controllers without each other's intervention, network virtualization based on FlowVisor should be implemented. For network resource virtualization, bandwidth isolation at allocated switches on a given slice and admission control are required. In this paper, we implemented admission control and minimum bandwidth guaranteeing scheme at the FlowVisor and tested the transmission performance of QoS-video streams on this testbed. Using our enhanced FlowVisor, we show that each user's bandwidth requirement can be guaranteed irrespective of other users' flow traffic.
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paper_title: NOX: towards an operating system for networks

paper_content:

As anyone who has operated a large network can attest, enterprise networks are difficult to manage. That they have remained so despite significant commercial and academic efforts suggests the need for a different network management paradigm. Here we turn to operating systems as an instructive example in taming management complexity. In the early days of computing, programs were written in machine languages that had no common abstractions for the underlying physical resources. This made programs hard to write, port, reason about, and debug. Modern operating systems facilitate program development by providing controlled access to high-level abstractions for resources (e.g., memory, storage, communication) and information (e.g., files, directories). These abstractions enable programs to carry out complicated tasks safely and efficiently on a wide variety of computing hardware. In contrast, networks are managed through low-level configuration of individual components. Moreover, these configurations often depend on the underlying network; for example, blocking a user’s access with an ACL entry requires knowing the user’s current IP address. More complicated tasks require more extensive network knowledge; forcing guest users’ port 80 traffic to traverse an HTTP proxy requires knowing the current network topology and the location of each guest. In this way, an enterprise network resembles a computer without an operating system, with network-dependent component configuration playing the role of hardware-dependent machine-language programming. What we clearly need is an “operating system” for networks, one that provides a uniform and centralized programmatic interface to the entire network. Analogous to the read and write access to various resources provided by computer operating systems, a network operating system provides the ability to observe and control a network. A network operating system does not manage the network itself; it merely provides a programmatic interface. Applications implemented on top of the network operating system perform the actual management tasks. The programmatic interface should be general enough to support a broad spectrum of network management applications. Such a network operating system represents two major conceptual departures from the status quo. First, the network operating system presents programs with a centralized programming model; programs are written as if the entire network were present on a single machine (i.e., one would use Dijkstra to compute shortest paths, not Bellman-Ford). This requires (as in [3, 8, 14] and elsewhere) centralizing network state. Second, programs are written in terms of high-level abstractions (e.g., user and host names), not low-level configuration parameters (e.g., IP and MAC addresses). This allows management directives to be enforced independent of the underlying network topology, but it requires that the network operating system carefully maintain the bindings (i.e., mappings) between these abstractions and the low-level configurations. Thus, a network operating system allows management applications to be written as centralized programs over highlevel names as opposed to the distributed algorithms over low-level addresses we are forced to use today. While clearly a desirable goal, achieving this transformation from distributed algorithms to centralized programming presents significant technical challenges, and the question we pose here is: Can one build a network operating system at significant scale?
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paper_title: Software defined virtualization platform based on double-FlowVisors in multiple domain networks

paper_content:

In this paper, we build a virtualization platform based on double-FlowVisors in multiple domains Production Network to abstract the underlying hardware and provision unified API to the APPS in application layer, which can increase resource utilization rate and reduce blocking probability. As a proof of concept, we implement an experimental scenario dealing with virtualization in multiple domain networks. Experimental demonstration is conducted with results of 5-9% blocking probability reduction and 10-15% resource utilization rate increasement.
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paper_title: Slicing the next mobile packet core network

paper_content:

The mobile network plays an important role in the evolution of humanity and society. However, due to the increase of users as well as of mobile applications, the current mobile network architecture faces many challenges. In this paper we describe V-Core, a new architecture for the mobile packet core network which is based on Software Defined Networking and Network Function Virtualization. Then, we introduce a MobileVisor which is a machine to slice the above mobile packet core network into different control platforms according to either different mobile operators or different technologies (e.g. 3G or 4G). With our architecture, the mobile network operators can reduce their costs for deployment and operation as well as use network resources efficiently.
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paper_title: Optical FlowVisor: An OpenFlow-based optical network virtualization approach

paper_content:

A novel impairment aware optical network virtualization mechanism (Optical FlowVisor) based on software defined networking (OpenFlow-based) paradigm is experimentally demonstrated. End-to-end flow setup time and the performance of virtual switches and OpenFlow controller are reported.
---
paper_title: Toward Software-Defined Cellular Networks

paper_content:

Existing cellular networks suffer from inflexible and expensive equipment, complex control-plane protocols, and vendor-specific configuration interfaces. In this position paper, we argue that software defined networking (SDN) can simplify the design and management of cellular data networks, while enabling new services. However, supporting many subscribers, frequent mobility, fine-grained measurement and control, and real-time adaptation introduces new scalability challenges that future SDN architectures should address. As a first step, we propose extensions to controller platforms, switches, and base stations to enable controller applications to (i) express high-level policies based on subscriber attributes, rather than addresses and locations, (ii) apply real-time, fine-grained control through local agents on the switches, (iii)perform deep packet inspection and header compression on packets, and (iv)remotely manage shares of base-station resources.
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paper_title: Experimental demonstration of an OpenFlow based software-defined optical network employing packet, fixed and flexible DWDM grid technologies on an international multi-domain testbed

paper_content:

Software defined networking (SDN) and flexible grid optical transport technology are two key technologies that allow network operators to customize their infrastructure based on application requirements and therefore minimizing the extra capital and operational costs required for hosting new applications. In this paper, for the first time we report on design, implementation & demonstration of a novel OpenFlow based SDN unified control plane allowing seamless operation across heterogeneous state-of-the-art optical and packet transport domains. We verify and experimentally evaluate OpenFlow protocol extensions for flexible DWDM grid transport technology along with its integration with fixed DWDM grid and layer-2 packet switching.
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paper_title: RadioVisor: a slicing plane for radio access networks

paper_content:

To cope with the exponential traffic growth, increasingly diverse traffic mix including voice, video, machine-tomachine(M2M), and the spectrum shortage, wireless networks have to get densely deployed and dynamically adapt to meet the distinct requirements of diverse traffic classes. However, current network architectures are ill-equipped to support a dense and dynamic wireless infrastructure. First, since it will be impossible to obtain regularly placed cell sites for an infrastructure with higher density, basestations will be deployed wherever possible in a chaotic fashion. However, a chaotic and dense wireless deployment will be very complex to manage, since it will experience highly variable loads and unpredictable inter-cell interference among other things. Further since spectrum is limited, very likely all the basestations will be operating on the same frequency (referred to as frequency reuse factor of one). This leads to a tremendous amount of inter-cell interference, and that becomes the limiting factor for network capacity. Second, a dense infrastructure is very expensive to deploy and operate. Current deployments are unaffordable except to the largest operators, so a deployment with significantly higher density will likely be enormously expensive even for the largest operators, preventing smaller operators from expanding and offering consumers the choices they need. Rather than looking at the radio access layer as a collection of independent base stations, SoftRAN [1] proposes that all base stations deployed in a geographical area should be abstracted as a virtual big-base station which is made up of radio elements (the individual physical base stations). A logically centralized control plane makes all decisions regarding handovers and interference management, while the radio elements are simpler devices with minimal control logic. Since all neighboring base stations are allocating from a fixed set of shared resources, SoftRAN abstracts the radio resources as a 3D resource grid of space, time, and frequency slots; and program them in a software defined fashion through a logically centralized radio access control plane. Rather than having a single entity controlling radio access networks which limits sharing as standardized by 3GPP on LTE [2], we build on SoftRAN and argue that the 3D resource grid should be dynamically sliced based on traffic among virtual operators. This will enable virtual operators to innovate in scheduling, interference management and even in physical layer (PHY). Operators should be able to flexibly define slices based on subscriber attributes and application types (e.g. voice, video) to support a wide range of application requirements. Such architecture raises unique challenges compared to data-center and enterprise networks. Indeed, radio resources are inherently coupled due to the shared nature of wireless media. Unlike FlowVisor [3] which slices the flow space and easily isolates the disjoint subspaces. Slicing radio resources would need to consider interference.
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paper_title: Review and status of wavelength-division-multiplexing technology and its application

paper_content:

Wavelength-division-multiplexing (WDM) technology is now recognized as one of the key technologies in optical communications systems. This is because it has great potential to enhance system design and flexibility. This paper reviews state-of-the-art optical multi/demultiplexers (MUX/DEMUX) and WDM system design. Various system applications are also summarized.
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paper_title: CoVisor: a compositional hypervisor for software-defined networks

paper_content:

We present CoVisor, a new kind of network hypervisor that enables, in a single network, the deployment of multiple control applications written in different programming languages and operating on different controller platforms. Unlike past hypervisors, which focused on slicing the network into disjoint parts for separate control by separate entities, CoVisor allows multiple controllers to cooperate on managing the same shared traffic. Consequently, network administrators can use CoVisor to assemble a collection of independently-developed "best of breed" applications--a firewall, a load balancer, a gateway, a router, a traffic monitor--and can apply those applications in combination, or separately, to the desired traffic. CoVisor also abstracts concrete topologies, providing custom virtual topologies in their place, and allows administrators to specify access controls that regulate the packets a given controller may see, modify, monitor, or reroute. The central technical contribution of the work is a new set of efficient algorithms for composing controller policies, for compiling virtual networks into concrete OpenFlow rules, and for efficiently processing controller rule updates. We have built a CoVisor prototype, and shown that it is several orders of magnitude faster than a naive implementation.
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paper_title: NOX: towards an operating system for networks

paper_content:

As anyone who has operated a large network can attest, enterprise networks are difficult to manage. That they have remained so despite significant commercial and academic efforts suggests the need for a different network management paradigm. Here we turn to operating systems as an instructive example in taming management complexity. In the early days of computing, programs were written in machine languages that had no common abstractions for the underlying physical resources. This made programs hard to write, port, reason about, and debug. Modern operating systems facilitate program development by providing controlled access to high-level abstractions for resources (e.g., memory, storage, communication) and information (e.g., files, directories). These abstractions enable programs to carry out complicated tasks safely and efficiently on a wide variety of computing hardware. In contrast, networks are managed through low-level configuration of individual components. Moreover, these configurations often depend on the underlying network; for example, blocking a user’s access with an ACL entry requires knowing the user’s current IP address. More complicated tasks require more extensive network knowledge; forcing guest users’ port 80 traffic to traverse an HTTP proxy requires knowing the current network topology and the location of each guest. In this way, an enterprise network resembles a computer without an operating system, with network-dependent component configuration playing the role of hardware-dependent machine-language programming. What we clearly need is an “operating system” for networks, one that provides a uniform and centralized programmatic interface to the entire network. Analogous to the read and write access to various resources provided by computer operating systems, a network operating system provides the ability to observe and control a network. A network operating system does not manage the network itself; it merely provides a programmatic interface. Applications implemented on top of the network operating system perform the actual management tasks. The programmatic interface should be general enough to support a broad spectrum of network management applications. Such a network operating system represents two major conceptual departures from the status quo. First, the network operating system presents programs with a centralized programming model; programs are written as if the entire network were present on a single machine (i.e., one would use Dijkstra to compute shortest paths, not Bellman-Ford). This requires (as in [3, 8, 14] and elsewhere) centralizing network state. Second, programs are written in terms of high-level abstractions (e.g., user and host names), not low-level configuration parameters (e.g., IP and MAC addresses). This allows management directives to be enforced independent of the underlying network topology, but it requires that the network operating system carefully maintain the bindings (i.e., mappings) between these abstractions and the low-level configurations. Thus, a network operating system allows management applications to be written as centralized programs over highlevel names as opposed to the distributed algorithms over low-level addresses we are forced to use today. While clearly a desirable goal, achieving this transformation from distributed algorithms to centralized programming presents significant technical challenges, and the question we pose here is: Can one build a network operating system at significant scale?
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paper_title: Scalable Network Virtualization in Software-Defined Networks

paper_content:

Network virtualization gives each "tenant" in a data center its own network topology and control over its traffic flow. Software-defined networking offers a standard interface between controller applications and switch-forwarding tables, and is thus a natural platform for network virtualization. Yet, supporting numerous tenants with different topologies and controller applications raises scalability challenges. The FlowN architecture gives each tenant the illusion of its own address space, topology, and controller, and leverages database technology to efficiently store and manipulate mappings between virtual networks and physical switches.
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paper_title: Extending Networking into the Virtualization Layer

paper_content:

The move to virtualization has created a new network access layer residing on hosts that connects the various VMs. Virtualized deployment environments impose requirements on networking for which traditional models are not well suited. They also provide advantages to the networking layer (such as software flexibility and welldefined end host events) that are not present in physical networks. To date, this new virtualization network layer has been largely built around standard Ethernet switching, but this technology neither satisfies these new requirements nor leverages the available advantages. We present Open vSwitch, a network switch specifically built for virtual environments. Open vSwitch differs from traditional approaches in that it exports an external interface for fine-grained control of configuration state and forwarding behavior. We describe how Open vSwitch can be used to tackle problems such as isolation in joint-tenant environments, mobility across subnets, and distributing configuration and visibility across hosts.
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paper_title: The war between mice and elephants

paper_content:

Recent measurement based studies reveal that most of the Internet connections are short in terms of the amount of traffic they carry (mice), while a small fraction of the connections are carrying a large portion of the traffic (elephants). A careful study of the TCP protocol shows that without help from an active queue management (AQM) policy, short connections tend to lose to long connections in their competition for bandwidth. This is because short connections do not gain detailed knowledge of the network state, and therefore they are doomed to be less competitive due to the conservative nature of the TCP congestion control algorithm. Inspired by the differentiated services (Diffserv) architecture, we propose to give preferential treatment to short connections inside the bottleneck queue, so that short connections experience less packet drop rate than long connections. This is done by employing the RIO (RED with In and Out) queue management policy which uses different drop functions for different classes of traffic. Our simulation results show that: (1) in a highly loaded network, preferential treatment is necessary to provide short TCP connections with better response time and fairness without hurting the performance of long TCP connections; (2) the proposed scheme still delivers packets in FIFO manner at each link, thus it maintains statistical multiplexing gain and does not misorder packets; (3) choosing a smaller default initial timeout value for TCP can help enhance the performance of short TCP flows, however not as effectively as our scheme and at the risk of congestion collapse; (4) in the worst case, our proposal works as well as a regular RED scheme, in terms of response time and goodput.
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paper_title: Traffic engineering with mpls in the internet

paper_content:

This article discusses traffic engineering with multiprotocol label switching (MPLS) in an Internet service provider's network. We first review MPLS, constraint-based routing, and enhanced link state interior gateway protocols to provide a background for traffic engineering. We then discuss the general issues of designing an MPLS system for traffic engineering. The design of GlobalCenter's MPLS system is presented. Based on our experiences, a generic procedure for deploying an MPLS system is proposed. We also discuss how to provide QoS in a network with MPLS. Putting these together, we present to readers the practical issues of traffic engineering and a working solution for traffic engineering with MPLS in the Internet.
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paper_title: Flow classification by histograms: or how to go on safari in the internet

paper_content:

In order to control and manage highly aggregated Internet traffic flows efficiently, we need to be able to categorize flows into distinct classes and to be knowledgeable about the different behavior of flows belonging to these classes. In this paper we consider the problem of classifying BGP level prefix flows into a small set of homogeneous classes. We argue that using the entire distributional properties of flows can have significant benefits in terms of quality in the derived classification. We propose a method based on modeling flow histograms using Dirichlet Mixture Processes for random distributions. We present an inference procedure based on the Simulated Annealing Expectation Maximization algorithm that estimates all the model parameters as well as flow membership probabilities - the probability that a flow belongs to any given class. One of our key contributions is a new method for Internet flow classification. We show that our method is powerful in that it is capable of examining macroscopic flows while simultaneously making fine distinctions between different traffic classes. We demonstrate that our scheme can address issues with flows being close to class boundaries and the inherent dynamic behaviour of Internet flows.
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paper_title: A survey of advanced ethernet forwarding approaches

paper_content:

The higher transmission rates currently supported by Ethernet lead to the possibility of expanding Ethernet beyond the local area network scope, bringing it into the core of large scale networks, of which a metropolitan area network (MAN) is a significant example. However, originally Ethernet was not devised to scale in such environments: its design does not contemplate essential requirements of larger and more complex networks, such as the need for resilience, scalability, or even integrated control features. Furthermore, its spanning-tree based forwarding results in slow convergence and weak resource efficiency. Specifically focusing on Ethernet's forwarding behaviour, this survey covers solutions that enhance the Ethernet's path computation, allowing it to scale in larger, more complex environments. General notions concerning the application of Ethernet in Metro areas are also provided, as a specific example of Ethernet's application in large scale networks.
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paper_title: AutoSlice: automated and scalable slicing for software-defined networks

paper_content:

We present AutoSlice, a virtualization layer that automates the deployment and operation of software-defined network (SDN) slices on top of shared network infrastructures. AutoSlice enables substrate providers to resell their SDN to multiple tenants while minimizing operator intervention. At the same time, tenants are given the means to lease programmable network slices enabling the deployment of arbitrary services based on SDN principles. We outline the control plane architecture of AutoSlice and discuss the most challenging aspects of the forwarding plane design with emphasis on scalability.
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paper_title: GENI: A federated testbed for innovative network experiments

paper_content:

GENI, the Global Environment for Networking Innovation, is a distributed virtual laboratory for transformative, at-scale experiments in network science, services, and security. Designed in response to concerns over Internet ossification, GENI is enabling a wide variety of experiments in a range of areas, including clean-slate networking, protocol design and evaluation, distributed service offerings, social network integration, content management, and in-network service deployment. Recently, GENI has been leading an effort to explore the potential of its underlying technologies, SDN and GENI racks, in support of university campus network management and applications. With the concurrent deployment of these technologies on regional and national R&E backbones, this will result in a revolutionary new national-scale distributed architecture, bringing to the entire network the shared, deeply programmable environment that the cloud has brought to the datacenter. This deeply programmable environment will support the GENI research mission and as well as enabling research in a wide variety of application areas.
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paper_title: Network Hypervisors: Managing the Emerging SDN Chaos

paper_content:

Software-Defined Networking (SDN) has been widely recognized as a promising way to deploy new services and protocols in future networks. The programmability and control offered by SDN networks enables users and applications to define virtually every aspect of the network architecture. Unfortunately, this flexibility comes at a cost - a cost that has the potential to significantly limit its adoption. First, in order to offer complete flexibility, today's SDN networks provide low-level API's on which almost any type of service can be written. In the process, it can actually become more difficult to implement the higher level complex services needed by future networks. Second, emerging SDN networks exhibit a heterogeneity reminiscent of the early Internet, with limited ability to piece together the various SDN platforms being deployed. In this paper we propose a new way to construct SDN networks consisting of multiple SDN providers offering virtualizable networking resources across the Internet. At the heart of our approach is a Network Hypervisor service that is capable of internetworking various SDN providers together. Moreover, our Network Hypervisor builds on the low-level APIs provided by SDNs to create a unified set of high-level abstractions and APIs that greatly simplify the task of building and deploying complex network services over SDN.
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paper_title: Towards a scalable software-defined network virtualization platform

paper_content:

Software-defined networking (SDN) has emerged to circumvent the difficulty of introducing new functionality into the network. The widespread adoption of SDN technologies, such as OpenFlow, can facilitate the deployment of novel network functions and new services. Network infrastructure providers can significantly benefit from the SDN paradigm by leasing network slices with SDN support to Service Providers and end-users. Currently, the deployment of arbitrary virtual SDN topologies entails significant configuration overhead for SDN operators. To this end, we present a SDN virtualization layer that orchestrates the deployment and management of virtual SDNs (vSDN). The so-called SDN hypervisor generates and installs the forwarding entries required for vSDN setup and also coordinates the necessary switch flow table modifications for seamless resource migration. Furthermore, the hypervisor transparently rewrites all control messages enforcing flowspace isolation while giving to the vSDN operator the illusion of exclusive access control. We explore the design space and prerequisites for SDN virtualization, including the selection and encoding of packet identifiers, the resolution of flowspace identifiers, and the configuration and consolidation of multiple virtual flow tables onto a single switch in order to provide support for arbitrary topologies. Furthermore, we discuss the scalability of the SDN control and data plane.
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paper_title: DFVisor: Scalable network virtualization for QoS management in cloud computing

paper_content:

Increasingly cloud-based virtual networking environments are required to provide fine-grained Quality of Service (QoS) management without sacrificing scalability. However, no single approach currently can meet these requirements simultaneously. This paper introduces a layered concept that uses a common overlay mechanism to virtualize networks and enable fine-grained QoS management through resource slicing. Based on this mechanism, a fully distributed network virtualization platform called Distributed FlowVisor (DFVisor) is proposed. It uses a layered overlay to improve the network addressing space, reduce flow setup latency, and remove the single point of failure in the network - the central slice controller. Through a distributed synchronized two-level database, DFVisor incorporates a push-based flow setup and statistics collecting mechanism using a dedicated data channel to address the scalability issues caused by the current pull-based mechanism and the limited control channel bandwidth shared by both control flows and network statistics. The potential issues in DFVisor implementation and evaluation are discussed for future research.
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paper_title: Elastic optical networking: a new dawn for the optical layer?

paper_content:

Optical networks are undergoing significant changes, fueled by the exponential growth of traffic due to multimedia services and by the increased uncertainty in predicting the sources of this traffic due to the ever changing models of content providers over the Internet. The change has already begun: simple on-off modulation of signals, which was adequate for bit rates up to 10 Gb/s, has given way to much more sophisticated modulation schemes for 100 Gb/s and beyond. The next bottleneck is the 10-year-old division of the optical spectrum into a fixed "wavelength grid," which will no longer work for 400 Gb/s and above, heralding the need for a more flexible grid. Once both transceivers and switches become flexible, a whole new elastic optical networking paradigm is born. In this article we describe the drivers, building blocks, architecture, and enabling technologies for this new paradigm, as well as early standardization efforts.
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paper_title: FlowVisor: A Network Virtualization Layer

paper_content:

Network virtualization has long been a goal of of the network research community. With it, multiple isolated logical networks each with potentially different addressing and forwarding mechanisms can share the same physical infrastructure. Typically this is achieved by taking advantage of the flexibility of software (e.g. [20, 23]) or by duplicating components in (often specialized) hardware[19]. In this paper we present a new approach to switch virtualization in which the same hardware forwarding plane can be shared among multiple logical networks, each with distinct forwarding logic. We use this switch-level virtualization to build a research platform which allows multiple network experiments to run side-by-side with production traffic while still providing isolation and hardware forwarding speeds. We also show that this approach is compatible with commodity switching chipsets and does not require the use of programmable hardware such as FPGAs or network processors. We build and deploy this virtualization platform on our own production network and demonstrate its use in practice by running five experiments simultaneously within a campus network. Further, we quantify the overhead of our approach and evaluate the completeness of the isolation between virtual slices.
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paper_title: OpenSlice: An OpenFlow-based control plane for spectrum sliced elastic optical path networks

paper_content:

A control plane is a key enabling technique for dynamic and intelligent end-to-end path provisioning in optical networks. In this paper, we present an OpenFlow-based control plane for spectrum sliced elastic optical path networks, called OpenSlice, for dynamic end-to-end path provisioning and IP traffic offloading. Experimental demonstration and numerical evaluation show its overall feasibility and efficiency.
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paper_title: The Design and Implementation of Open vSwitch

paper_content:

We describe the design and implementation of Open vSwitch, a multi-layer, open source virtual switch for all major hypervisor platforms. Open vSwitch was designed de novo for networking in virtual environments, resulting in major design departures from traditional software switching architectures. We detail the advanced flow classification and caching techniques that Open vSwitch uses to optimize its operations and conserve hypervisor resources. We evaluate Open vSwitch performance, drawing from our deployment experiences over the past seven years of using and improving Open vSwitch.
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paper_title: Network Virtualization in Multi-tenant Datacenters

paper_content:

Multi-tenant datacenters represent an extremely challenging networking environment. Tenants want the ability to migrate unmodified workloads from their enterprise networks to service provider datacenters, retaining the same networking configurations of their home network. The service providers must meet these needs without operator intervention while preserving their own operational flexibility and efficiency. Traditional networking approaches have failed to meet these tenant and provider requirements. Responding to this need, we present the design and implementation of a network virtualization solution for multi-tenant datacenters.
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paper_title: An OpenFlow Based Network Virtualization Framework for the Cloud

paper_content:

The Cloud computing paradigm entails a challenging networking scenario. Due to the economy of scale, the Cloud is mainly supported by Data Center infrastructures. Therefore, virtualized environment manageability, seamless migration of virtual machines, inter-domain communication issues and scalability problems are some of the main concerns that should be addressed. A recently proposed abstract model is used as a reference for the Cloud computing architecture. This paper introduces a network virtualization framework for the Cloud based on this model. Accordingly, a proper abstraction of network elements (vhost, vnode and vlink) is defined in order to virtualize the physical infrastructure. Moreover, a novel Layer 2 network virtualization approach based on a new MAC addressing scheme is presented: we propose to build locally administered MAC addresses that hold context information, such as virtual operator, domain, node and host identifiers. In addition, implementation details are suggested, describing how the Open Flow technology can lead to an implementation of the proposed approach.
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paper_title: Memory resource management in VMware ESX server

paper_content:

VMware ESX Server is a thin software layer designed to multiplex hardware resources efficiently among virtual machines running unmodified commodity operating systems. This paper introduces several novel ESX Server mechanisms and policies for managing memory. A ballooning technique reclaims the pages considered least valuable by the operating system running in a virtual machine. An idle memory tax achieves efficient memory utilization while maintaining performance isolation guarantees. Content-based page sharing and hot I/O page remapping exploit transparent page remapping to eliminate redundancy and reduce copying overheads. These techniques are combined to efficiently support virtual machine workloads that overcommit memory.
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paper_title: Experimental demonstration of 400 Gb/s multi-flow, multi-rate, multi-reach optical transmitter for efficient elastic spectral routing

paper_content:

We demonstrate a multi-flow/multi-rate/multi-reach optical transmitter and spectral routing of total 400 Gb/s optical flows. The number of optical flows, bit rate, and optical reach can be adjusted to enable efficient elastic spectral routing.
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paper_title: AutoVFlow: Autonomous Virtualization for Wide-Area OpenFlow Networks

paper_content:

It is expected that clean-slate network designs will be implemented for wide-area network applications. Multi-tenancy in OpenFlow networks is an effective method to supporting a clean-slate network design, because the cost-effectiveness is improved by the sharing of substrate networks. To guarantee the programmability of OpenFlow for tenants, a complete flow space (i.e., header values of the data packets) virtualization is necessary. Wide-area substrate networks typically have multiple administrators. We therefore need to implement a flow space virtualization over multiple administration networks. In existing techniques, a third party is solely responsible for managing the mapping of header values for flow space virtualization for substrate network administrators and tenants, despite the severity of a third party failure. In this paper, we propose an AutoVFlow mechanism that allows flow space virtualization in a wide-area networks without the need for a third party. Substrate network administrators implement a flow space virtualization autonomously. They are responsible for virtualizing a flow space involving switches in their own substrate networks. Using a prototype of AutoVFlow, we measured the virtualization overhead, the results of which show a negligible amount of overhead.
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paper_title: Experimental demonstration of an OpenFlow based software-defined optical network employing packet, fixed and flexible DWDM grid technologies on an international multi-domain testbed

paper_content:

Software defined networking (SDN) and flexible grid optical transport technology are two key technologies that allow network operators to customize their infrastructure based on application requirements and therefore minimizing the extra capital and operational costs required for hosting new applications. In this paper, for the first time we report on design, implementation & demonstration of a novel OpenFlow based SDN unified control plane allowing seamless operation across heterogeneous state-of-the-art optical and packet transport domains. We verify and experimentally evaluate OpenFlow protocol extensions for flexible DWDM grid transport technology along with its integration with fixed DWDM grid and layer-2 packet switching.
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paper_title: On Controller Performance in Software-Defined Networks

paper_content:

Network architectures in which the control plane is decoupled from the data plane have been growing in popularity. Among the main arguments for this approach is that it provides a more structured software environment for developing network-wide abstractions while potentially simplifying the data plane. As has been adopted elsewhere [11], we refer to this split architecture as Software-Defined Networking (SDN). While it has been argued that SDN is suitable for some deployment environments (such as homes [17, 13], data centers [1], and the enterprise [5]), delegating control to a remote system has raised a number of questions on control-plane scaling implications of such an approach. Two of the most often voiced concerns are: (a) how fast can the controller respond to data path requests?; and (b) how many data path requests can it handle per second? There are some references to the performance of SDN systems in the literature [16, 5, 3]. For example, an oft-cited study shows that a popular network controller (NOX) handles around 30k flow initiation events1 per second while maintaining a sub-10ms flow install time [14]. Unfortunately, recent measurements of some deployment environments suggests that these numbers are far from sufficient. For example, Kandula et al. [9] found that a 1500-server cluster has a median flow arrival rate of 100k flows per second. Also, Benson et al. [2] show that a network with 100 switches can have spikes of 10M flows arrivals per second in the worst case. In addition, the 10ms flow setup delay of an SDN controller would add a 10% delay to the majority of flows (short-lived) in such a network. This disconnect between relatively poor controller performance and high network demands has motivated a
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paper_title: Demonstration of SDN orchestration in optical multi-vendor scenarios

paper_content:

SDN brings automation to network operation and abstracts the complexity of optical networks. An orchestration layer is required to support multivendor interoperability scenarios. This work demonstrates that an ABNO architecture enables SDN controlled domain interoperability.
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paper_title: Carrier-grade Network Management Extensions to the SDN Framework

paper_content:

The concept of software-defined networking (SDN)recently gained huge momentum in the industry, driven mainlyby IT companies interested in datacenter applications. In thispaper, however, we consider SDN applied in the carrier domain,which poses additional requirements on the network architecture,including network management functions. We derive concreterequirements for the use-case of a virtualized multi-provideraccess/aggregation network based on carrier-grade SDN. Wethen provide initial architectural considerations for integrationof network management extensions to the SDN framework asdefined by the Open Networking Foundation (ONF). Architec-tural considerations include definition of the required entities andtheir interactions. Finally, we apply the proposed architecture onthe access/aggregation network use-case, outlining procedures ofhow the network management extensions can enable networkwide and node specific management & configuration
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paper_title: OpenVirteX: A Network Hypervisor.

paper_content:

Virtualized environments have been around for a long time, but until recently these have focused solely on compute virtualization and left the network behind. Network virtualization enables multiple tenants to share the same physical infrastructure by decoupling the physical network from the virtual network. In this paper, we introduce OpenVirteX, a Network Virtualization Platform which provides virtual Software Defined Networks (vSDNs). Each vSDN is customizable in terms of topology as well as addressing scheme. Introduction. Techniques for virtualizing network infrastructure have lagged behind that of compute resource virtualization. This has hampered the ability of operators to provide full virtualization that extends down to the network. In the ideal case, operators would be able to provide networks whose topologies, management schemes, and use cases are under the full control of their tenants. Realization of this scheme requires the ability to construct virtual networks that are not only logically isolated, but also have fully configurable topologies and properties akin to virtual machines, e.g., can be created, destroyed, snapshotted, and migrated on demand. Such a mechanism would provide operators with the ability to give a tenant the illusion that they have full control of topology, addressing, and management of the infrastructure despite sharing it with other tenants. Here we present OpenVirteX, a network hypervisor that enables operators to provide this form of network virtualization to their customers. We leverage the growing focus on Software Defined Networks (SDN) amongst infrastructure providers aiming to simplify and add flexibility to the process of provisioning networks. In specific, OpenVirteX builds on OpenFlow [1] as the SDN medium, and our experiences with FlowVisor [2] for design. Like FlowVisor, OpenVirteX functions as a proxy within the control channel, presenting OpenFlow networks to tenants, while controlling the underlying physical infrastructure via the southbound OpenFlow interface. Figure 1 depicts this architecture. By exposing OpenFlow networks, OpenVirteX allows tenants to use their own network OS (NOS) to control the network resources corresponding to their virtual network. In other words, OpenVirteX creates multiple virtual software defined networks out of one. Unlike FlowVisor, which simply slices the entire flowspace amongst the tenants, OpenVirteX provides each tenant with a fully virtualized network featuring a tenant-specified topology and a full header space. Motivation. OpenVirteX offers a pragmatic approach to meeting the requirements of both operators and tenants in increasingly common computing situations: • Cloud: OVX facilitates the migration of an enterprise to a Cloud Infrastructure. Each customer can request an exact copy of his/her physical network, with the same address scheme and topology of the current network. The level of abstraction offered by OpenVirteX creates the illusion that the Cloud physical infrastructure fits exactly the client requirements, in terms of isolation, topology and addressing scheme. • Provider: Similarly, in a WAN scenario, virtualization is essential, e.g. to allow multiple enterprises to connect their remote sites. With OVX, this could be done easily, spawning virtual networks that provide inherited traffic isolation, security, and flexibility. Moreover, with OpenVirteX, the tenant can still control how traffic is forwarded inside his network through a NOS and can apply policies (e.g. firewall, load balancer) that in a standard network are completely managed by the ISP. The remainder of this abstract describes the virtualization approach taken by OpenVirteX, and its current state. Topology Virtualization. OpenVirteX maintains internal representations of the physical and virtual networks as a collection of software switches, links, and end hosts. The physical topology representation is the basis upon which virtual networks are mapped. Tenants can request a topology by supplying a mapping between the elements in the physical topology and their desired virtual network. Virtual topologies can range from an exact copy or subset of the physical network, over a giant virtual switch that abstracts away all physical switches and links, to any custom topology as described by the tenant. The ability to control topology abstraction allows tenants to simplify their NOS, or operators to implement policies in the network. For example, a tenant may forego loop resolution in their NOS by requesting a loop-free topology, or an operator can require traffic to pass through chosen nodes by modifying the connecting path of a virtual link or between the ports of a giant switch. The mapping between virtual and physical elements are stored in a global map, but otherwise kept separate. This allows tenant networks to be reconfigured, halted, and re-initialized by simply modifying this mapping, i.e. pointing keys to different values. Finally, since virtual topologies need not correspond to the physical network, resilience can be enabled in the former Fig. 1: Network virtualization with OpenVirteX. Fig. 2: The address virtualization process. by allowing tenants to specify multiple backup paths for any virtual links between switches, or within giant switches, between ports. Address Virtualization. OpenVirteX grants tenants the ability to choose address assignments for their end hosts, allowing multiple, potentially-overlapping IP address blocks to exist in the same physical network. To differentiate hosts, OpenVirteX generates globally unique tenant IDs for each tenant, and for each host, a physical IP addresses that encodes the host’s membership using the tenant ID. Collisions of addresses are avoided by installing flow rules to rewrite addresses at the edge switches of the network, from tenant-assigned address to physical IP address at the ingress edge, and vice-versa at the egress edge. The translation process is illustrated in Figure 2. Importantly, this procedure is invisible to a tenant’s NOS or hosts, implying that a NOS used to control a virtual network created by OpenVirteX doesn’t need to be modified in any way to properly function. In addition to preventing address aliasing in a transparent way, the mapping created by the procedure is used by OpenVirteX to demultiplex northbound control messages so that they reach the correct tenant networks. Control Function Virtualization. Each virtual network may run its own NOS to program the virtual switches. OpenVirteX makes this possible by mapping various control functions for the virtual network on to the corresponding physical network resources. The translations can get complex, since an operation for one virtual switch may map onto multiple switches and links in the physical network. OpenVirteX leverages its position as proxy that allows it to intercept and manipulate the control packets before they reach their intended destination, which OpenVirteX also determines based on its virtual-physical mapping. Implementation. We have implemented a preliminary version of OpenVirteX in Java. This version currently supports OpenFlow 1.0, and supports the creation of custom topologies under overlapping IP address spaces, the ability to start and stop virtual networks and their components, and persistent storage using Mongo DB. Backup paths for resilient links and giant switches can be manually configured, or automatically generated with a simple SPF algorithm. A JSONRPC API is provided to enable configuration and monitoring of both tenant and infrastructure networks. This API has been used for an implementation of a GUI, as well as a topology embedder that generates virtual-physical mappings as configurations to OpenVirteX. Currently on-going work includes the addition of features such as virtual network snapshotting and migration, dynamic configuration of virtual networks, and external and inter-tenant connectivity. In the future topics such as HA and scalability may be explored.
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paper_title: A Datapath-Centric Virtualization Mechanism for OpenFlow Networks

paper_content:

The adoption of a robust and scalable network virtualization framework is a key requirement in order to make the vision of a shareable network infrastructure a reality. To this aim, one of the most suitable approaches is the one which takes advantage of the emerging paradigm of Software-Defined Networking (SDN) and OpenFlow, its de-facto standard. Several virtualization frameworks have been proposed in the last few years, however, they are either based on proxy-based solutions that raises scalability and robustness issues (FlowVisor), or they rely on a simplified view of the data path (generally based on Open vSwitch instances) that have little chances to be adopted in production network settings. This paper presents a novel OpenFlow-based network virtualization mechanism exploiting a recent open-source data path project named extensible Data path Daemon (xDPd), the proposed multi-platform data path is based on a robust distributed virtualization architecture that is able to run on multi-version OpenFlow switch network scenarios, has a minimal overhead from a performance point of view and can be easily ported on several hardware platforms via xDPd libraries.
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paper_title: OpenVirteX: make your virtual SDNs programmable

paper_content:

We present OpenVirteX, a network virtualization platform that enables operators to create and manage virtual Software Defined Networks (vSDNs). Tenants are free to specify the topology and addressing scheme of their vSDN, and run their own Network Operating System (NOS) to control it. Since OpenVirteX logically decouples vSDNs from the infrastructure, it also enables the introduction of features such as link and switch resiliency, and network snapshotting and migration of these tenant networks. OpenVirteX builds on the design of FlowVisor, and functions as an OpenFlow controller proxy between an operator's network and the tenants' network OSes. Our evaluations of this implementation show that i) OpenVirteX is capable of presenting tenants with configurable vSDNs while incurring a modest overhead to the control channel, and ii) that our architecture enables the introduction of features and enhancements such as link resilience to tenant networks.
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paper_title: Spectrum-efficient and scalable elastic optical path network: architecture, benefits, and enabling technologies

paper_content:

The sustained growth of data traffic volume calls for an introduction of an efficient and scalable transport platform for links of 100 Gb/s and beyond in the future optical network. In this article, after briefly reviewing the existing major technology options, we propose a novel, spectrum- efficient, and scalable optical transport network architecture called SLICE. The SLICE architecture enables sub-wavelength, superwavelength, and multiple-rate data traffic accommodation in a highly spectrum-efficient manner, thereby providing a fractional bandwidth service. Dynamic bandwidth variation of elastic optical paths provides network operators with new business opportunities offering cost-effective and highly available connectivity services through time-dependent bandwidth sharing, energy-efficient network operation, and highly survivable restoration with bandwidth squeezing. We also discuss an optical orthogonal frequency-division multiplexing-based flexible-rate transponder and a bandwidth-variable wavelength cross-connect as the enabling technologies of SLICE concept. Finally, we present the performance evaluation and technical challenges that arise in this new network architecture.
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paper_title: Implementation and Evaluation of a Carrier-Grade OpenFlow Virtualization Scheme

paper_content:

Software Defined Networking (SDN) concepts are seen as suitable enablers for network virtualization, especially in the Data Center Network domain. However, also carrier network operators can benefit from network virtualization, since it allows new business models, promising economical benefits through sharing the cost of network infrastructure in e.g. multi-tenancy or service-isolation scenarios. Such use-cases pose additional requirements on virtualization schemes, including strict performance and information isolation, transparency of the virtualization system, high availability, as well as low CAPEX and OPEX demands. In order to fulfill these requirements, we previously proposed a flexible virtualization scheme for OpenFlow. In this paper we discuss the implementation of the proposed scheme and point out relevant lessons learned during the process, leading to architectural and technological updates. We then evaluate the system in terms of data path performance: the impact on forwarding latency is negligible, while the impact on network throughput is depending on the type of traffic and the choice of encapsulation technology. In summary, the overhead can be kept small and would not significantly affect a production network. Thus, we conclude that the minor performance degradations are outweighed by the benefits of the virtualization system.
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paper_title: ONOS: towards an open, distributed SDN OS

paper_content:

We present our experiences to date building ONOS (Open Network Operating System), an experimental distributed SDN control platform motivated by the performance, scalability, and availability requirements of large operator networks. We describe and evaluate two ONOS prototypes. The first version implemented core features: a distributed, but logically centralized, global network view; scale-out; and fault tolerance. The second version focused on improving performance. Based on experience with these prototypes, we identify additional steps that will be required for ONOS to support use cases such as core network traffic engineering and scheduling, and to become a usable open source, distributed network OS platform that the SDN community can build upon.
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paper_title: OpenFlow Virtualization Framework with Advanced Capabilities

paper_content:

Due to its simplicity, transparency and performance, Flow Visor takes it all in today's virtualization tools for OpenFlow networks. We argue that this effectiveness comes at the price of intolerance towards diverse OpenFlow versions used simultaneously and also limited switch functionality. What is more Flow Visor based management frameworks cannot run and configure the network controllers. In this paper we present an integrated OpenFlow virtualization framework, that is capable of (i) running and managing multiple instances of OpenFlow switches with different forwarding capabilities and OpenFlow versions, (ii) running and configuring full controllers or network applications designed for controlling a virtual network under the management of the proposed framework, and (iii) configuring QoS in the network. Besides introducing the architecture we share implementation and deployment details in our prototype system.
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paper_title: Onix: A Distributed Control Platform for Large-scale Production Networks

paper_content:

Computer networks lack a general control paradigm, as traditional networks do not provide any network-wide management abstractions. As a result, each new function (such as routing) must provide its own state distribution, element discovery, and failure recovery mechanisms. We believe this lack of a common control platform has significantly hindered the development of flexible, reliable and feature-rich network control planes. ::: ::: To address this, we present Onix, a platform on top of which a network control plane can be implemented as a distributed system. Control planes written within Onix operate on a global view of the network, and use basic state distribution primitives provided by the platform. Thus Onix provides a general API for control plane implementations, while allowing them to make their own trade-offs among consistency, durability, and scalability.
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paper_title: Demonstrating a Distributed and Version-Agnostic OpenFlow Slicing Mechanism

paper_content:

Several virtualization frameworks have been proposed in the last few years for Software Defined Networks (SDN), however, they are either based on proxy-based solutions that raises scalability and robustness issues (FlowVisor), or they leverage on a simplified view of the data-path (generally based on Open vSwitch instances) that have little chances to be adopted in production network settings. In our demonstration we present preliminary results obtained by deploying and using a novel OpenFlow-based network virtualization mechanism. The mechanism is based on a recently proposed distributed virtualization architecture that is able to run on multi-version OpenFlow scenarios.
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paper_title: Experimental validation and performance evaluation of OpenFlow-based wavelength path control in transparent optical networks.

paper_content:

OpenFlow, as an open-source protocol for network virtualization, is also widely regarded as a promising control plane technique for heterogeneous networks. But the utilization of the OpenFlow protocol to control a wavelength switched optical network has not been investigated. In this paper, for the first time, we experimentally present a proof-of-concept demonstration of OpenFlow-based wavelength path control for lightpath provisioning in transparent optical networks. We propose two different approaches (sequential and delayed approaches) for lightpath setup and two different approaches (active and passive approaches) for lightpath release by using the OpenFlow protocol. The overall feasibility of these approaches is experimentally validated and the network performances are quantitatively evaluated. More importantly, all the proposed methodologies are demonstrated and evaluated on a real transparent optical network testbed with both OpenFlow-based control plane and data plane, which allows their feasibility and effectiveness to be verified, and valuable insights of the proposed solutions to be obtained for deploying into real OpenFlow controlled optical networks.
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paper_title: Distributed FlowVisor: a distributed FlowVisor platform for quality of service aware cloud network virtualisation

paper_content:

Cloud-based virtual networking environments are required to provide fine-grained quality of service (QoS) control without sacrificing scalability. However, no single approach can currently achieve these two goals simultaneously. FlowVisor is a building block to virtualise networks with fine-grained QoS support; however, scalability issues caused by the OpenFlow protocol and the centralised control model are a major concern. This study introduces a distributed FlowVisor (DFVisor) platform to address these scalability issues. The proposed DFVisor uses a layered overlay mechanism to improve network addressing space and switch capacity. DFVisor uses a distributed synchronised two-level database system with a synchronisation mechanism to enable the centralised control functions in the current FlowVisor platform in distributed control modules within the virtual network controllers. Therefore it removes a single point of failure in the network and reduces the flow setup latency without sacrificing the centralised network configuration and management capabilities. More importantly, the proposed DFVisor platform enables an advanced push-based flow setup and statistics collection mechanism to address scalability issues caused by the current pull-based flow setup and statistics collection method. A DFVisor prototype and an evaluation of this distributed synchronised two-level database are presented, and key issues for future research are discussed.
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paper_title: HyperFlex: Demonstrating control-plane isolation for virtual software-defined networks

paper_content:

We present a demonstration of HyperFlex [1], a Software-Defined Networking (SDN) virtualization architecture with flexible hypervisor function allocation guaranteeing control-plane virtualization. Network Virtualization (NV) is expected to overcome the ossification of today's communication networks. SDN is seen as an enabler for programmable network control. In order to fully virtualize software-defined networks, not only the virtualization of the data-plane, but also the virtualization of the control-plane has to be considered. HyperFlex is a virtualization hypervisor that ensures isolated control-plane slices for virtual SDN networks. Control-plane isolation also protects the hypervisor resources from exhaustion. Furthermore, virtualization hypervisors have to be scalable and flexible in order to provide the best possible performance for the virtual software-defined networks. They should be able to adapt to the current state of the network and the divergent demands of virtual SDN networks. HyperFlex distributes the hypervisor functions flexibly and dynamically in order to adapt to the current network state.
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paper_title: HyperFlex: An SDN virtualization architecture with flexible hypervisor function allocation

paper_content:

Network Virtualization (NV) and Software-Defined Networking (SDN) are both expected to increase the flexibility and programmability of today's communication networks. Combining both approaches may even be a further step towards increasing the efficiency of network resource utilization. Multiple solutions for virtualizing SDN networks have already been proposed, however, they are either implemented in software or they require special network hardware. We propose HyperFlex, an SDN hypervisor architecture that relies on the decomposition of the hypervisor into functions that are essential for virtualizing SDN networks. The hypervisor functions can be flexibly executed in software or hosted on SDN network elements. Furthermore, existing hypervisor solutions focus on data-plane virtualization mechanisms and neglect the virtualization of the control-plane of SDN networks. HyperFlex provides control-plane virtualization by adding a control-plane isolation function, either in software or on network elements. The isolation function ensures that the resources of the control-plane are shared correctly between each virtual SDN network while it also protects the hypervisor resources from resource exhaustion.
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paper_title: OpenTM: traffic matrix estimator for OpenFlow networks

paper_content:

In this paper we present OpenTM, a traffic matrix estimation system for OpenFlow networks. OpenTM uses built-in features provided in OpenFlow switches to directly and accurately measure the traffic matrix with a low overhead. Additionally, OpenTM uses the routing information learned from the OpenFlow controller to intelligently choose the switches from which to obtain flow statistics, thus reducing the load on switching elements. We explore several algorithms for choosing which switches to query, and demonstrate that there is a trade-off between accuracy of measurements, and the worst case maximum load on individual switches, i.e., the perfect load balancing scheme sometimes results in the worst estimate, and the best estimation can lead to worst case load distribution among switches. We show that a non-uniform distribution querying strategy that tends to query switches closer to the destination with a higher probability has a better performance compared to the uniform schemes. Our test-bed experiments show that for a stationary traffic matrix OpenTM normally converges within ten queries which is considerably faster than existing traffic matrix estimation techniques for traditional IP networks.
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paper_title: Experience in black-box OSPF measurement

paper_content:

OSPF (Open Shortest Path First) is a widely used intra-domain routing protocol in IP networks. Internal processing delays in OSPF implementations impact the speed at which updates propagate in the network, the load on individual routers, and the time needed for both intra-domain and inter-domain routing to reconverge following an internal topology or a configuration change. An OSPF user, such as an Internet Service Provider, typically has no access to the software implementation, and no way to estimate these delays directly. In this paper, we present black-box methods (i.e., measurements that rely only on external observations) for estimating and trending delays for key internal tasks in OSPF: processing Link State Advertisements (LSAs), performing Shortest Path First calculations, updating the Forwarding Information Base, and flooding LSAs. Corresponding measurements are reported for production routers from Cisco Systems. To help validate the methodology, black-box and white-box (i.e., measurements that rely on internal instrumentation) are reported for a open source OSPF implementation, GateD.
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paper_title: OpenNetMon: Network monitoring in OpenFlow Software-Defined Networks

paper_content:

We present OpenNetMon, an approach and open-source software implementation to monitor per-flow metrics, especially throughput, delay and packet loss, in OpenFlow networks. Currently, ISPs over-provision capacity in order to meet QoS demands from customers. Software-Defined Networking and OpenFlow allow for better network control and flexibility in the pursuit of operating networks as efficiently as possible. Where OpenFlow provides interfaces to implement fine-grained Traffic Engineering (TE), OpenNetMon provides the monitoring necessary to determine whether end-to-end QoS parameters are actually met and delivers the input for TE approaches to compute appropriate paths. OpenNetMon polls edge switches, i.e. switches with flow end-points attached, at an adaptive rate that increases when flow rates differ between samples and decreases when flows stabilize to minimize the number of queries. The adaptive rate reduces network and switch CPU overhead while optimizing measurement accuracy. We show that not only local links serving variable bit-rate video streams, but also aggregated WAN links benefit from an adaptive polling rate to obtain accurate measurements. Furthermore, we verify throughput, delay and packet loss measurements for bursty scenarios in our experiment testbed.
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paper_title: OFTEN Testing OpenFlow Networks

paper_content:

Software-defined networking and OpenFlow in particular enable independent development of network devices and software that controls them. Such separation of concerns eases the introduction of new network functionality, however, it leads to distributed responsibility for bugs. Despite the common interface, separate development entails the need to test an integrated network before deployment. In this work-in-progress paper, we identify the challenges of creating an environment that simplifies and systematically conducts such tests. We discuss optimizations required for efficient and reliable OpenFlow switch black-box testing and present a possible approach to address other challenges. In our preliminary prototype, we combine systematic state-space exploration techniques with real switches execution to explore an integrated network behavior. Our initial results show that such methods help detect previously unrevealed inconsistencies in the network.
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paper_title: VeriCon: towards verifying controller programs in software-defined networks

paper_content:

Software-defined networking (SDN) is a new paradigm for operating and managing computer networks. SDN enables logically-centralized control over network devices through a "controller" software that operates independently from the network hardware, and can be viewed as the network operating system. Network operators can run both inhouse and third-party SDN programs (often called applications) on top of the controller, e.g., to specify routing and access control policies. SDN opens up the possibility of applying formal methods to prove the correctness of computer networks. Indeed, recently much effort has been invested in applying finite state model checking to check that SDN programs behave correctly. However, in general, scaling these methods to large networks is challenging and, moreover, they cannot guarantee the absence of errors. We present VeriCon, the first system for verifying that an SDN program is correct on all admissible topologies and for all possible (infinite) sequences of network events. VeriCon either confirms the correctness of the controller program on all admissible network topologies or outputs a concrete counterexample. VeriCon uses first-order logic to specify admissible network topologies and desired network-wide invariants, and then implements classical Floyd-Hoare-Dijkstra deductive verification using Z3. Our preliminary experience indicates that VeriCon is able to rapidly verify correctness, or identify bugs, for a large repertoire of simple core SDN programs. VeriCon is compositional, in the sense that it verifies the correctness of execution of any single network event w.r.t. the specified invariant, and can thus scale to handle large programs. To relieve the burden of specifying inductive invariants from the programmer, VeriCon includes a separate procedure for inferring invariants, which is shown to be effective on simple controller programs. We view VeriCon as a first step en route to practical mechanisms for verifying network-wide invariants of SDN programs.
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paper_title: A Flexible OpenFlow-Controller Benchmark

paper_content:

Software defined networking (SDN) promises a way to more flexible networks that can adapt to changing demands. At the same time these networks should also benefit from simpler management mechanisms. This is achieved by moving the network control out of the forwarding devices to purpose-tailored software-applications on top of a "networking operating system". Currently, the most notable representative of this approach is OpenFlow. In the OpenFlow architecture the operating system is represented by the OpenFlow controller. As the key component of the OpenFlow ecosystem, the behavior and performance of the controller are significant for the entire network. Therefore, it is important to understand these influence factors, when planning an OpenFlow-based SDN deployment. In this work, we introduce a tool to help achieving just that - a flexible OpenFlow controller benchmark. The benchmark creates a set of message-generating virtual switches, which can be configured independently from each other to emulate a certain scenario and also keep their own statistics. This way a granular controller performance analysis is possible.
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paper_title: Advanced study of SDN/OpenFlow controllers

paper_content:

This paper presents an independent comprehensive analysis of the efficiency indexes of popular open source SDN/OpenFlow controllers (NOX, POX, Beacon, Floodlight, MuL, Maestro, Ryu). The analysed indexes include performance, scalability, reliability, and security. For testing purposes we developed the new framework called hcprobe. The test bed and the methodology we used are discussed in detail so that everyone could reproduce our experiments. The result of the evaluation show that modern SDN/OpenFlow controllers are not ready to be used in production and have to be improved in order to increase all above mentioned characteristics.
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paper_title: What you need to know about SDN control and data planes

paper_content:

SDN and OpenFlow are actively being standardized and deployed. These deployments rely on switches that come from various vendors and differ in terms of their performance and available features. Understanding these differences and basic performance characteristics is essential for ensuring efficient deployments. In this paper we measure, report, and explain the performance characteristics of the controland data-planes in three hardware OpenFlow switches. Our results can help controller developers to make their programs efficient. Further, we also highlight differences between the OpenFlow specification and its implementations, that if ignored, pose a serious threat to network security and correctness.
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paper_title: On Controller Performance in Software-Defined Networks

paper_content:

Network architectures in which the control plane is decoupled from the data plane have been growing in popularity. Among the main arguments for this approach is that it provides a more structured software environment for developing network-wide abstractions while potentially simplifying the data plane. As has been adopted elsewhere [11], we refer to this split architecture as Software-Defined Networking (SDN). While it has been argued that SDN is suitable for some deployment environments (such as homes [17, 13], data centers [1], and the enterprise [5]), delegating control to a remote system has raised a number of questions on control-plane scaling implications of such an approach. Two of the most often voiced concerns are: (a) how fast can the controller respond to data path requests?; and (b) how many data path requests can it handle per second? There are some references to the performance of SDN systems in the literature [16, 5, 3]. For example, an oft-cited study shows that a popular network controller (NOX) handles around 30k flow initiation events1 per second while maintaining a sub-10ms flow install time [14]. Unfortunately, recent measurements of some deployment environments suggests that these numbers are far from sufficient. For example, Kandula et al. [9] found that a 1500-server cluster has a median flow arrival rate of 100k flows per second. Also, Benson et al. [2] show that a network with 100 switches can have spikes of 10M flows arrivals per second in the worst case. In addition, the 10ms flow setup delay of an SDN controller would add a 10% delay to the majority of flows (short-lived) in such a network. This disconnect between relatively poor controller performance and high network demands has motivated a
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paper_title: A roadmap for traffic engineering in SDN-OpenFlow networks

paper_content:

Software Defined Networking (SDN) is an emerging networking paradigm that separates the network control plane from the data forwarding plane with the promise to dramatically improve network resource utilization, simplify network management, reduce operating cost, and promote innovation and evolution. Although traffic engineering techniques have been widely exploited in the past and current data networks, such as ATM networks and IP/MPLS networks, to optimize the performance of communication networks by dynamically analyzing, predicting, and regulating the behavior of the transmitted data, the unique features of SDN require new traffic engineering techniques that exploit the global network view, status, and flow patterns/characteristics available for better traffic control and management. This paper surveys the state-of-the-art in traffic engineering for SDNs, and mainly focuses on four thrusts including flow management, fault tolerance, topology update, and traffic analysis/characterization. In addition, some existing and representative traffic engineering tools from both industry and academia are explained. Moreover, open research issues for the realization of SDN traffic engineering solutions are discussed in detail.
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paper_title: Traffic engineering in software defined networks

paper_content:

Software Defined Networking is a new networking paradigm that separates the network control plane from the packet forwarding plane and provides applications with an abstracted centralized view of the distributed network state. A logically centralized controller that has a global network view is responsible for all the control decisions and it communicates with the network-wide distributed forwarding elements via standardized interfaces. Google recently announced [5] that it is using a Software Defined Network (SDN) to interconnect its data centers due to the ease, efficiency and flexibility in performing traffic engineering functions. It expects the SDN architecture to result in better network capacity utilization and improved delay and loss performance. The contribution of this paper is on the effective use of SDNs for traffic engineering especially when SDNs are incrementally introduced into an existing network. In particular, we show how to leverage the centralized controller to get significant improvements in network utilization as well as to reduce packet losses and delays. We show that these improvements are possible even in cases where there is only a partial deployment of SDN capability in a network. We formulate the SDN controller's optimization problem for traffic engineering with partial deployment and develop fast Fully Polynomial Time Approximation Schemes (FPTAS) for solving these problems. We show, by both analysis and ns-2 simulations, the performance gains that are achievable using these algorithms even with an incrementally deployed SDN.
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paper_title: OFLOPS: An Open Framework for OpenFlow Switch Evaluation

paper_content:

Recent efforts in software-defined networks, such as OpenFlow, give unprecedented access into the forwarding plane of networking equipment. When building a network based on OpenFlow however, one must take into account the performance characteristics of particular OpenFlow switch implementations. In this paper, we present OFLOPS, an open and generic software framework that permits the development of tests for OpenFlow-enabled switches, that measure the capabilities and bottlenecks between the forwarding engine of the switch and the remote control application. OFLOPS combines hardware instrumentation with an extensible software framework. ::: ::: We use OFLOPS to evaluate current OpenFlow switch implementations and make the following observations: (i) The switching performance of flows depends on applied actions and firmware. (ii) Current OpenFlow implementations differ substantially in flow updating rates as well as traffic monitoring capabilities. (iii) Accurate OpenFlow command completion can be observed only through the data plane. These observations are crucial for understanding the applicability of Open- Flow in the context of specific use-cases, which have requirements in terms of forwarding table consistency, flow setup latency, flow space granularity, packet modification types, and/or traffic monitoring abilities.
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paper_title: Libra: divide and conquer to verify forwarding tables in huge networks

paper_content:

Data center networks often have errors in the forwarding tables, causing packets to loop indefinitely, fall into black-holes or simply get dropped before they reach the correct destination. Finding forwarding errors is possible using static analysis, but none of the existing tools scale to a large data center network with thousands of switches and millions of forwarding entries. Worse still, in a large data center network the forwarding state is constantly in flux, which makes it hard to take an accurate snapshot of the state for static analysis. ::: ::: We solve these problems with Libra, a new tool for verifying forwarding tables in very large networks. Libra runs fast because it can exploit the scaling properties of MapReduce. We show how Libra can take an accurate snapshot of the forwarding state 99.9% of the time, and knows when the snapshot cannot be trusted. We show results for Libra analyzing a 10,000 switch network in less than a minute, using 50 servers.
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paper_title: Terminology for Forwarding Information Base (FIB) based Router Performance", RFC 3222

paper_content:

This document describes the terms to be used in a methodology that determines the IP packet forwarding performance of IP routers as a function of the forwarding information base installed within a router. The forwarding performance of an IP router may be dependent upon or may be linked to the composition and size of the forwarding information base installed within a router.
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paper_title: Debugging the data plane with anteater

paper_content:

Diagnosing problems in networks is a time-consuming and error-prone process. Existing tools to assist operators primarily focus on analyzing control plane configuration. Configuration analysis is limited in that it cannot find bugs in router software, and is harder to generalize across protocols since it must model complex configuration languages and dynamic protocol behavior. This paper studies an alternate approach: diagnosing problems through static analysis of the data plane. This approach can catch bugs that are invisible at the level of configuration files, and simplifies unified analysis of a network across many protocols and implementations. We present Anteater, a tool for checking invariants in the data plane. Anteater translates high-level network invariants into boolean satisfiability problems (SAT), checks them against network state using a SAT solver, and reports counterexamples if violations have been found. Applied to a large university network, Anteater revealed 23 bugs, including forwarding loops and stale ACL rules, with only five false positives. Nine of these faults are being fixed by campus network operators.
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paper_title: OFCProbe: A platform-independent tool for OpenFlow controller analysis

paper_content:

I. INTRODUCTION The key component in the Software Defined Networking architecture is the controller or ”networking operating system”. The controller provides a platform for the operation of diverse network control and management applications. However, little is known about the stability and performance of current controller applications, which is a requirement for a smooth operation of the network. In case of OpenFlow, the currently most popular realization of SDN, the controller is not specified by the standard. Its performance depends on the specific implementation. As a consequence, some controllers are more suitable for certain tasks than others. Choosing the right controller for a task requires a thorough analysis of the available candidates in terms of system behavior and performance. In this paper, we present the extended platformindependent and flexible OpenFlow controller performance analyzer ”OFCProbe” as a follow up to our previous work with ”OFCBenchmark”. The new tool features a scalable and modular architecture that allows a deep granular analysis of a controller’s behavior and characteristics. It allows the emulation of virtual switches that each provide sophisticated statistics about different aspects of the controller’s performance. The virtual switches are arrangeable into topologies to emulate different scenarios and traffic patterns. This way a detailed insight and deep analysis of possible bottlenecks concerning the controller performance or unexpected behavior is possible. Key features of the re-implementation are a more flexible, simulation-style packet generation system as well as Java Selector-based connection handling. In order to highlight the tool’s features, we perform some experiments for the Nox and Floodlight controllers in different scenarios. The remainder of this paper is structured as follows. In Section II, we discuss related work in terms of OpenFlow controller performance. The architecture and features of OFCProbe are then introduced in Section III. We show and discuss the results of our example experiments in Section IV before drawing our conclusions in Section V.
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paper_title: An Open Testing Framework for Next-Generation Openflow Switches

paper_content:

The deployment experience of OpenFlow support in production networks has highlighted variable limitations between network devices and vendors, while the recent integration of OpenFlow control abstractions in 10 GbE switches, increases further the performance requirements to support the switch control plane. This paper presents OFLOPS-Turbo, an effort to integrate OFLOPS, the OpenFlow switch evaluation platform, with OSNT, a hardware-accelerated traffic generation and capture system.
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paper_title: A novel approach to virtual networks embedding for SDN management and orchestration

paper_content:

The development of methodologies to manage and orchestrate virtualised resources and network functions is a fundamental enabler for optimally utilising physical ICT infrastructures. Algorithms for optimal location (embedding) of network functions, IT and CT resources, services and corresponding states, especially at the network edge, will enable new business models and provide a key competitive advantage to network administrators. This paper introduces a novel Mixed Integer Programming (MIP) formulation for a coordinated node and link mapping onto the underlying network infrastructure. Extensive simulation results show that the proposed algorithm outperforms prior art formulations: two digit gains were attained in terms of resources utilisation, embedding, revenues and, especially convergence time. The proposed methodology is applicable to a number of relevant use cases, as constraints and objective functions can be flexibly defined by network operators.
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paper_title: Progressive virtual topology embedding in OpenFlow networks

paper_content:

Future internet would provide a flexible and simpler architectural design by combining novel low level clean-slate techniques such as OpenFlow with high level design principles such as network virtualization. However, previous research outlined that at the core of network virtualization stands a new set of challenges for network resources allocation. In this work we focus on one such challenge, namely the problem of virtual topology embedding. In this context users need to leverage the infrastructure substrate by accomodating logical topologies with high degree of flexibility. The network provider, on the other hand, aims at maximizing its revenue in term of size and number of topologies accepted while minimizing costs accounting for the substrate network resources used. To this aim, we present VT-Planner a novel virtual network embedding technique with reduced computational cost and very efficient over substrate topologies encountered in practice. Extensive numerical simulations are provided comparing this technique with state- of-the-art solutions: our results show that VT-Planner is able to achieve a good balance in terms of complexity and performance.
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paper_title: A novel approach to virtual networks embedding for SDN management and orchestration

paper_content:

The development of methodologies to manage and orchestrate virtualised resources and network functions is a fundamental enabler for optimally utilising physical ICT infrastructures. Algorithms for optimal location (embedding) of network functions, IT and CT resources, services and corresponding states, especially at the network edge, will enable new business models and provide a key competitive advantage to network administrators. This paper introduces a novel Mixed Integer Programming (MIP) formulation for a coordinated node and link mapping onto the underlying network infrastructure. Extensive simulation results show that the proposed algorithm outperforms prior art formulations: two digit gains were attained in terms of resources utilisation, embedding, revenues and, especially convergence time. The proposed methodology is applicable to a number of relevant use cases, as constraints and objective functions can be flexibly defined by network operators.
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paper_title: Progressive virtual topology embedding in OpenFlow networks

paper_content:

Future internet would provide a flexible and simpler architectural design by combining novel low level clean-slate techniques such as OpenFlow with high level design principles such as network virtualization. However, previous research outlined that at the core of network virtualization stands a new set of challenges for network resources allocation. In this work we focus on one such challenge, namely the problem of virtual topology embedding. In this context users need to leverage the infrastructure substrate by accomodating logical topologies with high degree of flexibility. The network provider, on the other hand, aims at maximizing its revenue in term of size and number of topologies accepted while minimizing costs accounting for the substrate network resources used. To this aim, we present VT-Planner a novel virtual network embedding technique with reduced computational cost and very efficient over substrate topologies encountered in practice. Extensive numerical simulations are provided comparing this technique with state- of-the-art solutions: our results show that VT-Planner is able to achieve a good balance in terms of complexity and performance.
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paper_title: Virtual Network Embedding: A Survey

paper_content:

Network virtualization is recognized as an enabling technology for the future Internet. It aims to overcome the resistance of the current Internet to architectural change. Application of this technology relies on algorithms that can instantiate virtualized networks on a substrate infrastructure, optimizing the layout for service-relevant metrics. This class of algorithms is commonly known as "Virtual Network Embedding (VNE)" algorithms. This paper presents a survey of current research in the VNE area. Based upon a novel classification scheme for VNE algorithms a taxonomy of current approaches to the VNE problem is provided and opportunities for further research are discussed.
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paper_title: Investigating isolation between virtual networks in case of congestion for a Pronto 3290 switch

paper_content:

Performance isolation between virtual resources is one of the key features of network virtualization. It is typically realized by configuring queues with specific rate guarantees on the egress ports of network devices. The drawback of this architectural choice, however, is that traffic from several ingress ports may result in congestion on an egress port. Hence, the question arises to which extent isolation between virtual networks is realized in state-of-the-art hardware. This work aims at investigating whether congestion within one virtual network may affect the throughput performance of another virtual network. For that, measurements in a local testbed using a Pronto 3290 switch running an OpenFlow-enabling Pica8 firmware are performed.
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paper_title: Tango: Simplifying SDN Control with Automatic Switch Property Inference, Abstraction, and Optimization

paper_content:

A major benefit of software-defined networking (SDN) over traditional networking is simpler and easier control of network devices. The diversity of SDN switch implementation properties, which include both diverse switch hardware capabilities and diverse control-plane software behaviors, however, can make it difficult to understand and/or to control the switches in an SDN network. In this paper, we present Tango, a novel framework to explore the issues of understanding and optimization of SDN control, in the presence of switch diversity. The basic idea of Tango is novel, simple, and yet quite powerful. In particular, different from all previous SDN control systems, which either ignore switch diversity or depend on that switches can and will report diverse switch implementation properties, Tango introduces a novel, proactive probing engine that infers key switch capabilities and behaviors, according to a well-structured set of Tango patterns, where a Tango pattern consists of a sequence of standard OpenFlow commands and a corresponding data traffic pattern. Utilizing the inference results from Tango patterns and additional application API hints, Tango conducts automatic switch control optimization, despite diverse switch capabilities and behaviors. Evaluating Tango on both hardware switches and emulated software switches, we show that Tango can infer flow table sizes, which are key switch implementation properties, within less than 5% of actual values, despite diverse switch caching algorithms, using a probing algorithm that is asymptotically optimal in terms of probing overhead. We demonstrate cases where routing and scheduling optimizations based on Tango improves the rule installation time by up to 70% in our hardware switch testbed.
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paper_title: What you need to know about SDN control and data planes

paper_content:

SDN and OpenFlow are actively being standardized and deployed. These deployments rely on switches that come from various vendors and differ in terms of their performance and available features. Understanding these differences and basic performance characteristics is essential for ensuring efficient deployments. In this paper we measure, report, and explain the performance characteristics of the controland data-planes in three hardware OpenFlow switches. Our results can help controller developers to make their programs efficient. Further, we also highlight differences between the OpenFlow specification and its implementations, that if ignored, pose a serious threat to network security and correctness.
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paper_title: Towards a dynamic SDN virtualization layer: Control path migration protocol

paper_content:

Virtualization of software defined networks enables tenants to bring their own controller and manage their virtual resources with the full programmability provided by Software Defined Networking (SDN). Distributed SDN hypervisors are proposed to provide an efficient platform for the virtualization of physical SDN networks. They address the issue of scalability that a centralized hypervisor could suffer from. As virtualization provides the possibility to change virtual SDN networks on run time, a hypervisor layer needs efficient mechanisms to dynamically adapt to the changing requirements. Existing proposals provide only a static configuration setup for their distribution of the hypervisor instances. However, in order to satisfy the dynamics of virtual SDN networks, management protocols are needed to support dynamic changes. In this paper, we propose a control path migration protocol for distributed hypervisors. Such protocol is needed to support the dynamic adaptation of the virtualization layer. Our protocol is providing the missing procedure that allows a dynamic change of control connections between virtual SDN networks and the tenants' controllers, respectively. We provide a proof of concept implementation for our proposal. Through measurements in a real testbed setup, we show that our protocol is efficient in terms of control latency overhead and provides transparency to the controllers of the virtual SDN networks.
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paper_title: Pairing SDN with network virtualization: The network hypervisor placement problem

paper_content:

A network virtualization hypervisor for Software Defined Networking (SDN) is the essential component for the realization of virtual SDN networks (vSDNs). Virtualizing software defined networks enables tenants to bring their own SDN controllers in order to individually program the network control of their virtual SDN networks. A hypervisor acts as an intermediate layer between the tenant SDN controllers and their respective virtual SDN networks. The hypervisor consists of the network functions that are necessary for virtualization, e.g., translation or isolation functions. For scalability, the hypervisor can be realized via multiple physically distributed instances each hosting the needed virtualization functions. In this way, the physical locations of the instances, which realize the hypervisor, may impact the overall performance of the virtual SDN networks. Network virtualization adds new dimensions to the general SDN controller placement problem. This paper initiates the study of the network hypervisor placement problem (HPP). The HPP targets the following questions: How many hypervisor instances are needed? Where should the hypervisor instances be placed in the network? For our study of the HPP, we provide a mathematical model that solves the HPP for a case where node and link capacity constraints are not considered. We propose four latency metrics for optimizing placement solutions based on our model for vSDNs. Covering a real network topology, our evaluation quantifies the trade-offs between the new metrics when used as objectives. Furthermore, we analyze the impact of the physical network topology on the optimization results and identify potentials for improvement, e.g., in terms of runtime.
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paper_title: Reliability-aware controller placement for Software-Defined Networks

paper_content:

The Software-Defined Network (SDN) approach decouples control and forwarding planes. Such separation introduces reliability design issues of the SDN control network, since disconnection between the control and forwarding planes may lead to severe packet loss and performance degradation. This paper addresses the problem of placing controllers in SDNs, so as to maximize the reliability of control networks. After presenting a metric to characterize the reliability of SDN control networks, several placement algorithms are developed. We evaluate these algorithms and further quantify the impact of controller number on the reliability of control networks using real topologies. Our approach can significantly improve the reliability of SDN control networks without introducing unacceptable latencies.
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paper_title: The controller placement problem

paper_content:

Network architectures such as Software-Defined Networks (SDNs) move the control logic off packet processing devices and onto external controllers. These network architectures with decoupled control planes open many unanswered questions regarding reliability, scalability, and performance when compared to more traditional purely distributed systems. This paper opens the investigation by focusing on two specific questions: given a topology, how many controllers are needed, and where should they go? To answer these questions, we examine fundamental limits to control plane propagation latency on an upcoming Internet2 production deployment, then expand our scope to over 100 publicly available WAN topologies. As expected, the answers depend on the topology. More surprisingly, one controller location is often sufficient to meet existing reaction-time requirements (though certainly not fault tolerance requirements).
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paper_title: Software-Defined and Virtualized Future Mobile and Wireless Networks: A Survey

paper_content:

With the proliferation of mobile demands and increasingly multifarious services and applications, mobile Internet has been an irreversible trend. Unfortunately, the current mobile and wireless network (MWN) faces a series of pressing challenges caused by the inherent design. In this paper, we extend two latest and promising innovations of Internet, software-defined networking and network virtualization, to mobile and wireless scenarios. We first describe the challenges and expectations of MWN, and analyze the opportunities provided by the software-defined wireless network (SDWN) and wireless network virtualization (WNV). Then, this paper focuses on SDWN and WNV by presenting the main ideas, advantages, ongoing researches and key technologies, and open issues respectively. Moreover, we interpret that these two technologies highly complement each other, and further investigate efficient joint design between them. This paper confirms that SDWN and WNV may efficiently address the crucial challenges of MWN and significantly benefit the future mobile and wireless network.
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paper_title: OpenRAN: a software-defined ran architecture via virtualization

paper_content:

With the rapid growth of the demands for mobile data, wireless network faces several challenges, such as lack of efficient interconnection among heterogeneous wireless networks, and shortage of customized QoS guarantees between services. The fundamental reason for these challenges is that the radio access network (RAN) is closed and ossified. We propose OpenRAN, an architecture for software-defined RAN via virtualization. It achieves complete virtualization and programmability vertically, and benefits the convergence of heterogeneous network horizontally. It provides open, controllable, flexible and evolvable wireless networks.
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paper_title: Integrating network function virtualization with SDR and SDN for 4G/5G networks

paper_content:

The rapidly diversified market demands have presented a huge challenge to the conventional mobile broadband network architecture. On one hand, the limited machine room space and insufficient power supply make it impossible to accommodate exponentially growing amount of network equipment of operators. On the other hand, net heterogeneity caused by different specifications of wireless access equipment causes costly trouble related to management and optimization. This article, correspondingly, proposes a holistic solution involving different technologies, i.e. network function virtualization (NFV), software defined radio (SDR), and software defined network (SDN). In particular, we investigate both existing standards and possible extensions for 4G/5G mobile networks, followed by a few open issues for future research.
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paper_title: A survey on wireless sensor networks for smart grid

paper_content:

The traditional power grid in many countries suffers from high maintenance costs and scalability issues along with the huge expense of building new power stations, and lack of efficient system monitoring that could increase the overall performance by acting proactively in preventing potential failures. To address these problems, a next-generation electric power system, called the smart grid (SG), has been proposed as an evolutionary system for power generation, transmission, and distribution. To this end, the SGs utilize renewable energy generation, smart meters and modern sensing and communication technologies for effective power system management, and hence, succeeding in addressing many of the requirements of a modern power grid system while significantly increase its performance. Recently, wireless sensor networks (WSNs) have been recognized as a promising technology to achieve seamless, energy efficient, reliable, and low-cost remote monitoring and control in SG applications. In these systems, the required information can be provided to electric utilities by wireless sensor systems to enable them to achieve high system efficiency. The real-time information gathered from these sensors can be analyzed to diagnose problems early and serve as a basis for taking remedial action. In this paper, first WSN-based SG applications have been explored along with their technical challenges. Then, design challenges and protocol objectives have been discussed for WSN-based SG applications. After exploring applications and design challenges, communication protocols for WSN-based SG applications have been explained in detail. Here, our goal is to elaborate on the role of WSNs for smart grid applications and to provide an overview of the most recent advances in MAC and routing protocols for WSNs in this timely and exciting field.
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paper_title: Software defined virtual wireless network: framework and challenges

paper_content:

Due to inflexibility, design and control of existing networks are very complex. Therefore, SDN aims to separate control and data planes clearly, which is an innovative and effective approach to this problem. With SDN, a service provider can adjust the settings of a network according to various requirements dynamically and in a timely fashion. This feature is especially suitable for a wireless scenario with dynamic and unstable changing situations. Meanwhile, because various algorithms, such as traffic forwarding and quality of service, can be operated by a central controller, SDN is a natural optional technique for WNV. In this article, we illustrate the framework for combining SDN and WNV, review state-of-the-art related work, and discuss the challenges for future study.
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paper_title: A Genetic Algorithm based Methodology for Optimizing Multi-Service Convergence in a Metro WDM Network

paper_content:

We consider the multi-objective optimization of a multi-service arrayed-waveguide grating-based single-hop metro WDM network with the two conflicting objectives of maximizing throughput while minimizing delay. We develop and evaluate a genetic algorithm based methodology for finding the optimal throughput-delay tradeoff curve, the so-called Pareto-optimal frontier. Our methodology provides the network architecture (hardware) and the medium access control (MAC) protocol parameters that achieve the Pareto-optima in a computationally efficient manner. The numerical results obtained with our methodology provide the Pareto-optimal network planning and operation solutions for a wide range of traffic scenarios. The presented methodology is applicable to other networks with a similar throughput-delay tradeoff.
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paper_title: A Novel Wireless Sensor Networks Structure Based on the SDN

paper_content:

Since the SDN (Software Defined Network) technology based on OpenFlow was born, domestic and foreign research institutions have had increasing attention to this emerging field. The OpenFlow technology which is known for standardization and compatibility network virtualization has brought a lot of innovative solutions in the field of research. As the wireless sensor network node is complex and difficult to move and the network topology is changing rapidly with time, this requires a routing protocol for it to be able to adapt to this high topology change. Because traditional WSNS protocol communication needs to consider energy consumption, load balancing and other factors, it is difficult to find one to take into account all aspects of network algorithms. In this paper, we put forward a new solution for WSNS in accordance with the OpenFlow technology research in the application of traditional network.
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paper_title: A survey of visual sensor network platforms

paper_content:

Recent developments in low-cost CMOS cameras have created the opportunity of bringing imaging capabilities to sensor networks. Various visual sensor platforms have been developed with the aim of integrating visual data to wireless sensor applications. The objective of this article is to survey current visual sensor platforms according to in-network processing and compression/coding techniques together with their targeted applications. Characteristics of these platforms such as level of integration, data processing hardware, energy dissipation, radios and operating systems are also explored and discussed.
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paper_title: Cost, power consumption and performance evaluation of metro networks

paper_content:

We provide models for evaluating the performance, cost and power consumption of different architectures suitable for a metropolitan area network (MAN). We then apply these models to compare today's synchronous optical network/synchronous digital hierarchy metro rings with different alternatives envisaged for next-generation MAN: an Ethernet carrier grade ring, an optical hub-based architecture and an optical time-slotted wavelength division multiplexing (WDM) ring. Our results indicate that the optical architectures are likely to decrease power consumption by up to 75% when compared with present day MANs. Moreover, by allowing the capacity of each wavelength to be dynamically shared among all nodes, a transparent slotted WDM yields throughput performance that is practically equivalent to that of today's electronic architectures, for equal capacity.
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paper_title: Resource Optimization Using Software Defined Networking for Smart Grid Wireless Sensor Network

paper_content:

There has been a decade of extensive research on application specific wireless sensor networks (WSNs). The recent development in communication network technologies makes it practical to realize a new WSN paradigm or controlling the control plane with the new group of by software defined networking (SDN) based on Open Flow. The Open Flow technology which is known for standardization and compatibility network Virtualization has brought a lot of innovative solutions in the field of research. In WSNs, sensor node are complex, highly dense and hence difficult to move. Network topology fast changes with time by using routing protocol, network topology, load balancing, power optimization, security and other factors. In this paper, the concept of SDN in WNS is introduced where Open Flow is the controller part of network.
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paper_title: FlowVisor: A Network Virtualization Layer

paper_content:

Network virtualization has long been a goal of of the network research community. With it, multiple isolated logical networks each with potentially different addressing and forwarding mechanisms can share the same physical infrastructure. Typically this is achieved by taking advantage of the flexibility of software (e.g. [20, 23]) or by duplicating components in (often specialized) hardware[19]. In this paper we present a new approach to switch virtualization in which the same hardware forwarding plane can be shared among multiple logical networks, each with distinct forwarding logic. We use this switch-level virtualization to build a research platform which allows multiple network experiments to run side-by-side with production traffic while still providing isolation and hardware forwarding speeds. We also show that this approach is compatible with commodity switching chipsets and does not require the use of programmable hardware such as FPGAs or network processors. We build and deploy this virtualization platform on our own production network and demonstrate its use in practice by running five experiments simultaneously within a campus network. Further, we quantify the overhead of our approach and evaluate the completeness of the isolation between virtual slices.
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Title: Survey on Network Virtualization Hypervisors for Software Defined Networking

Section 1: Hypervisors: From Virtual Machines to Virtual Networks
Description 1: Discuss the evolution from traditional hypervisors for virtual machines to hypervisors for virtual networks and introduce the concept of network virtualization in the context of SDN.

Section 2: Combining Network Virtualization and Software Defined Networking
Description 2: Explore how network virtualization and SDN paradigms come together to enable multiple virtual networks on a single physical infrastructure and the benefits of such integration.

Section 3: Scope of this Survey
Description 3: Define the specific focus of this survey, which is on hypervisors that create, monitor, and manage virtual SDN networks.

Section 4: Contributions and Structure of this Article
Description 4: Outline the main contributions of the survey and provide an overview of the structure of the article, summarizing each section that will be discussed in detail.

Section 5: Background and Related Surveys
Description 5: Provide tutorial background on network virtualization and SDN, including a review of existing surveys in these areas.

Section 6: Virtualizing SDN Networks
Description 6: Explain the process of virtualizing SDN networks through hypervisors, highlighting the main functions and challenges.

Section 7: Classification Structure of Hypervisor Survey
Description 7: Introduce the classification framework for hypervisors based on their architecture and execution platform, and provide detailed explanations for each category.

Section 8: Centralized Hypervisors
Description 8: Conduct a comprehensive survey of centralized hypervisors, detailing their architectures, functionalities, and specific features.

Section 9: Distributed Hypervisors
Description 9: Survey distributed hypervisors, explaining their architecture, execution platforms, benefits, and challenges compared to centralized hypervisors.

Section 10: Summary Comparison of Surveyed Hypervisors
Description 10: Present a comparative summary of the surveyed SDN hypervisors across different abstraction and isolation attributes.

Section 11: Hypervisor Performance Evaluation Framework
Description 11: Outline a comprehensive evaluation framework for benchmarking the performance of SDN hypervisors, covering both data and control plane resources.

Section 12: Future Research Directions
Description 12: Discuss open research questions and potential future directions in the area of SDN hypervisors, including service level agreements, bootstrapping, reliability, and security concerns.

Section 13: Conclusion
Description 13: Summarize the key findings of the survey, emphasizing the importance of performance evaluation and the need for further research in advancing SDN hypervisors.