Inherently Safe Backup Routing with BGP

IP routing requires the cooperation of a large number of Autonomous Systems (ASes) via the Border Gateway Protocol (BGP). Each AS applies local policies for selecting routes and propagating routes to others, with important implications for the reliability and stability of the global system. In and of itself, BGP does not ensure that every pair of hosts can communicate. In addition, routing policies are not guaranteed be safe, and may cause persistent protocol oscillations. Backup routing is often used to increase the reliability of the network under link and router failures, at the possible expense of safety. This paper presents two models for backup routing that increase global network reliability without compromising safety. Indeed, our models are inherently safe in the sense that they remain safe under any combination of link and router failures.