Interactive end-of-chapter exercises


Supplement to Computer Networking: A Top Down Approach 8th Edition


"Tell me and I forget. Show me and I remember. Involve me and I understand." Chinese proverb

Textbook Cover

Bellman Ford Distance Vector Algorithm (for computing least cost paths)

Consider the 6-node network shown below, with the given link costs:



Bellman Ford Graphic




Question List


1. When the algorithm converges, what are the distance vectors from router 'U' to all routers? Write your answer as u,v,w,x,y

2. What are the initial distance vectors for router 'V'? Write your answer as u,v,w,x,y and if a distance is ∞, write 'x'

3. The phrase 'Good news travels fast' is very applicable to distance vector routing when link costs decrease; what is the name of the problem that can occur when link costs increase?




Solution


1. When the algorithm converges, router U has distance vectors (u,v,w,x,y) = (0,8,15,10,15)

2. The initial distance vectors of router V are: (u,v,w,x,y) = (8,0,8,2,x) where x is ∞

3. It is called the 'Count to Infinity' problem.



That's incorrect

That's correct

The answer was: 0,8,15,10,15

Question 1 of 3

The answer was: 8,0,8,2,x

Question 2 of 3

The answer was: Count to Infinity

Question 3 of 3

Try Another Problem

We gratefully acknowledge the programming and problem design work of John Broderick (UMass '21), which has really helped to substantially improve this site.

Copyright © 2010-2021 J.F. Kurose, K.W. Ross
Comments welcome and appreciated: kurose@cs.umass.edu