scope:

Call completion/call termination in today's Public Switched Telephone Network (PSTN)¹ depends on coordination between different service provider (SP) entities, each playing their part in setting up a workable connection between calling and called parties. As the PSTN has evolved through the Bell System divestiture, the Telecom Act of 1996, and the introduction of Internet Protocol (IP)-based technologies, the number and diversity of these entities has grown. In this context, problems with call completion may arise.

This handbook:

• Is a living document, which will be updated as applicable

• Describes some of the problems being encountered

• Discusses various industry standards and practices relevant to ensuring call completion, particularly signaling, routing, and trouble handling

• Attempts to relate these standards and practices to the call completion problems reported

• Offers best practices for ensuring call completion, especially in the management of intermediate SPs

Purpose

This handbook provides a resource to SPs to address issues as they are encountered related to intercarrier LD call completion/call termination.

¹ PSTN is used here to refer to the set of networks used to complete calls using E.164 number addressing.