New specifications ratified by ITU-T Study Group 11 will transfer some of the call control elements of SS7 to the IP world. SS7 is the signalling system used by telecoms operators worldwide to allow the efficient routing of calls, and its worldwide implementation has paved the way for an efficiently operating international telecommunication network.
The new Recommendation - Q.1980.1- defines narrowband signalling syntax (NSS), a flexible text-based syntax that can be used to transfer narrowband signalling information in protocols that cannot inherently transfer such information (eg the session initiation protocol (SIP)).
This NSS solution aims at helping operators reflect the services that they provide in the public switched telephone network (PSTN) in next generation IP based networks. It provides a standardized set of PSTN/ISDN services signalling parameters that can be mapped into the many SS7 ISDN user part (ISUP*) variations, to be transmitted transparently through IP networks. NSS has been designed to enable seamless interworking between the PSTN and IP networks and transition from legacy TDM (time division multiplexing) circuit switched networks to packet-based transport technologies without service degradation or changes.
* ISUP determines the procedures for setting-up, coordinating and taking down calls on an SS7 network. It provides calling party number information, call status checking, and controls tone and announcement delivery.