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(comp361)[2008](sum)midterm~2267^_10213.pdf
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THE HONGKONG UNIVERSITY OF SCIENCE & TECHNOLOGY
COMP361: Computer Communication Networks I
Summer, 2008
Wednesday, July 9, 2008

Mid-Term Examination

STUDENT NAME: __________________________________
STUDENT NUMBER: __________________________________
LAB NUMBER: __________________________________


Instructions to Students

1. There are 7 problems and 10 pages. Check that you have all 10 pages.

2. Write your name, student number and Section number on this page.

3. Write your student number on each of the following pages.

4. Answer all questions in the space provided. Be clear yet concise.

5. Rough work should be done only on the back pages and afterwards draw a diagonal line through it to show that it is not part of your answer.

6. Leave all pages stapled together.

7. The examination period will last for 2 hours and 30 minutes.

8. Stop writing immediately when the time is up.




For Grading Purpose Only

Problem 1 _______________ / 15

Problem 2 _______________ / 15

Problem 3 _______________ / 15

Problem 4 _______________ / 15

Problem 5 _______________ / 15

Problem 6 _______________ / 10

Problem 7 _______________ / 15



TOTAL: ______________ / 100

Problem 1 (15 points)
Answer the following true/false questions by underlining either T or F

1 Local domain name servers do not use caching to improve performance. They perform full name resolution each time they receive a name resolution request.

T F

2 Connectionless service does not possess flow control

T F

3 Circuit switching uses statistical multiplexing

T F

4 File transfer applications requires logical channels that guarantee that every message sent from the sender is received properly by the receiver.

T F

5 HTTP servers listen for the clients requests on protocol port 25

T F

6 DNS runs on top of TCP

T F

7 The mail-reader of the receiver of an email message uses SMTP to download the message from the receivers mailbox.

T F

8 Considering a long period of time, instantaneous throughputs of a link at any point in this period are larger than the average throughput over this period.

T F

9 Queuing delay is usually random in nature

T F

10 Internet is a network of networks

T F




Problem 2 (15 points)

Consider sending a large file of F bits from Host A to Host B. There are two links (and one switch) between A and B, and the links are uncongested (that is, no queuing delays). Host A segments the file into segments of S bits each and adds 40 bits of header to each segment, forming packets of L=40+S bits. Each link has a