GATE Papers >> CSE >> 2011 >> Question No 53

Question No. 53

Consider a network with five nodes, N1 to N5, as shown below The network uses a Distance Vector Routing Protocol.once the Route have stabilized, the distance vectors

at different nodes are as following
N1:(0,1, 7, 8, 4)
N2: (1, 0, 6, 7, 3)
N3: (7, 6, 0, 2, 6)
N4: (8,7, 2,0,4)
N5: (4, 3, 6, 4, 0)

Each distance vector is the distance of best known path at that instance to nodes, N1 to N5, where the distance to itself is 0. Also, all links are symmetric and the cost is identical in both directions. In each round, all nodes exchange their distance vectors with their respective neighbors. Then all nodes update the distance vectors. In between two rounds, any change in cost of a link will cause the two incident nodes to change only that entry in their distance vectors.

The cost of link N2-N3 reduces to 2 (in both directions). After the next round updates, what will be the new distance vector at node, N3?

At the update in the previous question ,the link N1-N2 goes down. N2 will reflect this change immediately in its distance vector as cost, $\infty$. After the NEXROUND of update, what will be the cost to N1 in the distance vector of N3?