ISO/IEC 21992:2003(E)规定了使用分组网络的功能，该分组网络使用因特网协议(IP)作为其网络层协议并且使用UDP和TCP作为其传输层协议，以互连形成专用综合业务网络(PISN)的一部分的两个专用综合业务网络交换机(PINX)。通过在传输控制协议(TCP)上直接携带PINX间信令协议和在实时传输协议(RTP)上携带PINX间用户信息(例如语音)来实现互连，RTP在用户数据报协议(UDP)上携带。假设PINX间信令协议是QSIG，如ISO/IEC 11572、ISO/IEC 11582和其他国际标准中所规定的。 ISO/IEC 21992:2003(E)规定了两种类型的互连: 按需，其中在每次呼叫开始时为QSIG建立单独的TCP连接，并在该呼叫结束时清除；和半永久，其中具有无限生存期的单个TCP连接代表许多单个调用携带QSIG。 ISO/IEC 21992:2003(E)适用于可以使用QSIG作为PINX间信令协议互连以形成PISN的PINX。

ISO/IEC 21992:2003(E) specifies functions for using a packet network that uses the Internet Protocol (IP) as its network layer protocol and UDP and TCP as its transport layer protocols, to interconnect two Private Integrated services Network eXchanges (PINXs) forming part of a Private Integrated Services Network (PISN). Interconnection is achieved by carrying the inter-PINX signalling protocol directly over the Transmission Control Protocol (TCP) and inter-PINX user information (e.g. voice) over the Real-time Transport Protocol (RTP), RTP being carried over the User Datagram Protocol (UDP). The inter-PINX signalling protocol is assumed to be QSIG, as specified in ISO/IEC 11572, ISO/IEC 11582 and other International Standards. ISO/IEC 21992:2003(E) provides for two types of interconnection:

• on-demand, where a separate TCP connection for QSIG is established at the start of each call and cleared down at the end of that call; and
• semi-permanent, where a single TCP connection with an indefinite lifetime carries QSIG on behalf of many single calls.

ISO/IEC 21992:2003(E) is applicable to PINXs that can be interconnected to form a PISN using QSIG as the inter-PINX signalling protocol.