A survey on energy efficiency in software defined networks
---
paper_title: A Survey and a Layered Taxonomy of Software-Defined Networking

paper_content:

Software-defined networking (SDN) has recently gained unprecedented attention from industry and research communities, and it seems unlikely that this will be attenuated in the near future. The ideas brought by SDN, although often described as a “revolutionary paradigm shift” in networking, are not completely new since they have their foundations in programmable networks and control-data plane separation projects. SDN promises simplified network management by enabling network automation, fostering innovation through programmability, and decreasing CAPEX and OPEX by reducing costs and power consumption. In this paper, we aim at analyzing and categorizing a number of relevant research works toward realizing SDN promises. We first provide an overview on SDN roots and then describe the architecture underlying SDN and its main components. Thereafter, we present existing SDN-related taxonomies and propose a taxonomy that classifies the reviewed research works and brings relevant research directions into focus. We dedicate the second part of this paper to studying and comparing the current SDN-related research initiatives and describe the main issues that may arise due to the adoption of SDN. Furthermore, we review several domains where the use of SDN shows promising results. We also summarize some foreseeable future research challenges.
---
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
---
paper_title: Software-Defined Networking: State of the Art and Research Challenges

paper_content:

Network usage and demands are growing at a rapid pace, while the network administrators are facing difficulties in tracking the frequent users’ access of the network. Consequently, managing the infrastructure supporting these demands has become a complicated and time-consuming task. Networks are also in a flux state, they are not only expanding but require reconfigurations to meet the business needs. Software defined networking (SDN) and network function virtualization (NFV) technologies have emerged as promising solutions that change the cost profile and agility of internet protocol (IP) networks. Conceptually, SDN separates the network control logic from its underlying hardware, enabling network administrators to exert more control over network functioning and providing a unified global view of the network. However, SDN and NFV can be merged and have the potential to mitigate the challenges of legacy networks. In this paper, our aim is to describe the benefits of using SDN in a multitude of environments such as in data centers, data center networks, and Network as Service offerings. We also present the various challenges facing SDN, from scalability to reliability and security concerns, and discuss existing solutions to these challenges.
---
paper_title: Energy-efficient networking: past, present, and future

paper_content:

The twenty-first century has witnessed major technological changes that have transformed the way we live, work, and interact with one another. One of the major technology enablers responsible for this remarkable transformation in our global society is the deployment and use of Information and Communication Technology (ICT) equipment. In fact, today ICT has become highly integrated in our society that includes the dependence on ICT of various sectors, such as business, transportation, education, and the economy to the point that we now almost completely depend on it. Over the last few years, the energy consumption resulting from the usage of ICT equipment and its impact on the environment have fueled a lot of interests among researchers, designers, manufacturers, policy makers, and educators. We present some of the motivations driving the need for energy-efficient communications. We describe and discuss some of the recent techniques and solutions that have been proposed to minimize energy consumption by communication devices, protocols, networks, end-user systems, and data centers. In addition, we highlight a few emerging trends and we also identify some challenges that need to be addressed to enable novel, scalable, cost-effective energy-efficient communications in the future.
---
paper_title: A Survey of Green Networking Research

paper_content:

Reduction of unnecessary energy consumption is becoming a major concern in wired networking, because of the potential economical benefits and of its expected environmental impact. These issues, usually referred to as "green networking", relate to embedding energy-awareness in the design, in the devices and in the protocols of networks. In this work, we first formulate a more precise definition of the "green" attribute. We furthermore identify a few paradigms that are the key enablers of energy-aware networking research. We then overview the current state of the art and provide a taxonomy of the relevant work, with a special focus on wired networking. At a high level, we identify four branches of green networking research that stem from different observations on the root causes of energy waste, namely (i) Adaptive Link Rate, (ii) Interface proxying, (iii) Energy-aware infrastructures and (iv) Energy-aware applications. In this work, we do not only explore specific proposals pertaining to each of the above branches, but also offer a perspective for research.
---
paper_title: A Survey of Software-Defined Networking: Past, Present, and Future of Programmable Networks

paper_content:

The idea of programmable networks has recently re-gained considerable momentum due to the emergence of the Software-Defined Networking (SDN) paradigm. SDN, often referred to as a "radical new idea in networking", promises to dramatically simplify network management and enable innovation through network programmability. This paper surveys the state-of-the-art in programmable networks with an emphasis on SDN. We provide a historic perspective of programmable networks from early ideas to recent developments. Then we present the SDN architecture and the OpenFlow standard in particular, discuss current alternatives for implementation and testing of SDN-based protocols and services, examine current and future SDN applications, and explore promising research directions based on the SDN paradigm.
---
paper_title: A survey of active network research

paper_content:

Active networks are a novel approach to network architecture in which the switches (or routers) of the network perform customized computations on the messages flowing through them. This approach is motivated by both lead user applications, which perform user-driven computation at nodes within the network today, and the emergence of mobile code technologies that make dynamic network service innovation attainable. The authors discuss two approaches to the realization of active networks and provide a snapshot of the current research issues and activities. They illustrate how the routers of an IP network could be augmented to perform such customized processing on the datagrams flowing through them. These active routers could also interoperate with legacy routers, which transparently forward datagrams in the traditional manner.
---
paper_title: A Survey and a Layered Taxonomy of Software-Defined Networking

paper_content:

Software-defined networking (SDN) has recently gained unprecedented attention from industry and research communities, and it seems unlikely that this will be attenuated in the near future. The ideas brought by SDN, although often described as a “revolutionary paradigm shift” in networking, are not completely new since they have their foundations in programmable networks and control-data plane separation projects. SDN promises simplified network management by enabling network automation, fostering innovation through programmability, and decreasing CAPEX and OPEX by reducing costs and power consumption. In this paper, we aim at analyzing and categorizing a number of relevant research works toward realizing SDN promises. We first provide an overview on SDN roots and then describe the architecture underlying SDN and its main components. Thereafter, we present existing SDN-related taxonomies and propose a taxonomy that classifies the reviewed research works and brings relevant research directions into focus. We dedicate the second part of this paper to studying and comparing the current SDN-related research initiatives and describe the main issues that may arise due to the adoption of SDN. Furthermore, we review several domains where the use of SDN shows promising results. We also summarize some foreseeable future research challenges.
---
paper_title: Ethane: taking control of the enterprise

paper_content:

This paper presents Ethane, a new network architecture for the enterprise. Ethane allows managers to define a single network-wide fine-grain policy, and then enforces it directly. Ethane couples extremely simple flow-based Ethernet switches with a centralized controller that manages the admittance and routing of flows. While radical, this design is backwards-compatible with existing hosts and switches. We have implemented Ethane in both hardware and software, supporting both wired and wireless hosts. Our operational Ethane network has supported over 300 hosts for the past four months in a large university network, and this deployment experience has significantly affected Ethane's design.
---
paper_title: Open Signaling for ATM, INTERNET and Mobile Networks (OPENSIG'98)

paper_content:

The ability to rapidly create and deploy new transport, control and management architectures in response to new service demands is a key factor driving the programmable networking community. Competition between service providers may hinge on the speed at which one provider can respond to new market demands over another. The notion of open programmable networks is having broad impact on service providers and vendors across a range of telecommunication sectors calling for major advances in open network control architecture, network programmability and distributed systems technology. In this paper we discuss the origins of the Open Signalling Working Group (OPENSIG) and present a summary of the fifth Workshop on Open Signaling for ATM, Internet and Mobile Networks (OPENSIG'98), which was held at the University of Toronto, Ontario, October, 1998. We also discuss a number of new initiatives in the area of open programmable networks that have recently emerged.
---
paper_title: A Survey of Software-Defined Networking: Past, Present, and Future of Programmable Networks

paper_content:

The idea of programmable networks has recently re-gained considerable momentum due to the emergence of the Software-Defined Networking (SDN) paradigm. SDN, often referred to as a "radical new idea in networking", promises to dramatically simplify network management and enable innovation through network programmability. This paper surveys the state-of-the-art in programmable networks with an emphasis on SDN. We provide a historic perspective of programmable networks from early ideas to recent developments. Then we present the SDN architecture and the OpenFlow standard in particular, discuss current alternatives for implementation and testing of SDN-based protocols and services, examine current and future SDN applications, and explore promising research directions based on the SDN paradigm.
---
paper_title: A clean slate 4D approach to network control and management

paper_content:

Today's data networks are surprisingly fragile and difficult to manage. We argue that the root of these problems lies in the complexity of the control and management planes--the software and protocols coordinating network elements--and particularly the way the decision logic and the distributed-systems issues are inexorably intertwined. We advocate a complete refactoring of the functionality and propose three key principles--network-level objectives, network-wide views, and direct control--that we believe should underlie a new architecture. Following these principles, we identify an extreme design point that we call "4D," after the architecture's four planes: decision, dissemination, discovery, and data. The 4D architecture completely separates an AS's decision logic from pro-tocols that govern the interaction among network elements. The AS-level objectives are specified in the decision plane, and en-forced through direct configuration of the state that drives how the data plane forwards packets. In the 4D architecture, the routers and switches simply forward packets at the behest of the decision plane, and collect measurement data to aid the decision plane in controlling the network. Although 4D would involve substantial changes to today's control and management planes, the format of data packets does not need to change; this eases the deployment path for the 4D architecture, while still enabling substantial innovation in network control and management. We hope that exploring an extreme design point will help focus the attention of the research and industrial communities on this crucially important and intellectually challenging area.
---
paper_title: Towards an active network architecture

paper_content:

Active networks allow their users to inject customized programs into the nodes of the network. An extreme case, in which we are most interested, replaces packets with "capsules" -- program fragments that are executed at each network router/switch they traverse. Active architectures permit a massive increase in the sophistication of the computation that is performed within the network. They will enable new applications, especially those based on application-specific multicast, information fusion, and other services that leverage network-based computation and storage. Furthermore, they will accelerate the pace of innovation by decoupling network services from the underlying hardware and allowing new services to be loaded into the infrastructure on demand. In this paper, we describe our vision of an active network architecture, outline our approach to its design, and survey the technologies that can be brought to bear on its implementation. We propose that the research community mount a joint effort to develop and deploy a wide area ActiveNet.
---
paper_title: The impact of information technology on energy consumption and carbon emissions

paper_content:

In this article the authors evaluate the impact of different sectors of information and communication technologies (ICT) on energy consumption and CO2 emissions. ICT is understood to cover computer and peripheral equipment including local area networks, telecommunication equipment and networks, and data centers.
---
paper_title: Techno-economic Analysis of Software Defined Networking as Architecture for the Virtualization of a Mobile Network

paper_content:

Worldwide mobile network operators have to spend billions to upgrade their own network to the latest standards for wireless communication of high-speed data for mobile phones (e.g. Long Term Evolution, LTE). This is in contrast with the decline in average revenue per user and threatens: (1) their profitability and (2) the fast adaptation of new standards. Investigating new mechanisms that can decrease the capital expenditures (capex) and operational expenditures (opex) of a mobile network is therefore essential. Enabling multiple mobile network operators on a common infrastructure is one such mechanism. Software defined networks can overcome this problem and a solution based on exploring OpenFlow (OF) as architecture for mobile network virtualization has been proposed. We investigate two network scenarios based on this OF solution in a techno-economic analysis: (scenario 1) software-defined, non-shared networks and (scenario 2) virtualized, shared networks and compare it against the current situation. By doing so, this paper provides insights on the relative cost savings that a mobile network operator can reach through Software Defined Networking (SDN) and network sharing. The techno-economic analysis indicates that SDN and virtualization of the first aggregation stage and second aggregation stage network infrastructure leads to substantial capex cost reductions for the mobile network operator. As a consequence, mobile network infrastructure virtualization through the use of OpenFlow could be one of the problem solvers to tackle the issue of rising costs and decreasing profitability. Still, we did not take into account the direct effect on operational expenditures and the indirect effect that network sharing can adversely affect the ability of the operators to differentiate themselves.
---
paper_title: Green network technologies and the art of trading-off

paper_content:

In this contribution, we focus on energy-aware devices able to reduce their energy requirements by adapting their performance. We propose an analytical model to accurately represent the impact of green network technologies (i.e., low power idle and adaptive rate) on network- and energy-aware performance indexes. The model has been validated with experimental results, performed by using energy-aware software routers and real-world traffic traces. The achieved results demonstrate how the proposed model can effectively represent energy- and network-aware performance indexes. Moreover, also an optimization procedure based on the model has been proposed and experimentally evaluated. The procedure aims at dynamically adapting the energy-aware device configuration to minimize energy consumption, while coping with incoming traffic volumes and meeting network performance constraints.
---
paper_title: Use of OSI IS-IS for routing in TCP/IP and dual environments

paper_content:

This RFC specifies an integrated routing protocol, based on the OSI Intra-Domain IS-IS Routing Protocol, which may be used as an interior gateway protocol (IGP) to support TCP/IP as well as OSI. This allows a single routing protocol to be used to support pure IP environments, pure OSI environments, and dual environments. This specification was developed by the IS-IS working group of the Internet Engineering Task Force.
---
paper_title: Software defined green data center network with exclusive routing

paper_content:

The explosive expansion of data center sizes ag- gravates the power consumption and carbon footprint, which has restricted the sustainable growth of cloud services and seriously troubled data center operators. In recent years, plenty of advanced data center network architectures have been proposed. They usually employ richly-connected topologies and multi-path routing to provide high network capacity. Unfortunately, they also undergo inefficient network energy usage during the traffic valley time. To address the problem, many energy-aware flow scheduling algorithms are proposed recently, primarily considering how to aggregate traffic by flexibly choosing the routing paths, with flows fairly sharing the link bandwidths. In this paper, we leverage software defined network (SDN) technique and explore a new solution to energy-aware flow scheduling, i.e., scheduling flows in the time dimension and using exclusive routing (EXR) for each flow, i.e., a flow always exclusively utilizes the links of its routing path. The key insight is that exclusive occupation of link resources usually results in higher link utilization in high-radix data center networks, since each flow does not need to compete for the link bandwidths with others. When scheduling the flows, EXR leaves flexibility to operators to define the priorities of flows, e.g., based on flow size, flow deadline, etc. Extensive simulations and testbed experiments both show that EXR can effectively save network energy compared with the regular fair-sharing routing (FSR), and significantly reduce the average flow completion time if assigning higher scheduling priorities to smaller flows. I. INTRODUCTION The explosive expansion of data center sizes aggravates the power consumption and carbon footprint. The statistics show that 1.5% of the global electricity usage came from data centers in 2011 (1), (2). The ever increasing energy consumption of data centers has restricted the sustainable growth of cloud services and raised economic and environmental concerns. Recently people pay attention to the contribution of networking part to the energy consumed by the whole data center. In typical data centers, the network accounts for 10-20% of the overall power consumption (3), while the proportion can be up to 50% if the mature server-side power management techniques are employed (4).
---
paper_title: SustNMS: Towards service oriented policy-based network management for energy-efficiency

paper_content:

Considering the increasing importance of carbon free networking solutions, several energy-efficient networking systems have been proposed and evaluated in literature. One significant challenge is how to encompass actions targeting energy savings and possible corresponding degradations in network QoS (Quality of Service). This paper presents an energy-efficient policy-based network management architecture that enables the enforcement of energy-efficiency according to high-level business decisions on how to coordinate the trade-off between energy savings and the potential impact on the network operation. The system integrates a real-time energy-efficiency assessment with a dynamic evaluation of network availability and performance. Its operation is presented and advantages are discussed.
---
paper_title: Fine-Grained Energy-Efficient Consolidation in SDN Networks and Devices

paper_content:

The constant evolution and expansion of the Internet and Internet-related technologies has exposed the limitations of the current networking infrastructures, which are represented by the unsustainable power consumption and low level of scalability. In fact, these infrastructures are still based on the typical, ossified architecture of the TCP/IP paradigm. In order to cope with the Future Internet requirements, recent contributions envisage an evolution towards more programmable and efficient paradigms. In this respect, this paper describes the basic issues, the technical approaches, and the methodologies for the implementation of power management primitives in the context of the emerging Software Defined Networking. In detail, we propose to extend one of the most prominent solutions aimed at increasing networking flexibility, the OpenFlow Protocol, to integrate the energy-aware capabilities offered by the Green Abstraction Layer (GAL). However, the mere introduction of node-level solutions would be of little or no use in the absence of a network-wide management scheme to guarantee inter-operability and effectiveness of the proposed architecture. In this respect, this work also proposes an analytical model for the management of a network with these capabilities. The results will show how our solutions are well suited to provide a scalable and efficient network architecture able to manage the orchestration and consolidation of the available resources.
---
paper_title: Saving energy in LAN switches: New methods of packet coalescing for Energy Efficient Ethernet

paper_content:

Small or home office (SOHO) Ethernet LAN switches consume about 8 TWh per year in the U.S. alone. Despite normally low traffic load and numerous periods of idleness, these switches typically stay fully powered-on at all times. With the standardization of Energy Efficient Ethernet (EEE), Ethernet interfaces can be put into a Low Power Idle (LPI) mode during idle periods when there are no packets to transmit. This paper proposes and evaluates a new EEE policy of synchronous coalescing of packets in network hosts and edge routers. This policy provides extended idle periods for all ports of a LAN switch and thus enables energy savings deeper than in the Ethernet PHY only. We evaluate our method using an ns-2 simulation model of a LAN switch. We show that our method can reduce the overall energy use of a LAN switch by about 40%, while introducing limited and controlled effects on typical Internet traffic and TCP.
---
paper_title: Reducing the Energy Consumption of Ethernet with Adaptive Link Rate (ALR)

paper_content:

The rapidly increasing energy consumption by computing and communications equipment is a significant economic and environmental problem that needs to be addressed. Ethernet network interface controllers (NICs) in the US alone consume hundreds of millions of US dollars in electricity per year. Most Ethernet links are underutilized and link energy consumption can be reduced by operating at a lower data rate. In this paper, we investigate adaptive link rate (ALR) as a means of reducing the energy consumption of a typical Ethernet link by adaptively varying the link data rate in response to utilization. Policies to determine when to change the link data rate are studied. Simple policies that use output buffer queue length thresholds and fine-grain utilization monitoring are shown to be effective. A Markov model of a state-dependent service rate queue with rate transitions only at service completion is used to evaluate the performance of ALR with respect to the mean packet delay, the time spent in an energy-saving low link data rate, and the oscillation of link data rates. Simulation experiments using actual and synthetic traffic traces show that an Ethernet link with ALR can operate at a lower data rate for over 80 percent of the time, yielding significant energy savings with only a very small increase in packet delay.
---
paper_title: GreenSDN: Bringing energy efficiency to an SDN emulation environment

paper_content:

A significant number of green, energy-saving network protocols have been invented in recent years in response to demand for reducing the amount of energy consumed by network infrastructure. In this paper, we report on the difficulties we encountered when building an SDN environment that could emulate energy saving protocols operating at different layers of the network. We propose solutions, based on the Mininet environment and the POX Openflow controller, that emulate the effects of three different energy saving protocols. Our approach is validated by comparing energy savings obtained by activating these protocols in an emulated network topology inspired by the Brazilian Research Network.
---
paper_title: Energy consumption optimization for software defined networks considering dynamic traffic

paper_content:

Today's networking hardware (e.g. switches, routers) is typically running 24/7, regardless of the traffic volume. This is because in current networks, the controlling and data forwarding functions are embedded in the same devices, and all L2/L3 network protocols are designed to work in a distributed manner. Therefore, network devices must be switched on all the time to handle the traffic. This consequently results in very high global energy consumption of communication networks. Software Defined Networking was recently introduced as a new networking paradigm, in which the control plane is physically separated from the forwarding plane and moved to a globally-aware software controller. As a consequence, traffic can be monitored in real time and rerouted very fast regarding certain objectives such as load balancing or QoS enhancement. Accordingly, it opens new opportunities to improve the overall network performance in general and the energy efficiency in particular. This paper proposes an approach that reconfigures the network in order to reduce the energy consumption, based on the current traffic load. Our main idea is to switch on a minimum amount of necessary switches/routers and links to carry the traffic. We first formulate the problem as a mixed integer linear programming (MILP) problem and further present a heuristic method, so called Strategic Greedy Heuristic, with four different strategies, to solve the problem for large networks. We have carried out extensive simulations for a typical campus network and arbitrary mesh networks with realistic traffic information and energy consumption, to prove the potential energy saving of the proposed approach. The results showed that we can save up to 45% of the energy consumption at nighttime.
---
paper_title: Energy-aware routing algorithms in Software-Defined Networks

paper_content:

The feature of centralized network control logic in Software-Defined Networks (SDNs) paves a way for green energy saving. Router power consumption attracts a wide spread attention in terms of energy saving. Most research on it is at component level or link level, i.e. each router is independent of energy saving. In this paper, we study global power management at network level by rerouting traffic through different paths to adjust the workload of links when the network is relatively idle. We construct the expand network topology according to routers' connection. A 0-1 integer linear programming model is formulated to minimize the power of integrated chassis and linecards that are used while putting idle ones to sleep under constraints of link utilization and packet delay. We proposed two algorithms to solve this problem: alternative greedy algorithm and global greedy algorithm. For comparison, we also use Cplex method just as GreenTe does since GreenTe is state of the art global traffic engineering mechanism. Simulation results on synthetic topologies and real topology of CERNET show the effectiveness of our algorithms.
---
paper_title: The Green Abstraction Layer: A Standard Power-Management Interface for Next-Generation Network Devices

paper_content:

In telecommunications networks, distributed power management across heterogeneous hardware requires a standardized representation of each system's capabilities to decouple distributed high-level algorithms from hardware specifics. The Green Abstraction Layer (GAL) provides this interface between high-level algorithms and a lower level representing the hardware and physical resources that directly exert energy management and actions in a network.
---
paper_title: Network traffic characteristics of data centers in the wild

paper_content:

Although there is tremendous interest in designing improved networks for data centers, very little is known about the network-level traffic characteristics of data centers today. In this paper, we conduct an empirical study of the network traffic in 10 data centers belonging to three different categories, including university, enterprise campus, and cloud data centers. Our definition of cloud data centers includes not only data centers employed by large online service providers offering Internet-facing applications but also data centers used to host data-intensive (MapReduce style) applications). We collect and analyze SNMP statistics, topology and packet-level traces. We examine the range of applications deployed in these data centers and their placement, the flow-level and packet-level transmission properties of these applications, and their impact on network and link utilizations, congestion and packet drops. We describe the implications of the observed traffic patterns for data center internal traffic engineering as well as for recently proposed architectures for data center networks.
---
paper_title: Energy models driven green routing for data centers

paper_content:

Energy consumption is becoming a serious issue for data centers. Minimizing the energy consumption of a data center is a complex problem. It consists of developing energy models for servers and network elements and investigating energy-aware (green) routing strategies using these models. In this paper, we adapt energy models for servers and network elements in a data center. The server energy model incorporates the impact of temperature and voltage of a server on its leakage energy. Using the server and network energy models, we propose a green routing scheme that minimizes the total combined energy consumption of servers and network elements in a data center under dynamic traffic. The proposed green routing scheme uses dynamic voltage scaling, rate adaptation, and anycast transmission for minimizing the total energy consumption. Extensive simulation results validate the effectiveness of the proposed green routing in minimizing the total energy consumption of a data center as compared to well-known existing approaches.
---
paper_title: Survey of Techniques and Architectures for Designing Energy-Efficient Data Centers

paper_content:

Cloud computing has emerged as the leading paradigm for information technology businesses. Cloud computing provides a platform to manage and deliver computing services around the world over the Internet. Cloud services have helped businesses utilize computing services on demand with no upfront investments. The cloud computing paradigm has sustained its growth, which has led to increase in size and number of data centers. Data centers with thousands of computing devices are deployed as back end to provide cloud services. Computing devices are deployed redundantly in data centers to ensure 24/7 availability. However, many studies have pointed out that data centers consume large amount of electricity, thus calling for energy-efficiency measures. In this survey, we discuss research issues related to conflicting requirements of maximizing quality of services (QoSs) (availability, reliability, etc.) delivered by the cloud services while minimizing energy consumption of the data center resources. In this paper, we present the concept of inception of data center energy-efficiency controller that can consolidate data center resources with minimal effect on QoS requirements. We discuss software- and hardware-based techniques and architectures for data center resources such as server, memory, and network devices that can be manipulated by the data center controller to achieve energy efficiency.
---
paper_title: Energy proportional datacenter networks

paper_content:

Numerous studies have shown that datacenter computers rarely operate at full utilization, leading to a number of proposals for creating servers that are energy proportional with respect to the computation that they are performing. In this paper, we show that as servers themselves become more energy proportional, the datacenter network can become a significant fraction (up to 50%) of cluster power. In this paper we propose several ways to design a high-performance datacenter network whose power consumption is more proportional to the amount of traffic it is moving -- that is, we propose energy proportional datacenter networks. We first show that a flattened butterfly topology itself is inherently more power efficient than the other commonly proposed topology for high-performance datacenter networks. We then exploit the characteristics of modern plesiochronous links to adjust their power and performance envelopes dynamically. Using a network simulator, driven by both synthetic workloads and production datacenter traces, we characterize and understand design tradeoffs, and demonstrate an 85% reduction in power --- which approaches the ideal energy-proportionality of the network. Our results also demonstrate two challenges for the designers of future network switches: 1) We show that there is a significant power advantage to having independent control of each unidirectional channel comprising a network link, since many traffic patterns show very asymmetric use, and 2) system designers should work to optimize the high-speed channel designs to be more energy efficient by choosing optimal data rate and equalization technology. Given these assumptions, we demonstrate that energy proportional datacenter communication is indeed possible.
---
paper_title: CARPO: Correlation-aware power optimization in data center networks

paper_content:

Power optimization has become a key challenge in the design of large-scale enterprise data centers. Existing research efforts focus mainly on computer servers to lower their energy consumption, while only few studies have tried to address the energy consumption of data center networks (DCNs), which can account for 20% of the total energy consumption of a data center. In this paper, we propose CARPO, a correlation-aware power optimization algorithm that dynamically consolidates traffic flows onto a small set of links and switches in a DCN and then shuts down unused network devices for energy savings. In sharp contrast to existing work, CARPO is designed based on a key observation from the analysis of real DCN traces that the bandwidth demands of different flows do not peak at exactly the same time. As a result, if the correlations among flows are considered in consolidation, more energy savings can be achieved. In addition, CARPO integrates traffic consolidation with link rate adaptation for maximized energy savings. We implement CARPO on a hardware testbed composed of 10 virtual switches configured with a production 48-port OpenFlow switch and 8 servers. Our empirical results with Wikipedia traces demonstrate that CARPO can save up to 46% of network energy for a DCN, while having only negligible delay increases. CARPO also outperforms two state-of-the-art baselines by 19.6% and 95% on energy savings, respectively. Our simulation results with 61 flows also show the superior energy efficiency of CARPO over the baselines.
---
paper_title: NetFPGA: reusable router architecture for experimental research

paper_content:

Our goal is to enable fast prototyping of networking hardware (e.g. modified Ethernet switches and IP routers) for teaching and research. To this end, we built and made available the NetFPGA platform. Starting from open-source reference designs, students and researchers create their designs in Verilog, and then download them to the NetFPGA board where they can process packets at line-rate for 4-ports of 1GE. The board is becoming widely used for teaching and research, and so it has become important to make it easy to re-use modules and designs. We have created a standard interface between modules, making it easier to plug modules together in pipelines, and to create new re-usable designs. In this paper we describe our modular design, and how we have used it to build several systems, including our IP router reference design and some extensions to it.
---
paper_title: ECODANE: A customizable hybrid testbed for green data center networks

paper_content:

In this paper we propose a new testbed architecture that combines hardware network devices with virtual emulation test environment to improve scalability, flexibility and accuracy. The testbed enables to design and experiment new concepts for energy-efficient data center. It is based on OpenFlow, a Software Defined Networking (SDN) technology that facilitates the deployment of energy-aware protocols and mechanisms.
---
paper_title: Simultaneously Reducing Latency and Power Consumption in OpenFlow Switches

paper_content:

The Ethernet switch is a primary building block for today's enterprise networks and data centers. As network technologies converge upon a single Ethernet fabric, there is ongoing pressure to improve the performance and efficiency of the switch while maintaining flexibility and a rich set of packet processing features. The OpenFlow architecture aims to provide flexibility and programmable packet processing to meet these converging needs. Of the many ways to create an OpenFlow switch, a popular choice is to make heavy use of ternary content addressable memories (TCAMs). Unfortunately, TCAMs can consume a considerable amount of power and, when used to match flows in an OpenFlow switch, put a bound on switch latency. In this paper, we propose enhancing an OpenFlow Ethernet switch with per-port packet prediction circuitry in order to simultaneously reduce latency and power consumption without sacrificing rich policy-based forwarding enabled by the OpenFlow architecture. Packet prediction exploits the temporal locality in network communications to predict the flow classification of incoming packets. When predictions are correct, latency can be reduced, and significant power savings can be achieved from bypassing the full lookup process. Simulation studies using actual network traces indicate that correct prediction rates of 97% are achievable using only a small amount of prediction circuitry per port. These studies also show that prediction circuitry can help reduce the power consumed by a lookup process that includes a TCAM by 92% and simultaneously reduce the latency of a cut-through switch by 66%.
---
paper_title: Optimizing rule placement in software-defined networks for energy-aware routing

paper_content:

Software-defined Networks (SDN), in particular OpenFlow, is a new networking paradigm enabling innovation through network programmability. Over past few years, many applications have been built using SDN such as server load balancing, virtual-machine migration, traffic engineering and access control. In this paper, we focus on using SDN for energy-aware routing (EAR). Since traffic load has a small influence on power consumption of routers, EAR allows to put unused links into sleep mode to save energy. SDN can collect traffic matrix and then computes routing solutions satisfying QoS while being minimal in energy consumption. However, prior works on EAR have assumed that the table of OpenFlow switch can hold an infinite number of rules. In practice, this assumption does not hold since the flow table is implemented with Ternary Content Addressable Memory (TCAM) which is expensive and power-hungry. In this paper, we propose an optimization method to minimize energy consumption for a backbone network while respecting capacity constraints on links and rule space constraints on routers. In details, we present an exact formulation using Integer Linear Program (ILP) and introduce efficient greedy heuristic algorithm. Based on simulations, we show that using this smart rule space allocation, it is possible to save almost as much power consumption as the classical EAR approach.
---
paper_title: Compact TCAM: Flow Entry Compaction in TCAM for Power Aware SDN

paper_content:

Low latency lookup (typically single cycle) has made Ternary Content Addressable Memory (TCAM) indispensable in high performance network switching devices. However, high power dissipation of TCAM makes it incongruous in switches for today’s power sensitive emerging network framework, viz., Software Defined Network (SDN). In this paper we propose Compact TCAM, an approach that reduces the size of the flow entries in TCAM. We use shorter tags for identifying flows than the original number of bits used to store the flow entries for SDN switches. We leverage the dynamic programming capability of SDN to route the packets using these tags. We show that our approach can be easily implemented using the new SDN framework while optimizing the TCAM space. Our experiments with real world and synthetic traffic show average reduction of TCAM power by 80% in SDN switching devices for a given number of flows.
---
paper_title: DevoFlow: cost-effective flow management for high performance enterprise networks

paper_content:

The OpenFlow framework enables flow-level control over Ethernet switching, as well as centralized visibility of the flows in the network. OpenFlow's coupling of these features comes with costs, however: the distributed-system costs of involving the OpenFlow controller on flow setups, and the switch-implementation costs of involving the switch's control plane too often. In this paper, we analyze the overheads, and we propose DevoFlow, a modification of the OpenFlow model in which we try to gently break the coupling between centralized control and centralized visibility, in a way that maintains a useful amount of visibility without imposing unnecessary costs.
---
paper_title: On virtualization-aware traffic engineering in OpenFlow Data Centers networks

paper_content:

Oversubscription of intra-Data Center network links and high volatility of VM deployments require a flexible and agile control of Data Center network infrastructures, also integrated with computing and storage resources. In this scenario, the Software-Defined Network paradigm and, specifically, the OpenFlow protocol, opens up new opportunities for the design of innovative resource management platforms that enable dynamic and fine-grain control of DC networks through traffic engineering algorithms. This paper investigates the performance of two different sets of cloud-fluent traffic engineering algorithms. Conceived to work during cloud service deployments, the main target of such algorithms is to achieve a better utilization of network resources by exploiting OpenFlow capabilities for traffic-aware deployments of Virtual Machines. The effectiveness of the proposed solutions is evaluated in terms of network link utilization against VM requests acceptance ratio through simulations and experimental tests carried out by using an ad-hoc emulator.
---
paper_title: EQVMP: Energy-efficient and QoS-aware virtual machine placement for software defined datacenter networks

paper_content:

To provide effective and reliable services, cloud datacenters need parallel computing and virtualization techniques. This work presents an improved virtual machine (VM) placement mechanism, called Energy efficiency and Quality of Service (QoS) aware VM Placement (EQVMP) to overcome the problem of unbalanced traffic load in switching on and off VMs for the purpose of energy saving. EQVMP combines three key techniques: (1) hop reduction, (2) energy saving and (3) load balancing. Hop reduction can regroup VMs to lower the traffic load among them. Energy saving techniques aim at choosing the appropriate servers. The proposed load balancing updates VM placement periodically. Our experimental results show that the proposed scheme can lower energy consumption and maintain QoS. We propose an evaluation score [1] to assess VM placement in terms of energy, delay and throughput. Comparing to other existing placement policies, our proposed mechanism can enhance system throughput by 25% and can have better evaluation score.
---
paper_title: Joint Host-Network Optimization for Energy-Efficient Data Center Networking

paper_content:

Data centers consume significant amounts of energy. As severs become more energy efficient with various energy saving techniques, the data center network (DCN) has been accounting for 20% or more of the energy consumed by the entire data center. While DCNs are typically provisioned with full bisection bandwidth, DCN traffic demonstrates fluctuating patterns. The objective of this work is to improve the energy efficiency of DCNs during off-peak traffic time by powering off idle devices. Although there exist a number of energy optimization solutions for DCNs, they consider only either the hosts or network, but not both. In this paper, we propose a joint optimization scheme that simultaneously optimizes virtual machine (VM) placement and network flow routing to maximize energy savings, and we also build an OpenFlow based prototype to experimentally demonstrate the effectiveness of our design. First, we formulate the joint optimization problem as an integer linear program, but it is not a practical solution due to high complexity. To practically and effectively combine host and network based optimization, we present a unified representation method that converts the VM placement problem to a routing problem. In addition, to accelerate processing the large number of servers and an even larger number of VMs, we describe a parallelization approach that divides the DCN into clusters for parallel processing. Further, to quickly find efficient paths for flows, we propose a fast topology oriented multipath routing algorithm that uses depth-first search to quickly traverse between hierarchical switch layers and uses the best-fit criterion to maximize flow consolidation. Finally, we have conducted extensive simulations and experiments to compare our design with existing ones. The simulation and experiment results fully demonstrate that our design outperforms existing hostor network-only optimization solutions, and well approximates the ideal linear program.
---
paper_title: Saving Energy in Partially Deployed Software Defined Networks

paper_content:

As power consumption of the Internet has been growing quickly in recent years, saving energy has become an important problem of networking research, for which the most promising solution is to find the minimum-power network subsets and shut down other unnecessary network devices and links to satisfy changing traffic loads. However, in traditional networks, it is difficult to implement a coordinated strategy among the network devices due to their distributed network control. On the other hand, the new networking paradigm—software defined network (SDN) provides us an efficient way of having a centralized controller with a global network view to control the power states. As an emerging technology, SDNs usually coexist with traditional networks at present. Therefore, we need to investigate how to save energy in partially deployed SDNs. In this paper, we formulate the optimization problem of finding minimum-power network subsets in partially deployed SDNs. After proving the problem is NP-hard, we propose a heuristic solution to approach its exact solution. Through extensive simulations, we demonstrate that our heuristic algorithm has a good performance; that is, on average we can save about 50 percent of total power consumption in the full SDN, having a distance less than 5 percent of the exact solution's power consumption. Moreover, it also achieves good performance in the partially deployed SDN, on average saving about 40 percent of the total power consumption when there are about 60 percent SDN nodes in the network. Meanwhile, it runs significantly faster than a general linear solver of this problem, by reducing the computation time of the network containing hundreds of nodes by 100× at least.
---
paper_title: PayLess: A low cost network monitoring framework for Software Defined Networks

paper_content:

Software Defined Networking promises to simplify network management tasks by separating the control plane (a central controller) from the data plane (switches). OpenFlow has emerged as the de facto standard for communication between the controller and switches. Apart from providing flow control and communication interfaces, OpenFlow provides a flow level statistics collection mechanism from the data plane. It exposes a high level interface for per flow and aggregate statistics collection. Network applications can use this high level interface to monitor network status without being concerned about the low level details. In order to keep the switch design simple, this statistics collection mechanism is implemented as a pull-based service, i.e. network applications and in turn the controller has to periodically query the switches about flow statistics. The frequency of polling the switches determines monitoring accuracy and network overhead. In this paper, we focus on this trade-off between monitoring accuracy, timeliness and network overhead. We propose PayLess - a monitoring framework for SDN. PayLess provides a flexible RESTful API for flow statistics collection at different aggregation levels. It uses an adaptive statistics collection algorithm that delivers highly accurate information in real-time without incurring significant network overhead. We utilize the Floodlight controller's API to implement the proposed monitoring framework. The effectiveness of our solution is demonstrated through emulations in Mininet.
---
paper_title: Power aware OpenFlow switch extension for energy saving in data centers

paper_content:

Data centers play an important role in our daily activities. The increasing demand for data centers in both scale and size has led to huge energy consumption. The cost and environmental impact of data centers increases due to large amounts of carbon emissions. One solution to this problem is to intelligently control the power consumption of switches used in data centers. This paper proposes an extension to OpenFlow switches to support different power saving modes. The extension includes defining new messages in Openflow standard and designing an OpenFlow Switch Controller (OSC) that is able to turn on/off switches and disable/enable ports. To prove the soundness of the proposed extension, the OSC has been used to control the NetFPGA based OpenFlow switches in the ECODANE framework. The results presented in this paper can aslo be used by the OpenFlow compliant switches manufacturer or by power aware research community.
---
paper_title: HyCell: Enabling GREEN Base Station Operations in Software-Defined Radio Access Networks

paper_content:

The radio access networks (RANs) need to support massive and diverse data traffic with limited spectrum and energy. To cope with this challenge, software-defined radio access network (SDRAN) architectures have been proposed to renovate the RANs. However, current researches lack the design and evaluation of network protocols. In this paper, we address this problem by presenting the protocol design and evaluation of hyper-cellular networks (HyCell), an SDRAN framework making base station (BS) operations globally resource-optimized and energy-efficient (GREEN). Specifically, we first propose a separation scheme to realize the decoupled air interface in HyCell. Then we design a BS dispatching protocol which determines and assigns the optimal BS for serving mobile users, and a BS sleeping protocol to improve the network energy efficiency. Finally, we evaluate the proposed design in our HyCell testbed. Our evaluation validates the feasibility of the proposed separation scheme, demonstrates the effectiveness of BS dispatching, and shows great potential in energy saving through BS sleeping control.
---
paper_title: Energy Efficiency in Telecom Optical Networks

paper_content:

Since the energy crisis and environmental protection are gaining increasing concerns in recent years, new research topics to devise technological solutions for energy conservation are being investigated in many scientific disciplines. Specifically, due to the rapid growth of energy consumption in ICT (Information and Communication Technologies), lot of attention is being devoted towards "green" ICT solutions. In this paper, we provide a comprehensive survey of the most relevant research activities for minimizing energy consumption in telecom networks, with a specific emphasis on those employing optical technologies. We investigate the energy-minimization opportunities enabled by optical technologies and classify the existing approaches over different network domains, namely core, metro, and access networks. A section is also devoted to describe energy-efficient solutions for some of today's important applications using optical network technology, e.g., grid computing and data centers. We provide an overview of the ongoing standardization efforts in this area. This work presents a comprehensive and timely survey on a growing field of research, as it covers most aspects of energy consumption in optical telecom networks. We aim at providing a comprehensive reference for the growing base of researchers who will work on energy efficiency of telecom networks in the upcoming years.
---
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.
---
paper_title: Energy Efficient Minimum Spanning Tree in OpenFlow Networks

paper_content:

Software Defined Networking and OpenFlow are enabling a new range of applications and services for tomorrow networks. At the same time, reducing the energy impact of datacentres and carrier networks will be an important topic in next years. The article presents Green MST, a simple OpenFlowcontroller that creates a loop-free layer2 topology according to application specified metrics and permits to reduce the network electric energy consumption. The design and the implementation on a virtual test bed of the controller's prototype are presented as well as the results of initial measurements.
---
paper_title: Poster: SDN based energy management system for optical access network

paper_content:

In recent years, Passive Optical Network (PON) is developing rapidly in the access network, in which the high energy consumption problem is attracting more and more attention. In the paper, SDN (Software Defined Network) is first introduced in optical access networks to implement an energy-efficient control mechanism through OpenFlow protocol. Some theoretical analysis work for the energy consumption of this architecture has been conducted. Numeric results show that the proposed SDN based control architecture can reduce the energy consumption of the access network, and facilitates integration of access and metro networks.
---
paper_title: Software-Defined Networking: State of the Art and Research Challenges

paper_content:

Network usage and demands are growing at a rapid pace, while the network administrators are facing difficulties in tracking the frequent users’ access of the network. Consequently, managing the infrastructure supporting these demands has become a complicated and time-consuming task. Networks are also in a flux state, they are not only expanding but require reconfigurations to meet the business needs. Software defined networking (SDN) and network function virtualization (NFV) technologies have emerged as promising solutions that change the cost profile and agility of internet protocol (IP) networks. Conceptually, SDN separates the network control logic from its underlying hardware, enabling network administrators to exert more control over network functioning and providing a unified global view of the network. However, SDN and NFV can be merged and have the potential to mitigate the challenges of legacy networks. In this paper, our aim is to describe the benefits of using SDN in a multitude of environments such as in data centers, data center networks, and Network as Service offerings. We also present the various challenges facing SDN, from scalability to reliability and security concerns, and discuss existing solutions to these challenges.
---
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.
---
paper_title: On virtualization-aware traffic engineering in OpenFlow Data Centers networks

paper_content:

Oversubscription of intra-Data Center network links and high volatility of VM deployments require a flexible and agile control of Data Center network infrastructures, also integrated with computing and storage resources. In this scenario, the Software-Defined Network paradigm and, specifically, the OpenFlow protocol, opens up new opportunities for the design of innovative resource management platforms that enable dynamic and fine-grain control of DC networks through traffic engineering algorithms. This paper investigates the performance of two different sets of cloud-fluent traffic engineering algorithms. Conceived to work during cloud service deployments, the main target of such algorithms is to achieve a better utilization of network resources by exploiting OpenFlow capabilities for traffic-aware deployments of Virtual Machines. The effectiveness of the proposed solutions is evaluated in terms of network link utilization against VM requests acceptance ratio through simulations and experimental tests carried out by using an ad-hoc emulator.
---
paper_title: Simultaneously Reducing Latency and Power Consumption in OpenFlow Switches

paper_content:

The Ethernet switch is a primary building block for today's enterprise networks and data centers. As network technologies converge upon a single Ethernet fabric, there is ongoing pressure to improve the performance and efficiency of the switch while maintaining flexibility and a rich set of packet processing features. The OpenFlow architecture aims to provide flexibility and programmable packet processing to meet these converging needs. Of the many ways to create an OpenFlow switch, a popular choice is to make heavy use of ternary content addressable memories (TCAMs). Unfortunately, TCAMs can consume a considerable amount of power and, when used to match flows in an OpenFlow switch, put a bound on switch latency. In this paper, we propose enhancing an OpenFlow Ethernet switch with per-port packet prediction circuitry in order to simultaneously reduce latency and power consumption without sacrificing rich policy-based forwarding enabled by the OpenFlow architecture. Packet prediction exploits the temporal locality in network communications to predict the flow classification of incoming packets. When predictions are correct, latency can be reduced, and significant power savings can be achieved from bypassing the full lookup process. Simulation studies using actual network traces indicate that correct prediction rates of 97% are achievable using only a small amount of prediction circuitry per port. These studies also show that prediction circuitry can help reduce the power consumed by a lookup process that includes a TCAM by 92% and simultaneously reduce the latency of a cut-through switch by 66%.
---
paper_title: A Survey and a Layered Taxonomy of Software-Defined Networking

paper_content:

Software-defined networking (SDN) has recently gained unprecedented attention from industry and research communities, and it seems unlikely that this will be attenuated in the near future. The ideas brought by SDN, although often described as a “revolutionary paradigm shift” in networking, are not completely new since they have their foundations in programmable networks and control-data plane separation projects. SDN promises simplified network management by enabling network automation, fostering innovation through programmability, and decreasing CAPEX and OPEX by reducing costs and power consumption. In this paper, we aim at analyzing and categorizing a number of relevant research works toward realizing SDN promises. We first provide an overview on SDN roots and then describe the architecture underlying SDN and its main components. Thereafter, we present existing SDN-related taxonomies and propose a taxonomy that classifies the reviewed research works and brings relevant research directions into focus. We dedicate the second part of this paper to studying and comparing the current SDN-related research initiatives and describe the main issues that may arise due to the adoption of SDN. Furthermore, we review several domains where the use of SDN shows promising results. We also summarize some foreseeable future research challenges.
---
paper_title: Software defined green data center network with exclusive routing

paper_content:

The explosive expansion of data center sizes ag- gravates the power consumption and carbon footprint, which has restricted the sustainable growth of cloud services and seriously troubled data center operators. In recent years, plenty of advanced data center network architectures have been proposed. They usually employ richly-connected topologies and multi-path routing to provide high network capacity. Unfortunately, they also undergo inefficient network energy usage during the traffic valley time. To address the problem, many energy-aware flow scheduling algorithms are proposed recently, primarily considering how to aggregate traffic by flexibly choosing the routing paths, with flows fairly sharing the link bandwidths. In this paper, we leverage software defined network (SDN) technique and explore a new solution to energy-aware flow scheduling, i.e., scheduling flows in the time dimension and using exclusive routing (EXR) for each flow, i.e., a flow always exclusively utilizes the links of its routing path. The key insight is that exclusive occupation of link resources usually results in higher link utilization in high-radix data center networks, since each flow does not need to compete for the link bandwidths with others. When scheduling the flows, EXR leaves flexibility to operators to define the priorities of flows, e.g., based on flow size, flow deadline, etc. Extensive simulations and testbed experiments both show that EXR can effectively save network energy compared with the regular fair-sharing routing (FSR), and significantly reduce the average flow completion time if assigning higher scheduling priorities to smaller flows. I. INTRODUCTION The explosive expansion of data center sizes aggravates the power consumption and carbon footprint. The statistics show that 1.5% of the global electricity usage came from data centers in 2011 (1), (2). The ever increasing energy consumption of data centers has restricted the sustainable growth of cloud services and raised economic and environmental concerns. Recently people pay attention to the contribution of networking part to the energy consumed by the whole data center. In typical data centers, the network accounts for 10-20% of the overall power consumption (3), while the proportion can be up to 50% if the mature server-side power management techniques are employed (4).
---
paper_title: Power aware OpenFlow switch extension for energy saving in data centers

paper_content:

Data centers play an important role in our daily activities. The increasing demand for data centers in both scale and size has led to huge energy consumption. The cost and environmental impact of data centers increases due to large amounts of carbon emissions. One solution to this problem is to intelligently control the power consumption of switches used in data centers. This paper proposes an extension to OpenFlow switches to support different power saving modes. The extension includes defining new messages in Openflow standard and designing an OpenFlow Switch Controller (OSC) that is able to turn on/off switches and disable/enable ports. To prove the soundness of the proposed extension, the OSC has been used to control the NetFPGA based OpenFlow switches in the ECODANE framework. The results presented in this paper can aslo be used by the OpenFlow compliant switches manufacturer or by power aware research community.
---
paper_title: Optimizing rule placement in software-defined networks for energy-aware routing

paper_content:

Software-defined Networks (SDN), in particular OpenFlow, is a new networking paradigm enabling innovation through network programmability. Over past few years, many applications have been built using SDN such as server load balancing, virtual-machine migration, traffic engineering and access control. In this paper, we focus on using SDN for energy-aware routing (EAR). Since traffic load has a small influence on power consumption of routers, EAR allows to put unused links into sleep mode to save energy. SDN can collect traffic matrix and then computes routing solutions satisfying QoS while being minimal in energy consumption. However, prior works on EAR have assumed that the table of OpenFlow switch can hold an infinite number of rules. In practice, this assumption does not hold since the flow table is implemented with Ternary Content Addressable Memory (TCAM) which is expensive and power-hungry. In this paper, we propose an optimization method to minimize energy consumption for a backbone network while respecting capacity constraints on links and rule space constraints on routers. In details, we present an exact formulation using Integer Linear Program (ILP) and introduce efficient greedy heuristic algorithm. Based on simulations, we show that using this smart rule space allocation, it is possible to save almost as much power consumption as the classical EAR approach.
---
paper_title: Compact TCAM: Flow Entry Compaction in TCAM for Power Aware SDN

paper_content:

Low latency lookup (typically single cycle) has made Ternary Content Addressable Memory (TCAM) indispensable in high performance network switching devices. However, high power dissipation of TCAM makes it incongruous in switches for today’s power sensitive emerging network framework, viz., Software Defined Network (SDN). In this paper we propose Compact TCAM, an approach that reduces the size of the flow entries in TCAM. We use shorter tags for identifying flows than the original number of bits used to store the flow entries for SDN switches. We leverage the dynamic programming capability of SDN to route the packets using these tags. We show that our approach can be easily implemented using the new SDN framework while optimizing the TCAM space. Our experiments with real world and synthetic traffic show average reduction of TCAM power by 80% in SDN switching devices for a given number of flows.
---
paper_title: DevoFlow: cost-effective flow management for high performance enterprise networks

paper_content:

The OpenFlow framework enables flow-level control over Ethernet switching, as well as centralized visibility of the flows in the network. OpenFlow's coupling of these features comes with costs, however: the distributed-system costs of involving the OpenFlow controller on flow setups, and the switch-implementation costs of involving the switch's control plane too often. In this paper, we analyze the overheads, and we propose DevoFlow, a modification of the OpenFlow model in which we try to gently break the coupling between centralized control and centralized visibility, in a way that maintains a useful amount of visibility without imposing unnecessary costs.
---
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.
---
paper_title: EQVMP: Energy-efficient and QoS-aware virtual machine placement for software defined datacenter networks

paper_content:

To provide effective and reliable services, cloud datacenters need parallel computing and virtualization techniques. This work presents an improved virtual machine (VM) placement mechanism, called Energy efficiency and Quality of Service (QoS) aware VM Placement (EQVMP) to overcome the problem of unbalanced traffic load in switching on and off VMs for the purpose of energy saving. EQVMP combines three key techniques: (1) hop reduction, (2) energy saving and (3) load balancing. Hop reduction can regroup VMs to lower the traffic load among them. Energy saving techniques aim at choosing the appropriate servers. The proposed load balancing updates VM placement periodically. Our experimental results show that the proposed scheme can lower energy consumption and maintain QoS. We propose an evaluation score [1] to assess VM placement in terms of energy, delay and throughput. Comparing to other existing placement policies, our proposed mechanism can enhance system throughput by 25% and can have better evaluation score.
---
paper_title: CARPO: Correlation-aware power optimization in data center networks

paper_content:

Power optimization has become a key challenge in the design of large-scale enterprise data centers. Existing research efforts focus mainly on computer servers to lower their energy consumption, while only few studies have tried to address the energy consumption of data center networks (DCNs), which can account for 20% of the total energy consumption of a data center. In this paper, we propose CARPO, a correlation-aware power optimization algorithm that dynamically consolidates traffic flows onto a small set of links and switches in a DCN and then shuts down unused network devices for energy savings. In sharp contrast to existing work, CARPO is designed based on a key observation from the analysis of real DCN traces that the bandwidth demands of different flows do not peak at exactly the same time. As a result, if the correlations among flows are considered in consolidation, more energy savings can be achieved. In addition, CARPO integrates traffic consolidation with link rate adaptation for maximized energy savings. We implement CARPO on a hardware testbed composed of 10 virtual switches configured with a production 48-port OpenFlow switch and 8 servers. Our empirical results with Wikipedia traces demonstrate that CARPO can save up to 46% of network energy for a DCN, while having only negligible delay increases. CARPO also outperforms two state-of-the-art baselines by 19.6% and 95% on energy savings, respectively. Our simulation results with 61 flows also show the superior energy efficiency of CARPO over the baselines.
---
paper_title: Joint Host-Network Optimization for Energy-Efficient Data Center Networking

paper_content:

Data centers consume significant amounts of energy. As severs become more energy efficient with various energy saving techniques, the data center network (DCN) has been accounting for 20% or more of the energy consumed by the entire data center. While DCNs are typically provisioned with full bisection bandwidth, DCN traffic demonstrates fluctuating patterns. The objective of this work is to improve the energy efficiency of DCNs during off-peak traffic time by powering off idle devices. Although there exist a number of energy optimization solutions for DCNs, they consider only either the hosts or network, but not both. In this paper, we propose a joint optimization scheme that simultaneously optimizes virtual machine (VM) placement and network flow routing to maximize energy savings, and we also build an OpenFlow based prototype to experimentally demonstrate the effectiveness of our design. First, we formulate the joint optimization problem as an integer linear program, but it is not a practical solution due to high complexity. To practically and effectively combine host and network based optimization, we present a unified representation method that converts the VM placement problem to a routing problem. In addition, to accelerate processing the large number of servers and an even larger number of VMs, we describe a parallelization approach that divides the DCN into clusters for parallel processing. Further, to quickly find efficient paths for flows, we propose a fast topology oriented multipath routing algorithm that uses depth-first search to quickly traverse between hierarchical switch layers and uses the best-fit criterion to maximize flow consolidation. Finally, we have conducted extensive simulations and experiments to compare our design with existing ones. The simulation and experiment results fully demonstrate that our design outperforms existing hostor network-only optimization solutions, and well approximates the ideal linear program.
---
paper_title: Energy consumption optimization for software defined networks considering dynamic traffic

paper_content:

Today's networking hardware (e.g. switches, routers) is typically running 24/7, regardless of the traffic volume. This is because in current networks, the controlling and data forwarding functions are embedded in the same devices, and all L2/L3 network protocols are designed to work in a distributed manner. Therefore, network devices must be switched on all the time to handle the traffic. This consequently results in very high global energy consumption of communication networks. Software Defined Networking was recently introduced as a new networking paradigm, in which the control plane is physically separated from the forwarding plane and moved to a globally-aware software controller. As a consequence, traffic can be monitored in real time and rerouted very fast regarding certain objectives such as load balancing or QoS enhancement. Accordingly, it opens new opportunities to improve the overall network performance in general and the energy efficiency in particular. This paper proposes an approach that reconfigures the network in order to reduce the energy consumption, based on the current traffic load. Our main idea is to switch on a minimum amount of necessary switches/routers and links to carry the traffic. We first formulate the problem as a mixed integer linear programming (MILP) problem and further present a heuristic method, so called Strategic Greedy Heuristic, with four different strategies, to solve the problem for large networks. We have carried out extensive simulations for a typical campus network and arbitrary mesh networks with realistic traffic information and energy consumption, to prove the potential energy saving of the proposed approach. The results showed that we can save up to 45% of the energy consumption at nighttime.
---
paper_title: ECODANE: A customizable hybrid testbed for green data center networks

paper_content:

In this paper we propose a new testbed architecture that combines hardware network devices with virtual emulation test environment to improve scalability, flexibility and accuracy. The testbed enables to design and experiment new concepts for energy-efficient data center. It is based on OpenFlow, a Software Defined Networking (SDN) technology that facilitates the deployment of energy-aware protocols and mechanisms.
---

Title: A Survey on Energy Efficiency in Software Defined Networks

Section 1: Introduction
Description 1: This section should introduce the topic, explain the need for energy efficiency in Software Defined Networks (SDN), outline the structure of SDN, and discuss the impact of Information and Communication Technology (ICT) on energy consumption and carbon emissions.

Section 2: Background
Description 2: This section should provide a detailed background on the evolution of SDN, including its key features, historical context, and components.

Section 3: Why do we need to save energy
Description 3: This section should highlight the importance of energy efficiency in SDN, providing statistics and discussing the environmental and operational impacts of energy consumption in networking.

Section 4: Energy efficient SDN approaches
Description 4: This section should review various approaches to achieving energy efficiency in SDN, broken down into several subcategories based on different methodologies and techniques.

Section 5: Flow-controlled energy-efficient SDN approaches
Description 5: This section should delve into approaches that use flow control to achieve energy efficiency, describing specific techniques and their effectiveness.

Section 6: Energy-aware SDN approaches for data center networks
Description 6: This section should focus on approaches tailored for data center networks, discussing methods for optimizing energy usage in these environments.

Section 7: Rule-placement and TCAM-based energy-aware SDN approaches
Description 7: This section should examine approaches that optimize rule placement and TCAM (Ternary Content Addressable Memory) usage to save energy.

Section 8: VM placement-based energy-aware SDN approaches
Description 8: This section should explore energy-saving methods that focus on the placement and management of Virtual Machines (VMs) within SDN structures.

Section 9: Different types of energy-aware SDN approaches
Description 9: This section should cover various innovative and miscellaneous energy-aware SDN approaches that do not fit neatly into the previously discussed categories.

Section 10: Evaluation of energy saving techniques and proposed approaches in SDN
Description 10: This section should evaluate the energy-saving techniques and approaches, summarizing their benefits and potential drawbacks, and providing a comparative analysis of the expected energy gains.

Section 11: Issues, challenges and future research directions
Description 11: This section should discuss the challenges and unresolved issues in achieving energy efficiency in SDN, and propose directions for future research.

Section 12: Conclusion
Description 12: This section should provide a conclusion that synthesizes the main findings of the paper and highlights the importance of integrated energy-saving mechanisms in SDN.