3. Host A and B are communicating over a TCP connection and Host B has already r
ID: 3688273 • Letter: 3
Question
3. Host A and B are communicating over a TCP connection and Host B has already received from A all bytes up through byte 126. Suppose Host A then send two segments to Host B back to back. The first and second segments contain 70 and 50 bytes of data, respectively. In the first segment, the sequence number is 127, the source port number is 302, and the destination port number is 80. Host B sends an acknowledgement whenever it receives a segment from Host A.
a. In the second segment sent from Host A to B, what are the sequence number, source port number, and destination port number?
b. If the first segment arrives before the second segment, in the acknowledgement of the first arriving segment, what is the acknowledgement number, source port number, and destination port number?
c. If the second segment arrives before the first segment, in the acknowledgement of the first arriving segment, what is the acknowledgement number?
d. Suppose the two segments sent by A arrive in order at B. The first acknowledgement is lost and the second acknowledgement arrives after the first timeout interval. Drawing a time diagram, showing these segments and all other segments and acknowledgements sent. (Assume there is no additional packet loss). For each segment in your figure, provide the sequence number and the number of bytes of data; for each acknowledgement you add, provide the acknowledgement number.
Explanation / Answer
Please find the answers below :
a)
sequence number : 127 + 50 = 197
source port number : 302
destination port number : 80
b)
acknowledgement number : sequence number of first segment = 127
source port number : 80
destination port number : 302
c)
acknowledgement number : sequence number of second segment = 197
source port number : 80
destination port number : 302
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