Written homework 4

CMPSCI 453/591
Computer Networking
Professor Jim Kurose

Written Homework 4

(covering lectures 17-19 [approximately])
Assigned: 11/17/05
Due: 11/29/05
Off campus: Postmarked seven days after viewing lecture 20 or receiving this (whichever is later)

Note: Problem numbers below refer to the 3rd edition of the text.. In all written assignmens, please show as muchof your work as you can. Even if you get a wrong answer, you can get partial credit if you show your work. If you make a mistake, it will also help the grader show you where you made a mistake.

Problem 1. (15 points) Page 494, problem 1, except suppose that theinformation context of a packet is 1001001001001001

Problem 2. (15 points) Page 494 problem 2. Also for the case of 16 data bits aranged in a 4x4 grid, given an example of four corrupted bits, that results in these four errors not being detected.

Problem 3. (15 points) Page 494, problem 4.

Problem 4. (15 points) Page 494, problem 8.

Problem 5. (20 points) Page 495, problem 9.

Problem 6. (20 points) Multiple access protocols. We studied a number of multiple access protocols including (1) TDMA, (2) CSMA, (3) Slotted Aloha and (4) Token passing.

Suppose you were charged with putting together a LAN to support IP telephony (only) and that multiple users may want to carry on a phone call at the same time. Recall that IP telephony digitizes and packetizes voice at a constant bit rate when a user is making an IP phone call. How well suited are these four protocols for this scenario? Provide a brief (e.g. one sentence) explanation of each answer.
Now suppose you were charged with putting together a LAN to support the occasional exchange of data between nodes. That is, any individual node does not have data to send very often. How well suited are these four protocols for this scenario? Provide a brief (e.g. one sentence) explanation of each answer.
Now suppose the LAN must support both voice and data and you must choose one of these multiple access strategies in order to support both applications on the same network, with the understanding that voice calls are more important than data. Which would you choose and why? How would voice and data be sent in this scenario? That is, which access protocol would you use, or adapt/modify, and why?