Achieving Sub-50 Milliseconds Recovery Upon BGP Peering Link Failures

Bonaventure, Olivier [UCL] Filsfils, Clarence [Cisco Systems Brussels, Belgium] François, Pierre [UCL]

We first show by measurements that BGP peering links fail as frequently as intradomain links and usually for short periods of time. We propose a new fast-reroute technique where routers are prepared to react quickly to interdomain link failures. For each of its interdomain links, each router precomputes a protection tunnel, i.e. an IP tunnel to an alternate nexthop which can reach the same destinations as via the protected link. We propose a BGP-based auto-discovery technique that allows each router to learn the candidate protection tunnels for its links. Each router selects the best protection tunnels for its links and when it detects an interdomain link failure, it immediately encapsulates the packets to send them through the protection tunnel. Our solution is applicable for the links between large transit ISPs and also for the links between multi-homed stub networks and their providers. Furthermore, we show that transient forwarding loops (and thus the corresponding packet losses) can be avoided during the routing convergence that follows the deactivation of a protection tunnel in BGP/MPLS VPNs and in IP networks using encapsulation.