Facility And Non-Facility Associated Signaling - Avaya Communication Manager Administrator's Manual

Feature Reference

Facility and Non-Facility Associated Signaling

Facility and Non-Facility Associated Signaling
Facility Associated Signaling (FAS) allows an ISDN-PRI T1/E1 interface D-channel to carry signaling
information for all the bearer (B) channels on its associated span.
Non-Facility Associated Signaling (NFAS) allows 1 ISDN-PRI T1/E1 interface D-channel to carry
signaling information for up to 300 bearer (B) channels on its associated spans. In other words, a
D-channel can carry signaling information for numerous B-channels located on different DS1 circuit
packs.
NOTE:
NFAS is only valid for T1/E1 Country Protocol 1. Digital T1 service is also sometimes
called "DS1" to distinguish it from analog T1 service.
ISDN-BRI trunks don't support Non-Facility Associated Signaling.
Brief Description
D-Channel Backup with NFAS
When NFAS is used, a backup D-channel can be administered to improve reliability. The system switches
to the backup D-channel if a signaling link failure occurs on the primary D-channel span.
One D-channel is administered as the Primary D-channel and another D-channel is administered as the
Secondary D-channel. These assignments ensure that both D-channels are in the same state at the same
time and neither can be used to carry B-channel traffic at any time. The Primary D-channel is given
precedence over the Secondary D-channel.
When D-Channel Backup is activated, all calls that have been answered are preserved. However, some
call-related information may be lost. Calls that are not answered when D-channels are switched also may
lose call-related information.
The figure below shows a possible configuration involving 3 ISDN-PRIs between a DEFINITY Server
and another DEFINITY Server or the public network.
1536 Administrator's Guide for Avaya Communication Manager
November 2003