On the impact of route processing and MRAI timers on BGP convergence times

Fast convergence of BGP (border gateway protocol) routes, coupled with reduced message complexity, form one of the key factors determining the stability and performance of inter-domain routing in the Internet. The paper characterizes the impact of topology and the message handling procedure of BGP on its convergence time. For BGP router networks characterized by random graphs, we obtain analytic expressions to evaluate the convergence times in terms of the number of minimum route advertisement interval (MRAI) timer rounds. We then isolate artifacts in the BGP message handling procedure which lead to redundant MRAI timer instances and propose minor, but effective, modifications which significantly reduce the convergence times. Simulation results show that the proposed changes can successfully eliminate all redundant instantiations of the MRAI timer, even in the worst case convergence scenarios resulting from route withdrawals.