Sliding window flow control:
An entity that has a list of sequence number that it is allowed to send and
other entity maintains a list of sequence numbers that is prepared to receive.
Each of this list can be through of as a window of frames. The operation is
referred to as sliding. Windows flow control.
In this approach, a station has data to send and an
acknowledgement to send, it sends both together in one frame, saving
communication capacity. If a station has an acknowledgement but no data to
send, it sends a separate acknowledgement frame. If a station has data to send
but no new acknowledgement to send, it must repeat the last acknowledgement
sequence number that it sent. This is because the data frame includes a field
for the acknowledgement number and some value must be put into that field. When
a station receives a duplicate acknowledgement it simply ignores it.
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