Stabilizing BGP, Safely

Route instability is widely recognized as a major problem in the Internet. Core routers are barraged with millions of updates daily, leading to massive infrastructural costs and worsened data-plane performance. Route flap damping provides some protection against instability, but introduces pathologies and reduces availability. With concerns about the scalability of the routing system prompting a renewed interest in stability, we believe it’s time for a more principled approach to stabilizing Internet routing. This paper takes a step towards that goal by characterizing the tradeoff between stability and availability. In a large-scale simulation of the BGP protocol supplied with traces of measured inter-AS adjacency failures, we bound the performance of theoretically optimal strategies and evaluate the performance of several implementable strategies. Motivated by the principle that any improvements to stability should not come at the price of availability, we argue for an approach which we call Stable Route Selection (SRS). Our numerical evaluation shows that SRS preserves the high availability of BGP without flap damping, while obtaining stability similar to BGP with flap damping. Although further evaluation is necessary, these results indicate a promising approach to safely stabilizing BGP.