Segment Routing: a Comprehensive Survey of Research Activities, Standardization Efforts and Implementation Results
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paper_title: Use Cases for IPv6 Source Packet Routing in Networking (SPRING)

paper_content:

The Source Packet Routing in Networking (SPRING) architecture ::: describes how Segment Routing can be used to steer packets through an ::: IPv6 or MPLS network using the source routing paradigm. This document ::: illustrates some use cases for Segment Routing in an IPv6-only ::: environment.
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paper_title: Source Packet Routing in Networking (SPRING) Problem Statement and Requirements

paper_content:

The ability for a node to specify a forwarding path, other than the ::: normal shortest path, that a particular packet will traverse, benefits ::: a number of network functions. Source-based routing mechanisms have ::: previously been specified for network protocols but have not seen ::: widespread adoption. In this context, the term "source" means "the ::: point at which the explicit route is imposed"; therefore, it is not ::: limited to the originator of the packet (i.e., the node imposing the ::: explicit route may be the ingress node of an operator's network). ::: This document outlines various use cases, with their requirements, ::: that need to be taken into account by the Source Packet Routing in ::: Networking (SPRING) architecture for unicast traffic. Multicast use ::: cases and requirements are out of scope for this document.
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paper_title: IPv6 Segment Routing Header (SRH)

paper_content:

Segment Routing can be applied to the IPv6 data plane using a new type ::: of Routing Extension Header called the Segment Routing Header. This ::: document describes the Segment Routing Header and how it is used by ::: Segment Routing capable nodes.
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paper_title: Segment Routing in Software Defined Networks: A Survey

paper_content:

Segment routing (SR) has emerged as a promising source-routing methodology to overcome the challenges in the current routing schemes. It has received noticeable attention both in industry and academia, due to its flexibility, scalability, and applicability, especially in software defined networks. The emerging cloud services require strict service level agreements such as packet loss, delay, and jitter. Studies have shown that traditional network architectures lack the essential flexibility and scalability to offer these services. To combat this, a more flexible and agile routing paradigm of SR enables a source node to steer an incoming packet along a performance engineered path represented as an ordered list of instructions called segment list. This is encoded as a multiprotocol label switching label stack or an IPv6 address list in the packet header. This paper provides a comprehensive review of the novel SR technology by describing its architecture, operations, and key applications to date. SR paradigm can be effectively applied to a wide range of network applications, such as traffic engineering, network resiliency, network monitoring, and service function chaining, to achieve efficient network solutions. Furthermore, this paper identifies an interesting set of future research directions and open issues that can help realize the full potential of the emergent SR paradigm.
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paper_title: Resiliency Use Cases in Source Packet Routing in Networking (SPRING) Networks

paper_content:

This document identifies and describes the requirements for a set of ::: use cases related to Segment Routing network resiliency on Source ::: Packet Routing in Networking (SPRING) networks.
---
paper_title: Segment Routing in Software Defined Networks: A Survey

paper_content:

Segment routing (SR) has emerged as a promising source-routing methodology to overcome the challenges in the current routing schemes. It has received noticeable attention both in industry and academia, due to its flexibility, scalability, and applicability, especially in software defined networks. The emerging cloud services require strict service level agreements such as packet loss, delay, and jitter. Studies have shown that traditional network architectures lack the essential flexibility and scalability to offer these services. To combat this, a more flexible and agile routing paradigm of SR enables a source node to steer an incoming packet along a performance engineered path represented as an ordered list of instructions called segment list. This is encoded as a multiprotocol label switching label stack or an IPv6 address list in the packet header. This paper provides a comprehensive review of the novel SR technology by describing its architecture, operations, and key applications to date. SR paradigm can be effectively applied to a wide range of network applications, such as traffic engineering, network resiliency, network monitoring, and service function chaining, to achieve efficient network solutions. Furthermore, this paper identifies an interesting set of future research directions and open issues that can help realize the full potential of the emergent SR paradigm.
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paper_title: The Segment Routing Architecture

paper_content:

Network operators anticipate the offering of an increasing variety of cloud-based services with stringent Service Level Agreements. Technologies currently supporting IP networks however lack the flexibility and scalability properties to realize such evolution. In this article, we present Segment Routing (SR), a new network architecture aimed at filling this gap, driven by use-cases defined by network operators. SR implements the source routing and tunneling paradigms, letting nodes steer packets over paths using a sequence of instructions (segments) placed in the packet header. As such, SR allows the implementation of routing policies without per-flow entries at intermediate routers. This paper introduces the SR architecture, describes its related ongoing standardization efforts, and reviews the main use-cases envisioned by network operators.
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paper_title: Source Packet Routing in Networking (SPRING) Problem Statement and Requirements

paper_content:

The ability for a node to specify a forwarding path, other than the ::: normal shortest path, that a particular packet will traverse, benefits ::: a number of network functions. Source-based routing mechanisms have ::: previously been specified for network protocols but have not seen ::: widespread adoption. In this context, the term "source" means "the ::: point at which the explicit route is imposed"; therefore, it is not ::: limited to the originator of the packet (i.e., the node imposing the ::: explicit route may be the ingress node of an operator's network). ::: This document outlines various use cases, with their requirements, ::: that need to be taken into account by the Source Packet Routing in ::: Networking (SPRING) architecture for unicast traffic. Multicast use ::: cases and requirements are out of scope for this document.
---
paper_title: Resiliency Use Cases in Source Packet Routing in Networking (SPRING) Networks

paper_content:

This document identifies and describes the requirements for a set of ::: use cases related to Segment Routing network resiliency on Source ::: Packet Routing in Networking (SPRING) networks.
---
paper_title: IPv6 Segment Routing Header (SRH)

paper_content:

Segment Routing can be applied to the IPv6 data plane using a new type ::: of Routing Extension Header called the Segment Routing Header. This ::: document describes the Segment Routing Header and how it is used by ::: Segment Routing capable nodes.
---
paper_title: Use Cases for IPv6 Source Packet Routing in Networking (SPRING)

paper_content:

The Source Packet Routing in Networking (SPRING) architecture ::: describes how Segment Routing can be used to steer packets through an ::: IPv6 or MPLS network using the source routing paradigm. This document ::: illustrates some use cases for Segment Routing in an IPv6-only ::: environment.
---
paper_title: Source Packet Routing in Networking (SPRING) Problem Statement and Requirements

paper_content:

The ability for a node to specify a forwarding path, other than the ::: normal shortest path, that a particular packet will traverse, benefits ::: a number of network functions. Source-based routing mechanisms have ::: previously been specified for network protocols but have not seen ::: widespread adoption. In this context, the term "source" means "the ::: point at which the explicit route is imposed"; therefore, it is not ::: limited to the originator of the packet (i.e., the node imposing the ::: explicit route may be the ingress node of an operator's network). ::: This document outlines various use cases, with their requirements, ::: that need to be taken into account by the Source Packet Routing in ::: Networking (SPRING) architecture for unicast traffic. Multicast use ::: cases and requirements are out of scope for this document.
---
paper_title: Resiliency Use Cases in Source Packet Routing in Networking (SPRING) Networks

paper_content:

This document identifies and describes the requirements for a set of ::: use cases related to Segment Routing network resiliency on Source ::: Packet Routing in Networking (SPRING) networks.
---
paper_title: Routing Perturbation for Traffic Matrix Evaluation in a Segment Routing Network

paper_content:

Traffic matrix (TM) assessment is a key issue for optimizing network management costs and quality of service. This paper presents a method to measure the intensity of ingress–egress traffic flows on an Internet service providers network that overcomes the limits of the classical measurement-based approaches. The proposed algorithm, called segment routing perturbation traffic (SERPENT), uses a routing perturbation approach enabled by the segment routing paradigm: The paths of a subset of flows are changed so that their intensities can be determined measuring the variation of the load of the network links. The TM is measured in successive steps, called snapshots, in which sets of flows are progressively re-routed and measured, under a maximum link utilization constraint. We state an integer linear programming (ILP) optimization problem to determine the flows to be rerouted in one snapshot. SERPENT is an heuristic offering an efficient solution to the stated ILP. Results show that SERPENT assesses the intensity of more than 80% of flows even when the network is highly stressed, while reducing the configuration cost with respect to classical approaches. Moreover, when used in conjunction with an estimation algorithm, SERPENT allows a reduction of the estimation error by more than 50% with fewer than 5 snapshots.
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paper_title: A Heuristic Approach to Assess the Traffic Matrix of an ISP Exploiting Segment Routing Flexibility

paper_content:

The Ingress Egress Traffic Matrix (IE TM) assessment is a fundamental step of the network management for an ISP network, since it represents the key input parameter used by any Traffic Engineering solution to optimize the resource utilization and to improve the Quality of Service. The actual TM assessment procedures are based on estimation algorithms or measurement based approaches. This paper presents a method to measure the intensity of traffic flows, that overcomes the limits of the classical measurement/estimation based approaches. The idea is to exploit the flexibility of the Segment Routing paradigm to implement controlled routing changes so that to measure the intensity of a subset of network flows. The main contribution of the work is to show the feasibility of the proposed approach by means of a low complexity heuristic, referred to as Path Cost Bases (PaCoB), able to identify the list of routing changes that allow to improve the TM assessment procedure. The heuristic is composed of successive steps, referred to as snapshots: in each snapshot the routing of a set of flows is changed so that to assess their intensities. The performance evaluation show thatPaCoB assesses the intensity of more than 90% of flows. Moreover, when used in conjunction with an estimation algorithm, PaCoB allows to reduce the estimation error by more than 50% performing only 10 snapshots.
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paper_title: Bandwidth-efficient network monitoring algorithms based on segment routing

paper_content:

Abstract We study the bandwidth-efficient network monitoring algorithms using segment routing on topologies that can be modelled as a symmetric directed graph. Aiming at directly minimizing the cycle cover length, four new two-phase algorithms, A, B, C and D, are proposed. Algorithm A is a simple extension of an existing algorithm. Algorithm B utilizes the notion of symmetric cycles. Algorithm C enhances B by adopting a new path metric. Algorithm D further improves C with a parallel and sequential cycle construction process. Since two-phase algorithms require a dedicated monitoring topology, the four two-phase algorithms are then enhanced to function without monitoring topology. Although the cycle cover length found is slightly increased, we argue that the cost saving in removing monitoring topology is far more significant.
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paper_title: Interface Counters in Segment Routing v6: a powerful instrument for Traffic Matrix Assessment

paper_content:

In this work we investigate the use of Segment Routing version 6 (SRv6) interface counters to improve the Traffic Matrix (TM) assessment of an ISP network. SRv6 is a source routing solution for IPv6 networks: it allows defining a network path as a sequence of routers, represented by Segments Identifiers (SID), to be crossed, i.e. a Segment List (SL). SRv6 provides a new set of interface counters able to measure the packets/bytes of Ingress/Egress flows exploiting the forwarding operations performed on the Segment Identifiers (SIDs) reported in the SLs. In this work, we formally define the contribution of SR counters in the TM computation procedure, by integrating them in the classical TM Assessment problem. The main outcome of the performance analysis are: i) SR counters can greatly reduce the estimation error and, ii) there is a correlation between the TM assessment improvement and the SLs structure.
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paper_title: SCMon: Leveraging segment routing to improve network monitoring

paper_content:

To guarantee correct operation of their networks, operators have to promptly detect and diagnose data-plane issues, like broken interface cards or link failures. Networks are becoming more complex, with a growing number of Equal Cost MultiPath (ECMP) and link bundles. Hence, some data-plane problems (e.g. silent packet dropping at one router) can hardly be detected with control-plane protocols or simple monitoring tools like ping or traceroute. In this paper, we propose a new technique, called SCMon, that enables continuous monitoring of the data-plane, in order to track the health of all routers and links. SCMon leverages the recently proposed Segment Routing (SR) architecture to monitor the entire network with a single box (and no additional monitoring protocol). In particular, SCMon uses SR to (i) force monitoring probes to travel over cycles; and (ii) test parallel links and bundles at a per-link granularity. We present original algorithms to compute cycles that cover all network links with a limited number of SR segments. Further, we prototype and evaluate SCMon both with simulations and Linux-based emulations. Our experiments show that SCMon quickly detects and precisely pinpoints data-plane problems, with a limited overhead.
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paper_title: Translating Traffic Engineering outcome into Segment Routing paths: The Encoding problem

paper_content:

Traffic Engineering (TE) algorithms aims at determining the packet routing paths in order to satisfy specific QoS requirements. These paths are normally established through control procedures e.g., exchange of RSVP messages in MPLS networks or links weights modification in pure IP networks. An increase of control traffic or long convergence time intervals, respectively, are the drawbacks of these solutions. Segment Routing (SR) is a new network paradigm able to implement TE routing strategies over legacy IP/MPLS networks with no need of dedicated signaling procedures. This result is obtained by inserting in each packet header an ordered list of instructions, called Segments List, that indicates the path to be crossed. This paper provides the formulation of the Segment List Encoding problem i.e., the detection of the proper Segment Lists to obtain TE network paths minimizing the Segment Lists sizes. The SL encoding procedure is composed of two steps: i) the creation of an auxiliary graph representing the forwarding paths between the couple of source and destination nodes; ii) the solution of a Multi-commodity Flow (MCF) problem over the auxiliary graph. The performance evaluation shows that properly performing SL encoding allows to implement TE outcome with a reduced reconfiguration cost with respect to E2E tunneling and Hop-by-Hop solutions; moreover a significant advantage in terms of packets overhead is obtained.
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paper_title: On Traffic Engineering with Segment Routing in SDN based WANs

paper_content:

Segment routing is an emerging technology to simplify traffic engineering implementation in WANs. It expresses an end-to-end logical path as a sequence of segments, each of which is represented by a middlepoint. In this paper, we arguably conduct the first systematic study of traffic engineering with segment routing in SDN based WANs. We first provide a theoretical characterization of the problem. We show that for general segment routing, where flows can take any path that goes through a middlepoint, the resulting traffic engineering is NP-hard. We then consider segment routing with shortest paths only, and prove that the traffic engineering problem can now be solved in (weakly) polynomial time when the number of middlepoints per path is fixed and not part of the input. Our results thus explain, for the first time, the underlying reason why existing work only focuses on segment routing with shortest paths. In the second part of the paper, we study practical traffic engineering using shortest path based segment routing. We note that existing methods work by taking each node as a candidate middlepoint. This requires solving a large-scale linear program which is prohibitively slow. We thus propose to select just a few important nodes as middlepoints for all traffic. We use node centrality concepts from graph theory, notably group shortest path centrality, for middlepoint selection. Our performance evaluation using realistic topologies and traffic traces shows that a small percentage of the most central nodes can achieve good results with orders of magnitude lower runtime.
---
paper_title: Novel SDN architecture for smart MPLS Traffic Engineering-DiffServ Aware management

paper_content:

Abstract Large scale networks are still a major challenge for management, guarantee a good level of Quality of Service (QoS) and especially optimization (rational use of network resources). Multi-Protocol Label Switching (MPLS), mainly used in the backbone of Internet service providers, must meet these three major challenges. Software-Defined Network (SDN), is a paradigm that allows, through the principle of orchestration and layers abstraction, to manage large scale networks through specific protocols. This paper presents a new SDN-based architecture for managing an MPLS Traffic Engineering Diffserv Aware (DS-TE) network. The architecture manages the QoS and routing with QoS constraints, following a new smart and dynamic model of allocation of the bandwidth (Smart Alloc). The proposed architecture is suitable for SDN equipment and especially the legacy equipment. We tested our architecture by simulation on a hybrid network made up of SDN equipment and another legacy. The results of the simulation showed that thanks to our architecture we can not only efficiently manage hybrid architectures but also achieve good QoS levels for convergent traffic. The performance evaluation was performed on VoIP, video, HTTP, and ICMP traffic increasing packet load.
---
paper_title: Semi-Oblivious Segment Routing with Bounded Traffic Fluctuations

paper_content:

Segment Routing (SR) is a recently proposed protocol by IETF to realize scalability and flexibility properties for internet traffic engineering. This protocol is an integration of source routing and tunneling paradigms. The paths are defined in terms of segments and each segment is specified by a label. In this paper we consider the problem of offline segment routing when traffic matrix is not fully known. Because of wide variation in traffic matrix over time, it is difficult to estimate traffic matrix accurately. So, we have developed a semi-oblivious segment routing algorithm that takes bounded traffic fluctuations based on an initial estimated traffic matrix. This makes it robust to traffic fluctuations and yet substantially improves the routing performance compared to oblivious routing techniques.
---
paper_title: SDN-Based Data Center Networking With Collaboration of Multipath TCP and Segment Routing

paper_content:

Large-scale data centers are major infrastructures in the big data era. Therefore, a stable and optimized architecture is required for data center networks (DCNs) to provide services to the applications. Many studies use software-defined network (SDN)-based multipath TCP (MPTCP) implementation to utilize the entire DCN’s performance and achieve good results. However, the deployment cost is high. In SDN-based MPTCP solutions, the flow allocation mechanism leads to a large number of forwarding rules, which may lead to storage consumption. Considering the advantages and limitations of the SDN-based MPTCP solution, we aim to reduce the deployment cost due to the use of an extremely expensive storage resource—ternary content addressable memory (TCAM). We combine MPTCP and segment routing (SR) for traffic management to limit the storage requirements. And to the best of our knowledge, we are among the first to use the collaboration of MPTCP and SR in multi-rooted DCN topologies. To explain how MPTCP and SR work together, we use four-layer DCN architecture for better description, which contains physical topology, SR over the topology, multiple path selection supplied by MPTCP, and traffic scheduling on the selected paths. Finally, we implement the proposed design in a simulated SDN-based DCN environment. The simulation results reveal the great benefits of such a collaborative approach.
---
paper_title: Demonstration of Segment Routing with SDN based label stack optimization

paper_content:

Segment Routing (SR) architecture is a promising technology. It is being standardized in collaboration between vendors and service providers. Through its simplistic control plane and the reuse of existing data planes namely MPLS and IPv6, SR helps operators to reduce the Operation Expense (OpEx) and the Capital Expense (CapEx). In the instantiation of SR over the MPLS data plane (SR-MPLS), a SR path gets encoded as a label stack that the ingress nodes push onto the client packet. However, the longer the path in term of traversed nodes the bigger the stack gets. In this demonstration, we couple the capabilities of an SDN controller and a path encoding engine to reduce that size of the label stack to express segment routing paths.
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paper_title: A Novel QoE-Centric SDN-Based Multipath Routing Approach for Multimedia Services over 5G Networks

paper_content:

The explosion of enhanced applications such as live video streaming, video gaming and Virtual Reality calls for efforts to optimize transport protocols to manage the increasing amount of data traffic on future 5G networks. Through bandwidth aggregation over multiple paths, the Multi-Path Transmission Control Protocol (MPTCP) can enhance the performance of network applications. MPTCP can split a large multimedia flow into subflows and apply a congestion control mechanism on each subflow. Segment Routing (SR), a promising source routing approach, has emerged to provide advanced packet forwarding over 5G networks. In this paper, we explore the utilization of MPTCP and SR in SDN-based networks to improve network resources utilization and end- user's QoE for delivering multimedia services over 5G networks. We propose a novel QoE-aware, SDN- based MPTCP/SR approach for service delivery. In order to demonstrate the feasibility of our approach, we implemented an intelligent QoE- centric Multipath Routing Algorithm (QoMRA) on an SDN source routing platform using Mininet and POX controller. We carried out experiments on Dynamic Adaptive video Steaming over HTTP (DASH) applications over various network conditions. The preliminary results show that, our QoE-aware SDN- based MPTCP/SR scheme performs better compared to the conventional TCP approach in terms of throughput, link utilization and the end-user's QoE.
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paper_title: Expect the unexpected: Sub-second optimization for segment routing

paper_content:

In this paper, we study how to perform traffic engineering at an extremely-small time scale with segment routing, addressing a critical need for modern wide area networks. Prior work has shown that segment routing enables to better engineer traffic, thanks to its ability to program detours in forwarding paths, at scale. Two main approaches have been explored for traffic engineering with segment routing, respectively based on integer linear programming and constraint programming. However, no previous work deeply investigated how quickly those approaches can react to unexpected traffic changes and failures. We highlight limitations of existing algorithms, both in terms of required execution time and amount of path changes to be applied. Thus, we propose a new approach, based on local search and focused on the quick re-arrangement of (few) forwarding paths. We describe heuristics for sub-second recomputation of segment-routing paths that comply with requirements on the maximum link load (e.g., for congestion avoidance). Our heuristics enable a prompt answer to sudden criticalities affecting network services and business agreements. Through extensive simulations, we indeed experimentally show that our proposal significantly outperforms previous algorithms in the context of time-constrained optimization, supporting radical traffic changes in few tens of milliseconds for realistic networks.
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paper_title: An efficient routing algorithm based on segment routing in software-defined networking

paper_content:

Software-defined networking (SDN) is an emerging architecture that offers advantages over traditional network architecture. Segment routing (SR) defines the path of information through the network via an ordered list of multi-protocol label switching (MPLS) mechanisms on the packet headers at the ingress device, and this system makes SDN routing management more simple and efficient. SR can also solve some scalability issues in SDN. In this paper, we propose a routing algorithm for SDN with SR that can meet the bandwidth requirements of routing requests. Our algorithm considers the balance of traffic load and reduces the extra cost of packet header size in a network. Simulation results show that the performance of our algorithm is better than that of previously developed algorithms in terms of the average network throughput and the average rejection rate of routing requests.
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paper_title: A scalable and bandwidth-efficient multicast algorithm based on segment routing in software-defined networking

paper_content:

Software-Defined Networking (SDN) is an emerging architecture and offers advantages over traditional network architecture, while there exist some scalability challenges. In this paper, we propose a multicast routing algorithm for SDN with segment routing to serve the bandwidth requirement of a multicast routing request. Our algorithm considers the balance of traffic load for network resource of link bandwidth and node flow entries both. Simulation results show that the performance of our algorithm is better than previous works in terms of average network throughput and average rejection rate of routing requests. Besides, the results also show that our multicast architecture improve scalability problem of original SDN model in terms of number of flow entries used.
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paper_title: Traffic Engineering with Segment Routing: SDN-Based Architectural Design and Open Source Implementation

paper_content:

Traffic Engineering (TE) in IP carrier networks is one of the functions that can benefit from the Software Defined Networking paradigm. However traditional per-flow routing requires a direct interaction between the SDN controller and each node that is involved in the traffic paths. Segment Routing (SR) may simplify the route enforcement delegating all the configuration and per-flow state at the border of the network. In this work we propose an architecture that integrates the SDN paradigm with SR based TE, for which we have provided an open source reference implementation. We have designed and implemented a simple TE/SR heuristic for flow allocation and we show and discuss experimental results.
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paper_title: Incremental Deployment of Segment Routing Into an ISP Network: a Traffic Engineering Perspective

paper_content:

Segment routing (SR) is a new routing paradigm to provide traffic engineering (TE) capabilities in an IP network. The main feature of SR is that no signaling protocols are needed, since extensions of the interior gateway protocol routing protocols are used. Despite the benefit that SR brings, introducing a new technology into an operational network presents many difficulties. In particular, the network operators consider both capital expenditure and performance degradation as drawbacks for the deployment of the new technology; for this reason, an incremental approach is preferred. In this paper, we face the challenge of managing the transition between a pure IP network to a full SR one while optimizing the network performances. We focus our attention on a network scenario where: 1) only a subset of nodes are SR-capable and 2) the TE objective is the minimization of the maximum link utilization. For such a scenario, we propose an architectural solution, named SR domain (SRD), to guarantee the proper interworking between the IP routers and the SR nodes. We propose a mixed integer linear programming formulation to solve the SRD design problem, consisting in identifying the subset of SR nodes; moreover, a strategy to manage the routing inside the SRD is defined. The performance evaluation shows that the hybrid IP/SR network based on SRD offers TE opportunities comparable to the one of a full SR network. Finally, a heuristic method to identify nodes to be inserted in the set of nodes composing the SRD is discussed.
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paper_title: Optimizing segment routing using evolutionary computation

paper_content:

Abstract Segment Routing (SR) combines the simplicity of Link-State routing protocols with the flexibility of Multiprotocol Label Switching (MPLS). By decomposing forwarding paths into segments, identified by labels, SR improves Traffic Engineering (TE) and enables new solutions for the optimization of network resources utilization. This work proposes an Evolutionary Computation approach that enables Path Computation Element (PCE) or Software-defined Network (SDN) controllers to optimize label switching paths for congestion avoidance while using at the most three labels to configure each label switching path.
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paper_title: An Optimization Routing Algorithm Based on Segment Routing in Software-Defined Networks

paper_content:

Software-defined networks (SDNs) are improving the controllability and flexibility of networks as an innovative network architecture paradigm. Segment routing (SR) exploits an end-to-end logical path and is composed of a sequence of segments as an effective routing strategy. Each segment is represented by a middle point. The combination of SR and SDN can meet the differentiated business needs of users and can quickly deploy applications. In this paper, we propose two routing algorithms based on SR in SDN. The algorithms aim to save the cost of the path, alleviate the congestion of networks, and formulate the selection strategy by comprehensively evaluating the value of paths. The simulation results show that compared with existing algorithms, the two proposed algorithms can effectively reduce the consumption of paths and better balance the load of the network. Furthermore, the proposed algorithms take into account the preferences of users, actualize differentiated business networks, and achieve a larger comprehensive evaluation value of the path compared with other algorithms.
---
paper_title: On Traffic Engineering with Segment Routing in SDN based WANs

paper_content:

Segment routing is an emerging technology to simplify traffic engineering implementation in WANs. It expresses an end-to-end logical path as a sequence of segments, each of which is represented by a middlepoint. In this paper, we arguably conduct the first systematic study of traffic engineering with segment routing in SDN based WANs. We first provide a theoretical characterization of the problem. We show that for general segment routing, where flows can take any path that goes through a middlepoint, the resulting traffic engineering is NP-hard. We then consider segment routing with shortest paths only, and prove that the traffic engineering problem can now be solved in (weakly) polynomial time when the number of middlepoints per path is fixed and not part of the input. Our results thus explain, for the first time, the underlying reason why existing work only focuses on segment routing with shortest paths. In the second part of the paper, we study practical traffic engineering using shortest path based segment routing. We note that existing methods work by taking each node as a candidate middlepoint. This requires solving a large-scale linear program which is prohibitively slow. We thus propose to select just a few important nodes as middlepoints for all traffic. We use node centrality concepts from graph theory, notably group shortest path centrality, for middlepoint selection. Our performance evaluation using realistic topologies and traffic traces shows that a small percentage of the most central nodes can achieve good results with orders of magnitude lower runtime.
---
paper_title: Novel SDN architecture for smart MPLS Traffic Engineering-DiffServ Aware management

paper_content:

Abstract Large scale networks are still a major challenge for management, guarantee a good level of Quality of Service (QoS) and especially optimization (rational use of network resources). Multi-Protocol Label Switching (MPLS), mainly used in the backbone of Internet service providers, must meet these three major challenges. Software-Defined Network (SDN), is a paradigm that allows, through the principle of orchestration and layers abstraction, to manage large scale networks through specific protocols. This paper presents a new SDN-based architecture for managing an MPLS Traffic Engineering Diffserv Aware (DS-TE) network. The architecture manages the QoS and routing with QoS constraints, following a new smart and dynamic model of allocation of the bandwidth (Smart Alloc). The proposed architecture is suitable for SDN equipment and especially the legacy equipment. We tested our architecture by simulation on a hybrid network made up of SDN equipment and another legacy. The results of the simulation showed that thanks to our architecture we can not only efficiently manage hybrid architectures but also achieve good QoS levels for convergent traffic. The performance evaluation was performed on VoIP, video, HTTP, and ICMP traffic increasing packet load.
---
paper_title: Semi-Oblivious Segment Routing with Bounded Traffic Fluctuations

paper_content:

Segment Routing (SR) is a recently proposed protocol by IETF to realize scalability and flexibility properties for internet traffic engineering. This protocol is an integration of source routing and tunneling paradigms. The paths are defined in terms of segments and each segment is specified by a label. In this paper we consider the problem of offline segment routing when traffic matrix is not fully known. Because of wide variation in traffic matrix over time, it is difficult to estimate traffic matrix accurately. So, we have developed a semi-oblivious segment routing algorithm that takes bounded traffic fluctuations based on an initial estimated traffic matrix. This makes it robust to traffic fluctuations and yet substantially improves the routing performance compared to oblivious routing techniques.
---
paper_title: SDN-Based Data Center Networking With Collaboration of Multipath TCP and Segment Routing

paper_content:

Large-scale data centers are major infrastructures in the big data era. Therefore, a stable and optimized architecture is required for data center networks (DCNs) to provide services to the applications. Many studies use software-defined network (SDN)-based multipath TCP (MPTCP) implementation to utilize the entire DCN’s performance and achieve good results. However, the deployment cost is high. In SDN-based MPTCP solutions, the flow allocation mechanism leads to a large number of forwarding rules, which may lead to storage consumption. Considering the advantages and limitations of the SDN-based MPTCP solution, we aim to reduce the deployment cost due to the use of an extremely expensive storage resource—ternary content addressable memory (TCAM). We combine MPTCP and segment routing (SR) for traffic management to limit the storage requirements. And to the best of our knowledge, we are among the first to use the collaboration of MPTCP and SR in multi-rooted DCN topologies. To explain how MPTCP and SR work together, we use four-layer DCN architecture for better description, which contains physical topology, SR over the topology, multiple path selection supplied by MPTCP, and traffic scheduling on the selected paths. Finally, we implement the proposed design in a simulated SDN-based DCN environment. The simulation results reveal the great benefits of such a collaborative approach.
---
paper_title: Reliable segment routing

paper_content:

Segment Routing (SR) is a novel traffic engineering technique compatible with traditional MPLS data plane. SR relies on label stacking to steer traffic flows throughout the network. Signaling protocol is not required, thus control plane operation is greatly simplified. SR can also be exploited upon network failures to promptly perform traffic recovery and, subsequently, to optimize the recovered traffic for avoiding network congestion. This study proposes a procedure to dynamically recover the traffic flows disrupted by a single failure in segment routing networks. The proposed procedure is evaluated in several network topologies to estimate the complexity of the required operations.
---
paper_title: Demonstration of Segment Routing with SDN based label stack optimization

paper_content:

Segment Routing (SR) architecture is a promising technology. It is being standardized in collaboration between vendors and service providers. Through its simplistic control plane and the reuse of existing data planes namely MPLS and IPv6, SR helps operators to reduce the Operation Expense (OpEx) and the Capital Expense (CapEx). In the instantiation of SR over the MPLS data plane (SR-MPLS), a SR path gets encoded as a label stack that the ingress nodes push onto the client packet. However, the longer the path in term of traversed nodes the bigger the stack gets. In this demonstration, we couple the capabilities of an SDN controller and a path encoding engine to reduce that size of the label stack to express segment routing paths.
---
paper_title: Optimizing restoration with segment routing

paper_content:

Segment routing is a new proposed routing mechanism for simplified and flexible path control in IP/MPLS networks. It builds on existing network routing and connection management protocols and one of its important features is the automatic rerouting of connections upon failure. Re-routing can be done with available restoration mechanisms including IGP-based rerouting and fast reroute with loop-free alternates. This is particularly attractive for use in Software Defined Networks (SDN) because the central controller need only be involved at connection set-up time and failures are handled automatically in a distributed manner. A significant challenge in restoration optimization in segment routed networks is the centralized determination of connections primary paths so as to enable the best sharing of restoration bandwidth over non-simultaneous network failures. We formulate this problem as a linear programming problem and develop an efficient primal-dual algorithm for the solution. We also develop a simple randomized rounding scheme for cases when there are additional constraints on segment routing. We demonstrate the significant capacity benefits achievable from this optimized restoration with segment routing.
---
paper_title: A Novel QoE-Centric SDN-Based Multipath Routing Approach for Multimedia Services over 5G Networks

paper_content:

The explosion of enhanced applications such as live video streaming, video gaming and Virtual Reality calls for efforts to optimize transport protocols to manage the increasing amount of data traffic on future 5G networks. Through bandwidth aggregation over multiple paths, the Multi-Path Transmission Control Protocol (MPTCP) can enhance the performance of network applications. MPTCP can split a large multimedia flow into subflows and apply a congestion control mechanism on each subflow. Segment Routing (SR), a promising source routing approach, has emerged to provide advanced packet forwarding over 5G networks. In this paper, we explore the utilization of MPTCP and SR in SDN-based networks to improve network resources utilization and end- user's QoE for delivering multimedia services over 5G networks. We propose a novel QoE-aware, SDN- based MPTCP/SR approach for service delivery. In order to demonstrate the feasibility of our approach, we implemented an intelligent QoE- centric Multipath Routing Algorithm (QoMRA) on an SDN source routing platform using Mininet and POX controller. We carried out experiments on Dynamic Adaptive video Steaming over HTTP (DASH) applications over various network conditions. The preliminary results show that, our QoE-aware SDN- based MPTCP/SR scheme performs better compared to the conventional TCP approach in terms of throughput, link utilization and the end-user's QoE.
---
paper_title: TI-MFA: Keep calm and reroute segments fast

paper_content:

Segment Routing (SR) promises to provide scalable and fine-grained traffic engineering. However, little is known today on how to implement resilient routing in SR, i.e., routes which tolerate one or even multiple failures. This paper initiates the theoretical study of static fast failover mechanisms which do not depend on reconvergence and hence support a very fast reaction to failures. We introduce formal models and identify fundamental tradeoffs on what can and cannot be achieved in terms of static resilient routing. In particular, we identify an inherent price in terms of performance if routing paths need to be resilient, even in the absence of failures. Our main contribution is a first algorithm which is resilient even to multiple failures and which comes with provable resiliency and performance guarantees. We complement our formal analysis with simulations on real topologies, which show the benefits of our approach over existing algorithms.
---
paper_title: Expect the unexpected: Sub-second optimization for segment routing

paper_content:

In this paper, we study how to perform traffic engineering at an extremely-small time scale with segment routing, addressing a critical need for modern wide area networks. Prior work has shown that segment routing enables to better engineer traffic, thanks to its ability to program detours in forwarding paths, at scale. Two main approaches have been explored for traffic engineering with segment routing, respectively based on integer linear programming and constraint programming. However, no previous work deeply investigated how quickly those approaches can react to unexpected traffic changes and failures. We highlight limitations of existing algorithms, both in terms of required execution time and amount of path changes to be applied. Thus, we propose a new approach, based on local search and focused on the quick re-arrangement of (few) forwarding paths. We describe heuristics for sub-second recomputation of segment-routing paths that comply with requirements on the maximum link load (e.g., for congestion avoidance). Our heuristics enable a prompt answer to sudden criticalities affecting network services and business agreements. Through extensive simulations, we indeed experimentally show that our proposal significantly outperforms previous algorithms in the context of time-constrained optimization, supporting radical traffic changes in few tens of milliseconds for realistic networks.
---
paper_title: An efficient routing algorithm based on segment routing in software-defined networking

paper_content:

Software-defined networking (SDN) is an emerging architecture that offers advantages over traditional network architecture. Segment routing (SR) defines the path of information through the network via an ordered list of multi-protocol label switching (MPLS) mechanisms on the packet headers at the ingress device, and this system makes SDN routing management more simple and efficient. SR can also solve some scalability issues in SDN. In this paper, we propose a routing algorithm for SDN with SR that can meet the bandwidth requirements of routing requests. Our algorithm considers the balance of traffic load and reduces the extra cost of packet header size in a network. Simulation results show that the performance of our algorithm is better than that of previously developed algorithms in terms of the average network throughput and the average rejection rate of routing requests.
---
paper_title: A scalable and bandwidth-efficient multicast algorithm based on segment routing in software-defined networking

paper_content:

Software-Defined Networking (SDN) is an emerging architecture and offers advantages over traditional network architecture, while there exist some scalability challenges. In this paper, we propose a multicast routing algorithm for SDN with segment routing to serve the bandwidth requirement of a multicast routing request. Our algorithm considers the balance of traffic load for network resource of link bandwidth and node flow entries both. Simulation results show that the performance of our algorithm is better than previous works in terms of average network throughput and average rejection rate of routing requests. Besides, the results also show that our multicast architecture improve scalability problem of original SDN model in terms of number of flow entries used.
---
paper_title: Segment routing based traffic engineering for energy efficient backbone networks

paper_content:

Energy consumption has become a limiting factor for deploying large-scale distributed infrastructures. This work1 seeks to improve the energy efficiency of backbone networks by providing an intra-domain Software Defined Network (SDN) approach to selectively turn off a subset of links. We propose the STREETE framework (SegmenT Routing based Energy Efficient Traffic Engineering) that dynamically adapts the number of powered-on links to the traffic load. The core of the solution relies on SPRING, a novel protocol being standardized by IETF. It is also known under the name of Segment Routing. The algorithms have been implemented and evaluated using the OMNET++ simulator. Experimental results show that the consumption of 44% of links can be reduced while preserving good quality of service.
---
paper_title: Demonstration of dynamic restoration in segment routing multi-layer SDN networks

paper_content:

Dynamic traffic recovery is designed and validated in a multi-layer network exploiting an SDN-based implementation of Segment Routing. Traffic recovery is locally performed from the node detecting the failure up to the destination node without involving the SDN controller. Experimental results demonstrate recovery time within 50 ms.
---
paper_title: Traffic duplication through segmentable disjoint paths

paper_content:

Ultra-low latency is a key component of safety-critical operations such as robot-assisted remote surgery or financial applications where every single millisecond counts. In this paper, we show how network operators can build upon the recently proposed Segment Routing architecture to provide a traffic duplication service to better serve the users of such demanding applications. We propose the first implementation of Segment Routing in the Linux kernel and leverage it to provide a traffic duplication service that sends packets over disjoint paths. Our experiments show that with such a service existing TCP stacks can preserve latency in the presence of packet losses. We also propose and evaluate an efficient algorithm that computes disjoint paths that can be realised by using segments. Our evaluation with real and synthetic network topologies shows that our proposed algorithms perform well in large networks.
---
paper_title: Traffic engineering in segment routing networks

paper_content:

Abstract Segment routing (SR) has been recently proposed as an alternative traffic engineering (TE) technology enabling relevant simplifications in control plane operations. In the literature, preliminary investigations on SR have focused on label encoding algorithms and experimental assessments, without carefully addressing some key aspects of SR in terms of the overall network TE performance. In this study, ILP models and heuristics are proposed and successfully utilized to assess the TE performance of SR-based packet networks. Results show that the default SR behavior of exploiting equal cost multiple paths (ECMP) may lead to several drawbacks, including higher network resource utilization with respect to cases where ECMP is avoided. Moreover, results show that, by properly performing segment list computations, it is possible to achieve very effective TE solutions by just using a very limited number of stacked labels, thus successfully exploiting the benefits of the SR technology.
---
paper_title: Robustly disjoint paths with segment routing

paper_content:

Motivated by conversations with operators and by possibilities to unlock future Internet-based applications, we study how to enable Internet Service Providers (ISPs) to reliably offer connectivity through disjoint paths as an advanced, value-added service. As ISPs are increasingly deploying Segment Routing (SR), we focus on implementing such service with SR. We introduce the concept of robustly disjoint paths, pairs of paths that are constructed to remain disjoint even after an input set of failures, with no external intervention (e.g., configuration change). We extend the routing theory, study the problem complexity, and design efficient algorithms to automatically compute SR-based robustly disjoint paths. Our algorithms enable a fully automated approach to offer the disjoint-path connectivity, based on configuration synthesis. Our evaluation on real topologies shows that such an approach is practical, and scales to large ISP networks.
---
paper_title: Local Fast Segment Rerouting on Hypercubes

paper_content:

Fast rerouting is an essential mechanism in any dependable communication network, allowing to quickly, i.e., locally, recover from network failures, without invoking the control plane. However, while locality ensures a fast reaction, the absence of global information also renders the design of highly resilient fast rerouting algorithms more challenging. In this paper, we study algorithms for fast rerouting in emerging Segment Routing (SR) networks, where intermediate destinations can be added to packets by nodes along the path. Our main contribution is a maximally resilient polynomial-time fast rerouting algorithm for SR networks based on a hypercube topology. Our algorithm is attractive as it preserves the original paths (and hence waypoints traversed along the way), and does not require packets to carry failure information. We complement our results with an integer linear program formulation for general graphs and exploratory simulation results.
---
paper_title: Solving Segment Routing Problems with Hybrid Constraint Programming Techniques

paper_content:

Segment routing is an emerging network technology that exploits the existence of several paths between a source and a destination to spread the traffic in a simple and elegant way. The major commercial network vendors already support segment routing, and several Internet actors are ready to use segment routing in their network. Unfortunately, by changing the way paths are computed, segment routing poses new optimization problems which cannot be addressed with previous research contributions. In this paper, we propose a new hybrid constraint programming framework to solve traffic engineering problems in segment routing. We introduce a new representation of path variables which can be seen as a lightweight relaxation of usual representations. We show how to define and implement fast propagators on these new variables while reducing the memory impact of classical traffic engineering models. The efficiency of our approach is confirmed by experiments on real and artificial networks of big Internet actors.
---
paper_title: PMSR - Poor Man's Segment Routing, a minimalistic approach to Segment Routing and a Traffic Engineering use case

paper_content:

The current specification of the Segment Routing (SR) architecture requires enhancements to the intradomain routing protocols (e.g. OSPF and IS-IS) so that the nodes can advertise the Segment Identifiers (SIDs). We propose a simpler solution called PMSR (Poor Man's Segment Routing), that does not require any enhancement to routing protocol. We compare the procedures of PMSR with traditional SR, showing that PMSR can reduce the operation and management complexity. We analyze the set of use cases in the current SR drafts and we claim that PMSR can support the large majority of them. Thanks to the drastic simplification of the control plane, we have been able to develop an open source prototype of PMSR. In the second part of the paper, we consider a Traffic Engineering use case, starting from a traditional flow assignment optimization problem, which allocates hop-by-hop paths to flows. We propose a SR path assignment algorithm and prove that it is optimal with respect to the number of segments allocated to a flow.
---
paper_title: Traffic Engineering with Segment Routing: SDN-Based Architectural Design and Open Source Implementation

paper_content:

Traffic Engineering (TE) in IP carrier networks is one of the functions that can benefit from the Software Defined Networking paradigm. However traditional per-flow routing requires a direct interaction between the SDN controller and each node that is involved in the traffic paths. Segment Routing (SR) may simplify the route enforcement delegating all the configuration and per-flow state at the border of the network. In this work we propose an architecture that integrates the SDN paradigm with SR based TE, for which we have provided an open source reference implementation. We have designed and implemented a simple TE/SR heuristic for flow allocation and we show and discuss experimental results.
---
paper_title: Optimized network traffic engineering using segment routing

paper_content:

Segment Routing is a proposed IETF protocol to improve traffic engineering and online route selection in IP networks. The key idea in segment routing is to break up the routing path into segments in order to enable better network utilization. Segment routing also enables finer control of the routing paths and can be used to route traffic through middle boxes. This paper considers the problem of determining the optimal parameters for segment routing in the offline and online cases. We develop a traffic matrix oblivious algorithm for robust segment routing in the offline case and a competitive algorithm for online segment routing. We also show that both these algorithms work well in practice.
---
paper_title: Incremental Deployment of Segment Routing Into an ISP Network: a Traffic Engineering Perspective

paper_content:

Segment routing (SR) is a new routing paradigm to provide traffic engineering (TE) capabilities in an IP network. The main feature of SR is that no signaling protocols are needed, since extensions of the interior gateway protocol routing protocols are used. Despite the benefit that SR brings, introducing a new technology into an operational network presents many difficulties. In particular, the network operators consider both capital expenditure and performance degradation as drawbacks for the deployment of the new technology; for this reason, an incremental approach is preferred. In this paper, we face the challenge of managing the transition between a pure IP network to a full SR one while optimizing the network performances. We focus our attention on a network scenario where: 1) only a subset of nodes are SR-capable and 2) the TE objective is the minimization of the maximum link utilization. For such a scenario, we propose an architectural solution, named SR domain (SRD), to guarantee the proper interworking between the IP routers and the SR nodes. We propose a mixed integer linear programming formulation to solve the SRD design problem, consisting in identifying the subset of SR nodes; moreover, a strategy to manage the routing inside the SRD is defined. The performance evaluation shows that the hybrid IP/SR network based on SRD offers TE opportunities comparable to the one of a full SR network. Finally, a heuristic method to identify nodes to be inserted in the set of nodes composing the SRD is discussed.
---
paper_title: Per-packet based energy aware segment routing approach for Data Center Networks with SDN

paper_content:

In today's scenario, energy efficiency has become one of the most crucial issues for Data Center Networks. This paper analyzes the energy saving capability of a Data Center Network (DCN) using Segment Routing (SR) based model within the SDN architecture. Apart from saving energy by turning off links, our work efficiently manages the traffic within the available links by using per-packet based load balancing approach to avoid congestion within DCNs and increases the sleeping time of inactive links. An algorithm for deciding the particular set of links to be turned off within a network is presented. Energy efficiency is measured in terms of number of links turned off and for how long the links remain in sleep mode. Results show that the proposed per-packet SR approach saves more energy and provides better performance as compared to per-flow based SR approach.
---
paper_title: Optimizing segment routing using evolutionary computation

paper_content:

Abstract Segment Routing (SR) combines the simplicity of Link-State routing protocols with the flexibility of Multiprotocol Label Switching (MPLS). By decomposing forwarding paths into segments, identified by labels, SR improves Traffic Engineering (TE) and enables new solutions for the optimization of network resources utilization. This work proposes an Evolutionary Computation approach that enables Path Computation Element (PCE) or Software-defined Network (SDN) controllers to optimize label switching paths for congestion avoidance while using at the most three labels to configure each label switching path.
---
paper_title: Segment routing for effective recovery and multi-domain traffic engineering

paper_content:

Segment routing is an emerging traffic engineering technique relying on Multi-protocol Label-Switched (MPLS) label stacking to steer traffic using the source-routing paradigm. Traffic flows are enforced through a given path by applying a specifically designed stack of labels (i.e., the segment list). Each packet is then forwarded along the shortest path toward the network element represented by the top label. Unlike traditional MPLS networks, segment routing maintains a per-flow state only at the ingress node; no signaling protocol is required to establish new flows or change the routing of active flows. Thus, control plane scalability is greatly improved. Several segment routing use cases have recently been proposed. As an example, it can be effectively used to dynamically steer traffic flows on paths characterized by low latency values. However, this may suffer from some potential issues. Indeed, deployed MPLS equipment typically supports a limited number of stacked labels. Therefore, it is important to define the proper procedures to minimize the required segment list depth. This work is focused on two relevant segment routing use cases: dynamic traffic recovery and traffic engineering in multi-domain networks. Indeed, in both use cases, the utilization of segment routing can significantly simplify the network operation with respect to traditional Internet Protocol (IP)/MPLS procedures. Thus, two original procedures based on segment routing are proposed for the aforementioned use cases. Both procedures are evaluated including a simulative analysis of the segment list depth. Moreover, an experimental demonstration is performed in a multi-layer test bed exploiting a software-defined-networking-based implementation of segment routing.
---
paper_title: An Optimization Routing Algorithm Based on Segment Routing in Software-Defined Networks

paper_content:

Software-defined networks (SDNs) are improving the controllability and flexibility of networks as an innovative network architecture paradigm. Segment routing (SR) exploits an end-to-end logical path and is composed of a sequence of segments as an effective routing strategy. Each segment is represented by a middle point. The combination of SR and SDN can meet the differentiated business needs of users and can quickly deploy applications. In this paper, we propose two routing algorithms based on SR in SDN. The algorithms aim to save the cost of the path, alleviate the congestion of networks, and formulate the selection strategy by comprehensively evaluating the value of paths. The simulation results show that compared with existing algorithms, the two proposed algorithms can effectively reduce the consumption of paths and better balance the load of the network. Furthermore, the proposed algorithms take into account the preferences of users, actualize differentiated business networks, and achieve a larger comprehensive evaluation value of the path compared with other algorithms.
---
paper_title: A Linux kernel implementation of Segment Routing with IPv6

paper_content:

Network operators seek more flexibility to provide added-value services to their customers. We propose to leverage the IPv6 Segment Routing architecture with a example usecase. We also provide an implementation of SR-IPv6 and we evaluate its performance on broadband routers.
---
paper_title: Reliable segment routing

paper_content:

Segment Routing (SR) is a novel traffic engineering technique compatible with traditional MPLS data plane. SR relies on label stacking to steer traffic flows throughout the network. Signaling protocol is not required, thus control plane operation is greatly simplified. SR can also be exploited upon network failures to promptly perform traffic recovery and, subsequently, to optimize the recovered traffic for avoiding network congestion. This study proposes a procedure to dynamically recover the traffic flows disrupted by a single failure in segment routing networks. The proposed procedure is evaluated in several network topologies to estimate the complexity of the required operations.
---
paper_title: Flexible failure detection and fast reroute using eBPF and SRv6

paper_content:

Segment Routing is a modern variant of source routing that is being gradually deployed by network operators. Large ISPs use it for traffic engineering and fast reroute purposes. Its IPv6 dataplane, named SRv6, goes beyond the initial MPLS dataplane, notably by enabling network programmability. With SRv6, it becomes possible to define transparent network functions on routers and endhosts. These functions are mapped to IPv6 addresses and their execution is scheduled by segments placed in the forwarded packets. We have recently extended the Linux SRv6 implementation to enable the execution of specific eBPF code upon reception of an SRv6 packet containing local segments. eBPF is a virtual machine that is included in the Linux kernel. We leverage this new feature of Linux 4.18 to propose and implement flexible eBPF-based fast-reroute and failure detection schemes. Our lab measurements confirm that they provide good performance and enable faster failure detections than existing BFD implementations on Linux routers and servers.
---
paper_title: Optimizing restoration with segment routing

paper_content:

Segment routing is a new proposed routing mechanism for simplified and flexible path control in IP/MPLS networks. It builds on existing network routing and connection management protocols and one of its important features is the automatic rerouting of connections upon failure. Re-routing can be done with available restoration mechanisms including IGP-based rerouting and fast reroute with loop-free alternates. This is particularly attractive for use in Software Defined Networks (SDN) because the central controller need only be involved at connection set-up time and failures are handled automatically in a distributed manner. A significant challenge in restoration optimization in segment routed networks is the centralized determination of connections primary paths so as to enable the best sharing of restoration bandwidth over non-simultaneous network failures. We formulate this problem as a linear programming problem and develop an efficient primal-dual algorithm for the solution. We also develop a simple randomized rounding scheme for cases when there are additional constraints on segment routing. We demonstrate the significant capacity benefits achievable from this optimized restoration with segment routing.
---
paper_title: Demonstration of dynamic restoration in segment routing multi-layer SDN networks

paper_content:

Dynamic traffic recovery is designed and validated in a multi-layer network exploiting an SDN-based implementation of Segment Routing. Traffic recovery is locally performed from the node detecting the failure up to the destination node without involving the SDN controller. Experimental results demonstrate recovery time within 50 ms.
---
paper_title: Traffic duplication through segmentable disjoint paths

paper_content:

Ultra-low latency is a key component of safety-critical operations such as robot-assisted remote surgery or financial applications where every single millisecond counts. In this paper, we show how network operators can build upon the recently proposed Segment Routing architecture to provide a traffic duplication service to better serve the users of such demanding applications. We propose the first implementation of Segment Routing in the Linux kernel and leverage it to provide a traffic duplication service that sends packets over disjoint paths. Our experiments show that with such a service existing TCP stacks can preserve latency in the presence of packet losses. We also propose and evaluate an efficient algorithm that computes disjoint paths that can be realised by using segments. Our evaluation with real and synthetic network topologies shows that our proposed algorithms perform well in large networks.
---
paper_title: Leveraging eBPF for programmable network functions with IPv6 Segment Routing

paper_content:

With the advent of Software Defined Networks (SDN), Network Function Virtualisation (NFV) or Service Function Chaining (SFC), operators expect networks to support flexible services beyond the mere forwarding of packets. The network programmability framework which is being developed within the IETF by leveraging IPv6 Segment Routing enables the realisation of in-network functions. In this paper, we demonstrate that this vision of in-network programmability can be realised. By leveraging the eBPF support in the Linux kernel, we implement a flexible framework that allows network operators to encode their own network functions as eBPF code that is automatically executed while processing specific packets. Our lab measurements indicate that the overhead of calling such eBPF functions remains acceptable. Thanks to eBPF, operators can implement a variety of network functions. We describe the architecture of our implementation in the Linux kernel. This extension has been released with Linux 4.18. We illustrate the flexibility of our approach with three different use cases: delay measurements, hybrid networks and network discovery. Our lab measurements also indicate that the performance penalty of running eBPF network functions on Linux routers does not incur a significant overhead.
---
paper_title: Segment routing for effective recovery and multi-domain traffic engineering

paper_content:

Segment routing is an emerging traffic engineering technique relying on Multi-protocol Label-Switched (MPLS) label stacking to steer traffic using the source-routing paradigm. Traffic flows are enforced through a given path by applying a specifically designed stack of labels (i.e., the segment list). Each packet is then forwarded along the shortest path toward the network element represented by the top label. Unlike traditional MPLS networks, segment routing maintains a per-flow state only at the ingress node; no signaling protocol is required to establish new flows or change the routing of active flows. Thus, control plane scalability is greatly improved. Several segment routing use cases have recently been proposed. As an example, it can be effectively used to dynamically steer traffic flows on paths characterized by low latency values. However, this may suffer from some potential issues. Indeed, deployed MPLS equipment typically supports a limited number of stacked labels. Therefore, it is important to define the proper procedures to minimize the required segment list depth. This work is focused on two relevant segment routing use cases: dynamic traffic recovery and traffic engineering in multi-domain networks. Indeed, in both use cases, the utilization of segment routing can significantly simplify the network operation with respect to traditional Internet Protocol (IP)/MPLS procedures. Thus, two original procedures based on segment routing are proposed for the aforementioned use cases. Both procedures are evaluated including a simulative analysis of the segment list depth. Moreover, an experimental demonstration is performed in a multi-layer test bed exploiting a software-defined-networking-based implementation of segment routing.
---
paper_title: Evolve carrier ethernet architecture with SDN and segment routing

paper_content:

Ethernet technology has been evolving to become the main Wide Area Network transport technology. To address the rising CAPEX and OPEX issues, service providers are deploying Unified MPLS technology to consolidate various networks into one an integrated carrier ethernet network. Although Unified MPLS has simplified MPLS deployment in many aspects, it is still deemed complex and it is not as agile as what clouding computing demands. This paper proposes a further evolution of carrier ethernet architecture by coupling the emerging segment routing and Software-Defined Network (SDN) technologies. This new architecture will significantly simplify the network infrastructure while providing rich converged services with embedded high availability and agility.
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paper_title: SDN Architecture and Southbound APIs for IPv6 Segment Routing Enabled Wide Area Networks

paper_content:

The SRv6 architecture (segment routing based on IPv6 data plane) is a promising solution to support services like Traffic Engineering, service function chaining and virtual private networks in IPv6 backbones and datacenters. The SRv6 architecture has interesting scalability properties as it reduces the amount of state information that needs to be configured in the nodes to support the network services. In this paper, we describe the advantages of complementing the SRv6 technology with an software defined networking (SDN) based approach in backbone networks. We discuss the architecture of a SRv6 enabled network based on Linux nodes. In addition, we present the design and implementation of the Southbound API between the SDN controller and the SRv6 device. We have defined a data-model and four different implementations of the API, respectively based on gRPC, REST, NETCONF, and remote command line interface. Since it is important to support both the development and testing aspects we have realized an Intent-based emulation system to build realistic and reproducible experiments. This collection of tools automate most of the configuration aspects relieving the experimenter from a significant effort. Finally, we have realized an evaluation of some performance aspects of our architecture and of the different variants of the Southbound APIs and we have analyzed the effects of the configuration updates in the SRv6 enabled nodes.
---
paper_title: Demonstration of SDN-based orchestration for multi-domain Segment Routing networks

paper_content:

This work demonstrates a hierarchical control plane architecture for Software Defined Networking (SDN)-based Segment Routing (SR) in multi-domain networks. An orchestrator application, on top of multiple open source SDN controllers, creates a hierarchical control plane architecture using northbound RESTFul APIs of controllers. The orchestrator has control, visibility and traffic engineering capabilities to manage multi-domain SR service creation. Standard southbound interfaces with proper SR extensions are exploited to manage SR tunnels in the MPLS data plane.
---
paper_title: Software Resolved Networks: Rethinking Enterprise Networks with IPv6 Segment Routing

paper_content:

Enterprise networks often need to implement complex policies that match business objectives. They will embrace IPv6 like ISP networks in the coming years. Among the benefits of IPv6, the recently proposed IPv6 Segment Routing (SRv6) architecture supports richer policies in a clean manner. This matches very well the requirements of enterprise networks. In this paper, we propose Software Resolved Networks (SRNs), a new architecture for IPv6 enterprise networks. We apply the fundamental principles of Software Defined Networks, i.e., the ability to control the operation of the network through software, but in a different manner that also involves the endhosts. We leverage SRv6 to enforce and control network paths according to the network policies. Those paths are computed by a centralized controller that interacts with the endhosts through the DNS protocol. We implement a Software Resolved Network on Linux endhosts, routers and controllers. Through benchmarks and simulations, we analyze the performance of those SRNs, and demonstrate that they meet the expectations of enterprise networks.
---
paper_title: Path Encoding in Segment Routing

paper_content:

Segment Routing (SR) is emerging as an innovative traffic engineering technique compatible with traditional MPLS data plane. SR relies on label stacking, without requiring a signaling protocol. This greatly simplifies network operations in transit nodes. However, it may introduce scalability issues at the ingress node and packet overhead. Therefore, specific algorithms are required to efficiently compute the label stack for a given path. This study proposes two algorithms for SR label stack computation of strict routes that guarantee minimum label stack depth. Then, SR scalability performance is investigated. Results show that, in most of the cases, SR uses label stacks composed of few labels and introduces a limited packet overhead. However, relevant scalability issues may arise in specific cases, e.g., large planar topologies.
---
paper_title: Efficient label encoding in segment-routing enabled optical networks

paper_content:

The currently standardized GMPLS protocol suite for packet over optical networks relies on hierarchical instances of signaling sessions. Such sessions have to be established and maintained also in transit nodes, leading to complex and weighty control plane implementations. A novel technology called Segment Routing (SR) has been recently proposed to address these issues. SR relies on the source routing paradigm to provide traffic engineering solutions. In particular, the computed route for a given request is expressed as a segment list applied as an header to data packets at the ingress node. Specific algorithms are then required to perform the path computation and express the computed path through an effective segment list encoding (i.e., label stack), minimizing the segment list depth (SLD) (i.e., the number of labels included in the segment list). So far, no algorithms have been proposed to jointly provide path and segment list computation in SR-based networks. In this study, an efficient segment list encoding algorithm is proposed, guaranteeing optimal path computation and limited SLD in SR-based networks. The algorithm also accounts for equal-cost multiple paths and multiple constraints. The proposed algorithm is successfully applied to different network scenarios, demonstrating its flexibility in several use cases and showing effective performance in terms of segment list depth and introduced packet overhead.
---
paper_title: First demonstration of SDN-based segment routing in multi-layer networks

paper_content:

Segment Routing enabling dynamic optical bypass in a multi-layer network is experimentally demonstrated. Edge nodes are efficiently configured by an enhanced SDN controller, showing effective scalability performance under different label stacking conditions.
---
paper_title: Service chaining in multi-layer networks using segment routing and extended BGP FlowSpec

paper_content:

Effective service chaining enforcement along TE paths is proposed using Segment Routing and extended BGP Flowspec for micro-flows mapping. The proposed solution is experimentally evaluated with a deep packet inspection service supporting dynamic flow enforcement.
---
paper_title: PMSR - Poor Man's Segment Routing, a minimalistic approach to Segment Routing and a Traffic Engineering use case

paper_content:

The current specification of the Segment Routing (SR) architecture requires enhancements to the intradomain routing protocols (e.g. OSPF and IS-IS) so that the nodes can advertise the Segment Identifiers (SIDs). We propose a simpler solution called PMSR (Poor Man's Segment Routing), that does not require any enhancement to routing protocol. We compare the procedures of PMSR with traditional SR, showing that PMSR can reduce the operation and management complexity. We analyze the set of use cases in the current SR drafts and we claim that PMSR can support the large majority of them. Thanks to the drastic simplification of the control plane, we have been able to develop an open source prototype of PMSR. In the second part of the paper, we consider a Traffic Engineering use case, starting from a traditional flow assignment optimization problem, which allocates hop-by-hop paths to flows. We propose a SR path assignment algorithm and prove that it is optimal with respect to the number of segments allocated to a flow.
---
paper_title: SCMon: Leveraging segment routing to improve network monitoring

paper_content:

To guarantee correct operation of their networks, operators have to promptly detect and diagnose data-plane issues, like broken interface cards or link failures. Networks are becoming more complex, with a growing number of Equal Cost MultiPath (ECMP) and link bundles. Hence, some data-plane problems (e.g. silent packet dropping at one router) can hardly be detected with control-plane protocols or simple monitoring tools like ping or traceroute. In this paper, we propose a new technique, called SCMon, that enables continuous monitoring of the data-plane, in order to track the health of all routers and links. SCMon leverages the recently proposed Segment Routing (SR) architecture to monitor the entire network with a single box (and no additional monitoring protocol). In particular, SCMon uses SR to (i) force monitoring probes to travel over cycles; and (ii) test parallel links and bundles at a per-link granularity. We present original algorithms to compute cycles that cover all network links with a limited number of SR segments. Further, we prototype and evaluate SCMon both with simulations and Linux-based emulations. Our experiments show that SCMon quickly detects and precisely pinpoints data-plane problems, with a limited overhead.
---
paper_title: Network service chaining using segment routing in multi-layer networks

paper_content:

Network service chaining, originally conceived in the network function virtualization (NFV) framework for software defined networks (SDN), is becoming an attractive solution for enabling service differentiation enforcement to microflows generated by data centers, 5G fronthaul and Internet of Things (IoT) cloud/fog nodes, and traversing a metro-core network. However, the current IP/MPLS-over optical multi-layer network is practically unable to provide such service chain enforcement. First, MPLS granularity prevents microflows from being conveyed in dedicated paths. Second, service configuration for a huge number of selected flows with different requirements is prone to scalability concerns, even considering the deployment of a SDN network. In this paper, effective service chaining enforcement along traffic engineered (TE) paths is proposed using segment routing and extended traffic steering mechanisms for mapping micro-flows. The proposed control architecture is based on an extended SDN controller encompassing a stateful path computation element (PCE) handling microflow computation and placement supporting service chains, whereas segment routing allows automatic service enforcement without the need for continuous configuration of the service node. The proposed solution is experimentally evaluated in segment routing over an elastic optical network (EON) network testbed with a deep packet inspection service supporting dynamic and automatic flow enforcement using Border Gateway Protocol with Flow Specification (BGP Flowspec) and OpenFlow protocols as alternative traffic steering enablers. Scalability of flow computation, placement, and steering are also evaluated showing the effectiveness of the proposed solution.
---
paper_title: Translating Traffic Engineering outcome into Segment Routing paths: The Encoding problem

paper_content:

Traffic Engineering (TE) algorithms aims at determining the packet routing paths in order to satisfy specific QoS requirements. These paths are normally established through control procedures e.g., exchange of RSVP messages in MPLS networks or links weights modification in pure IP networks. An increase of control traffic or long convergence time intervals, respectively, are the drawbacks of these solutions. Segment Routing (SR) is a new network paradigm able to implement TE routing strategies over legacy IP/MPLS networks with no need of dedicated signaling procedures. This result is obtained by inserting in each packet header an ordered list of instructions, called Segments List, that indicates the path to be crossed. This paper provides the formulation of the Segment List Encoding problem i.e., the detection of the proper Segment Lists to obtain TE network paths minimizing the Segment Lists sizes. The SL encoding procedure is composed of two steps: i) the creation of an auxiliary graph representing the forwarding paths between the couple of source and destination nodes; ii) the solution of a Multi-commodity Flow (MCF) problem over the auxiliary graph. The performance evaluation shows that properly performing SL encoding allows to implement TE outcome with a reduced reconfiguration cost with respect to E2E tunneling and Hop-by-Hop solutions; moreover a significant advantage in terms of packets overhead is obtained.
---
paper_title: SDN and PCE implementations for segment routing

paper_content:

Segment Routing (SR) technology has been proposed to enforce effective routing strategies without relying on signaling protocols. In this paper, two SR implementations are presented and successfully demonstrated in two different network testbeds. The first implementation focuses on a software defined networking (SDN) scenario where nodes consist of OpenFlow switches and the SR Controller is a specifically designed enhanced version of an OpenFlow Controller. The second implementation includes a novel Path Computation Element (PCE) scenario where nodes consist of commercially available IP/MPLS routers and the SR Controller is a new extended version of a PCE solution. Both implementations have been successfully applied to demonstrate dynamic traffic rerouting. In particular, by enforcing different segment list configurations at the ingress node, rerouting is effectively achieved with no packet loss and without requiring the use of signaling protocols.
---
paper_title: A SDN-based network architecture for cloud resiliency

paper_content:

In spite of their commercial success, Cloud services are still subject to two major weak points: data security and infrastructure resiliency. In this paper, we propose an original Cloud network architecture aiming at improving the resiliency of Cloud network infrastructures interconnecting remote datacenters. The main originality of this architecture consists in exploiting the principles of Software Defined Networking (SDN) in order to adapt the rerouting strategies in case of network failure according to a set of requirements. In existing Cloud networks configurations, network recovery after a fiber cut is achieved by means of the usage of redundant bandwidth capacity preplanned through backup links. Such an approach has two drawbacks. First, it induces at a large scale a non-negligible additional cost for the Cloud Service Providers (CSP). Second, the pre-computation of the rerouting strategy may not be suited to the specific quality of service requirements of the various data flows that were transiting on the failing link. To prevent these two drawbacks, we propose that CSPs deploy their services in several redundant datacenters and make sure that those datacenters are properly interconnected via the Internet. For that purpose, we propose that a CSP may use the services of multiple (typically two) Internet Service Providers to interconnect its datacenters via the Internet. In practice, we propose that a set of “routing inflection points” may form an overlay network exploiting a specific routing strategy. We propose that this overlay is coordinated by a Software Defined Networking-based centralized controller. Thus, such a CSP may choose the network path between two datacenters the most suited to the underlying traffic QoS requirement. The proposed approach enables this CSP a certain independency from its network providers. In this paper, we present this new Cloud architecture. We outline how our approach mixes concepts taken from both SDN and Segment Routing. Unlike the protection techniques used by existing CSPs, we explain how this approach can be used to implement fast rerouting strategy for inter-datacenter data exchanges.
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paper_title: Label encoding algorithm for MPLS Segment Routing

paper_content:

Segment Routing is a new architecture that leverages the source routing mechanism to enhance packet forwarding in networks. It is designed to operate over either an MPLS (SR-MPLS) or an IPv6 control plane. SR-MPLS encodes a path as a stack of labels inserted in the packet header by the ingress node. This overhead may violate the Maximum SID Depth (MSD), the equipment hardware limitation which indicates the maximum number of labels an ingress node can push onto the packet header. Currently, the MSD varies from 3 to 5 depending on the equipment manufacturer. Therefore, the MSD value considerably limits the number of paths that can be implemented with SR-MPLS, leading to an inefficient network resource utilization and possibly to congestion. We propose and analyze SR-LEA, an algorithm for an efficient path label encoding that takes advantage of the existing IGP shortest paths in the network. The output of SR-LEA is the minimum label stack to express SR-MPLS paths according to the MSD constraint. Therefore, SR-LEA substantially slackens the impact of MSD and restores the path diversity that MSD forbids in the network.
---
paper_title: Optimizing Segment Routing With the Maximum SLD Constraint Using Openflow

paper_content:

Segment routing is an emerging routing technology that was initially driven by commercial vendors to achieve scalable, flexible, and controllable routing. In segment routing, multiple multi-protocol label switch labels are stacked in the packet header to complete end-to-end transmission, which may lead to a large label stack and a long packet header. Thus, scalability issues may occur when segment routing is applied to large-scale networks. To address this issue, multiple mechanisms and algorithms have been proposed for minimizing the label stack size. However, we argue that these methods ignore the constraint on the maximum segment list depth (SLD), since the typical network equipment can currently only support three to five layers of labels. In this paper, we study segment routing with the maximum SLD constraint and demonstrate that issues, such as explosive increases in the size of the label space and the management overheads will arise when the maximum SLD constraint is imposed. To address these issues, we make contributions from two main aspects. First, based on the network programmability that is provided by openflow, a novel segment routing architecture with improved data plane is proposed that reduces the overhead of additional flow entries and label space. Second, a new path encoding scheme is designed to minimize the SLD under the given maximum constraint, while taking multiple types of overhead into consideration. Moreover, we also perform simulations under different scenarios to evaluate the performances of the proposed algorithms. The simulation results demonstrate that the proposed mechanisms and algorithms can address the issues of segment routing when there is a constraint on the maximum SLD.
---
paper_title: Segment routing in hybrid software-defined networking

paper_content:

Software-defined networking (SDN) decouples the network into different layers, bringing many new attributes over traditional network. But SDN also comes with its own set of challenges and limitations. Combining the mature traditional network with new benefits of SDN, hybrid SDN has attracted significant attention. On the other hand, segment routing keeps partial routing information within packet header so that switch can directly dispatch without calculate routing path or looking flow entry table. In this paper, we first propose a mechanism which integrates segment routing into hybrid SDN that can reduce the needs of flow entries of SDN switch. Then we formulate a routing algorithm for this mechanism. Our algorithm considers the balance of traffic load and reduces the needs of flow entries in each switch. Simulation results show that the performance of our mechanism significantly reduces the number of flow entries than compared solution, and achieves better load balance compared with previous routing protocols.
---
paper_title: Exploring various use cases for IPv6 Segment Routing

paper_content:

IPv6 Segment Routing (SRv6) is a modern version of source routing that is being standardised within the IETF to address a variety of use cases in ISP, datacenter and entreprise networks. Its inclusion in recent versions of the Linux kernel enables researchers to explore and extend this new protocol. We leverage and extend the SRv6 implementation in the Linux kernel to demonstrate two very different usages of this new protocol. We first show how entreprise networks can leverage SRv6 to better control the utilisation of their infrastructure and demonstrate how DNS resolvers can act as SDN controllers. We then demonstrate how SRv6Pipes can be used to efficiently implement network functions that need to process bytestreams on top of a packet-based SRv6 network.
---
paper_title: Implementation of virtual network function chaining through segment routing in a linux-based NFV infrastructure

paper_content:

This paper presents an architecture to support Vir- tual Network Functions (VNFs) chaining using the IPv6 Segment Routing (SR) network programming model. Two classes of VNFs are considered: SR-aware and SR-unaware. The operations to support both SR-aware and SR-unaware VNFs are described at an architectural level and we propose a solution for SR-unaware VNFs hosted in a NFV node. An Open Source implementation of the proposed solution for a Linux based NFV host is available and a set of performance measurements have been carried out in a testbed.
---
paper_title: SERA: SEgment Routing Aware Firewall for Service Function Chaining scenarios

paper_content:

In this paper we consider the use of IPv6 Segment Routing (SRv6) for Service Function Chaining (SFC) in an NFV infrastructure. We first analyze the issues of deploying Virtual Network Functions (VNFs) based on SR-unaware applications, which require the introduction of SR proxies in the NFV infrastructure, leading to high complexity in the configuration and in the packet processing. Then we consider the advantages of SR-aware applications, focusing on a firewall application. We present the design and implementation of the SERA (SEgment Routing Aware) firewall, which extends the Linux iptables firewall. In its basic mode the SERA firewall works like the legacy iptables firewall (it can reuse an identical set of rules), but with the great advantage that it can operate on the SR encapsulated packets with no need of an SR proxy. Moreover we define an advanced mode, in which the SERA firewall can inspect all the fields of an SR encapsulated packet and can perform SR-specific actions. In the advanced mode the SERA firewall can fully exploit the features of the IPv6 Segment Routing network programming model. A performance evaluation of the SERA firewall is discussed, based on its result a further optimized prototype has been implemented and evaluated.
---
paper_title: Efficient label encoding in segment-routing enabled optical networks

paper_content:

The currently standardized GMPLS protocol suite for packet over optical networks relies on hierarchical instances of signaling sessions. Such sessions have to be established and maintained also in transit nodes, leading to complex and weighty control plane implementations. A novel technology called Segment Routing (SR) has been recently proposed to address these issues. SR relies on the source routing paradigm to provide traffic engineering solutions. In particular, the computed route for a given request is expressed as a segment list applied as an header to data packets at the ingress node. Specific algorithms are then required to perform the path computation and express the computed path through an effective segment list encoding (i.e., label stack), minimizing the segment list depth (SLD) (i.e., the number of labels included in the segment list). So far, no algorithms have been proposed to jointly provide path and segment list computation in SR-based networks. In this study, an efficient segment list encoding algorithm is proposed, guaranteeing optimal path computation and limited SLD in SR-based networks. The algorithm also accounts for equal-cost multiple paths and multiple constraints. The proposed algorithm is successfully applied to different network scenarios, demonstrating its flexibility in several use cases and showing effective performance in terms of segment list depth and introduced packet overhead.
---
paper_title: SRLB: The Power of Choices in Load Balancing with Segment Routing

paper_content:

Network load-balancers generally either do not take application state into account, or do so at the cost of a centralized monitoring system. This paper introduces a load-balancer running exclusively within the IP forwarding plane, i.e. in an application protocol agnostic fashion - yet which still provides application-awareness and makes real-time, decentralized decisions. To that end, IPv6 Segment Routing is used to direct data packets from a new flow through a chain of candidate servers, until one decides to accept the connection, based on its local state. This way, applications themselves naturally decide on how to share incoming connections, while incurring minimal network overhead, and no out-of-band signaling. Tests on different workloads - including realistic workloads such as replaying actual Wikipedia access traffic towards a set of replica Wikipedia instances - show significant performance benefits, in terms of shorter response times, when compared to a traditional random load-balancer.
---
paper_title: A Content-aware Data-plane for Efficient And Scalable Video Delivery

paper_content:

Internet users consume increasing quantities of video content with higher Quality of Experience (QoE) expectations. Network scalability thus becomes a critical problem for video delivery as traditional Content Delivery Networks (CDN) struggle to cope with the demand. In particular, content-awareness has been touted as a tool for scaling CDNs through clever request and content placement. Building on that insight, we propose a network paradigm that provides application-awareness in the network layer, enabling the offload of CDN decisions to the data-plane. Namely, it uses chunk-level identifiers encoded into IPv6 addresses. These identifiers are used to perform network-layer cache admission by estimating the popularity of requests with a Least-Recently-Used (LRU) filter. Popular requests are then served from the edge cache, while unpopular requests are directly redirected to the origin server, circumventing the HTTP proxy. The parameters of the filter are optimized through analytical modeling and validated via both simulation and experimentation with a testbed featuring real cache servers. It yields improvements in QoE while decreasing the hardware requirements on the edge cache. Specifically, for a typical content distribution, our evaluation shows a 22% increase of the hit rate, a 36% decrease of the chunk download-time, and a 37% decrease of the cache server CPU load.
---
paper_title: SRv6Pipes: enabling in-network bytestream functions

paper_content:

IPv6 Segment Routing is a recent IPv6 extension that is generating a lot of interest among researchers and in industry. Thanks to IPv6 SR, network operators can better control the paths followed by packets inside their networks. This provides enhanced traffic engineering capabilities and is key to support Service Function Chaining (SFC). With SFC, an end-to-end service is the composition of a series of in-network services. Simple services such as NAT, accounting or stateless firewalls can be implemented on a per-packet basis. However, more interesting services like transparent proxies, transparent compression or encryption, transcoding, etc. require functions that operate on the bytestream.In this paper, we extend the IPv6 implementation of Segment Routing in the Linux kernel to enable network functions that operate on the bytestream and not on a per-packet basis. Our SRv6Pipes enable network architects to design end-to-end services as a series of in-network functions. We evaluate the performance of our implementation with different microbenchmarks.
---
paper_title: PMSR - Poor Man's Segment Routing, a minimalistic approach to Segment Routing and a Traffic Engineering use case

paper_content:

The current specification of the Segment Routing (SR) architecture requires enhancements to the intradomain routing protocols (e.g. OSPF and IS-IS) so that the nodes can advertise the Segment Identifiers (SIDs). We propose a simpler solution called PMSR (Poor Man's Segment Routing), that does not require any enhancement to routing protocol. We compare the procedures of PMSR with traditional SR, showing that PMSR can reduce the operation and management complexity. We analyze the set of use cases in the current SR drafts and we claim that PMSR can support the large majority of them. Thanks to the drastic simplification of the control plane, we have been able to develop an open source prototype of PMSR. In the second part of the paper, we consider a Traffic Engineering use case, starting from a traditional flow assignment optimization problem, which allocates hop-by-hop paths to flows. We propose a SR path assignment algorithm and prove that it is optimal with respect to the number of segments allocated to a flow.
---
paper_title: Translating Traffic Engineering outcome into Segment Routing paths: The Encoding problem

paper_content:

Traffic Engineering (TE) algorithms aims at determining the packet routing paths in order to satisfy specific QoS requirements. These paths are normally established through control procedures e.g., exchange of RSVP messages in MPLS networks or links weights modification in pure IP networks. An increase of control traffic or long convergence time intervals, respectively, are the drawbacks of these solutions. Segment Routing (SR) is a new network paradigm able to implement TE routing strategies over legacy IP/MPLS networks with no need of dedicated signaling procedures. This result is obtained by inserting in each packet header an ordered list of instructions, called Segments List, that indicates the path to be crossed. This paper provides the formulation of the Segment List Encoding problem i.e., the detection of the proper Segment Lists to obtain TE network paths minimizing the Segment Lists sizes. The SL encoding procedure is composed of two steps: i) the creation of an auxiliary graph representing the forwarding paths between the couple of source and destination nodes; ii) the solution of a Multi-commodity Flow (MCF) problem over the auxiliary graph. The performance evaluation shows that properly performing SL encoding allows to implement TE outcome with a reduced reconfiguration cost with respect to E2E tunneling and Hop-by-Hop solutions; moreover a significant advantage in terms of packets overhead is obtained.
---
paper_title: An Efficient Linux Kernel Implementation of Service Function Chaining for Legacy VNFs Based on IPv6 Segment Routing

paper_content:

We consider the IPv6 Segment Routing (SRv6) technology for Service Function Chaining of Virtual Network Functions (VNFs). Most of the VNFs are legacy VNFs (not aware of the SRv6 technology) and expect to process traditional IP packets. An SR proxy is needed to support them. We have extended the implementation of SRv6 in the Linux kernel, realizing an open source SR-proxy, referred to as SRNK (SR-Proxy Native Kernel). The performance of the proposed solution (SRNKvl) has been evaluated, identifying a poor scalability with respect to the number of VNFs to be supported in a node. Therefore we provided a second design (SRNKv2), enhancing the Linux Policy Routing framework. The performance of SRNKv2 is independent from the number of supported VNFs in a node. We compared the performance of SRNKv2 with a reference scenario not performing the encapsulation and decapsulation operation and demonstrated that the overhead of SRNKv2 is very small, on the order of 3.5%.
---
paper_title: Label encoding algorithm for MPLS Segment Routing

paper_content:

Segment Routing is a new architecture that leverages the source routing mechanism to enhance packet forwarding in networks. It is designed to operate over either an MPLS (SR-MPLS) or an IPv6 control plane. SR-MPLS encodes a path as a stack of labels inserted in the packet header by the ingress node. This overhead may violate the Maximum SID Depth (MSD), the equipment hardware limitation which indicates the maximum number of labels an ingress node can push onto the packet header. Currently, the MSD varies from 3 to 5 depending on the equipment manufacturer. Therefore, the MSD value considerably limits the number of paths that can be implemented with SR-MPLS, leading to an inefficient network resource utilization and possibly to congestion. We propose and analyze SR-LEA, an algorithm for an efficient path label encoding that takes advantage of the existing IGP shortest paths in the network. The output of SR-LEA is the minimum label stack to express SR-MPLS paths according to the MSD constraint. Therefore, SR-LEA substantially slackens the impact of MSD and restores the path diversity that MSD forbids in the network.
---
paper_title: Optimizing Segment Routing With the Maximum SLD Constraint Using Openflow

paper_content:

Segment routing is an emerging routing technology that was initially driven by commercial vendors to achieve scalable, flexible, and controllable routing. In segment routing, multiple multi-protocol label switch labels are stacked in the packet header to complete end-to-end transmission, which may lead to a large label stack and a long packet header. Thus, scalability issues may occur when segment routing is applied to large-scale networks. To address this issue, multiple mechanisms and algorithms have been proposed for minimizing the label stack size. However, we argue that these methods ignore the constraint on the maximum segment list depth (SLD), since the typical network equipment can currently only support three to five layers of labels. In this paper, we study segment routing with the maximum SLD constraint and demonstrate that issues, such as explosive increases in the size of the label space and the management overheads will arise when the maximum SLD constraint is imposed. To address these issues, we make contributions from two main aspects. First, based on the network programmability that is provided by openflow, a novel segment routing architecture with improved data plane is proposed that reduces the overhead of additional flow entries and label space. Second, a new path encoding scheme is designed to minimize the SLD under the given maximum constraint, while taking multiple types of overhead into consideration. Moreover, we also perform simulations under different scenarios to evaluate the performances of the proposed algorithms. The simulation results demonstrate that the proposed mechanisms and algorithms can address the issues of segment routing when there is a constraint on the maximum SLD.
---
paper_title: Zero-Loss Virtual Machine Migration with IPv6 Segment Routing

paper_content:

With the development of large-scale data centers, Virtual Machine (VM) migration is a key component for resource optimization, cost reduction, and maintenance. From a network perspective, traditional VM migration mechanisms rely on the hypervisor running at the destination host advertising the new location of the VM once migration is complete. However, this creates a period of time during which the VM is not reachable, yielding packet loss.This paper introduces a method to perform zero-loss VM migration by using IPv6 Segment Routing (SR). Rather than letting the hypervisor update a locator mapping after VM migration is complete, a logical path consisting of the source and destination hosts is pre-provisioned. Packets destined to the migrating VM are sent through this path using SR, shortly before, during, and shortly after migration - the virtual router on the source host being in charge of forwarding packets locally if the VM migration has not completed yet, or to the destination host otherwise. The proposed mechanism is implemented as a VPP plugin, and feasibility of zero-loss VM migration is demonstrated with various workloads. Evaluation shows that this yields benefits in terms of session opening latency and TCP throughput.
---
paper_title: A Linux kernel implementation of Segment Routing with IPv6

paper_content:

Network operators seek more flexibility to provide added-value services to their customers. We propose to leverage the IPv6 Segment Routing architecture with a example usecase. We also provide an implementation of SR-IPv6 and we evaluate its performance on broadband routers.
---
paper_title: Implementation of virtual network function chaining through segment routing in a linux-based NFV infrastructure

paper_content:

This paper presents an architecture to support Vir- tual Network Functions (VNFs) chaining using the IPv6 Segment Routing (SR) network programming model. Two classes of VNFs are considered: SR-aware and SR-unaware. The operations to support both SR-aware and SR-unaware VNFs are described at an architectural level and we propose a solution for SR-unaware VNFs hosted in a NFV node. An Open Source implementation of the proposed solution for a Linux based NFV host is available and a set of performance measurements have been carried out in a testbed.
---
paper_title: SERA: SEgment Routing Aware Firewall for Service Function Chaining scenarios

paper_content:

In this paper we consider the use of IPv6 Segment Routing (SRv6) for Service Function Chaining (SFC) in an NFV infrastructure. We first analyze the issues of deploying Virtual Network Functions (VNFs) based on SR-unaware applications, which require the introduction of SR proxies in the NFV infrastructure, leading to high complexity in the configuration and in the packet processing. Then we consider the advantages of SR-aware applications, focusing on a firewall application. We present the design and implementation of the SERA (SEgment Routing Aware) firewall, which extends the Linux iptables firewall. In its basic mode the SERA firewall works like the legacy iptables firewall (it can reuse an identical set of rules), but with the great advantage that it can operate on the SR encapsulated packets with no need of an SR proxy. Moreover we define an advanced mode, in which the SERA firewall can inspect all the fields of an SR encapsulated packet and can perform SR-specific actions. In the advanced mode the SERA firewall can fully exploit the features of the IPv6 Segment Routing network programming model. A performance evaluation of the SERA firewall is discussed, based on its result a further optimized prototype has been implemented and evaluated.
---
paper_title: SRLB: The Power of Choices in Load Balancing with Segment Routing

paper_content:

Network load-balancers generally either do not take application state into account, or do so at the cost of a centralized monitoring system. This paper introduces a load-balancer running exclusively within the IP forwarding plane, i.e. in an application protocol agnostic fashion - yet which still provides application-awareness and makes real-time, decentralized decisions. To that end, IPv6 Segment Routing is used to direct data packets from a new flow through a chain of candidate servers, until one decides to accept the connection, based on its local state. This way, applications themselves naturally decide on how to share incoming connections, while incurring minimal network overhead, and no out-of-band signaling. Tests on different workloads - including realistic workloads such as replaying actual Wikipedia access traffic towards a set of replica Wikipedia instances - show significant performance benefits, in terms of shorter response times, when compared to a traditional random load-balancer.
---
paper_title: SRv6Pipes: enabling in-network bytestream functions

paper_content:

IPv6 Segment Routing is a recent IPv6 extension that is generating a lot of interest among researchers and in industry. Thanks to IPv6 SR, network operators can better control the paths followed by packets inside their networks. This provides enhanced traffic engineering capabilities and is key to support Service Function Chaining (SFC). With SFC, an end-to-end service is the composition of a series of in-network services. Simple services such as NAT, accounting or stateless firewalls can be implemented on a per-packet basis. However, more interesting services like transparent proxies, transparent compression or encryption, transcoding, etc. require functions that operate on the bytestream.In this paper, we extend the IPv6 implementation of Segment Routing in the Linux kernel to enable network functions that operate on the bytestream and not on a per-packet basis. Our SRv6Pipes enable network architects to design end-to-end services as a series of in-network functions. We evaluate the performance of our implementation with different microbenchmarks.
---
paper_title: Leveraging IPv6 Segment Routing for Service Function Chaining

paper_content:

Network operators seek more flexibility with solutions like Network Function Virtualization and Service Function Chain- ing (SFC). Thanks to these techniques operators can define on-the-fly which services have to be applied to which pack- ets. We propose to use IPv6 Segment Routing to support SFC and describe and evaluate the performance of our im- plementation in the Linux kernel.
---
paper_title: An Efficient Linux Kernel Implementation of Service Function Chaining for Legacy VNFs Based on IPv6 Segment Routing

paper_content:

We consider the IPv6 Segment Routing (SRv6) technology for Service Function Chaining of Virtual Network Functions (VNFs). Most of the VNFs are legacy VNFs (not aware of the SRv6 technology) and expect to process traditional IP packets. An SR proxy is needed to support them. We have extended the implementation of SRv6 in the Linux kernel, realizing an open source SR-proxy, referred to as SRNK (SR-Proxy Native Kernel). The performance of the proposed solution (SRNKvl) has been evaluated, identifying a poor scalability with respect to the number of VNFs to be supported in a node. Therefore we provided a second design (SRNKv2), enhancing the Linux Policy Routing framework. The performance of SRNKv2 is independent from the number of supported VNFs in a node. We compared the performance of SRNKv2 with a reference scenario not performing the encapsulation and decapsulation operation and demonstrated that the overhead of SRNKv2 is very small, on the order of 3.5%.
---
paper_title: Zero-Loss Virtual Machine Migration with IPv6 Segment Routing

paper_content:

With the development of large-scale data centers, Virtual Machine (VM) migration is a key component for resource optimization, cost reduction, and maintenance. From a network perspective, traditional VM migration mechanisms rely on the hypervisor running at the destination host advertising the new location of the VM once migration is complete. However, this creates a period of time during which the VM is not reachable, yielding packet loss.This paper introduces a method to perform zero-loss VM migration by using IPv6 Segment Routing (SR). Rather than letting the hypervisor update a locator mapping after VM migration is complete, a logical path consisting of the source and destination hosts is pre-provisioned. Packets destined to the migrating VM are sent through this path using SR, shortly before, during, and shortly after migration - the virtual router on the source host being in charge of forwarding packets locally if the VM migration has not completed yet, or to the destination host otherwise. The proposed mechanism is implemented as a VPP plugin, and feasibility of zero-loss VM migration is demonstrated with various workloads. Evaluation shows that this yields benefits in terms of session opening latency and TCP throughput.
---
paper_title: Implementing IPv6 Segment Routing in the Linux Kernel

paper_content:

IPv6 Segment Routing is a major IPv6 extension that provides a modern version of source routing that is currently being developed within the Internet Engineering Task Force (IETF). We propose the first open-source implementation of IPv6 Segment Routing in the Linux kernel. We first describe it in details and explain how it can be used on both endhosts and routers. We then evaluate and compare its performance with plain IPv6 packet forwarding in a lab environment. Our measurements indicate that the performance penalty of inserting IPv6 Segment Routing Headers or encapsulating packets is limited to less than 15%. On the other hand, the optional HMAC security feature of IPv6 Segment Routing is costly in a pure software implementation. Since our implementation has been included in the official Linux 4.10 kernel, we expect that it will be extended by other researchers for new use cases.
---
paper_title: Field trial of a software defined network (SDN) using carrier Ethernet and segment routing in a tier-1 provider

paper_content:

Software Defined Networking (SDN) has brought a paradigmatic shift in the networking industry and has led to significant benefits in the data-center and enterprise network domains. The service provider networks that form the largest segment of networking industry, are now evaluating SDN technologies for adoption. In this paper, we present a SDN framework for service provider networks and report the first field trial of SDN in a tier-1 service provider domain. The proposed SDN framework is built using Carrier Ethernet and augmented with recently proposed Segment Routing paradigm manifested through Software Defined-Carrier Ethernet Switch Routers (SD-CESRs). Carrier Ethernet on account of its distinct, programmable control plane and Segment Routing through its source routing capabilities facilitates SDN implementation. The SD-CESRs are deployed in a tier-1 service provider network in the metropolis of Mumbai. The SDN framework is extended through specific APIs to enhance revenue bearing services portfolio of the service provider and performance results from the field are shown to validate the benefits of SDN adoption.
---
paper_title: Control Exchange Points: Providing QoS-enabled End-to-End Services via SDN-based Inter-domain Routing Orchestration

paper_content:

Introduction. This paper presents the vision of the Control Exchange Point (CXP) architectural model. The model is motivated by the inflexibility and ossification of today’s inter-domain routing system, which renders critical QoS-constrained end-toend (e2e) network services difficult or simply impossible to provide. CXPs operate on slices of ISP networks and are built on basic Software Defined Networking (SDN) principles, such as the clean decoupling of the routing control plane from the data plane and the consequent logical centralization of control. The main goal of the architectural model is to provide e2e services with QoS constraints across domains. This is achieved through defining a new type of business relationship between ISPs, which advertise partial paths (so-called pathlets [7]) with specific properties, and the orchestrating role of the CXPs, which dynamically stitch them together and provision e2e QoS. Revenue from value-added services flows from the clients of the CXP to the ISPs participating in the service. The novelty of the approach is the combination of SDN programmability and dynamic path stitching techniques for inter-domain routing, which extends the value proposition of SDN over multiple domains. We first describe the challenges related to e2e service provision with the current inter-domain routing and peering model, and then continue with the benefits of our approach. Subsequently, we describe the CXP model in detail and report on an initial feasibility analysis. Motivation and Challenges. Complexity and ossification: The notorious complexity of the inter-domain routing system renders its management difficult and error-prone, leading to various inefficiencies such as suboptimal inter-domain paths. Indicatively, 60% of all Internet paths today are suffering from triangle inequality violations [9]. The current ossification of the system, hindering the introduction of new solutions, aggravates the problem further. Highly popular inter-domain services, such as highdefinition e2e real-time video streaming, already test the limits of the status quo, or are simply impossible. This is because such services require tight coordination along entire chains of ISPs demanding QoS provisioning. More advanced and mission-critical services, such as telemedical applications, are usually out of the question.
---
paper_title: IPv6 Segment Routing Header (SRH)

paper_content:

Segment Routing can be applied to the IPv6 data plane using a new type ::: of Routing Extension Header called the Segment Routing Header. This ::: document describes the Segment Routing Header and how it is used by ::: Segment Routing capable nodes.
---
paper_title: Performance of IPv6 Segment Routing in Linux Kernel

paper_content:

IPv6 Segment Routing (SRv6) is a promising solution to support advanced services such as Traffic Engineering, Service Function Chaining, Virtual Private Networks, and Load Balancing. The SRv6 data-plane is supported in many different forwarding engines including the Linux kernel. It has been introduced into the 4.10 release of the Linux kernel to support both endhost and router functionalities. The implementation has been updated several times, with every new kernel release, to include new features and also to improve the performance of existing ones. In this paper, we present SRPerf, a performance evaluation framework for software and hardware implementations of SRv6. SRPerf is able to perform different benchmarking tests such as throughput and latency. The architecture of SRPerf can be easily extended to support new benchmarking methodologies as well as different SRv6 implementations. We have used SRPerf to evaluate the performance of the SRv6 implementation in the Linux kernel.
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paper_title: Segment Routing IPv6 for Mobile User Plane

paper_content:

This document shows the applicability of SRv6 (Segment Routing IPv6) ::: to the user-plane of mobile networks. The network programming nature ::: of SRv6 accomplish mobile user-plane functions in a simple manner. The ::: statelessness of SRv6 and its ability to control both service layer ::: path and underlying transport can be beneficial to the mobile user- ::: plane, providing flexibility, end-to-end network slicing and SLA ::: control for various applications. This document describes the SRv6 ::: mobile user plane behavior and defines the SID functions for that.
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paper_title: SERA: SEgment Routing Aware Firewall for Service Function Chaining scenarios

paper_content:

In this paper we consider the use of IPv6 Segment Routing (SRv6) for Service Function Chaining (SFC) in an NFV infrastructure. We first analyze the issues of deploying Virtual Network Functions (VNFs) based on SR-unaware applications, which require the introduction of SR proxies in the NFV infrastructure, leading to high complexity in the configuration and in the packet processing. Then we consider the advantages of SR-aware applications, focusing on a firewall application. We present the design and implementation of the SERA (SEgment Routing Aware) firewall, which extends the Linux iptables firewall. In its basic mode the SERA firewall works like the legacy iptables firewall (it can reuse an identical set of rules), but with the great advantage that it can operate on the SR encapsulated packets with no need of an SR proxy. Moreover we define an advanced mode, in which the SERA firewall can inspect all the fields of an SR encapsulated packet and can perform SR-specific actions. In the advanced mode the SERA firewall can fully exploit the features of the IPv6 Segment Routing network programming model. A performance evaluation of the SERA firewall is discussed, based on its result a further optimized prototype has been implemented and evaluated.
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paper_title: Flexible failure detection and fast reroute using eBPF and SRv6

paper_content:

Segment Routing is a modern variant of source routing that is being gradually deployed by network operators. Large ISPs use it for traffic engineering and fast reroute purposes. Its IPv6 dataplane, named SRv6, goes beyond the initial MPLS dataplane, notably by enabling network programmability. With SRv6, it becomes possible to define transparent network functions on routers and endhosts. These functions are mapped to IPv6 addresses and their execution is scheduled by segments placed in the forwarded packets. We have recently extended the Linux SRv6 implementation to enable the execution of specific eBPF code upon reception of an SRv6 packet containing local segments. eBPF is a virtual machine that is included in the Linux kernel. We leverage this new feature of Linux 4.18 to propose and implement flexible eBPF-based fast-reroute and failure detection schemes. Our lab measurements confirm that they provide good performance and enable faster failure detections than existing BFD implementations on Linux routers and servers.
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paper_title: Leveraging eBPF for programmable network functions with IPv6 Segment Routing

paper_content:

With the advent of Software Defined Networks (SDN), Network Function Virtualisation (NFV) or Service Function Chaining (SFC), operators expect networks to support flexible services beyond the mere forwarding of packets. The network programmability framework which is being developed within the IETF by leveraging IPv6 Segment Routing enables the realisation of in-network functions. In this paper, we demonstrate that this vision of in-network programmability can be realised. By leveraging the eBPF support in the Linux kernel, we implement a flexible framework that allows network operators to encode their own network functions as eBPF code that is automatically executed while processing specific packets. Our lab measurements indicate that the overhead of calling such eBPF functions remains acceptable. Thanks to eBPF, operators can implement a variety of network functions. We describe the architecture of our implementation in the Linux kernel. This extension has been released with Linux 4.18. We illustrate the flexibility of our approach with three different use cases: delay measurements, hybrid networks and network discovery. Our lab measurements also indicate that the performance penalty of running eBPF network functions on Linux routers does not incur a significant overhead.
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paper_title: Implementing IPv6 Segment Routing in the Linux Kernel

paper_content:

IPv6 Segment Routing is a major IPv6 extension that provides a modern version of source routing that is currently being developed within the Internet Engineering Task Force (IETF). We propose the first open-source implementation of IPv6 Segment Routing in the Linux kernel. We first describe it in details and explain how it can be used on both endhosts and routers. We then evaluate and compare its performance with plain IPv6 packet forwarding in a lab environment. Our measurements indicate that the performance penalty of inserting IPv6 Segment Routing Headers or encapsulating packets is limited to less than 15%. On the other hand, the optional HMAC security feature of IPv6 Segment Routing is costly in a pure software implementation. Since our implementation has been included in the official Linux 4.10 kernel, we expect that it will be extended by other researchers for new use cases.
---
paper_title: Implementation of virtual network function chaining through segment routing in a linux-based NFV infrastructure

paper_content:

This paper presents an architecture to support Vir- tual Network Functions (VNFs) chaining using the IPv6 Segment Routing (SR) network programming model. Two classes of VNFs are considered: SR-aware and SR-unaware. The operations to support both SR-aware and SR-unaware VNFs are described at an architectural level and we propose a solution for SR-unaware VNFs hosted in a NFV node. An Open Source implementation of the proposed solution for a Linux based NFV host is available and a set of performance measurements have been carried out in a testbed.
---
paper_title: Software Resolved Networks: Rethinking Enterprise Networks with IPv6 Segment Routing

paper_content:

Enterprise networks often need to implement complex policies that match business objectives. They will embrace IPv6 like ISP networks in the coming years. Among the benefits of IPv6, the recently proposed IPv6 Segment Routing (SRv6) architecture supports richer policies in a clean manner. This matches very well the requirements of enterprise networks. In this paper, we propose Software Resolved Networks (SRNs), a new architecture for IPv6 enterprise networks. We apply the fundamental principles of Software Defined Networks, i.e., the ability to control the operation of the network through software, but in a different manner that also involves the endhosts. We leverage SRv6 to enforce and control network paths according to the network policies. Those paths are computed by a centralized controller that interacts with the endhosts through the DNS protocol. We implement a Software Resolved Network on Linux endhosts, routers and controllers. Through benchmarks and simulations, we analyze the performance of those SRNs, and demonstrate that they meet the expectations of enterprise networks.
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paper_title: Hybrid IP/SDN Networking: Open Implementation and Experiment Management Tools

paper_content:

The introduction of SDN in large-scale IP provider networks is still an open issue and different solutions have been suggested so far. In this paper, we propose a hybrid approach that allows the coexistence of traditional IP routing with SDN based forwarding within the same provider domain. The solution is called OSHI—Open Source Hybrid IP/SDN networking, as we have fully implemented it combining and extending open source software. We discuss the OSHI system architecture and the design and implementation of advanced services like pseudo wires and virtual switches. In addition, we describe a set of open source management tools for the emulation of the proposed solution using either the Mininet emulator or distributed physical testbeds. We refer to this suite of tools as Mantoo (management tools). Mantoo includes an extensible Web-based graphical topology designer, which provides different layered network “views” (e.g., from physical links to service relationships among nodes). The suite can validate an input topology, automatically deploy it over a Mininet emulator or a distributed SDN testbed and allows access to emulated nodes by opening consoles in the web GUI. Mantoo provides also tools to evaluate the performance of the deployed nodes.
---
paper_title: SRv6Pipes: enabling in-network bytestream functions

paper_content:

IPv6 Segment Routing is a recent IPv6 extension that is generating a lot of interest among researchers and in industry. Thanks to IPv6 SR, network operators can better control the paths followed by packets inside their networks. This provides enhanced traffic engineering capabilities and is key to support Service Function Chaining (SFC). With SFC, an end-to-end service is the composition of a series of in-network services. Simple services such as NAT, accounting or stateless firewalls can be implemented on a per-packet basis. However, more interesting services like transparent proxies, transparent compression or encryption, transcoding, etc. require functions that operate on the bytestream.In this paper, we extend the IPv6 implementation of Segment Routing in the Linux kernel to enable network functions that operate on the bytestream and not on a per-packet basis. Our SRv6Pipes enable network architects to design end-to-end services as a series of in-network functions. We evaluate the performance of our implementation with different microbenchmarks.
---
paper_title: Mantoo - A Set of Management Tools for Controlling SDN Experiments

paper_content:

OSHI -- Open Source Hybrid IP/SDN networking is a hybrid approach allowing the coexistence of traditional IP routing with SDN based forwarding within the same provider domain. In this demo, we will show a set of Open Source management tools for the emulation of the proposed solution over the Mininet emulator and over distributed test beds. We refer to this suite of tools as Mantoo (Management tools). Mantoo includes an extensible web-based graphical topology designer providing different layered network "views" (e.g. From physical links to service relationships among nodes). The framework is able to validate a topology, to automatically deploy it over a Mininet emulator or a distributed SDN test bed, to access nodes by opening consoles directly via the web GUI.
---
paper_title: PMSR - Poor Man's Segment Routing, a minimalistic approach to Segment Routing and a Traffic Engineering use case

paper_content:

The current specification of the Segment Routing (SR) architecture requires enhancements to the intradomain routing protocols (e.g. OSPF and IS-IS) so that the nodes can advertise the Segment Identifiers (SIDs). We propose a simpler solution called PMSR (Poor Man's Segment Routing), that does not require any enhancement to routing protocol. We compare the procedures of PMSR with traditional SR, showing that PMSR can reduce the operation and management complexity. We analyze the set of use cases in the current SR drafts and we claim that PMSR can support the large majority of them. Thanks to the drastic simplification of the control plane, we have been able to develop an open source prototype of PMSR. In the second part of the paper, we consider a Traffic Engineering use case, starting from a traditional flow assignment optimization problem, which allocates hop-by-hop paths to flows. We propose a SR path assignment algorithm and prove that it is optimal with respect to the number of segments allocated to a flow.
---
paper_title: Traffic Engineering with Segment Routing: SDN-Based Architectural Design and Open Source Implementation

paper_content:

Traffic Engineering (TE) in IP carrier networks is one of the functions that can benefit from the Software Defined Networking paradigm. However traditional per-flow routing requires a direct interaction between the SDN controller and each node that is involved in the traffic paths. Segment Routing (SR) may simplify the route enforcement delegating all the configuration and per-flow state at the border of the network. In this work we propose an architecture that integrates the SDN paradigm with SR based TE, for which we have provided an open source reference implementation. We have designed and implemented a simple TE/SR heuristic for flow allocation and we show and discuss experimental results.
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paper_title: An Efficient Linux Kernel Implementation of Service Function Chaining for Legacy VNFs Based on IPv6 Segment Routing

paper_content:

We consider the IPv6 Segment Routing (SRv6) technology for Service Function Chaining of Virtual Network Functions (VNFs). Most of the VNFs are legacy VNFs (not aware of the SRv6 technology) and expect to process traditional IP packets. An SR proxy is needed to support them. We have extended the implementation of SRv6 in the Linux kernel, realizing an open source SR-proxy, referred to as SRNK (SR-Proxy Native Kernel). The performance of the proposed solution (SRNKvl) has been evaluated, identifying a poor scalability with respect to the number of VNFs to be supported in a node. Therefore we provided a second design (SRNKv2), enhancing the Linux Policy Routing framework. The performance of SRNKv2 is independent from the number of supported VNFs in a node. We compared the performance of SRNKv2 with a reference scenario not performing the encapsulation and decapsulation operation and demonstrated that the overhead of SRNKv2 is very small, on the order of 3.5%.
---
paper_title: Implementing IPv6 Segment Routing in the Linux Kernel

paper_content:

IPv6 Segment Routing is a major IPv6 extension that provides a modern version of source routing that is currently being developed within the Internet Engineering Task Force (IETF). We propose the first open-source implementation of IPv6 Segment Routing in the Linux kernel. We first describe it in details and explain how it can be used on both endhosts and routers. We then evaluate and compare its performance with plain IPv6 packet forwarding in a lab environment. Our measurements indicate that the performance penalty of inserting IPv6 Segment Routing Headers or encapsulating packets is limited to less than 15%. On the other hand, the optional HMAC security feature of IPv6 Segment Routing is costly in a pure software implementation. Since our implementation has been included in the official Linux 4.10 kernel, we expect that it will be extended by other researchers for new use cases.
---
paper_title: Exploring various use cases for IPv6 Segment Routing

paper_content:

IPv6 Segment Routing (SRv6) is a modern version of source routing that is being standardised within the IETF to address a variety of use cases in ISP, datacenter and entreprise networks. Its inclusion in recent versions of the Linux kernel enables researchers to explore and extend this new protocol. We leverage and extend the SRv6 implementation in the Linux kernel to demonstrate two very different usages of this new protocol. We first show how entreprise networks can leverage SRv6 to better control the utilisation of their infrastructure and demonstrate how DNS resolvers can act as SDN controllers. We then demonstrate how SRv6Pipes can be used to efficiently implement network functions that need to process bytestreams on top of a packet-based SRv6 network.
---
paper_title: IPv6 Segment Routing Header (SRH)

paper_content:

Segment Routing can be applied to the IPv6 data plane using a new type ::: of Routing Extension Header called the Segment Routing Header. This ::: document describes the Segment Routing Header and how it is used by ::: Segment Routing capable nodes.
---

Title: Segment Routing: a Comprehensive Survey of Research Activities, Standardization Efforts and Implementation Results

Section 1: THE SEGMENT ROUTING (SR) ARCHITECTURE
Description 1: This section includes a short introduction to the main SR architectural aspects.

Section 2: MPLS dataplane (SR-MPLS)
Description 2: This section discusses the specifics of the MPLS dataplane and how Segment Routing is implemented over MPLS.

Section 3: IPv6 dataplane (SRv6)
Description 3: This section explores the implementation of Segment Routing over IPv6, including the Segment Routing Header (SRH) and SRv6 functions.

Section 4: Control plane for SR and relation with SDN
Description 4: This section describes the control plane operations for Segment Routing, considering distributed, centralized, and hybrid approaches.

Section 5: Segment Routing motivations and use cases
Description 5: This section identifies the motivations behind Segment Routing and various use cases it addresses.

Section 6: RESEARCH ACTIVITIES
Description 6: This section provides a comprehensive review of the research activities on Segment Routing, classified into different categories.

Section 7: STANDARDIZATION ACTIVITIES
Description 7: This section describes the standardization efforts related to Segment Routing, classified into various categories.

Section 8: SR IMPLEMENTATIONS AND TOOLS
Description 8: This section outlines the implementation results related to Segment Routing, including software and hardware implementations and interoperability efforts.