Virginia Tech

Department of Computer Science

CS4254 Computer Network Architecture and Programming

Spring 2006

Homework 3 (Total 40 pts)

Due in class on Thursday February 16^th, 2006

Please hand in a hardcopy of your homework in a folder, which has your name and course number, in class on Thursday Feb. 16^th, 2006. (Always keep a copy of the homework you hand in). Each solution must include all calculations and an explanation of why the given solution is correct. In particular, write complete sentences. A correct answer without an explanation is worth no credit. No late homework will be accepted. Electronic preparation of your solutions is mandatory.

Q1. (5 pts) TCP assumes an MSS of 536 if it does not receive an MSS option from the peer. Why is that value used?

Q2. (5 pts) Do port addresses need to be universally unique? Why or why not?

Q3. (10 pts) A TCP Connection is using a window size of 10,000 bytes, and the previous acknowledgment number was 22,001. It receives a segment with acknowledgment number 24,001. Draw a diagram to show the situation of the window before and after.

Q4. (10 pts) “In the TCP acknowledgment mechanism, a lost acknowledgment (sent by the receiving TCP) may not even be noticed by the source TCP”. Comment on the validity of this statement explaining your answer. In addition, give a numerical example supporting your answer.

Q5. (10 pts) “A source TCP can receive a zero window-size advertisement from the receiving TCP”.

a) Explain what is the source TCP reaction to such reception?

b) Do you see a potential problem in such situation? Explain your answer?

c) Research how TCP designers handled this problem. List any references you consult.