ABSTRACT: This document defines the Telcordia Technologies view of generic requirements for the Call Forwarding Interface Busy feature over an Integrated Services Digital Network (ISDN) Primary Rate Interface (PRI). The Call Forwarding Interface Busy (CFIB) allows calls terminated to an ISDN PRI to be automatically redirected to another Directory Number (DN) when all B-channels on the PRI interface are busy. ISDN PRI CFIB is assigned on the PRI-interface basis that allows circuit-mode calls to be forwarded based on the bearer capability of the incoming call. At this time, the only subfeature of ISDN PRI Call Forwarding being defined is the ISDN PRIC CFIB subfeature. In the future, other subfeatures of ISDN PRI CF may be added.

The requirements in this document apply to the following bearer capabilities: Circuit-Mode/Speech, Circuit-Mode 3.1-kHz Audio, Circuit-Mode Unrestricted Digital Information (64 kbps), and Circuit-Mode Unrestricted Information-Rate Adapted from 56 kbps to 64 kbps.