Question

Suppose two hosts use a TCP connection to transfer a large file. Which of the following statements is/ar FALSE with respect to the TCP connection?

1. If the sequence number of a segment is m, then the sequence number of the subsequent segment is always m + 1
2. If the estimated round trip time at any given point of time is t sec. the value of the retransmission timeout is always set to greater than or equal to t sec
3. The size of the advertised window never changes during the course of the TCP connection.
4. The number of unacknowledged bytes at the sender is always less than or equal to the advertised window.

Answer 1

Statement 1 is false because, the sequence number of the subsequent segments depends on the number of bytes characters in the current segment.
Statement 2 True, because RTO timer is always $\ge$ Estimated RTT.
Statement 3 False. Receiver window is used to give the sender and idea of how much free buffer space is available at the receiver.
Statement 4 is true , TCP is not permitted to overflow the allocated receiver buffer.
Hence when the sender cannot send any more data receiver window would be 0 and hence. The buffer would have unacknowledged data.