Reliable Data Transfer: Go-back-n

In the last lesson, we discovered that a sending sliding window alone is not enough to ensure detection and retransmission of lost packets. In order to do that, we will look at two protocols:

1. Go-back-n
2. Selective Repeat

Go-back-n

The simplest sliding window protocol uses go-back-n recovery.

Go-back-n Receiver

Intuitively, go-back-n receiver operates as follows:

1. It only accepts the segments that arrive in-sequence.
2. It discards any out-of-sequence segment that it receives.
3. When it receives a data segment, it always returns an acknowledgment containing the sequence number of the last in-sequence segment that it has received.

Cumulative Acknowledgements

This acknowledgment is said to be cumulative. When a go-back-receiver sends an acknowledgment for sequence ...