# hw1 - The generator polynomial is x 3 + 1. Show the actual...

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CNT 6107 Advanced Computer Networks, Spring 2012 Assignment 1 given by Jonathan C.L. Liu Out: Feb. 01 (Wednesday), 2012 Due: Beginning of the lecture on Feb. 08 (Wednesday), 2012 The problem sets form an important part of the learning in this course. Thus you are required to do them in order to pass. Try to be as clear and precise as possible in your presentation. Sloppy answers may be at a disadvantage, i.e., likely to receive fewer points. No late assignments are accepted !! Problem 1 A system has an n -layer protocol hierarchy. Applications generate messages of length M bytes. At each of the layers, an h -byte header is added. What fraction of the network bandwidth is ±lled with headers? Try some practical values of n , M and h to get the rough estimation (in term of percentage) of the header overhead. Problem 2 A bit stream 10011101 is transmitted using the standard CRC method covered in the review.

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Unformatted text preview: The generator polynomial is x 3 + 1. Show the actual bit string transmitted. Suppose the third bit from the left is inverted during the transmission. Show that this error can be detected at the receivers end. Problem 3 In most networks, transmission errors are handled by requesting the damaged packets to be re-transmitted. If the probability of a packet being damaged is p , what is the mean number of transmissions required to send a packet if acknowledgments are never lost? Problem 4 Two Ethernet CSMA/CD stations are trying to transmit a few long video les. After each frame is sent, they contend for the channel using the binary exponential back-o algorithm. What is the probability that the contention ends on round k, and what is the mean number of rounds per contention period? Please calculate Frst few terms to get the approximated answer....
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hw1 - The generator polynomial is x 3 + 1. Show the actual...

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