Improving the Convergence of IP Routing Protocols Pierre Francois Thesis submitted in partial fulfillment of the requirements for the Degree of Doctor in Applied Sciences October 30, 2007 Département d’Ingénierie Informatique Faculté des Sciences Appliquées Université catholique de Louvain Louvain-la-Neuve Belgium Thesis Committee: Yves Deville (Chair) Université catholique de Louvain, BE Clarence Filsfils Cisco Systems Laurent Mathy Lancaster University, UK Jennifer Rexford Princeton University, USA Roch Guérin University of Pennsylvania, USA Guy Leduc Université de Liège, BE Olivier Bonaventure (Advisor) Université catholique de Louvain, BE Philippe Delsarte Université catholique de Louvain, BE Preamble The IP protocol suite has been initially designed to provide best effort reachability among the nodes of a network or an inter-network. The goal was to design a set of routing solutions that would allow routers to automatically provide end-to-end connectivity among hosts. Also, the solution was meant to recover the connectivity upon the failure of one or multiple devices supporting the service, without the need of manual, slow, and error-prone reconfigurations. In other words, the requirement was to have an Internet that "converges" on its own. Along with the "Internet Boom", network availability expectations increased, as e-business emerged and companies started to associate loss of Internet connec- tivity with loss of customers... and money. So, Internet Service Providers (ISPs) relied on best practice rules for the design and the configuration of their networks, in order to improve their Quality of Service. The same routing suite is now used by Internet Service Providers that have to cope with more and more stringent Service Level Agreements (SLAs). These new SLAs are justified by the increasing use of IP networks to transport voice, video, TV broadcast, and Real-Time online Business traffic accross their networks. Such SLAs generally define upper bounds on the packet loss ratio and on the duration of losses of connectivity. To ensure that these constraints are respected, and reach the five 9’s network availability target, resilient IP technologies are re- quired. The goal of this thesis is to complement the IP routing suite so as to improve its resiliency. The Internet is organized as a set of interconnected Autonomous Systems (AS), which are managed by autonomous domains such as organizations and companies. The technology used to establish connectivity inside an AS (intra-domain routing) is not the same as the one used to provide inter-domain connectivity (inter-domain routing). Hence, the recovery process upon a topological change is different, and will be improved in different ways in this thesis. i ii Bibliographic notes Most of the work presented in this thesis appeared in previously published confer- ence proceedings and journals. The list of related publications is presented here- after : • Achieving subsecond IGP convergence in large IP networks, Pierre Francois, Clarence Filsfils, John Evans, Olivier Bonaventure, In ACM SIGCOMM Computer Communications Review, 35(3):35-44, July 2005. • An evaluation of IP-based Fast Reroute Techniques, Pierre François, Olivier Bonaventure, In Proceedings of ACM CoNEXT 2005, 244-245, Toulouse, France, October 2005 • Loop-free convergence using ordered FIB updates, IETF Working Group Document, draft-ietf-rtgwg-ordered-fib-00, Pierre François, Olivier Bonaventure, Mike Shand, Stefano Previdi, Stewart Bryant, December 2006 • ISIS extensions for ordered FIB updates, Internet-Draft, draft-bonaventure-isis-ordered-00, Olivier Bonaventure, Pierre François, Mike Shand, Stefano Previdi, Febru- ary 2006 • Avoiding transient loops during IGP Convergence in IP Networks, Pierre Francois, Olivier Bonaventure, In IEEE INFOCOM 2005, Miami, March 2005. • Avoiding transient loops during the Convergence of Link-State routing pro- tocols, Pierre Francois, Olivier Bonaventure, To Appear in IEEE/ACM Transactions on Networking. • Disruption free topology reconfiguration in OSPF Networks without proto- col modifications, Pierre Francois, Mike Shand, Olivier Bonaventure, In IEEE INFOCOM 2007, Anchorage, May 2007 iii iv • Achieving sub-50 milliseconds recovery upon BGP peering link failures Olivier Bonaventure, Clarence Filsfils, Pierre Francois In Proceedings of ACM CoNEXT 2005, 31-42, October 2005, Toulouse, France Extended Version To Appear in IEEE/ACM Transactions on Networking • Avoiding disruptions during maintenance operations on BGP sessions Pierre Francois, Pierre-Alain Coste, Bruno Decraene, Olivier Bonaventure To appear in IEEE Transactions on Network and Service Management v Acknowledgments I would like to thank Olivier Bonaventure for having teached me Networking the way he did when I was a master student and during my thesis. His taste for applied research and his knowledge of the real world of networking was a major driver for my research. Olivier knows in detail how routers (the real ones) work, as well as how the people operating them work. His devotion to his work was also a major source of motivation. It’s been an extraordinary experience to achieve the goals of our projects in his close company. Doing research with Olivier does not mean that you report your research results to him. It actually means that you are doing research with him, which is as rare as motivating. I would also like to acknowledge his generosity, as he’s always acting for the best interest of the members of his team. I would like to thank Clarence Filsfils, Jennifer Rexford, Roch Guerin, Laurent Mathy, Guy Leduc, Philippe Delsarte, and Yves Deville for their participation in the jury of this thesis. I have been impressed by the number of comments they provided. As I retrieved their copies of my thesis after the private defense, I actu- ally figured out that they heavily annotated the thesis with corrections, comments, questions, clarifications, personnal thoughts, and even ideas for future papers. Clarence Filsfils is the kind of guy that any researcher would like to interact with when doing a Ph. D. thesis. I never lacked of problems to solve because Clarence always had some to share. I don’t know how many times Olivier and I came back from his office with a todo list that would occupy us for months. He trustfully shared critical information about Cisco routers and not-yet-on-the-shelve features, waiting for our comments and driving our research. My thesis is not about the hottest topic in research in networking, it is about what was hot for Clarence, and what was hot for some of his customers. This was a strong motivation for doing my job. Also, Clarence has been the toughest reviewer for our ideas; when he closed a meeting with a “good job”, we actually knew that we were following the right tracks. And when it was with an “it will never work”, he told us why and it became much easier to cut the wrong branches. Last but not least, I would like to thank him for being our champion for the four fundings that we received from Cisco Systems. Other people from Cisco brought a lot to this thesis. I would like to thank Jane Butler for trusting our project and funding my Ph. D. budget. I would like to thank Mike Shand and Stewart Bryant for all the discussions we had about loop avoidance mechanisms and Fast Reroute Solutions. It’s been a real fun to interact with such creative folks. I owe a lot to Stefano Previdi for having been my IS-IS mentor. It’s much easier to work on IS-IS when you know you can ask questions to the guy who implements it in Cisco routers. I would also like to thank these three guys for trusting me in the standardisation process of oFIB. John Evans did a great measurement job on the performances of IS-IS, and his work was the main enabler for the first chapter of the thesis. I also thank Pranav Mehta and Pradosh Mohapatra for the information they provided on Cisco’s BGP implementations. vi I would like to thank Cisco Systems for its trustful support. Any opinions, findings, and conclusions or recommendations expressed in this thesis are mine and those of the other contributors, and do not necessarily reflect the views of Cisco Systems. I have also been partially supported by the Walloon government under the TOTEM project. I would like to thank Bruno Decraene and Pierre-Alain Coste for the collab- oration we had on the BGP maintenance issues. Pierre-Alain did a great job on evaluating the performance of the solutions. Bruno has also been a great compan- ion during the IETF meetings we attended. I would like to thank the IETF folks at the RTG, IDR, IS-IS, OSPF, and at the IRTF RRG working groups for the various discussions we had during IETF meetings. I can now confirm that IETF folks are open to discuss with people from the academia. Among them, I am especially thankful to Alia Atlas, Don Fedyk, Jean-Philippe Vasseur (thanks for the dinner in Dallas ;-)), Dimitri Papadimitriou, Robert Raszuk, Dave Ward, Alex Zinin, . I would like to thank Xiaowei Yang, Ang Li, and Xin Liu for their hospitality when I visited their team at UC Irvine. I thank Amund Kvalbein and Tarik Cicic for the interesting discussions we had about IP Fast Reroute, and for their hospitality when I visited their Lab in Oslo. I owe a big thank you to all the past and current members of my team. I enjoyed the numerous discussions I had on BGP, MPLS, and about routing in general with Cristel Pelsser, Bruno Quoitin, Sébastien Tandel, Steve Uhlig, and Virginie Van den Schrieck. I also had interesting interactions with Xavier Brouckaert, Cédric Delaunois, Sébastien Barré, Damien Leroy, Luigi Iannone, Benoit Donnet, and Stefano Iasi. All of them have been valuable for my work, and I also had a lot of fun with them at work and when we partied.