Isup Signaling In The Us

This section outlines ISUP signaling in U.S. networks. The U.S. version of ISUP has been standardized by the American National Institute (ANSI) and Bellcore [9-12].

11.9.1 Services

The services supported by the U.S. version of ISUP are largely similar to those of CCITT-ISUP. They include call forwarding, and all services that require the transfer of the calling party number to the terminating exchange.

Not included are user-to-user signaling for ISDN users, and closed user group (CUG) service. However, U.S. ISUP supports CUG on international transit calls. For example, if an international switching center (ISC) on the west coast receives an IAM for a trunk from Japan (Fig. 11.9-1), the call destination is in the U.K., and the IAM includes a Par.9 and Par. 17 (closed user group interlock code, and optional forward call indicators), these parameters are included in the IAMs for the trunks in the U.S., and in the IAM for the outgoing international trunk.

Some services and procedures provided in the U.S., but not in other countries, are outlined below.

11.9.2 Business Group Services [9]

In the U.S. a group of lines, or a private branch exchange (PBX), can be part of a business group (BG). Business groups can be established when requested by a business customer, a government agency, etc. Business groups have some similarities with closed user groups (CUG). At the request of individual

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