scope:

Carrier Service Provider Identification (CSPI) information is intended to identify to intermediate switches all presubscribed carriers associated with a calling party. Identifiable carrier service providers include the preferred intraLATA toll carrier, the preferred interLATA carrier, and the international carrier. Other carrier types may be included as the need arises.

Purpose

SPI may identify one carrier that had been selected to transport a call as dialed. CSPI should identify all other associated presubscribed carriers as potential carriers. A potential carrier may become the selected carrier if the called party number is changed at an intermediate switch.

For appropriate call types, an originating switch should include CSPI information in a call setup message sent to an intermediate switch.

Application

CSPI should be used for PSTN, non-ISDN and ISDN circuit mode (Basic and Primary Rate) calls.