Computing Delay-Constrained Least-Cost Paths for Segment Routing is Easier Than You Think

With the growth of demands for quasi-instantaneous communication services such as real-time video streaming, cloud gaming, and industry 4.0 applications, multi-constraint Traffic Engineering (TE) becomes increasingly important. While legacy TE management planes have proven laborious to deploy, Segment Routing (SR) drastically eases the deployment of TE paths and thus became the most appropriate technology for many operators. The flexibility of SR sparked demands in ways to compute more elaborate paths. In particular, there exists a clear need in computing and deploying Delay-Constrained Least-Cost paths (DCLC) for real-time applications requiring both low delay and high bandwidth routes. However, most current DCLC solutions are heuristics not specifically tailored for SR. In this work, we leverage both inherent limitations in the accuracy of delay measurements and an operational constraint added by SR. We include these characteristics in the design of BEST2COP, an exact but efficient ECMP-aware algorithm that natively solves DCLC in SR domains. Through an extensive performance evaluation, we first show that BEST2COP scales well even in large random networks. In real networks having up to thousands of destinations, our algorithm returns all DCLC solutions encoded as SR paths in way less than a second

Convergence du routage sans perturbation : calcul de séquences minimales de mises à jour d’états des liens

The use of real time media or mission critical applications over IP networks is making strong pressure on service providers to operate disruption free networks. However, after any topological change, link-state Interior Gateway Protocols (IGPs), such as IS-IS or OSPF, enter a convergence phase during which transient forwarding loops may occur. Such loops increase the network latency and cause packet losses for several seconds. In this thesis, we propose and evaluate innovative solutions to prevent these perturbations in case a planned modification on a link or a router. Our approach only relies on core functionalities of link-state routing protocols, thus being incrementally deployable in any network. Intuitively, it consists in implicitly controlling the routers update order through successive IGP weight reconfigurations on a subset of links. For example, progressively increasing the weight of a link forces farthest routers to update their routes first, before closest ones. Hence, finely tuning such changes may allow to spread the update of routers potentially implied in a loop across multiple steps. This operation can be repeated until the component to be removed is no longer used to forward traffic in the network, thus allowing its removal with no impact on the routing decisions.Avec le développement des applications temps-réel sur Internet, telles que la télévision, la voix sur IP et les jeux en ligne, les fournisseurs d'accès à Internet doivent faire face à des contraintes de plus en plus fortes quant aux performances de leurs services. Cependant, après chaque changement topologique, les protocoles de routage à état des liens, utilisés dans les réseaux de cœur de ces opérateurs, entrent dans une période de convergence durant laquelle des boucles de routage peuvent apparaître. Ce phénomène dégrade les performances du réseau (latence, congestions, pertes de paquets) et peut durer plusieurs secondes. Dans le cadre de cette thèse, nous proposons de nouvelles solutions permettant de prévenir ces perturbations dans le cas de reconfigurations sur un lien ou un routeur. Notre approche a pour particularité de ne reposer que sur les mécanismes de base des protocoles de routage à état des liens, et d’être ainsi déployable de manière incrémentale dans n’importe quel réseau. Intuitivement, il s’agit de contrôler implicitement l’ordre de mise à jour des routeurs, à travers une modification progressive du poids d’un sous-ensemble de liens. Par exemple, l’augmentation du poids d’un lien aura pour effet de forcer les routeurs les plus éloignés de ce composant à se mettre à jour avant les routeurs plus proches. En adaptant finement l’amplitude de tels changements, il est alors possible de répartir la mise à jour de routeurs potentiellement impliqués dans une boucle sur plusieurs étapes. Cette opération peut ensuite être répétée jusqu’à ce que le composant ne soit plus utilisé pour acheminer des données dans le réseau, permettant un retrait sans impact sur le routage

Puits Nomade dans un Réseau de Capteurs : Vers une Collecte Efficace de Données

International audienceLes contraintes énergétiques dans les réseaux de capteurs nécessitent de limiter les opérations coûteuses sur certains nœuds sans compromettre l'application de surveillance. Nous nous intéressons ici au cas d'un puits nomade cherchant à collecter efficacement les données du réseau. Nous proposons un mécanisme fonction de deux objectifs : l'énergie consommée par le réseau (i.e. proportion de nœuds relais) et l'efficacité du routage (i.e. longueur des chemins). Afin d'ajuster l'équilibre entre le nombre de relais et l'efficacité du routage nous introduisons un paramètre régulant ce compromis. Lorsque l'efficacité énergétique est le critère prioritaire, notre solution est plus performante qu'une 2- approximation centralisée pour la construction d'un MLST. Lorsque l'efficacité du routage est prioritaire, nos résultats mettent en évidence la faible proportion de relais supplémentaires nécessaires

Puits Nomade dans un Réseau de Capteurs : Vers une Collecte Efficace de Données

International audienceLes contraintes énergétiques dans les réseaux de capteurs nécessitent de limiter les opérations coûteuses sur certains nœuds sans compromettre l'application de surveillance. Nous nous intéressons ici au cas d'un puits nomade cherchant à collecter efficacement les données du réseau. Nous proposons un mécanisme fonction de deux objectifs : l'énergie consommée par le réseau (i.e. proportion de nœuds relais) et l'efficacité du routage (i.e. longueur des chemins). Afin d'ajuster l'équilibre entre le nombre de relais et l'efficacité du routage nous introduisons un paramètre régulant ce compromis. Lorsque l'efficacité énergétique est le critère prioritaire, notre solution est plus performante qu'une 2- approximation centralisée pour la construction d'un MLST. Lorsque l'efficacité du routage est prioritaire, nos résultats mettent en évidence la faible proportion de relais supplémentaires nécessaires

Graceful convergence in link-state IP Networks: a lightweight algorithm ensuring minimal operational impact

The use of real-time multimedia or mission-critical applications over IP networks puts strong pressure on service providers to operate disruption-free networks. However, after any topological change, link-state Interior Gateway Protocols (IGPs), such as IS-IS or OSPF, enter a convergence phase during which transient forwarding loops may occur. Such loops increase the network latency and cause packet losses. In this paper, we propose and evaluate an efficient algorithm aimed at avoiding such traffic disruptions without modifying these IGPs. In case of an intentional modification of the weight of a link (e.g., to shut it down for maintenance operations or to perform traffic engineering), our algorithm iteratively changes this weight, splitting the modification into a sequence of loop-free transitions. The number of weight increments that need to be applied on the link to reach its target state is minimized in order to remain usable in existing networks. Analysis performed on inferred and real Internet service provider (ISP) topologies shows that few weight increments are required to handle most link shutdown events (less than two intermediate metrics for more than 85% of the links). The evaluation of our implementation also reveals that these minimal sequences can be computed in a reasonable time

Deploying Near-Optimal Delay-Constrained Paths with Segment Routing in Massive-Scale Networks

With a growing demand for quasi-instantaneous communication services such as real-time video streaming, cloud gaming, and industry 4.0 applications, multi-constraint Traffic Engineering (TE) becomes increasingly important. While legacy TE management planes have proven laborious to deploy, Segment Routing (SR) drastically eases the deployment of TE paths and is thus increasingly adopted by Internet Service Providers (ISP). There is a clear need in computing and deploying Delay-Constrained Least-Cost paths (DCLC) with SR for real-time interactive services. However, most current DCLC solutions are not tailored for SR. They also often lack efficiency or guarantees. Similarly to approximation schemes, we argue that the challenge is to design an algorithm providing both performances and guarantees. However, conversely to most of these schemes, we also consider operational constraints to provide a practical, high-performance implementation. We leverage the inherent limitations of delay measurements and account for the operational constraint added by SR to design a new algorithm, best2cop, providing guarantees and performance in all cases. Best2cop outperforms a state-of-the-art algorithm on both random and real networks of up to 1000 nodes. Relying on commodity hardware with a single thread, our algorithm retrieves all non-superfluous 3-dimensional routes in only 250ms and 100ms respectively. This execution time is further reduced using multiple threads, as the design of best2cop enables a speedup almost linear in the number of cores. Finally, we extend best2cop to deal with massive scale ISP by leveraging the multi-area partitioning of these deployments. Thanks to our new topology generator specifically designed to model the realistic patterns of such massive IP networks, we show that best2cop solves DCLC-SR in approximately 1 second even for ISP having more than 100000 routers

Software Resolved Networks: Rethinking Enterprise Networks with IPv6 Segment Routing

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