Signaling Protocol - Nortel DMS-100 Series Maintenance Manual

4-2 Signaling for RLCM
Message channels
The RLCM requires a minimum of two DS-1 links to the host. These links
are the primary links. The LCM part of the RLCM requires two message
channels to the host XPM.
The LCM message channels occupy channel 1 on each of the primary DS-1
links to the host. The remote maintenance module (RMM) requires two
message channels to the host XPM. These channels occupy channel 2 on the
primary links.
The emergency stand-alone (ESA) processor requires two message channels
to the host. These channels occupy channel 3 on the primary links. If the
ESA processor is not provisioned, channel 3 is available for speech traffic.

Signaling protocol

The message channels on the primary DS-1 links have nailed-up connections
to the DMS central control (CC). The message channels use the DMS-X
protocol to communicate with the host.
The DMS-X is a half-duplex, byte-oriented protocol implemented with a full
duplex message channel like the DS-1 links. The LCM processor handles
the DMS-X message protocol on message channels to the host.
The RMM control card processes DMS-X messages, trunk messages and
pulse code modulation (PCM) data. The ESA processor is the interface that
communicates with the host XPM. The ESA processor communicates
through DMS-X protocol when the RLCM is in ESA mode.
DMS-X protocol
The DMS-X protocol is a state-driven code. This code requires handshake
messaging between the RLCM and host at each stage of data transfer. This
handshake messaging allows the communicating terminals to delay the
message transfer if a terminal is not ready.
The following figure shows a general form of handshaking protocol that
makes up DMS-X protocol.
297–8351–550 Standard 04.01 August 1999