Overview

The Signaling System 7 (SS7) network is a packet-switched network (separate from the voice network) that is used solely for the purpose of connecting telephone calls. It provides two types of services: circuit-related and non-circuit-related services. Circuit-related signaling is used for the setup and teardown of voice connections in both time division multiplexing (TDM) networks and packet-switched networks [ voice-over-IP (VoIP)]. Non-circuit-related services are all the other services provided by the network, such as database access for translations and subscriber information and network management.

The network is deployed as two distinct levels or planes: the international plane, which uses the International Telecommunications Union Telecommunications Standardization Sector (ITU-TS) standard of the SS7 protocol, and the national plane. The national plane uses whatever standard exists within the country in which it is deployed. For example, in the United States, the American National Standards Institute (ANSI) is the standard for the national plane. Telcordia standards are an extension of the ANSI protocol and ensure the reliability required to interwork with networks of the regional Bell operating companies (RBOCs).

Other nations may have one or several different versions of national protocols for SS7. In situations where these national variants must interwork with one another, a protocol converter is sometimes used. The protocol converter maps parameters from one country variant to another. All countries are capable of communicating with one another through gateways that convert the national version of the SS7 protocol to the international version. This ensures that...