NFAS - technical definition

A signaling and control technique by which the signaling and control information associated with a communications channel is not carried within the communications channel, itself, or in a separate channel permanently associated with that communications channel. Rather, that signaling and control information is carried in a separate channel, perhaps over a separate subnetwork. NFAS typically refers to an ISDN technique in which signaling and control functions for multiple primary rate interface (PRI) trunks is accomplished using a common Signaling System 7 (SS7) D channel associated with one of them, thereby freeing the D channels associated with the other trunks and allowing them to be used as B channels for user payload transmission. SS7 is a Common Channel Signaling (CCS) system. Contrast with CAS (Channel-Associated Signaling). See also B channel, CCS, channel, D channel, ISDN, NFAS, PRI, signaling and control, SS7, and trunk.