Persistent route oscillations in inter-domain routing

Hop-by-hop inter-domain routing protocols, such as BGP and IDRP, use independent route selection to realize domains' local policies. A domain chooses its routes based on path attributes present in a route. It is widely believed that these inter-domain routing protocols always converge. We show that there exist domain policies that cause BGP/IDRP to exhibit persistent oscillations. In these oscillations, each domain repeatedly chooses a sequence of routes to a destination. Complex oscillation patterns can occur even in very simple topologies. We analyze the conditions for persistent route oscillations in a simple class of interdomain topologies and policies. Using this analysis, we evaluate ways to prevent or avoid persistent oscillations in general topologies. We conclude that if a hop-by-hop inter-domain routing protocol allows unconstrained route selection at a domain, the protocol may be susceptible to route oscillations. Constraining route selection to a provably "safe&q...

• Type: Journal
• Year: 2000
• Where: CN
• Authors: Kannan Varadhan, Ramesh Govindan, Deborah Estrin
• Keywords: CN 2000, Hop-by-hop Inter-domain Routing, Inter-domain Routing Protocol, Oscillations