Question

Two adjacent nodes A and B use Selective Repeat sliding window protocol with 3-bit
sequence numbers and a send window size of 4. We assume that A is transmitting to
B. What is the window position for A and B by drawing the sequence diagram after :
 A sends frames 0,1,2,3.
 B acknowledges frames 0,1,2,3 and these acks are received by A.
 A sends frames 4,5,6,7, frames 5 and 6 are lost.
 B acknowledges frames 4 and 7, the ack for 4 is lost.
 The acks for 7 are received by A.
Which frames are resent? Explain your answer.

Answer 1

Given,

Number of bit in the sequence number = 3

Window size = 7

Frame send by P = 0, 1, 2, 3,4, 5,7 from lost 5

Q acknowledges frame = 0,1,2,3,4 all received by P

except for acknowledge 2 and acknowledge 3