An NFAS group is a set of bearer channels (DS0s) that are controlled by a NI2C signaling channel (D-channel). This set of bearer channels is one or more T1 or E1 spans. An NFAS group is an interface to which calls can be routed on the GW. An NFAS group can be specified in an outgoing POTS dial-peer on the GW as the destination interface to which calls can be routed. On the SC2200 the NFAS group is called a NAS signaling path (NAS sigPath or naspath).
In wholesale voice applications the T1/E1 interfaces on the GW may be connected to different PSTN switches. Calls to different switches must be routed to different NFAS groups.
The current limitation is that only one NFAS group can be configured per RLM group and this allows routing to one PSTN switch only.