Jurisdictional routing is another name for call routing decisions based on both the calling and called number. How a call gets rated depends on where the calling party is located and what regulatory body has jurisdiction. Paradoxically intra-state calls cost more than inter-state calls. For a service provider to optimize their least cost routing, they must have multiple tables, one for intra-state calls and a second for inter-state calls.
Jurisdictional routing is determined by the ANI (Automatic Number Identification), or telephone number, of the calling party. With VoIP calls, it is common for the ANI to be an invalid value, such as a random number that is not a telephone number or the SIP URI of the calling party. Calls with an invalid ANI are also called inderterminate calls since call jurisdiction cannot be determined. Some major carriers will block calls that do not have a valid ANI. However, most carriers will accept and rate calls with an invalid ANI at the higher intra-state rate if they are completed. Indeterminate calls are effectively a third type of jurisdictional call and full optimization requires a third least cost routing table. One for inter-state, one for intra-state and a third for indeterminate calls with invalid ANIs.
Inter and intra-LATA calls are yet another form of jurisdictional calls. LATAs (Local Transport and Access Areas) where defined by the Department of Justice in 1984 as the operating demarcation between local and long distance telephone companies. Jurisdictional routing based on LATA was ubiquitous before the 1996 telecom deregulation act, but now rarely used.
Local routing is another form of jurisdictional call routing which is determined by the NPA-NXX-X of the calling party and the called party. Interconnection of local calls is usually charged at very low rates, much less than intra-state, and offers another least cost routing optimization. The major challenge of local call routing is the lack of a uniform definition of local calling areas. State and LATA boundaries are well defined, but there is no analogy for local calling areas which are defined in tariffs filed by each Local Exchange Carrier (LEC). Local calling areas can range from very small, such as a wire centers which are defined in the Local Exchange Routing Guide (LERG) to LATA-wide calling areas which can include multiple area codes. (A telephone Area code is also known as Numbering Plan Area or NPA.) In between wire center and LATAs there are various local calling area definitions such as expand local calling areas and local toll areas. Several firms maintain databases of all tariffs filed by local telephone companies and their defined local calling areas. These firms include Telcordia, CCMI and Telecomdb. An additional challenge with local call routing for most VoIP providers is the size of the table which defines the source and destination NPA-NXX-X combinations for each local calling area. Unlike Local Exchange Carrier switches that serve limited geographic areas, a VoIP service provider’s softswitch can serve customers anywhere in the US. A table that defines all the local calling areas in the US would have over a billion NPA-NXX-X combinations.
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Types of Jurisdictional Routing
Local Routing – Determined by the number blocks, or NPA-NXX-X, of the calling and called parties
Intra-State Routing – Calls between two points that are within the same state
Inter-State Routing – Calls made from one point in one state to another point in a secondary state
Intra-LATA Routing – Calls between two points that are in the same LATA (Local Transport and Access Area)
Inter-LATA Routing – Calls made from one point in one LATA to another point in another LATA
International Routing – Calls made between countries
Invalid ANI or Indeterminate Routing – calling number is any value other than a valid telephone number usually rated at the Intra-State rate