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(Comp361)[2006](s)midterm~cmsiu^_78994.pdf
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COMP 361 Computer Networks
Spring Semester 2006
Final Examination Solution
Date: May 25, 2006 Time: 4:30 pm C 7:00 pm

Name:_____________________ Student ID: ________________Email:__________________
Instructions
1.
Please write your name, student ID and email address on this page.

2.
Please answer all questions within the space provided on the examination paper. You may use back of the pages for your rough work. Please be concise, and this is NOT an essay contest.

3.
This paper consists of 8 questions and 12 pages. The last question is a bonus question.

4.
You have total 150 minutes to complete exam, thus each 10 points question roughly requires 15 minutes, please manage your time wisely.

5.
Please read each question very carefully and answer the questions carefully and clearly to the point. Make sure your answers are neatly written, legible, and readable.

6.
Show all the steps used in deriving your answer, wherever appropriate.


Question Points Score
1 10
2 10
3 20
4 10
5 20
6 15
7 15
8 20
Total 100+20
COMP 361 (Spring 2006) Final Exam


1. Answer the following true/false questions by circling either T or F [10 points] a) The Ethernet achieves better utilization than Token Ring under heavy load T F b) The Subnet mask is used to identify the host within a network T F c) Both Router and Switch are plug-and-play devices T F d) The maximum throughput of ALOHA is twice than that of slotted ALOHA T F e) A hub is a physical layer repeater and a switch is a store-and-forward device. T F f) BGP is a Distance-Vector (DV) based protocol using the shortest path routing. T F g) OSPF is the only intra-AS routing protocol (an intra-AS is a protocol that routes packets within an Autonomous System) use in the Internet. T F h) In a Go-Back-N protocol, the loss of a single packet can cause the retransmission
of many correctly received packets T F i) Error correction is provided in the transport layer. T F j) Class-C networks contain 24-bit subnet addresses T F
Explanation:
a) Ethernet as a random access protocol does not work well under heavy traffic, while Token

Ring can do much better
b) Subnet mask is used to determine the network ID, nit host
c) Routers are not plug-and-play devices, they must be configured manually, with interface IP
address and forwarding (routing) tables d) Slotted ALOHA performs twice as good as unslotted ALOHA, since in an unslotted ALOHA,
a transmission can possibly collide with up to two slots transmissions
e) This is true
f) BGP is a distance vector protocol, not based on the shortest path routing
g) OSPF is not the only one, recall that RIP is another one
h) This is true
i) Transport layer function does not include any error control, which is usually done at the link
layer level j) This is true, the first three bytes are used to specify the network ID
2. Consider the following network with 4 hosts and 3 r