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 70 and 50 bytes of data, respectively. If 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 (no delayed ACKs).
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, the source port number, and the destination port number?
In the second segment sent from Host A to B, what are the sequence number, source port number and destination port number
a). Seq=197
source port=302
dest= 80
b). 197, 80, 302
To answer these questions, let's go step by step and analyze the scenario:
a. In the second segment sent from Host A to B, the sequence number, source port number, and destination port number are not specifically mentioned in the given context. However, we can assume that the sequence number of the second segment would be the sum of the sequence number of the first segment and the number of bytes in the first segment.
In this case, the sequence number of the second segment would be:
Sequence number = 127 + 70 = 197
The source port number and destination port number remain unchanged from the first segment, which are:
Source port number = 302
Destination port number = 80
b. In the scenario where the first segment arrives before the second segment, the acknowledgement of the first arriving segment would acknowledge all the data bytes received up until byte 126. Therefore, the acknowledgement number would be 127 (since byte 126 has already been received).
Regarding the source port number and destination port number for the acknowledgement, they would be swapped from the source and destination of the original sender. In this case, Host B becomes the sender of the acknowledgement, so the source port number would be 80 (destination port of the original sender) and the destination port number would be 302 (source port of the original sender).
To summarize:
- Acknowledgement number: 127
- Source port number (of the acknowledgement): 80
- Destination port number (of the acknowledgement): 302
a. Yes
b. No