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(COMP361)midterm_spring05_Solution.pdf
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COMP 361 Computer Communications Networks
Spring Semester 2005 - Midterm Examination C Solution Key
Date March 22, 2005, Time 20:00 C21:30





Instructions:
1. This is a closed book exam

2. This examination paper consists of 15 pages and 8 questions

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

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

5. 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. Each question is on a separate page. This is for clarity and is not meant to imply that each question requires a full page answer. Many can be answered using only a few lines.

6. 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.

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

8. 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 do so.



Question
Points
Score

1
9


2
10


3
15


4
10


5
5


6
15


7
20


8
16



TOTAL
100






Name:______________________Student ID:________________Email:_______________


1. (9 points) Answer the following true/false questions by circling either T or F

(a) Circuit Switching uses statistical multiplexing


(b) Doubling the Timeout Interval in TCP is a limited form of congestion control



(c) FTP uses out-of-band control


(d) The user-agent of the sender of an email message uses the POP3 protocol to send the message to the local mail server.



(e) UDP provides a simple flow-control mechanism.

(f) Napster is a classic example of a P2P file-sharing system with a centralized directory.

(g) If peers A and B are neighbors in a Gnutella overlay network, then A and B must be geographically near to each other.

(h) In TCP, slow start refers to the additive-increase multiplicative-decrease (AIDM) changing of the congestion window.

(i) Two distinct web pages, e.g., www.mit.edu/research.html and www.mit.edu/students.html, can be sent over the same persistent connection.

























T F

T F

T F

T F



T F

T F

T F


T F


T F

2. (10 pts)
In class we said that the TCP reliable data transfer protocol is a hybrid (mixture)