ABSTRACT: ISDN Call Forwarding (I-CF) enables a user to have circuit-mode calls redirected from the user's directory to another directory number.
The Stored Program Control switching System (SPCS) serving the user performs the redirection function. I-CF is assigned on the basis
of the directory number for a particular call type that allows calls to be forwarded based on the call type of the incoming call. For
example, the user may have voiceband information calls forwarded, while circuit-mode calls terminate normally.
Subfeatures, or variations, of I-CF permit redirection of incoming calls of a particular type under different circumstances. These
include ISDN Call Forwarding Variable (I-CFV), ISDN Call Forwarding Interface Busy (I-CFIB),and ISDN Call forwarding Don't Answer
(I-CFDA). This document presents the Telcordia view of proposed generic requirements for call forwarding, including requirements to
support National ISDN Enhancement #102 ("Call Forwarding on User Busy") and clarifications regarding the use of redirecting subaddress
for alignment with other requirements documents (e.g.,TR-NWT-001187), and on the operation of ISDN Call Forwarding over Private
Facilities with respect to the automatic answer indication sent towards the calling user when a call is forwarded.
GR-853 replaced TR-TSY-000853, TR-TSY-000853-SUP01, and TR-TSY-000853-SUP02.