scope:

The present document specifies signalling intenvorking between "QSIG" and the Session Initiation Protocol (SIP) in support of basic services within a corporate telecommunication network (CN).

"QSIG" is a signalling protocol that operates between Private Integrated Services exchanges (PINX) within a Private Integrated Services Network (PISN). A PISN provides circuit-switched basic services and supplementary services to its users. QSIG is specified in other ECMA Standards, in particular ECMA-143 [2] (call control in support of basic services), ECMA-165 [4] (generic functional protocol for the support of supplementary services) and a number of Standards speciSling individual supplementary services.

SIP is an application layer protocol for establishing, terminating and modiSling multimedia sessions. It is typically carried over the Internet Protocol (IP) (IETF RFC 791 [7] and IETF RFC 2460 [12]). Telephone calls are considered as a type of multimedia session where just audio is exchanged. SIP is defined in IETF RFC 3261 [14].

The present document specifies signalling interworking for basic services that provide a bi-directional transfer capability for speech, DTMF, facsimile and modem media between a PISN employing QSIG and a corporate IP network employing SIP. Call-related and call-independent signalling in support of supplementary services is outside the scope of the present document, but support for certain supplementary services (e.g. call transfer, call diversion) could be the subject of future work.

Interworking between QSIG and SIP permits a call originating at a user of a PISN to terminate at a user of a corporate IP network, or a call originating at a user of a corporate IP network to terminate at a user of a PISN.

Interworking between a PISN employing QSIG and a public IP network employing SIP is outside the scope of the present document. However, the functionality specified in the present document is in principle applicable to such a scenario when deployed in conjunction with other relevant functionality (e.g. number translation, security functions, etc.).

The present document is applicable to any intenvorking unit that can act as a gateway between a PISN employing QSIG and a corporate IP network employing SIP.

A brief assessment of security considerations in the IP network resulting from the intenvorking specified in the present document is given in annex C.