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

Fixed and mobile telecom operators, enterprise network operators and cloud providers strive to face the challenging demands coming from the evolution of IP networks (e.g. huge bandwidth requirements, integration of billions of devices and millions of services in the cloud). Proposed in the early 2010s, Segment Routing (SR) architecture helps face these challenging demands, and it is currently being adopted and deployed. SR architecture is based on the concept of source routing and has interesting scalability properties, as it dramatically reduces the amount of state information to be configured in the core nodes to support complex services. SR architecture was first implemented with the MPLS dataplane and then, quite recently, with the IPv6 dataplane (SRv6). IPv6 SR architecture (SRv6) has been extended from the simple steering of packets across nodes to a general network programming approach, making it very suitable for use cases such as Service Function Chaining and Network Function Virtualization. In this paper we present a tutorial and a comprehensive survey on SR technology, analyzing standardization efforts, patents, research activities and implementation results. We start with an introduction on the motivations for Segment Routing and an overview of its evolution and standardization. Then, we provide a tutorial on Segment Routing technology, with a focus on the novel SRv6 solution. We discuss the standardization efforts and the patents providing details on the most important documents and mentioning other ongoing activities. We then thoroughly analyze research activities according to a taxonomy. We have identified 8 main categories during our analysis of the current state of play: Monitoring, Traffic Engineering, Failure Recovery, Centrally Controlled Architectures, Path Encoding, Network Programming, Performance Evaluation and Miscellaneous...Comment: SUBMITTED TO IEEE COMMUNICATIONS SURVEYS & TUTORIAL

Towards Robust Traffic Engineering in IP Networks

To deliver a reliable communication service it is essential for the network operator to manage how traffic flows in the network. The paths taken by the traffic is controlled by the routing function. Traditional ways of tuning routing in IP networks are designed to be simple to manage and are not designed to adapt to the traffic situation in the network. This can lead to congestion in parts of the network while other parts of the network is far from fully utilized. In this thesis we explore issues related to optimization of the routing function to balance load in the network. We investigate methods for efficient derivation of the traffic situation using link count measurements. The advantage of using link counts is that they are easily obtained and yield a very limited amount of data. We evaluate and show that estimation based on link counts give the operator a fast and accurate description of the traffic demands. For the evaluation we have access to a unique data set of complete traffic demands from an operational IP backbone. Furthermore, we evaluate performance of search heuristics to set weights in link-state routing protocols. For the evaluation we have access to complete traffic data from a Tier-1 IP network. Our findings confirm previous studies who use partial traffic data or synthetic traffic data. We find that optimization using estimated traffic demands has little significance to the performance of the load balancing. Finally, we device an algorithm that finds a routing setting that is robust to shifts in traffic patterns due to changes in the interdomain routing. A set of worst case scenarios caused by the interdomain routing changes is identified and used to solve a robust routing problem. The evaluation indicates that performance of the robust routing is close to optimal for a wide variety of traffic scenarios. The main contribution of this thesis is that we demonstrate that it is possible to estimate the traffic matrix with good accuracy and to develop methods that optimize the routing settings to give strong and robust network performance. Only minor changes might be necessary in order to implement our algorithms in existing networks

Towards a software defined network based multi-domain architecture for the internet of things

The current communication networks are heterogeneous, with a diversity of devices and services that challenge traditional networks, making it difficult to meet quality of service (QoS) requirements. With the advent of software-defined networks (SDN), new tools have emerged to design more flexible networks. SDN offers centralized management for data streams in distributed sensor networks. Thus, the main goal of this dissertation is to investigate a solution that meets the QoS requirements of traffic originating on Internet of Things (IoT) devices. This traffic is transmitted to the Internet in a distributed system with multiple SDN controllers. To achieve the goal, we designed a multi-controller network topology, each managed by its controller. Communication between the domains is done via an SDN traffic domain with the Open Network Operating System (ONOS) controller SDN-IP application. We also emulated a network to test QoS through OpenvSwitch queues. The goal is to create traffic priorities in a network with traditional and simulated IoT devices. According to our tests, we have been able to ensure the SDN inter-domain communication and have proven that our proposal is reactive to a topology failure. In the QoS scenario we have shown that through the insertion of OpenFlow rules, we are able to prioritize traffic and provide guarantees of quality of service. This proves that our proposal is promising for use in scenarios with multiple administrative domains.As redes atuais de comunicação são heterogéneas, com uma diversidade de dispositivos e serviços, que desafiam as redes tradicionais, dificultando a satisfação dos requisitos de qualidade de serviço (QoS). Com o advento das Redes Definidas por Software (SDN), novas ferramentas surgiram para projetar redes mais flexíveis. O SDN oferece uma gestão centralizada para os fluxos de dados em redes distribuídas de sensores. Assim, o principal objetivo desta dissertação é de investigar uma solução que cumpra os requisitos de QoS do tráfego originado em dispositivos de Internet das coisas (IoT). Este tráfego é transmitido para a Internet, num sistema distribuído com múltiplos controladores SDN. Para atingir o objetivo, projetamos uma topologia de rede com múltiplos domínios, cada um gerido pelo seu controlador. A comunicação entre os domínios, é feita através dum domínio de trânsito SDN com a aplicação SDN-IP do controlador Sistema Operativo de Rede Aberta (ONOS). Emulamos também uma rede para testar a QoS através de filas de espera do OpenvSwitch. O objetivo é criar prioridades de tráfego numa rede com dispositivos tradicionais e de IoT simulados. De acordo com os testes realizados, conseguimos garantir a comunicação entre domínios SDN e comprovamos que a nossa proposta é reativa a uma falha na topologia. No cenário do QoS demostramos que, através da inserção de regras OpenFlow, conseguimos priorizar o tráfego e oferecer garantias de qualidade de serviço. Desta forma comprovamos que a nossa proposta é promissora para ser utilizada em cenários com múltiplos domínios administrativos

Aspects of proactive traffic engineering in IP networks

To deliver a reliable communication service over the Internet it is essential for the network operator to manage the traffic situation in the network. The traffic situation is controlled by the routing function which determines what path traffic follows from source to destination. Current practices for setting routing parameters in IP networks are designed to be simple to manage. This can lead to congestion in parts of the network while other parts of the network are far from fully utilized. In this thesis we explore issues related to optimization of the routing function to balance load in the network and efficiently deliver a reliable communication service to the users. The optimization takes into account not only the traffic situation under normal operational conditions, but also traffic situations that appear under a wide variety of circumstances deviating from the nominal case. In order to balance load in the network knowledge of the traffic situations is needed. Consequently, in this thesis we investigate methods for efficient derivation of the traffic situation. The derivation is based on estimation of traffic demands from link load measurements. The advantage of using link load measurements is that they are easily obtained and consist of a limited amount of data that need to be processed. We evaluate and demonstrate how estimation based on link counts gives the operator a fast and accurate description of the traffic demands. For the evaluation we have access to a unique data set of complete traffic demands from an operational IP backbone. However, to honor service level agreements at all times the variability of the traffic needs to be accounted for in the load balancing. In addition, optimization techniques are often sensitive to errors and variations in input data. Hence, when an optimized routing setting is subjected to real traffic demands in the network, performance often deviate from what can be anticipated from the optimization. Thus, we identify and model different traffic uncertainties and describe how the routing setting can be optimized, not only for a nominal case, but for a wide range of different traffic situations that might appear in the network. Our results can be applied in MPLS enabled networks as well as in networks using link state routing protocols such as the widely used OSPF and IS-IS protocols. Only minor changes may be needed in current networks to implement our algorithms. The contributions of this thesis is that we: demonstrate that it is possible to estimate the traffic matrix with acceptable precision, and we develop methods and models for common traffic uncertainties to account for these uncertainties in the optimization of the routing configuration. In addition, we identify important properties in the structure of the traffic to successfully balance uncertain and varying traffic demands

Understading Multiple Origin AS Conflicts

Internet routing problems are often difficult to detect and diagnose because one address prefix can be originated by multiple ASes. There is, however, no comprehensive analysis on the causes of Multiple Origin AS (MOAS) conflicts. In this paper, we study the characteristics of MOAS conflicts and compare them with those from 10 years ago. We also provide an in-depth examination of four MOAS causes--IXP, anycast, false origin AS, and origin-AS transition. Furthermore, we propose two heuristics to identify MOAS conflicts caused by false origin ASes and origin-AS transitions. The findings from our study and proposed heuristics can help us design effective mechanisms to distinguish legitimate MOAS conflicts from illegitimate ones, thus improving the reliability and security of Internet routing

SDN Architecture and Southbound APIs for IPv6 Segment Routing Enabled Wide Area Networks

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 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 (CLI). 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