User`s manual

Mediant 2000 & TP-1610 & TP-260
SIP User's Manual 244 Document #: LTRT-68805
Relevant parameters (described in Table 6-11 on page 189):

ISDNRxOverlap

ISDNRxOverlap_x
 TimeBetweenDigits
 MaxDigits

ISDNInCallsBehavior
 DigitMapping
10.3 Using ISDN NFAS
In regular (non-NFAS) T1 ISDN trunks, a single 64 kbps channel carries signaling for the
other 23 B-channels of that particular T1 trunk. This channel is called the D-channel and
usually resides on timeslot # 24.
The ISDN Non-Facility Associated Signaling (NFAS) feature enables use of a single D-
channel to control multiple PRI interfaces.
With NFAS it is possible to define a group of T1 trunks, called an NFAS group, in which a
single D-channel carries ISDN signaling messages for the entire group. The NFAS group’s
B-channels are used to carry traffic, such as voice or data. The NFAS mechanism also
enables definition of a backup D-channel on a different T1 trunk, to be used if the primary
D-channel fails.
The NFAS group comprises several T1 trunks. Each T1 trunk is called an ‘NFAS member’.
The T1 trunk whose D-channel is used for signaling is called the ‘Primary NFAS Trunk’.
The T1 trunk whose D-channel is used for backup signaling is called the ‘Backup NFAS
Trunk’. The primary and backup trunks each carry 23 B-channels while all other NFAS
trunks each carry 24 B-channels.
The gateway supports multiple NFAS groups. Each group should contain different T1
trunks.
The NFAS group is identified by an NFAS GroupID number (possible values are 1, 2, 3 and
4). To assign a number of T1 trunks to the same NFAS group, use the parameter
‘NFASGroupNumber_x = groupID’. ‘x’ stands for the physical trunkID (0 to 7).
The parameter ‘DchConfig_x = Trunk_type’ is used to define the type of NFAS trunk.
Trunk_type is set to 0 for the primary trunk, to 1 for the backup trunk and to 2 for an
ordinary NFAS trunk. ‘x’ stands for the physical trunkID (0 to 7).
For example, to assign the first four gateway T1 trunks to NFAS group #1, in which trunk
#0 is the primary trunk and trunk #1 is the backup trunk, use the following configuration:
NFASGroupNumber_0 = 1
NFASGroupNumber_1 = 1
NFASGroupNumber_2 = 1
NFASGroupNumber_3 = 1
DchConfig_0 = 0 ;Primary T1 trunk
DchConfig_1 = 1 ;Backup T1 trunk
DchConfig_2 = 2 ;24 B-channel NFAS trunk
DchConfig_3 = 2 ;24 B-channel NFAS trunk
The NFAS parameters are described in Table 6-11 on page 189.
Note: In the current version the NFAS parameters cannot be configured via the
‘Trunk Settings’ screen in the Embedded Web Server. Use ini file
configuration instead.