Routage résilient dans les réseaux SDN

International audienceLes réseaux SDN (software-defined networking) permettentàpermettent`permettentà un contrôleur centralisé de décider du routage. Afin d'´ etablir des routes fiables, il est souvent nécessaire de trouver plusieurs chemins dans le réseau ne partageant pas les mêmes ressouresàressoures`ressouresà risque, communément appelé SRLG pour Shared Risk Link Group. Tout en assurant cette fiabilité, l'objectif est aussi de minimiser un coût, qui intègre des indicateurs de congestion ou de latence. Ceprobì eme peutêtrepeutˆpeutêtre modélisé par un programme linéaire en nombres entiers (ILP). Nous proposons ici une méthode efficace pour sa résolution qui utilise une relaxation fractionnaire bien choisie, dont nous montrerons qu'elle m` ene en fait la plupart du tempsàtemps`tempsà une solutionentì ere. La résolution de ceprobì eme relaxé utilise une méthode de génération de colonnes (CG), o` u chaque colonne représente un chemin dans le réseau avec une notion de coût modifié prenant en compte les SRLGs ; les nouvelles colonnes peuventêtrepeuventˆpeuventêtre obtenues par un algorithme efficace de programmation dynamique quí etend les algorithmes classiques de calcul de plus court chemin. Afin de limiter l'explosion combinatoire potentielle, nous présentonsprésentons´présentonségalement une heuristique qui accélére le calcul d'une solution résiliente tout en préservant de très bonnes performances. Les résultats numériques montrent que notre approche donne une solution de très bonne qualité dans un temps de calcul raisonnable sur des instances de réseau réalistes

Routing Metrics Depending on Previous Edges: The Mn Taxonomy and its Corresponding Solutions

The routing algorithms used by current operators aim at coping with the demanded QoS requirements while optimizing the use of their network resources. These algorithms rely on the optimal substructure property (OSP), which states that an optimal path contains other optimal paths within it. However, we show that QoS metrics such as queuing delay and buffer consumption do not satisfy this property, which implies that the used algorithms lose their optimality and/or completeness. This negatively impacts the operator economy by causing a waste of network resources and/or violating Service Level Agreements (SLAs). In this paper, we propose a new so-called Mn taxonomy defining new metric classes. An Mn metric corresponds to a metric which requires the knowledge of the n previously traversed edges to compute its value at a given edge. Based on this taxonomy, we present three solutions for solving routing problems with the newly defined classes of metrics. We show that state-of-the-art algorithms based on the OSP indeed lose their original optimality and/or completeness properties while our proposed solutions do not, at the price of an increased computation time.Comment: 2018 International Conference on Communications (ICC 2018), Kansas City, MO (USA

QOS routing source routing problems and solutions

The notion of Quality-of-Service has been proposed to capture qualitatively or quantitatively defined performance contracts between the service provider and the user applications. Integrated network services are designed to support Quality-of-Service (QoS). One of the primary goals for the integrated network services is to find the paths that satisfy given QoS requirements, namely QoS routing. The challenging issue in this area is to route packets subjected to multiple uncorrelated constraints because the problem is inherently NP-complete. This thesis studies the source routing heuristic approaches that bring the time complexity down to the polynomial-time for the multi-constrained path (MCP) problem. A new source routing framework (SRDE) is further proposed to tackle this problem. The theoretical analysis and simulation results demonstrate that the proposed framework is capable of integrating existing source routing algorithms, resulting in better performance in terms of the time complexity and success ratio

Optimal joint path computation and rate allocation for real-time traffic

Computing network paths under worst-case delay constraints has been the subject of abundant literature in the past two decades. Assuming Weighted Fair Queueing scheduling at the nodes, this translates to computing paths and reserving rates at each link. The problem is NP-hard in general, even for a single path; hence polynomial-time heuristics have been proposed in the past, that either assume equal rates at each node, or compute the path heuristically and then allocate the rates optimally on the given path. In this paper we show that the above heuristics, albeit finding optimal solutions quite often, can lead to failing of paths at very low loads, and that this could be avoided by solving the problem, i.e., path computation and rate allocation, jointly at optimality. This is possible by modeling the problem as a mixed-integer second-order cone program and solving it optimally in split-second times for relatively large networks on commodity hardware; this approach can also be easily turned into a heuristic one, trading a negligible increase in blocking probability for one order of magnitude of computation time. Extensive simulations show that these methods are feasible in today's ISPs networks and they significantly outperform the existing schemes in terms of blocking probability

Situation-Aware QoS Routing Algorithm for Vehicular Ad hoc Networks

A wide range of services has been developed for Vehicular Ad hoc Networks (VANETs) ranging from safety to infotainment applications. An essential requirement for such services is that they are offered with Quality of Service (QoS) guarantees in terms of service reliability and availability. Searching for feasible routes subject to multiple QoS constraints is in general an NP-hard problem. Besides, routing reliability needs to be paid special attention as communication links frequently break in VANETs. In this paper, we propose employing the Situational Awareness (SA) concept and an Ant Colony System (ACS) based algorithm to develop a Situation-Aware Multi-constrained QoS (SAMQ) routing algorithm for VANETs. SAMQ aims to compute feasible routes between the communicating vehicles subject to multiple QoS constraints and pick the best computed route, if such a route exists. To mitigate the risks inherited from selecting the best computed route that may turn out to fail at any moment, SAMQ utilises the SA levels and ACS mechanisms to prepare certain countermeasures with the aim of assuring a reliable data transmission. Simulation results demonstrate that SAMQ is capable of achieving a reliable data transmission as compared to the existing QoS routing algorithms even when the network topology is highly dynamic