Proactive vs Reactive Approaches to Failure Resilient Routing

Date of Submission: 
August 6, 2003
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Dealing with network failures effectively is a major operational challenge for Internet Service Providers. Commonly deployed link state routing protocols such as OSPF react to link failures through global (i.e., network wide) link state advertisements and routing table recomputations, causing significant forwarding discontinuity after a failure. The drawback with these protocols is that they need to trade off routing stability and forwarding continuity. To improve failure resiliency without jeopardizing routing stability, we propose a proactive local rerouting based approach called failure insensitive routing. The proposed approach prepares for failures using interface-specific forwarding, and upon a failure, suppresses the link state advertisement and instead triggers local rerouting using a backwarding table. In this paper, we formally analyze routing stability and network availability under both proactive and reactive approaches, and show that FIR provides better stability and availability than OSPF.