Question

1. (8 pts) Consider a network with the following topology. Unless indicated otherwise, all links have distance = 1. (a) Use the first four steps of using the Dijkistra shortest path algorithm to find the shortest paths from A to the rest of the nodes. (b) Let's assume the distance vector routing algorithm is used. At t = 0, each node only knows the distances to its neighbors. The distances to the other nodes will be set to infinity. Nodes will exchange their routing tables at t = 1, 2, 3, etc. At t = 1.5, what is the routing table in A?

Answer 1

Sol (a) Let us first redraw the network metion cing all the distances between the nodes. [-] [oo] | Now, shortest distance of node 'A' from itself is abivously D. Now let us assume distance of each node from A is of Now look at the following table :- Step ABCDEFGH 1) A [0] o os o 2 B 1 [1] 32 3 1 3 2 - 0 0 5 W W UT 8 8 [3] [3] G < 1 [ 44 -

u Now, explaining the steps stepy: The distance of node A from A is zero and distance of all other nodes is infinity. - Calculating distance to neighbour nodes B, C.D. Step 2: y Now the distance to node B is smallest hence in this step hence locking Bl and calculating distance of neighbours nodes of 'B' from B- in the third step. - e s is step 3: is found to have the smallest distance hence locking hode 'D' from step 4 onwards and calculating distances to its neighbour. nodes. of a node In calculating distances from different modes in various steps if the new distance is less than previous one then we replace it by the new distance (Updation) & 2 3 2 2 2 Finally in this manner we reach step & with G value 4. This the distance of each node from node 'A' is " A BICOLELELGIH A0/1/3 23 146413