PP Presentation

Go Back N Protocol
Suppose the transmission time required for a frame to arrive at the receiver plus the transmission time for the ack to come back is non-trivial.
E.g. a 50 kbps satellite channel could have a 500 ms round trip time. To xmit a 1000 bit frame takes 20 ms, but it is not until 520 ms that the sender gets an ack and so is blocked 500/520 = 96% of the time.
Let w=#of frames to xmit before blocking.
at 20 ms per frame and 500 ms/ack we should set w=(500+20)/20=26 frames (at least)
This is known as pipelining