Stop and Wait ARQ
This is the simplest ARQ method where the transmitter waits after each
message for an acknowledgement of correct reception (known as an ACK) from the receiver.
If the message is received in error, a negative acknowledgment (NAK) is returned. While
this process is taking place, any new messages must be stored in a buffer at the
transmitter site. |
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Go Back N ARQ
As the name suggests, the transmitter in this case continues to transmit messages in
sequence until a NAK is received. The NAK identifies
which message was in error and the transmitter then 'back-tracks' to this message,
starting to retransmit all messages in the sequence from when the error occurred. Clearly,
this has less signalling overhead (no ACKs used) than the Stop and Wait protocol.
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