Nortel DMS-100 Series Maintenance Manual page 157

DMS-X handshaking protocol
Message header:
DMS-X
Message data
Checksum or cyclic
redundancy check
The DMS-X protocol includes a cyclic redundancy check (CRC) code for
error detection. Message time-out and message checksum or CRC
calculation perform message error detection.
If protocol, checksum or CRC failure occurs on an outgoing message, the
sending node attempts the send sequence again. On an incoming message
failure, the sending node routes the message over an alternate central-side
(C-side) link. Hardware redundancies provide for at least one alternative
path to and from a node.
The format of DMS-X messages appear in the following figure.
DMS-100 Family RLCM Maintenance Manual XPM12 and up
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Signaling for RLCM 4-3
Link control messages
(request to send, send)
Message
Link control messages
(acknowledgment)