Consider the graph representation of a network depicted on Figure 2. The nodes a
ID: 3571655 • Letter: C
Question
Consider the graph representation of a network depicted on Figure 2. The nodes are the routers and the edges are the communication links with the costs of communication on them. Execute the (synchronous) distance vector algorithm: show the distance tables of all nodes after the initialization step, show the distance tables of nodes A, B, C and D after the first distance vector exchange step, and show the distance table of node A after the second distance vector exchange step, together with the distance vectors these nodes receive from their neighbors. In each distance table, indicate which new minimum cost values are distributed during the next distance vector exchange. Based on the final distance table, find a routing decision for node A toward destination node F.Explanation / Answer
A routing algorithm tells a router which outgoing line an incoming packet should be placed on.
In the given network diagram
Distances are
A – B – 1
B – C – 2
A – C - 2
A – D – 1
D – E – 4
D – C – 3
C – E – 2
C – F – 4
distance-vector routing algorithm is tells each node knows the cost of the link to each of its directly connected neighbors.
Distance->
Start Node
A
B
C
D
E
F
A
0
1
2
1
2+2
2+4
B
1
0
2
1+1
2+2
2+4
C
2
2
0
3
2
4
D
1
1+1
3
0
4
4+1
E
2+2
2+2
2
4
0
1
F
4+2
4+2
4
1+4
1
0
The routing decision for the given network path is
A to F is A -> C -> F in this the cost from A to C is 2 and C to F is 4 so the total is 6.
Or
A -> D -> E -> F
In this path A -> D is 1 and D -> E is 4 and E -> F is 1 so the total is 6
So there is no difference in both paths but preferable is ACF because nodes are less.
Distance->
Start Node
A
B
C
D
E
F
A
0
1
2
1
2+2
2+4
B
1
0
2
1+1
2+2
2+4
C
2
2
0
3
2
4
D
1
1+1
3
0
4
4+1
E
2+2
2+2
2
4
0
1
F
4+2
4+2
4
1+4
1
0