ISDN-SGR (ISDN-PRI Signaling Group)

Table 34. ISDN-SGR (ISDN-PRI Signaling Group)

MO Name (in Alarm Log)	Alarm Level	Initial Command to Run*	Full Name of MO
ISDN-SGR	MINOR	test sig-group grp#	ISDN-PRI Signaling Group
ISDN-SGR	WARNING	test sig-group grp#	ISDN-PRI Signaling Group
*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-channels refers to ISDN-TRKs or PE-BCHLs, depending on the application under investigation.

The MM710 Interface Media Module, which has a direct interface to the packet bus, is required for D-channel signaling. There 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)
• Nonfacility-associated (NFAS) simplex signaling
• NFAS duplex signaling

In a FAS signaling group, the 24th port of the DS1 MM 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 MM Interface can carry D-channel signaling for B-channels on several other DS1 Media Module as well, including TN767s and TN464Bs. The 24th port on the other Media Modules can be used for B-channels. A D-channel in an NFAS group can signal for B-channels on a total of 20 DS1 Media Modules.

NFAS duplex signaling provides increased reliability, which is highly desirable since NFAS permits the D-channel to signal for many more B-channels. NFAS Duplex allows the administration of a backup D-channel which remains in a standby state until the active D-channel goes down. If the active D-Channel does go down, the backup D-Channel takes over and provides signaling for all the B-channels 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-MM Interface Media Module on which the D-channels reside and the system link that is carried over the packet bus to the processor. When there are problems with the ISDN-PRI signaling group, also investigate ISDN-LNK, DS1-MM, and SYS-LINK.