The GBN protocol allows the sender to potentially “fill the pipeline” in Figure 3.17
with packets, thus avoiding the channel utilization problems we noted with stop-
and-wait protocols. There are, however, scenarios in which GBN itself suffers from
performance problems. In particular, when the window size and bandwidth-delay
product are both large, many packets can be in the pipeline. A single packet error
can thus cause GBN to retransmit a large number of packets, many unnecessarily.
As the probability of channel errors increases, the pipeline can become filled with