Selective Repeat Dilemma

networking, tcp

Solution

When the receiver receives a pkt0 he doesn't know if this packet is:

- A retransmission of the previous pkt0 (in a case where ACK0 has been lost).

or

- if this is a new packet with seqnum 0.

Solution:

Maximum allowable window size = half the sequence number space.

Problem

I'm not understanding what is the dilemma in this figure. I only understood that if the window size is smaller than the sequence number then it's going to lead to some problems. This picture is addressing one of these problems:

Original source