Lossless Migrations of Link-State IGPs

Laurent Vanbever, Stefano Vissicchio, Cristel Pelsser, Pierre Francois and Olivier Bonaventure

Network-wide migrations of a running network, such as the replacement of a routing protocol or the modification of its configuration, can improve the performance, scalability, manage- ability, and security of the entire network. However, such migra- tions are an important source of concerns for network operators as the reconfiguration campaign can lead to long, service-disrupting outages. In this paper, we propose a methodology that addresses the problem of seamlessly modifying the configuration of link-state Interior Gateway Protocols (IGPs). We illustrate the benefits of our methodology by considering several migration scenarios, in- cluding the addition and the removal of routing hierarchy in a run- ning IGP, and the replacement of one IGP with another. We prove that a strict operational ordering can guarantee that the migration will not create any service outage. Although finding a safe ordering is NP-complete, we describe techniques that efficiently find such an ordering and evaluate them using several real-world and in- ferred ISP topologies. Finally, we describe the implementation of a provisioning system that automatically performs the migration by pushing the configurations on the routers in the appropriate order while monitoring the entire migration process.

To appear in IEEE/ACM Transactions on Networking, 2012.

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