Persistent route oscillations in inter-domain routing
2000; Elsevier BV; Volume: 32; Issue: 1 Linguagem: Inglês
10.1016/s1389-1286(99)00108-5
ISSN1872-7069
AutoresK. Varadhan, Ramesh Govindan, Deborah Estrin,
Tópico(s)Network Packet Processing and Optimization
ResumoHop-by-hop inter-domain routing protocols, such as border gateway protocol (BGP) and inter-domain routing protocol (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 inter-domain 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" procedure (such as shortest path) can reduce the number of realizable policies. Alternatively, a routing policy registry can help detect unsafe policies.
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