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(COMP361)Final_Exam_sp05_sol.pdf
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COMP 361 Computer Communications Networks
Spring Semester 2005
Final Examination C Solution key C version of 5/25/2005 10:58 AM

Date: May 21, 2005. Time: 12:30pm C 3:30pm. Venue: Rm 3007




Instructions:

1. This examination paper consists of 20 pages and 10 questions

2. Please write your name, student ID and Email on this page.

3. For each subsequent page, please write your student ID at the top of the page in the space provided.

4. Please answer all the questions within the space provided on the examination paper. You may use the back of the pages for your rough work.

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

6. Show all the steps you use in deriving your answer, where ever appropriate.

7. For each of the questions assume that the concepts are known to the graders. Concentrate on answering to the point what is asked. Do not define or describe the concepts unless specifically asked to.



Question
Points
Score

1
8


2
15


3
12


4
8


5
12


6
10


7
12


8
7


9
10


6


10
TOTAL

100







Name:______________________Student ID:________________Email:_______________

The notice at the bottom of this page, noting two typos in Q3 and answering one question concerning Q7 was handed out with the exam. The typos noted in Q3 were corrected in this answer sheet. Also, at the time of the exam, another typo in Q3 (the swapping of the labeling of the 802.11 and 803 boxes in Q3 b) was noted and described on the board. This typo has also been fixed in this answer sheet.




Addendum to COMP361 L1 Spring 2005 C Final Exam

Question 3)
. The binary-backoff algorithm is another name for the exponential-backoff algorithm we learnt in class

. In part (b), in the first line after the 2nd box there is a typographical error. Original: What is the reason that step ii is different than step ii. Corrected: What is the reason that step ii is different than step ii? That is, the last ii should be changed into ii (with no prime ) and a question mark ( ? ) should be added.



Question 7)
. When answering parts (b) and (c) of the question you should describe what happens in both TCP Reno and TCP Tahoe and when it happens (in cases in which there is a difference between TCP Reno and TCP Tahoe then you should make the difference clear in your answer)





1) Answer the following true/false questions by circling either T or F. (8 points)



a) CDMA is a random-access MAC protocol used by many wireless networks


b) The 802.3 Ethernet protocol is an unslotted protocol

c) The value in the PPP control field signifies the uppe