Summary

TCAP provides a standard mechanism for telephony services to exchange information across the network. It is designed to be generic so it can interface with a variety of services.

TCAP resides at Level 4 of the SS7 protocol and depends on SCCP's transport services. It is comprised of a transaction sublayer and a component sublayer. The transaction sublayer correlates the exchange of associated messages, while the component sublayer handles the remote operation requests.

All information elements in the TCAP message are defined and encoded using the syntax and BER of ASN.1. The ITU Q.771—Q.775 series of specifications defines the TCAP protocol. Specifications such as the ETSI.300.374 INAP series build on the ITU Q Series Recommendations to provide additional information needed for implementing network services. The ANSI T1.114 defines the TCAP specifications for ANSI networks. ANSI defines a number of national operations and parameters on which basic services can be built. Similar to ITU, many specifications build upon the basic TCAP provisions as defined in T1.114. For example, the Telcordia GR-1298 and GR-1299 AIN specifications provide the North American equivalent of the ETSI INAP service framework for IN services.

TCAP traffic on telephony signaling networks has increased in recent years because of an increase in services such as LNP, Calling Name Delivery, and Short Messaging Service (SMS), which rely on TCAP communication. This upward trend is likely to continue as IN services are more widely deployed, thereby making TCAP an increasingly important component in the role of network services.