ISO/IEC 23916:2005规定了企业电信网络（CN，也称为企业网络）内会话发起协议（SIP）和“QSIG”之间的呼叫转移互通。 “QSIG”是一种信令协议，在专用综合业务网（PISN）内的专用综合业务网交换机（PINX）之间运行。PISN为用户提供电路交换的基本业务和补充业务。 SIP是用于建立、终止和修改多媒体会话的应用层协议。它通常通过IP进行传输。电话通话被认为是一种仅交换音频的多媒体会话。 随着公司网络中对电话技术的支持从电路交换技术发展到互联网技术，这两种技术将在一段时间内，甚至几年内，在许多网络中共存。 因此，需要能够建立、修改、终止和传输涉及SIP网络参与者和QSIG网络参与者的会话。此类呼叫由在SIP和QSIG之间执行互通的网关支持。 ISO/IEC 23916:2005规定了采用QSIG的PISN和采用SIP的企业IP网络之间传输服务的SIP-QSIG信令互通。

ISO/IEC 23916:2005 specifies call transfer interworking between the Session Initiation Protocol (SIP) and "QSIG" within corporate telecommunication networks (CN), also known as enterprise networks. "QSIG" is a signalling protocol that operates between Private Integrated services Network eXchanges (PINX) within a Private Integrated Services Network (PISN). A PISN provides circuit-switched basic services and supplementary services to its users. SIP is an application layer protocol for establishing, terminating and modifying multimedia sessions. It is typically carried over IP. Telephone calls are considered as a type of multimedia session where just audio is exchanged. As the support of telephony within corporate networks evolves from circuit-switched technology to Internet technology, the two technologies will co-exist in many networks for a period, perhaps several years. Therefore, there is a need to be able to establish, modify, terminate and transfer sessions involving participants in the SIP network and participants in the QSIG network. Such calls are supported by gateways that perform interworking between SIP and QSIG. ISO/IEC 23916:2005 specifies SIP-QSIG signalling interworking for transfer services between a PISN employing QSIG and a corporate IP network employing SIP.