grp# is the signaling group number (1–166); the test sequence can be either short or long.
An ISDN-PRI Signaling Group is a collection of B-Channels for which a given ISDN-PRI Signaling Channel Port (D-channel) carries signaling information. B-Channels carry voice or data and can be assigned to DS1 ISDN trunks (ISDN-TRK) or PRI endpoint ports (PE-BCHL).
Note:
Throughout this discussion, the term B-Channel refers to an ISDN-TRK or PE-BCHL, depending on the application under investigation.
The following media modules are supported in the implementation of ISDN-PRI:
Media module
Channel types
Interface
MM710
B- and D-Channels
24 or 32 channel
These are two types of DS1 interfaces:
24 DS0 channels on a 1.544-Mbps link
31 DS0 channels + 1 framing channel on a 2.048-Mbps link
The following discussion describes 24-channel interface signaling groups. The 32-channel interface works the same way, except that only port number 16 is used for signaling instead of port number 24. Ports 1 through 15 and 17 through 31 are used for B-Channels. The 32nd channel (port 0) is always used for framing.
ISDN-PRI D-channel signaling can be combined with a group of B-Channels in three basic ways:
Facility-Associated Signaling (FAS)
Non-Facility-Associated Signaling (NFAS)
Backup NFAS signaling
In a FAS signaling group, the 24th port of the DS1 Interface Media Module carries D-channel signaling for up to 23 B-Channel ports on the same media module.
In an NFAS signaling group, the 24th port of one DS1 Interface Media Module can carry D-channel signaling for B-Channels on several other DS1 Media Modules. The 24th port on the other media modules can be used as a B-Channel. A D-Channel in an NFAS group can signal for B channels on a total of 20 DS1 media modules.
D-channel backup provides increased reliability, which is highly desirable since NFAS permits a D-Channel to signal for many more B-Channels. NFAS allows the administration of a backup D-Channel that remains in a standby state until the active D-Channel goes down. If so, the backup D-Channel takes over and provides signaling for every B channel in the signaling group.
The operation of the entire ISDN-PRI signaling group depends on several other entities:
The ISDN-PRI signaling channel ports, the DS1 Interface Media Module, on which the D-Channels reside, and the system link that is carried over the packet bus to the processor.
