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Q5: Host A and B are communicating over a TCP connection, and Host B has already

ID: 3717037 • Letter: Q

Question

Q5: 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 sends two segments to Host B back-to-back. The first and second segments contain 80 and 40 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 acknowledgment whenever it receives a segment from Host A. What is the sequence number of the second segment sent from Host A to B?

Explanation / Answer

When a tcp packet sent from one host another then its sequence number is calculated by adding sequence number with its payload.So in this case, the first segment sequence number is 127.then the second segement's seqence number is calculated by adding previous packet sequence no with its payload.

Sequence number of host 2 :

sequence no of host A + Payload of host A

127+80=207