Frame Pipelining

If the distance (in time) between sender and receiver is long (e.g. a satellite transmission taking 540 milliseconds round-trip time), or expensive (e.g. single-company leased lines), then bandwidth should be maximized.

The solution is to permit multiple outstanding frames.

This is made possible by having the sender transmit many frames until the medium is 'full', and then wait for acknowledgements indicating that frames have been received correctly before proceeding.

The obvious question is 'what do we do when either data frames or acknowledgements are lost?'

We shall look at two solutions:

• the go-back-N protocol, and
• the selective repeat protocol.