PBX Networking: ANI/SID

ANI is delivery of the originating calling party’s 10-digit billing telephone number to an ISDN subscriber’s premises communications system and/or desktop terminal equipment. When a telephone call is made from an equal access CO, the ANI is passed from the local exchange carrier network to the interexchange carrier network for transport across Common Channel Signaling System 7 (CCSS7) packet switched facilities to the destination local CO exchange. The ANI is included in the call setup message using Q.931 message format over the D-channel. ANI is delivered with ISDN BRI or PRI trunk services.

ANI is an interexchange carrier service often confused with local exchange carrier CLID service. CLID is a local access transport area (LATA) service feature that is one of the commonly available customized local access signaling system (CLASS) features. ANI is a service feature offering that was originally developed in support of long distance telephone calls placed to inbound call center operations, with a requirement for ISDN trunking to the customer premises. PBX/ACD systems receiving the ANI can use the information for call screening, analysis, decision making, and routing procedures, including a database lookup procedure to match the ANI with a customer file. ANI also can be used to identify the geographic location of the calling party, because the area code is included in the digit string. ANI is no longer used exclusively for call center applications but is considered an important element for enhanced call screening functions at the system or desktop level. Another useful ANI benefit is preidentifying the calling party for network security purposes.

An ISDN feature similar to ANI is SID. SID is usually more useful than ANI because the feature delivers the originating caller’s telephone number behind a PBX system. ANI is the trunk billing number of the PBX trunk circuits and does not identify individual callers provisioned behind the switching system. SID can distinguish station users to a greater degree than ANI.

ANI and SID are useful features for a variety of customer applications that do not include formal in-bound call center systems. Collecting ANI/SID data allows PBX customers to better track and analyze incoming long distance calls by geographic area (regional and local). Collecting and storing ANI/SID in-bound call data in a call log database can support improved out-bound customer service and telemarketing operations. PBX customers can use a variety of network carrier services to route incoming calls to different PBX systems by using ANI/SID data to load-balance calls across locations for increased call handling efficiency and performance.