Consider a computer network using the distance vector routing algorithm in its network layer. The partial topology of the network is as shown below. The objective is to find the shortest-cost path from the router R to routers P and Q. Assume that R does not initially know the shortest routes to P and Q. Assume that R has three neighbouring routers denoted as X, Y, and Z. During one iteration, R measures its distance to its neighbours X, Y, and Z as 3, 2, and 5, respectively. Router R gets routing vectors from its neighbours that indicate that the distance to router P from routers X, Y, and Z are 7, 6, and 5, respectively. The routing vector also indicates that the distance to router Q from routers X, Y, and Z are 4, 6, and 8, respectively. Which of the following statement(s) is/are correct with respect to the new routing table of R, after updation during this iteration ?
Consider a computer network using the distance vector routing algorithm in its network layer. The partial topology of the network is as shown below. The objective is to find the shortest-cost path from the router R to routers P and Q. Assume that R does not initially know the shortest routes to P and Q. Assume that R has three neighbouring routers denoted as X, Y, and Z. During one iteration, R measures its distance to its neighbours X, Y, and Z as 3, 2, and 5, respectively. Router R gets routing vectors from its neighbours that indicate that the distance to router P from routers X, Y, and Z are 7, 6, and 5, respectively. The routing vector also indicates that the distance to router Q from routers X, Y, and Z are 4, 6, and 8, respectively. Which of the following statement(s) is/are correct with respect to the new routing table of R, after updation during this iteration ? Correct Answer The next hop router for a packet from R to P is Y., The distance from R to Q will be stored as 7
Explanation:
given data
|
R → X |
3 |
|
R → Y |
2 |
|
R → Z |
5 |
To Router P
|
Cost |
From |
|
7 |
X |
|
6 |
Y |
|
5 |
Z |
To Router Q
|
Cost |
From |
|
4 |
X |
|
6 |
Y |
|
8 |
Z |
Cost of R → P = Min (R → X + X → P, R → Y + Y → P, R → Z + Z → P)
Cost of R → P = Min (3 + 7, 2 + 6, 5 + 5)
Cost of R → P = Min (10, 8, 10) = 8
Cost of R → P = 8 and next hop is Y.
Cost of R → Q = Min (R → X + X → Q, R → Y + Y → Q, R → Z + Z → Q)
Cost of R → Q = Min (3 + 4, 2 + 6, 5 + 8)
Cost of R → Q = Min (7, 8, 13)
Cost of R → Q = 7 and next hop is X.
