04-02

Improving network agility with seamless BGP reconfigurations

Today, the network infrastructure of Internet Service Providers (ISPs) undergoes constant evolution. Whenever new requirements arise (e.g., the deployment of a new point-of-presence, or a change in the business relationships with a neighboring ISP), network operators need to modify the BGP configuration of their network. Due to the complexity of BGP, and the lack of methodologies and tools, maintaining service availability during reconfigurations that involve BGP is a challenge for network operators.

In this talk, we address the problem of deploying a new BGP configuration in a running ISP with no impact on the data-plane traffic. First, we show that the current best practices to reconfigure BGP (eBGP and iBGP) do not provide guarantees with respect to packet loss. In particular, we show that long-lasting routing and forwarding anomalies can occur even when the initial and the final BGP configurations are anomaly-free. Then, we study the problem of finding an operational ordering of the reconfiguration steps which guarantees no packet loss. Unfortunately, such an operational ordering, when it exists, is computationally hard to find. Finally, to enable disruption-free reconfigurations, we propose a framework which extends current carrier-grade routers to run two BGP control-planes in parallel. We present a prototype implementation and show its effectiveness through a case study.