ANSI T1.671:2000 pdf free download – Signaling System Number 7 (SS7) – Carrier Service Provider Identification (CSPI)
5.1 General Description When a calling party dials a called party number, the originating switch determines which carrier should handle the call as dialed. The originating switch then routes the call within or toward, that carrier’s network. Certain network services, such as operator services, allow a network service operating at an intermediate switch to change the called party from that which had been originally dialed. In support of such network services, the CSPI information identifies the carrier selected for the call as dialed, if other than the local service provider. Where the carrier for the call as dialed is the local service provider, Local Service Provider Ildentification (L SPI) information will allow proper identification of the carrier. CSPI also identifies any other known carriers associated with the calling party. Thus, LSPI and CSPI together identify the several service providers that are actually or potentially associated with providing service to a call. This includes the service providers that provide dial tone (LSPI) and that route the call beyond the network service switch (CSPI). Networks beyond the network used by the network service switch to route the call toward its destination are not included in CSPI because they do not directly impact the network service that uses CSPI. CSPI information is not used to select the operator system or other network service switch for routing purposes, but it may be used by the network service switch to select the carrier for routing onward from the network service switch. Thus, CSPI does not interact with network routing information that may be used to identify a transit network used to access a network services switch. CSPI information may be obtained from provisioning data associated with the calling party or from interactions between the originating switch and other network elements, as determined by the network provider. This information is provided as part of the call setup message sent from the originating switch to an intermediate switch.
If the originating switch and the intermediate switch that requires CSPI information are in different networks, the transmission of CSPI information and related procedures defined herein may require appropriate agreements between the originating and receiving networks. Such agreements are beyond the scope of this document.
5.1.1 Configuration Model
The following configuration models depict typical CSPI network scenarios. Other network scenarios are possible. LE is a local exchange serving as an originating switch. OSS is an operator services system serving as an intermediate switch. TR is a transit exchange serving as an intermediate switch. Model 1 shows a direct connection from a local exchange to an operator services system; Model 2 shows a local exchange connected to an operator services system via a transit exchange; Model 3 shows a local exchange connected to a second operator services system via a first operator services system.