Managing Multiplexers
1-27
6800-A2-GB21-10
August 1994
NMS recognizes three types of SDLs, embedded, external, and synchronous. These types are
described as follows.
embedded
By default, the 731/74x multiplexer is configured with half a time slot (32 kbps)
dedicated to SDL traffic, embedded in the first time slot of each physical link. If needed,
the other half of time slot 1 can be used for network traffic. The 74x-56K multiplexer
provides a default 1.2 kbps SDL embedded in the 56K/64K aggregate link. By
configuring an embedded SDL between each node in the network, complete SDL
connectivity within the entire network can be achieved. This is easily accomplished if all
the nodes in the network are Series 700. The 745 has 16 physical links and each link can
have an embedded SDL. By using its routing table, it is able to route data packets using
the SDL of the appropriate link to the addressed node. This capability ensures a fully
connected SDL network.
An embedded SDL is known by a 740 node as SDL 0 and by a 745 node as SDL 0 to
SDL 15. Since each 740 supports only one embedded SDL per physical T1, NAP tail
circuits (see synchronous SDL below) can be used to provide supervisory connectivity
from the central site 740 to the other remote 740s.
external
NAP tail circuits, using synchronous data channels that are carried on the link in stub
channel groups, can be used to provide additional SDL connectivity. These channels are
configured as synchronous data channels, and placed in stub channel groups (bit-mapped
channel groups that originate and terminate on the same node). The remote end must have
a similar configuration.
synchronous SDL (only for currently available ACCULINK 740/741 models)
A combination of embedded and synchronous SDLs allows you to configure SDLs at all
remote 740s to be configured as embedded, while a central site 740 can terminate one
embedded SDL and deliver multiple synchronous SDLs to channel cards that are
connected directly to NAPs or to a 719/72x NETWORKER.
The allowable speeds are 8, 16, 32, and 1.2 kbps. The 1.2 kbps setting is only applicable
as the speed when the synchronous SDL connects to the embedded SDL of a 74x-56K.
The 740 recognizes the synchronous SDLs and automatically places them in the proper
position in the time slot without assigning them to a channel group.