Assignment #7
ECE 487 (Data Communications Networks) Section B1
1. (6 points) The following figure shows a virtual circuit network. Station A is going to send
information to Station B, through two switches: S1 and S2. A virtual circuit is set up for this
communication: A --> S1 --> S2 --> B. For this virtual circuit, the VCIs over the three hops are
24, 15, and 66, respectively.
i) Who are responsible to assign the three VCIs?
ii) Please give the switching tables at the two switches.
iii) For communication from Station A to Station B, please give the VCI numbers included in the
frames over the three hops.
2. (5 points) In a domain applying a distance vector routing protocol, station A and station B are
neighbors. At a moment, the routing tables at the two stations are:
Station A Station B
To Cost Next To Cost Next
A 0 - A 4 -
B 4 - B 0 -
C 12 B C 9 -
D 13 - D 5 -
E 10 - E 9 -
And subsequently, station B shares its routing table with station A. Please determine the contents
in station A's routing table after the sharing.
(Question 3 on the next page)
3. (9 points) For the following network topology, please use the Dijkstra algorithm to find the
shortest path tree for Station A, and based on the shortest path tree, give the routing table at
Station A. Please show your steps. Please use a square to represent a station in the permanent
list, and a circle to represent a station in the tentative list.
