TCP sequence numbers and acknowledgements Hosts A and B are communicating over a
ID: 3864443 • Letter: T
Question
TCP sequence numbers and acknowledgements Hosts A and B are communicating over a TCP connection. Host B has already received from A all bytes up through byte 148. Suppose Host A then sends two segments to Host B back-to-back. The first and second segments contain 40 and 60 bytes of data respectively. In the first segment, the sequence number is 149, the source port number is 503, 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 Host B, what are the sequence number, source port number, and destination port number? (b) Suppose the first segment arrives before the second segment. Host B sends an acknowledgement in response to the first segment: what is the acknowledgment number, the source port number, and the destination port number? (c) Suppose the second segment arrives before the first segment. Host B sends an acknowledgement in response to the first segment. What is the acknowledgement number?Explanation / Answer
(a) sequence no =189, src port no = 503, dest port no =80
(b) ack no = 189, src port no =80, dest port no = 503
(c) ack no =109 (because lenght of second segment is 60. hence ack no is 49+60)
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