Signaling Protocol - Nortel DMS-100 Series Maintenance Manual

2-4 Signaling for RLCM-EDC
Data link layer
The LTC+ converts two standard DS-1 frames to one internal DS60 frame.
Timeslot 1 of links 0 and 2 are extracted from the DS-1 interface. The
timeslots are wired directly to the first network message interface (NMIF)
channel in the correct LTC+ message card. The speech bus interface (SBIF)
directs messages along the speech bus until the messages reach the
messaging card. Each timeslot on the speech bus can be a messaging
channel toward the C-side or P-side of the shelf. The DMS-X protocol uses
channel 1 on each link.

Signaling protocol

Two data link protocols are in use between an LTC and RLCM-EDC. The
two data link protocols are DMS-X and high data link control (HDLC). To
apply a data link protocol on a specified timeslot, the system declares a
specified channel a data link. The timeslots can be the C-side of an
RLCM-EDC or P-side of an LTC+. This data link is assigned to a specified
node entity. Additional data links are created in the LTC+ and RLCM-EDC.
HDLC protocol
High data link controller (HDLC) protocol is a current LTC+ to
RLCM-EDC message protocol. The HDLC applies to the extended distance
capability (EDC) application. The NTMX76BA messaging card implements
this protocol. The NTMX76BA messaging card in the host LTC+ replaces
the NT6X69 card. The same links serve as message links between the LTC+
and the RLCM EDC. The use of timeslot 6 occurs through speech bus
interface (SBIF).
The system cannot apply HDLC protocol through the NMIF. The speech
bus requires two additional timeslots. The system cannot use these timeslots
for speech.
297-8381-550 Standard 02.02 April 1999
The data link layer (level 2) provides the mechanism required to transfer
messages from one node to another node. This other node connects
directly to the first node. The network layer selects the route for the
transfer of messages. The data link layer performs error detection and
notification. The data link layer maintains the sequence order of
messages and allows the activation and deactivation of links that support
messages.
The network layer (level 3) provides application software. This software
contains the mechanism required to send a message from one node to
another node in the network. The network layer selects a route to send
the message toward the desired destination node. The network starts the
necessary service from the message link layer.