A Study of Packet Delivery Performance during Routing Convergence

Internet measurements have shown that network failures happen frequently, and that existing routing protocols can take multiple seconds, or even minutes, to converge after a failure. During these routing convergence periods, some packets may already be en-route to their destinations and new packets may be sent. These in-flight packets can encounter routing loops, delays, and losses. However, little is known about how many packets are delivered (or not delivered) during routing convergence periods. In this paper, we study the impact of topological connectivity and routing protocol designs on the packet delivery during routing convergence. We examine three distributed routing protocols: RIP, Distributed Bellman Ford and BGP through protocol analysis and simulation experiments. Our study shows that the packet delivery ratio improves as the network connectivity becomes richer. However differences in routing protocol designs impact their ability to fully utilize the topological redundancy in face of component failures. Two factors in routing protocol design, keeping alternate path information at each router and quickly propagating new reachability information, appear to have the most impact on the packet delivery behavior during con-