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

Fast reroute using segment routing for smart grids

Tese de mestrado, Engenharia Informática (Arquitectura, Sistemas e Redes de Computadores) Universidade de Lisboa, Faculdade de Ciências, 2016A rede eléctrica tem contribuído de forma extraordinária para o nosso dia-a-dia nas últimas décadas e, como tal, tornou-se essencial para a nossa sociedade. Hoje em dia, estão a ser tomadas decisões para a modernizar, de modo a que seja possível fornecer novos serviços. Graças ao aumento da produção¸ ão de electricidade através de energias renováveis (energia solar, hídrica e eólica), e ao aumento do consumo de energia, é vista como necessária uma reestruturação da rede eléctrica. Para atingir estes objectivos, foi proposta uma nova geração destas redes, as Smart Grids (SG). As SG são compostas por dispositivos electrónicos inteligentes, sensores com e sem fios e contadores inteligentes que necessitam de se coordenar para funcionarem correctamente. Como tal, é fundamental ter uma rede de comunicação moderna capaz de suportar estes desafios [1]. Um conjunto de propriedades de que se destacam a escalabilidade, disponibilidade e segurança, são fulcrais para o funcionamento das SG. Para as SG a infra-estrutura de comunicação tem um papel particularmente importante para que se possam cumprir estas necessidades. As tecnologias actuais baseadas em Internet Protocol (IP) e em Multiprotocol Layer Switching (MPLS) tˆem conseguido corresponder a estas necessidades. O protocolo IP é um dos alicerces para a comunicação mundial, enquanto que o MPLS tem sido adoptado pelas suas capacidades de engenharia de tráfego. No entanto, as redes de IP tradicionais são difíceis de gerir e tornam complicado o desenho de soluções que permitam utilização eficiente de recursos e que possibilitem comunicação resiliente. Por outro lado, o MPLS tem problemas de escalabilidade devido ao uso de protocolos complexos como o Resource Reservation Protocol with Traffic Engineering (RSVP-TE). As Software Defined Networks (SDN) promete resolver alguns dos problemas mencionados anteriormente, a partir do desacoplamento do plano de dados do plano de controlo, que passa a ser gerido por um controlador logicamente centralizado [2][3][4]. Deste modo, as aplicações que são executadas no controlador têm uma visão centralizada do estado da rede, o que facilita a procura de soluções de gestão de redes. No entanto, os operadores de SG poderão apresentar alguma relutância ao mover todos os seus elementos da rede para uma SDN. Felizmente, foi proposto recentemente um novo protocolo pela Internet Engineering Task Force (IETF) – Segment Routing (SR) [5] – que permite a centralização lógica oferecida por uma SDN num ambiente de uma rede MPLS. SR ´e muito semelhante ao MPLS, na medida em que utiliza segmentos que se comportam como etiquetas MPLS. A comutação de pacotes, baseada também nestas etiquetas, é gerida por comutadores que usam as mesmas acções do MPLS (push, pop e swap). No entanto, ao contrário do MPLS, o SR não necessita de protocolos complexos como o RSVP-TE, simplificando a gestão da rede. O SR utiliza uma forma de source routing, facilitadora da sua integração. Desta forma o SR pode ser integrado com os controladores SDN e outras aplicações. Para implementar SR, o controlador SDN apenas precisa de enviar uma lista ordenada de segmentos para o encaminhador que a insere no cabeçalho dos pacotes quando necessitarem de serem enviados. Isto torna possível a criação de uma solução mais simples e escalável para engenharia de tráfego. Nesta tese vamos explorar o uso de SR para avaliar a resiliencia da rede. O objectivo passa por desenhar e avaliar as soluções que forneçam reencaminhamento rápido após uma falha de uma ligação entre nós. Em particular, fornece a capacidade de realizar reencaminhamento rápido enquanto fornece uma grande percentagem de cobertura. Aproveitando as características das SDN e de SR, as nossas soluções permitem que o controlador pré compute os caminhos de backup necessários para instalar nos encaminhadores, mantendo o plano de dados em MPLS inalterado. A contribuição principal desta tese pode ser resumida em dois pontos: 1. Desenho de uma solução de reencaminhamento rápido em caso de faltas para Smart Grids, usando SR e SDN. 2. Fornecer uma avaliação exaustiva do algoritmo de modo a que se consiga compreender os seus benefícios e limitações. O algoritmo proposto utiliza vários comutadores que são utilizados como destinos intermédios, que garantem a entrega dos pacotes após a falha de uma ligação entre nós. Como tal, também propomos dois selectores de segmentos que fornecem reencaminhamento rápido mas com características diferentes. A primeira solução, Fast Segment Drop (FSD), selecciona um segmento próximo da origem do caminho em vez do segmento mais próximo do destino. Isto permite que os pacotes que atravessam a rede causem o menor overhead possível. O overhead devese ao número de segmentos usados em cada nó durante o caminho. Assim sendo, se escolhermos um segmento mais próximo do destino o overhead será maior. A segunda solução, Congestion Avoidance Segment (CAS), escolhe segmentos que podem aumentar o overhead mas que, em contraste, fornecem a capacidade de escolher o caminho com menor utilização. Deste modo pode-se evitar estrangulamentos existentes na rede. Para compararmos as nossas soluções implementamos um selector aleatório e o algoritmo TI-LFA [6]. Os resultados demonstram que para a maioria das topologias uma falha entre nós pode ser tolerada utilizando Loop Free Alternatives (LFA). No entanto ainda existem cerca de 20% dos casos que necessitam de utilizar um segmento para tolerar uma falha, enquanto que dois segmentos raramente são necessários. Também foi possível concluir que o nosso algoritmo fornece mais flexibilidade na escolha de segmentos do que TI-LFA visto que permite uma maior escolha de segmentos. Utilizando CAS é possível reduzir ligeiramente a congestão das ligações na rede em grids e em topologias reais.With the increase of power generation from renewable sources and with a growing energy demand, the traditional communication network underpinning the actual electric power grid needs an overhaul. As a response, the Smart Grid is a new generation of electric grids that aims to fulfill this goal. Smart Grids demand a set of properties that range from high availability to scalability and security. Therefore, the communication infrastructure plays an important role. Current Internet Protocol-based and Multiprotocol Layer Switching (MPLS) technologies have been suggested capable in achieving those needs. However, IP networks have problems to offer traffic engineering solutions and MPLS faces scalability problems due to the use of complex protocols such as RSVP-TE. A new network paradigm, Software-Defined Networks (SDN), is revolutionizing the way computer networks are built and operated, and is leading to the “softwarization” of networking. Showing promise to solve some of the above problems. However, smart grid operators may be reluctant to move all their network elements to SDN anytime soon. Fortunately, Segment routing, recently proposed by the IETF, allows SDN to be used in the context of MPLS networks. The data plane of Segment Routing is similar to MPLS as it uses segments that behave as MPLS labels and is managed in switches using similar actions. In this thesis we present algorithms for fast reroute in SR networks. We propose two solutions: Fast Segment Drop (FSD) that aims to minimize packet overhead and segment list size; and Congestion Avoidance Segment (CAS), a solution that provides traffic engineering by minimizing the maximum link load. The results indeed show that by using CAS reduces network congestion when compared with other algorithms. FSD provides higher coverage using just one segment thus reducing overhead

Smart Sensor Technologies for IoT

The recent development in wireless networks and devices has led to novel services that will utilize wireless communication on a new level. Much effort and resources have been dedicated to establishing new communication networks that will support machine-to-machine communication and the Internet of Things (IoT). In these systems, various smart and sensory devices are deployed and connected, enabling large amounts of data to be streamed. Smart services represent new trends in mobile services, i.e., a completely new spectrum of context-aware, personalized, and intelligent services and applications. A variety of existing services utilize information about the position of the user or mobile device. The position of mobile devices is often achieved using the Global Navigation Satellite System (GNSS) chips that are integrated into all modern mobile devices (smartphones). However, GNSS is not always a reliable source of position estimates due to multipath propagation and signal blockage. Moreover, integrating GNSS chips into all devices might have a negative impact on the battery life of future IoT applications. Therefore, alternative solutions to position estimation should be investigated and implemented in IoT applications. This Special Issue, “Smart Sensor Technologies for IoT” aims to report on some of the recent research efforts on this increasingly important topic. The twelve accepted papers in this issue cover various aspects of Smart Sensor Technologies for IoT

Energy management in communication networks: a journey through modelling and optimization glasses

The widespread proliferation of Internet and wireless applications has produced a significant increase of ICT energy footprint. As a response, in the last five years, significant efforts have been undertaken to include energy-awareness into network management. Several green networking frameworks have been proposed by carefully managing the network routing and the power state of network devices. Even though approaches proposed differ based on network technologies and sleep modes of nodes and interfaces, they all aim at tailoring the active network resources to the varying traffic needs in order to minimize energy consumption. From a modeling point of view, this has several commonalities with classical network design and routing problems, even if with different objectives and in a dynamic context. With most researchers focused on addressing the complex and crucial technological aspects of green networking schemes, there has been so far little attention on understanding the modeling similarities and differences of proposed solutions. This paper fills the gap surveying the literature with optimization modeling glasses, following a tutorial approach that guides through the different components of the models with a unified symbolism. A detailed classification of the previous work based on the modeling issues included is also proposed

Improving Efficiency and Effectiveness of Multipath Routing in Computer Networks

In this dissertation, we studied methods for improving efficiency and effectiveness of multipath routing in computer networks. We showed that multipath routing can improve network performance for failure recovery, load balancing, Quality of Service (QoS), and energy consumption. We presented a method for reducing the overhead of computing dynamic path metrics, one of the obstacles for implementing dynamic multipath routing in real world networks. In the first part, we proposed a method for building disjoint multipaths that could be used for local failure recovery as well as for multipath routing. Proactive failure recovery schemes have been recently proposed for continuous service of delay-sensitive applications during failure transients at the cost of extra infrastructural support in the form of routing table entries, extra addresses, etc. These extra infrastructure supports could be exploited to build alternative disjoint paths in those frameworks, while keeping the lengths of the alternative paths close to those of the primary paths. The evaluations showed that it was possible to extend the proactive failure recovery schemes to provide support for nearly-disjoint paths which could be employed in multipath routing for load balancing and QoS. In the second part, we proposed a method for reducing overhead of measuring dynamic link state information for multipath routing, specifically path delays used in Wardrop routing. Even when dynamic routing could be shown to offer convergence properties without oscillations, it has not been widely adopted. One of reasons was that the expected cost of keeping the link metrics updated at various nodes in the network. We proposed threshold-based updates to propagate the link state only when the currently measured link state differs from the last updated state consider- ably. Threshold-based updates were shown through analysis and simulations to offer bounded guarantees on path quality while significantly reducing the cost of propagating the dynamic link metric information. The simulation studies indicated that threshold based updates can reduce the number of link updates by up to 90-95% in some cases. In the third part, we proposed methods of using multipath routing for reducing energy consumption in computer networks. Two different approaches have been advocated earlier, from traffic engineering and topology control to hardware-based approaches. We proposed solutions at two different time scales. On a finer time granularity, we employed a method of forwarding through alternate paths to enable longer sleep schedules of links. The proposed schemes achieved more energy saving by increasing the usage of active links and the down time of sleeping links as well as avoiding too frequent link state changes. To the best of our knowledge, this was the first technique combining a routing scheme with hardware scheme to save energy consumption in networks. In our evaluation, alternative forwarding reduced energy consumption by 10% on top of a hardware-based sleeping scheme. On a longer time granularity, we proposed a technique that combined multipath routing with topology control. The proposed scheme achieved increased energy savings by maximizing the link utilization on a reduced topology where the number of active nodes and links are minimized. The proposed technique reduced energy consumption by an additional 17% over previous schemes with single/shortest path routing

Bringing Energy Aware Routing closer to Reality with SDN Hybrid Networks

Energy aware routing aims at reducing the energy consumption of ISP networks. The idea is to adapt routing to the traffic load in order to turn off some hardware. However, it implies to make dynamic changes to routing configurations which is almost impossible with legacy protocols. The Software Defined Network (SDN) paradigm bears the promise of allowing a dynamic optimization with its centralized controller.In this work, we propose SENAtoR, an algorithm to enable energy aware routing in a scenario of progressive migration from legacy to SDN hardware. Since in real life, turning off network equipments is a delicate task as it can lead to packet losses, SENAtoR provides also several features to safely enable energy saving services: tunneling for fast rerouting, smooth node disabling and detection of both traffic spikes and link failures.We validate our solution by extensive simulations and by experimentation. We show that SENAtoR can be progressively deployed in a network using the SDN paradigm. It allows to reduce the energy consumption of ISP networks by 5 to 35% depending on the penetration of SDN hardware, while, strikingly, diminishing the packet loss rate compared to legacy protocols

Resilient and Scalable Forwarding for Software-Defined Networks with P4-Programmable Switches

Traditional networking devices support only fixed features and limited configurability. Network softwarization leverages programmable software and hardware platforms to remove those limitations. In this context the concept of programmable data planes allows directly to program the packet processing pipeline of networking devices and create custom control plane algorithms. This flexibility enables the design of novel networking mechanisms where the status quo struggles to meet high demands of next-generation networks like 5G, Internet of Things, cloud computing, and industry 4.0. P4 is the most popular technology to implement programmable data planes. However, programmable data planes, and in particular, the P4 technology, emerged only recently. Thus, P4 support for some well-established networking concepts is still lacking and several issues remain unsolved due to the different characteristics of programmable data planes in comparison to traditional networking. The research of this thesis focuses on two open issues of programmable data planes. First, it develops resilient and efficient forwarding mechanisms for the P4 data plane as there are no satisfying state of the art best practices yet. Second, it enables BIER in high-performance P4 data planes. BIER is a novel, scalable, and efficient transport mechanism for IP multicast traffic which has only very limited support of high-performance forwarding platforms yet. The main results of this thesis are published as 8 peer-reviewed and one post-publication peer-reviewed publication. The results cover the development of suitable resilience mechanisms for P4 data planes, the development and implementation of resilient BIER forwarding in P4, and the extensive evaluations of all developed and implemented mechanisms. Furthermore, the results contain a comprehensive P4 literature study. Two more peer-reviewed papers contain additional content that is not directly related to the main results. They implement congestion avoidance mechanisms in P4 and develop a scheduling concept to find cost-optimized load schedules based on day-ahead forecasts