CS 428/528
Instructor: Anand Seetharam
Homework 4: Network Layer
Problem 1 (30 points)
Consider the following network. With the indicated link costs, use Dijkstra’s shortest-path
algorithm to compute the shortest path from
a) x to all network nodes.
b) t to all network nodes.
c) v to all network nodes.
Show how the algorithm works by computing a table similar to
Table 4.3.
Problem 2 (40 points)
Consider the network shown below, and assume that each node initially knows the cost to each
of its neighbors. Consider the distance-vector algorithm and show the working of the algorithm
till it converges. You need to show all the steps (i.e., how the tables are being exchanged
between the nodes and how they are being updated). You will not be given credit for just writing
the final answer.
Problem 3 (30 points)
Perform a Traceroute between source and destination on the same continent at three different
hours of the day. You need to provide screenshots to show that you have done all these
experiments. Please do not try websites such as google.com, amazon.com etc as these websites
make extensive use of CDNs and you will not get useful results.
a. Find the average and standard deviation of the round-trip delays at each of the three
hours.
b. Find the number of routers in the path at each of the three hours. Did the paths change
during any of the hours?
c. Try to identify the number of ISP networks that the Traceroute packets pass through from
source to destination. Routers with similar names and/or similar IP addresses should be
considered as part of the same ISP. In your experiments, do the largest delays occur at the
peering interfaces between adjacent ISPs?
d. Repeat the above for a source and destination on different continents. Compare the intracontinent and inter-continent results.
Submit a single pdf file with answers to the above questions. The naming convention of the file
should be HW5_yourlastname.pdf