Host X and Y are communicating over a TCP connection, and Host Y has already rec
ID: 644758 • Letter: H
Question
Host X and Y are communicating over a TCP connection, and Host Y has already received from X all bytes up through byte 1024. Suppose Host X then sends 2 segments to Host Y back-to-back. The 1st and 2nd segments contain 70 and 20 bytes of data, respectively. In the 1st segment, the sequence number is 1025, the source port number is 17226, and the destination port number is 80. Host Y sends an acknowledgement whenever it receives a segment from Host X.
a) In the 2nd segment sent from Host X to Y, 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 1st arriving segment, what is the acknowledgment number, the source port number, and the destination port number?
c) If the second segment arrives before the 1st segment, in the acknowledgement of the 1st arriving segment, what is the acknowledgment number?
Explanation / Answer
Answer:
a) In the second segment from Host X to Y, the sequence number is 1095, source port number is 17226 and destination port number is 80.
b) If the first segment arrives before the second, in the acknowledgement of the first arriving segment, the acknowledgement number is 1095, the source port number is 80 and the destination port number is 302.
c) If the second segment arrives before the first segment, in the acknowledgement of the first arriving segment, the acknowledgement number is 1025, indicating that it is still waiting for bytes 1025 and onwards
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