Consider the simple network in Figure 3.54, 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 3.54)

(E) A (B)