The protocol should provide reliable communication. Since DS link
networks are very reliable, we decide to accept the maximum BER of
for our purposes. The consequence is that the
occurrence of an error in the network will result in unspecified
system behaviour. We assume that the DS network does not to lose or
corrupt any data, however, we should also avoid data being lost by
the message receiver due to overflowing buffers. Therefore, a means
of end-to-end flow control is required.
We choose not to implement end-to-end flow control via the DS per-link flow control, holding data reception as soon as the buffers are full, since this blocks the network until the receiver executes a receive operation, and therefore leads to poor network performance and possibly deadlock. We use credit based end-to-end flow control: the receiver allows a sender to start message transmission by sending it a credit.