Suppose Host A sends two TCP segments back to back to Host B

Suppose Host A sends two TCP segments back to back to Host B over a TCP connection. The first segment has sequence number 526; the second has sequence number 1526. a, How much data is in the first segment? b, Suppose that the first segment is lost but the second segment arrives at B. In the acknowledgement that Host B sends to Host A, what will be the acknowledgement number

Solution

In a three way handshake TCP connection, when a sender sends a data segment with some sequence number \'X\' to receiver. The receiver in turn replies with an acknowledegement on receiving the packet plus the window size( the ssegment size) it can accomodate. then the sender sets its sequence number according to the receiver\'s window size.

Here in this problem, first segment has a sequence number 526 and the second segment has a sequence number of 1526 it implies that the size of the data in the first segment is 1526-526=1000.

if the first  segment is lost but the second segment arrives at B, the acknowledgement that Host B sends to Host A will be 526 even when it has received a data segmment with sequence number 1526 because it TCP accepts out of order packets and it will inform sender about the loss of segment using the sequence number 526.