Consider Figure 5.7. Suppose there is another router w, connected to router y and z. The costs of all links are given as follows: c(x,v) 4, c(x,z) = 50, c(v,w) = 1, cz,w) = 1. c(v.z) = 3. Suppose that poisoned reverse is used in the distance-vector routing algorithm.

a. When the distance vector routing is stabilized, router w, y, and z inform their distances to x to each other. What distance values do they tell each other?

b. Now suppose that the link cost between x and y increases to 60. Will there be a count-to-infinity problem even if poisoned reverse is used? Why or why not? If there is a count-to-infinity problem, then how many iterations are needed for the distance-voter routing to reach a stable state again? Justify your answer.

c. How do you modify cy,z) such that there is no count-to-infinity problem at all if exchanges from 4 to 60?

Figure 5.7

60, 4. 50 50 b. a.