HW-3 Solutions

# HW-3 Solutions - Chapter 3 Problems Problem 1 source port...

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Problem 1. source port number - destination port number a) A S 4670 - 23 b) B S 5130 - 23 c) S A 23 - 4670 d) S B 23 - 5130 e) Yes. Different client hosts may have the same client (high) port number. f) No. A host can not have TCP sockets with the same local port number and the same remote host IP and port numbers. . Problem 2. Suppose the IP addresses of the hosts A, B, and C are a, b, c, respectively. (Note that a,b,c are distinct.) To host A: Source port =80, source IP address = b, dest port = 26145, dest IP address = a To host C, left process: Source port =80, source IP address = b, dest port = 7532, dest IP address = c To host C, right process: Source port =80, source IP address = b, dest port = 26145, dest IP address = c Problem 3. 0 1 0 1 0 1 0 1 + 0 1 1 1 0 0 0 0 1 1 0 0 0 1 0 1 1 1 0 0 0 1 0 1 + 0 1 0 0 1 1 0 0 1 0 0 0 1 0 0 0 1 -> 1 0 0 0 1 0 0 1 0 One's complement = 1 1 1 0 1 1 0 1. To detect errors, the receiver adds the four words (the three original words and the checksum). The sum bits should be all 1's. If the sum contains a zero bit, the receiver knows there has been an error. Note that all 1's is a second form of "zero" in 1's compliment number systems. -11111111 = 00000000 Single-bit errors will be detected, but two-bit errors can be undetected (e.g., if the last digit of the first word is converted to a 0 and the last digit of the second word is converted to a

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## This note was uploaded on 10/28/2008 for the course ECE 3076 taught by Professor Copeland during the Spring '08 term at Georgia Tech.

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HW-3 Solutions - Chapter 3 Problems Problem 1 source port...

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