ANF-PR is a feature which applies to an established call, allowing that call's connection between PINXs to be replaced by a new connection.
The Q reference point is defined in ISO/IEC 11579-1.
Service specifications are produced in three stages and according to the method specified in ETS 300 387. ISO/IEC 13874:2003 contains the stage 3 specification for the Q reference point and satisfies the requirements identified by the stage 1 and stage 2 specifications in ISO/IEC 13863.
The signalling protocol for ANF-PR operates on top of the signalling protocol for basic circuit switched call control, as specified in ISO/IEC 11572, and uses certain aspects of the generic procedures for the control of supplementary services specified in ISO/IEC 11582.
ISO/IEC 13874:2003 also specifies additional signalling protocol requirements for the support of interactions at the Q reference point between ANF-PR and other supplementary services and ANFs.
ISO/IEC 13874:2003 is applicable to PINXs which can interconnect to form a PISN.