@conference {104, title = {Traffic engineering for multiple spanning tree protocol in large data centers}, booktitle = {23rd International Teletraffic Congress }, year = {2011}, publisher = {IEEE Explorer}, organization = {IEEE Explorer}, address = {San Francisco, CA }, abstract = {The size of the capacity of data centers have been growing significantly during the last years. Most data centers rely on switched Ethernet networks. A drawback of the Ethernet technology is that it relies on the spanning tree protocol (or variants of it) to select the links that are used to forward packets inside the data center. In this paper we propose a Constrained-Based Local Search optimization scheme that is able to efficiently compute the optimum spanning tree in large data center networks. Our technique exploits the division of the data center network in VLANs. We evaluate its performance based on traffic matrices collected in data center networks and show good improvements compared to the standard spanning tree protocol with up to 16 VLANs.}, author = {Trong-Viet Ho and Yves Deville and Olivier Bonaventure and Pierre Francois} } @conference {itc2010_lsa4stp, title = {Using Local Search for Traffic Engineering in Switched Ethernet Networks}, booktitle = {22nd International Teletraffic Congress (ITC-22)}, year = {2010}, address = {Amsterdam, Netherlands}, abstract = {Large switched Ethernet networks are deployed in campus networks, data centers and metropolitan area networks to support various types of services. Congestion is usually handled by deploying more switches and installing higher bandwidth link bundles, although a better use of the existing infrastructure would allow to deal with congestion at lower cost. In this paper, we use constrained- based local search and the COMET language to develop an efficient traffic engineering technique that improves the use of the infrastructure by the spanning tree protocol. We evaluate the performance of our scheme by considering several types of network topologies and traffic matrices. We also compare the performance of our technique with the performance that a routing-based deployment supported by an IP traffic engineering technique would obtain.}, author = {Trong-Viet Ho and Pierre Francois and Yves Deville and Quang Dung Pham and Olivier Bonaventure} } @proceedings { , title = {Implementation of a traffic engineering technique that preserves IP Fast Reroute in COMET}, journal = {Rencontres Francophones sur les Aspects Algorithmiques des T{\'e}l{\'e}communications (Algotel)}, year = {2009}, abstract = {With Intradomain Routing Protocols, by optimizing the configuration (Trafic Engineering -TE) of link weights, operators can significantly improve the load of their links, which is known to be an NP-hard problem. Another emerging issue for ISP networks is the fast restoration of IP services in the case of failures. Recently, Fast Reroute techniques have been proposed for pure IP networks. The Loop Free Alternates (LFA) is one of the most promising technique. An LFA for a router A, for a destination d, is a neighbor C of A which does not use A to reach d, so that A can prepare itself to directly reroute the traffic destined to d along its link with C upon the failure of the link that A is using to reach d. Our objective is to provide a TE technique that takes the coverage of LFAs into account during the network resource usage optimization. Constraint Programming and Constraint-Based Local Search are well suited for solving such complex combinatorial problems. Especially in COMET, some classical problems can be modeled in only about a dozen lines of code. So, we have chosen a local search algorithm implemented in COMET for solving our traffic engineering problem.}, author = {Trong-Viet Ho and Pierre Francois and Yves Deville and Olivier Bonaventure} }