ImprovingNetworkAgilitywith.PDF

1 Improving Network Agility with Seamless BGP Reconfigurations Stefano Vissicchio, Laurent Vanbever, Cristel Pelsser, Luca Cittadini, Pierre Francois, Olivier Bonaventure Abstract—The network infrastructure of Internet Service fine-tuning of IGP weights [3]. Unfortunately, IGP configu- Providers (ISPs) undergoes constant evolution. Whenever new ration adjustments can affect iBGP routing choices, possibly requirements arise (e.g., the deployment of a new Point of leading to routing and forwarding inconsistencies [4], [5], as Presence, or a change in the business relationship with a well as undesired side effects on internal and external traffic neighboring ISP), operators need to change the configuration of the network. Due to the complexity of BGP and to the lack of flows [6]. IGP changes may thus require iBGP configuration methodologies and tools, maintaining service availability during changes. Similarly, eBGP configuration need to be changed. reconfigurations that involve BGP is a challenge for operators. A typical use case is the provisioning of a new customer, In this paper, we show that the current best practices to which requires to establish new eBGP sessions on some border reconfigure BGP do not provide guarantees with respect to traffic routers. As commercial relationships between ISPs change, disruptions. Then, we study the problem of finding an operational ordering of BGP reconfiguration steps wh