Gateway control protocol: Re-answer package
|Publication Date:||1 June 2008|
This Recommendation defines an H.248 package in order to request the MG to detect re-answer line signal on a particular TDM termination which supports CAS signalling, and to notify the MGC when the signal is detected. The re-answer capability supplements the basic call service and belongs, thus, to a supplementary service. Such a supplementary service was supported in legacy PSTN, leading to particular call control signalling information elements at the network-to-network (NNI) interface, such as CAS-based NNIs or CCS-based NNIs (e.g., SS7 telephone user part; TUP according to [ITU-T Q.723], [ITU-T Q.724]).
This H.248 package allows the support of emulation of such a service in NGN environments (like e.g., a PSTN emulation subsystem).
The application of the re-answer package is limited on H.248 TDM terminations controlled via CAS or SS7 TUP call control signalling.
Difference between "answer" and "re-answer" signals
The semantic difference is indicated by the signal definitions in clauses 3.1.1 and 3.1.2. The syntactical difference is dependent on the encoding format of the correspondent call control signalling protocol.