Path computation in multi-layer networks: Complexity and algorithms

Carrier-grade networks comprise several layers where different protocols coexist. Nowadays, most of these networks have different control planes to manage routing on different layers, leading to a suboptimal use of the network resources and additional operational costs. However, some routers are able to encapsulate, decapsulate and convert protocols and act as a liaison between these layers. A unified control plane would be useful to optimize the use of the network resources and automate the routing configurations. Software-Defined Networking (SDN) based architectures, such as OpenFlow, offer a chance to design such a control plane. One of the most important problems to deal with in this design is the path computation process. Classical path computation algorithms cannot resolve the problem as they do not take into account encapsulations and conversions of protocols. In this paper, we propose algorithms to solve this problem and study several cases: Path computation without bandwidth constraint, under bandwidth constraint and under other Quality of Service constraints. We study the complexity and the scalability of our algorithms and evaluate their performances on real topologies. The results show that they outperform the previous ones proposed in the literature.Comment: IEEE INFOCOM 2016, Apr 2016, San Francisco, United States. To be published in IEEE INFOCOM 2016, \<http://infocom2016.ieee-infocom.org/\&g

Multi-constrained path computation for inter-domain QoS-capable services

International audienceComputing inter-domain MultiProtocol Label Switching Traffic Engineering Label Switched Path (MPLS-TE LSP) using the Path Computation Element (PCE) through a predetermined sequence of domains is quite straight. Each PCE, using the Backward Recursive PCE-based Computation (BRPC), knows who is the next to be contacted in order to continue the computation. The optimality of the inter-domain MPLS-TE LSP path depends strongly on the choice of the predetermined sequence of domains on which the calculation works. In this paper we propose a novel procedure allowing a forward discovery of multiple inter-domain sequences and the computation of constrained inter-domain paths for MPLS-TE LSPs over these domains sequences. Other issues around the inter-domain path computation, such as route discovery and inter-domain loop avoidance, are investigated. Experimental evaluation shows that our solution is effective in terms of protocol and algorithmic efficiency and provides satisfiable performance with high success rate, reasonable message overhead and runtime

Algorithmes distribués pour la négociation de contrats de qualité de service dans les réseaux multi-domaines

Déployer des services (ex: vidéo-conférence) sur la topologie multi-domaines ("X-domaines") d'Internet implique de garantir la Qualité de Service (QdS) de bout-en-bout agrégeant plusieurs paramètres. Ainsi, des contrats de QdS sont établis entre domaines. Les éléments clés à prendre en compte sont l'hétérogénéité, l'indépendance des domaines et la confidentialité des contrats. Avant d'établir un service, un processus de négociation de la QdS s'exécute: il s'agit de la sélection de contrats pair-à-pair formant une chaîne satisfaisant une QdS de bout-en-bout (sujette à des effets d'accumulations: les délais s'additionnent, les disponibilités se multiplient, etc.) et optimisant une fonction objectif. Nous étudions différents problèmes de négociation. Ces problèmes se réduisent à des problèmes de "sac à dos", qui sont NP-difficiles. Nous proposons des algorithmes distribués utilisant la Programmation Dynamique et fournissons également des mécanismes d'auto-réparation en cas d'échec ou de violations de contrats. Négocier chaque requête peut s'avérer un processus lent. Il peut être préférable de pré-négocier des chaînes de contrats. Ainsi, nous considérons le problème de la négociation de tuyaux: un domaine sollicite un nombre de connexions pour une QdS requise. Nous proposons un modèle de flots et une version distribuée de l'algorithme de Busacker-Gowen pour résoudre ce problème. En outre, nous étudions la négociation avec exploration de plusieurs routes pour atteindre le domaine cible et y répondons par des mécanismes de détection de cycles et de terminaison. Enfin, nous discutons de l'application de la négociation en "milieu ouvert" où les domaines s'organisent éventuellement en cartels ou coalitions.Deploying services (e.g. video-conference) over the Internet X-domain topology requires guaranteeing an end-to-end QoS composed of several parameters. For this, QoS contracts are committed between domains. The key factors to consider are the heterogeneity, independence of domains and privacy of contracts. Before establishing a service, a negotiation occurs: it consists in selecting a chain of pair-wise commitments that satisfies the end-to-end QoS requirements and optimizes an objective function, given that global QoS is subject to accumulation effects (e.g. delays sum up along a path). We address different negotiation problems. They reduce to knapsack problems, which are NP-Hard. Domain independence and contract privacy constrain us to design distributed solutions based on Dynamic Programming principles. We develop also self-repairing mechanisms in case of negotiation failures and contract violations. Negotiation per request can be slow. It may be preferable to pre-negotiate QoS contract chains. Thus, we address the problem of pipe negotiation: a domain asks for a number of connections satisfying a required QoS. We propose a network flow model and a distributed version of the Busacker-Gowen algorithm. We also consider the negotiation when several routes are explored to reach the target domain and describe some mechanisms to detect cycles and termination. Finally, we study negotiation in an "open world" where domains potentially organize themselves as cartels or coalitions.RENNES1-BU Sciences Philo (352382102) / SudocRENNES-INRIA Rennes Irisa (352382340) / SudocSudocFranceF

A~protocol for QoS contract negotiation and its implementation using web Services

International audienceThe way Internet is used changes: demand grows for critical services that cross several provider networks; guaranteeing a required end-to-end Quality of Service (QoS) across several networks becomes a challenge. Some critical services (e.g. video-conference, VPN etc.) can not be satisfied in a best effort fashion. The use of QoS contracts (Service Level Agreements, SLAs) is effective for management of such services. However, the problem of meeting end-to-end QoS requirement remains: no centralized entity can compute overall QoS for chains of contracts, and a fortiori, such contract chains can not be optimized centrally. Thus, the following problem has to be solved: given an end-to-end QoS request and collections of available SLAs on each participating domain, establish an end-to-end contract committing a chain of providers and giving optimal service under most reliable guarantees available

Distributed Busacker-Gowen algorithm for end-to-end QoS pipe negotiation in X-domain networks

International audienceMultimedia services and other critical multisite services (e.g., VPN) are becoming mainstream, and they require a guaranteed quality of service (QoS). Services need to be established across several autonomous systems (ASes), often to connect end-users. Thus, provisioning and control of end-to-end QoS requirements arise as one of the main challenges in inter-AS management. The contractual approach, consisting in using service-level agreements (SLAs) defined by each crossed AS, allows to negotiate contract chains that satisfy end-to-end requirements. However, establishing such chains by on-demand negotiations does not scale up for large numbers of requests. Hence, we propose a negotiation process to occur before users' requests to establish service are received. The proposed negotiation process results in the selection of aggregated contract chains, called pipes, and a distribution between them. Such a distribution would indicate, for each chain of a pipe, the connection flow it may accept. In this paper, we address the pipe negotiation problem as a network flow problem. We also propose a distributed adaptation of an algorithm for network flow problems

Path Computation in Multi-layer Multi-domain Networks

Part 8: LISP and Multi-domain RoutingInternational audienceCarrier-grade networks have often multiple layers of protocols. To tackle this heterogeneity, the Pseudo-Wire architecture provides encapsulation and decapsulation functions of protocols over Packet-Switched Networks. At the scale of multi-domain networks, computing a path to support an end-to-end service requires various encapsulations and decapsulations that can be nested but for which manual configurations are needed. Graph models are not expressive enough for this problem. In this paper, we propose an approach using graphs and Push-Down Automata (PDA) to capture the compatibility among encapsulations and decapsulations along an inter-domain path. They are respectively modeled as pushes and pops on a PDA’s stacks. We provide polynomial algorithms that compute either the shortest path in hops, or in the number of encapsulations and decapsulations to optimize interfaces’ configuration

Path computation in multi-layer multi-domain networks: A language theoretic approach

International audienceMulti-layer networks are networks in which several protocols may coexist at different layers. The Pseudo-Wire architecture provides encapsulation and de-capsulation functions of protocols over Packet-Switched Networks. In a multi-domain context, computing a path to support end-to-end services requires the consideration of encapsulation and decapsulation capabilities. It appears that graph models are not expressive enough to tackle this problem. In this paper, we propose a new model of heterogeneous networks using Automata Theory. A network is modeled as a Push-Down Automaton (PDA) which is able to capture the encapsulation and decapsulation capabilities, the PDA stack corresponding to the stack of encapsulated protocols. We provide polynomial algorithms that compute the shortest path either in hops or in the number of encapsulations and decapsulations along the inter-domain path, the latter reducing manual configurations and possible loops in the path

QoS commitment between vertically integrated autonomous systems

Vertically integrated autonomous systems bargain to provide quality of service guarantees and revenue sharing. Depending on the perceived quality of service and access price, consumers determine whether they subscribe to the access provider's service. Four types of contracts are compared: (i) best effort, (ii) bilateral bargaining, (iii) cascade negotiations and (iv) grand coalition cooperation; the impact of the consumers' QoS sensitivity parameter and power relation are tested for each contract. Assuming that the consumers' quality of service sensitivity parameter is unknown and might evolve dynamically due to error judgement, word-of-mouth effect or competition pressure, a learning algorithm is detailed and implemented by each integrated autonomous systems under asymmetrical information. Its convergence and the influence of bias introduction by the most informed autonomous system is analyzed.Bilateral bargaining Supply chain Shapley value Learning