CS 3251 - Computer Networks I
Homework 2 - Assigned: Thursday, October 6 Due:
Thursday, October 13
Unless otherwise stated, all homeworks for this class will be submitted in class on
paper.
- Kurose and Ross, Chapter 4, problem 15: Consider sending a
3,000-byte datagram into a link that has an MTU of 500 bytes. Suppose the
original datagram is stamped with the identification number 422. How many
fragments are generated? What are their characteristics? Remember that MTU
is the length of the largest link-layer frame that can be sent on a link.
- Kurose and Ross, Chapter 4, problem 21: Consider the network
shown in the text. With the
indicated link costs, use Dijkstra’s algoirhtm to compute the shorted path from x to all
network nodes. Show how the
algorithm works by computing a table similar to Table 4.3. The network has the following links:
(s,t,1), (s,u,4), (t,u,2), (t,v,9), (t,y,4), (t,z,2), (u,v,1), (u,w,3),
(v,w,1), (v,x,3), (v,y,1), (w,x,1), (x,y,6), (y,z,14).
- Give the pseudocode for the
processing at a node A that receives a link state message from a node C.
Assume that the link state message contains the identity of the sender, a
list of links directly connected to the sender (with costs), a sequence
number, and a time-to-live. Be sure to check if node A needs to re-run Dijkstra's algorithm as a result of receiving the link
state message.
- Kurose and Ross, Chapter 4, problem 23: Consider the network
shown in the text, and assume that each node initially knows the costs to
each of its neighbors. Consider the
distance vector algorithm and show the distance table entries at node z. The network has the following links:
(u,v,1), (u,x,2), (v,y,15), (v,z,5), (x,y,1), (x,z,2), (y,z,10).
- Kurose and Ross, Chapter 4, problem 25: Consider the network
fragment shown in the text. x has only two attached neighbors, w and y. w has a minimum-cost
path to destination u (not shown) of cost 5, and y has a minimum-cost path
to u of cost 6. The complete paths
from w and y to u (and between w and y) are not shown. All link costs in the network have
strictly positive integer values.
The network fragment has the following links: (w,y,4), (x,w,1)
- Give x’s distance
vector for destinations w, y and u.
- Give a link-cost change for either c(x,w) or c(x,y) such that x will inform its neighbors of a new
minimum-cost path to u as a result of executing the distance vector
algorithm.
- Give a link-cost change for either c(x,w) or c(x,y) such that x will not inform its neighbors of a new minimum-cost path to u as a
result of executing the distance vector algorithm.
Last
modified: Thursday October 6 09:30:00 Eastern Standard Time 2005