BGP convergence in an MRAI-free Internet

Abstract

In this paper, we study the effect of reducing the use of BGP’s MRAI mechanism in the Internet. MRAI stands for Minimum Route Advertisement Interval and it is a timer that rate-limits BGP route announcements. In particular, we look into the effects of MRAI removal by simulating router topologies representing all the Autonomous Systems (ASes) in the Internet. We consider the two main MRAI implementation flavors, namely per-session and out-delay MRAI. Reducing the fraction of MRAI-enabled ASes is positive in terms of convergence performance, until the adoption reaches 10% of Internet ASes. Below this threshold, the number of messages exchanged when routes are removed sharply increases, and thus the router load. Depending on the time that it takes for routers to process BGP messages, further reductions in the fraction may even increase convergence time for removing a route. We show that keeping MRAI enabled in few highly connected ASes, the tier-1 ASes, provides some protection against the increase in the computing demand of the routers.