Consider the simple network in Figure 4.50, in which A and B exchange distance vector routing information. All links have cost 1. Suppose the A-E link fails.
(a) Give a sequence of routing table updates that leads to a routing loop between A and B.
(b) Estimate the probability of the scenario in (a), assuming A and B send out routing updates at random times, each at the same average rate.
(c) Estimate the probability of a loop forming if A broadcasts an updated report within 1 second of discovering the A-E failure, and B broadcasts every 60 seconds uniformly.
Figure 4.50
