Glossary of terms


Molly Katolas



Application Programming Interface. A set of rules used to allow interaction between different software components. In more simple terms, it's a way to use services that a web portal offers, but it's a "behind the scenes" approach that developers generally use.


In NPAC terms, a group of 1,000 contiguous telephone numbers in a range of NPA-NXX-X000 to X999.

Block Assignee/Holder/Owner

The service provider to who has been assigned the 1,000 block of numbers.

Block Available

A 1,000 block of numbers that's not assigned to a service provider.


Bell Operating Company / Regional Bell Operating Company. This is identified as any company that was owned or controlled by AT&T prior to the AT&T divestiture action. Regional BOCs are a combination of the 7 companies formed.


Often referred to as Bonded Carriers, E-bonded Carriers, or Non-bonded Carriers. Bonding refers to the connectivity and method for sending/receiving information between customer/vendor and a CLEC/LEC/TP. A bonded carrier allows electronic system-to-system order entry, sending and responses, while non-bonded carriers are managed in a manual method like a fax, GUI (portal), email or paper form.


Billing Telephone Number / Account Telephone Number. Sometimes these are used interchangeably, and other times they are used as separate items, based on the carrier of record. Generally speaking, the BTN is the main telephone number on a customer's account.


Centrex is a feature line on a telephone number that an end user has activated with their carrier. It works like a PBX line by providing switching services at a central office rather than the customer premise. Most carriers require this feature to be disabled/removed prior to porting.

Class 1/2/3 Interconnected VoIP

Class 1: A VoIP service provider that interfaces directly with the PSTN and is able to receive numbering assignments from the North American Numbering Plan Administration (NANPA).

Class 2: A VoIP service provider that relies on a provider for PSTN access, and access to telephone numbers.

Class 3: A reseller of Class 1 and 2 VoIP providers.


Competitive Local Exchange Carrier. This is one of the many terms to identify an organization offering local telephone services.


Caller Name. This service is a subscription to Caller ID with Name services.


Copy of Bill or Bill Copy.


Customer Service Record. This is the record of information that the current carrier keeps on file, and what they reference against when receiving a request to port a number.


Direct Inward Dial. This is another way of saying telephone number.

Dry Loop

Also known as standalone DSL. In the earlier years of DSL service it was required that a customer have what is known as a dry loop, which is a dedicated DSL line as opposed to today's shared-line DSL. Shared-line DSL indicates a line used only for internet and not shared for voice services.


Digital Subscriber Line. This is the technology that provides internet access via the transmission of digital data across the local telephone network.


End User. This is generally the person actually picking up the telephone and making a call.


Federal Communications Commission. The FCC is the organization that regulates interstate and international communications by radio, television, wire, satellite, and cable in all 50 states, the District of Columbia and U.S. territories.


Firm Order Commitment. This is the "permission" the current carrier gives to a winning carrier to port a number. Once an order has received FOC, it's been approved to port.


Interconnection Agreement. This is a business contract between LEC/CLECs for the purpose of interconnecting their networks and exchanging telecommunications traffic. These are typically very complex contractual agreements that can take months to set up and come at a large expense.


Incumbent Local Exchange Carrier. This is one of many terms to identify an organization offering local telephone services.

Intermodal porting

The process of porting telephone numbers between wireline and wireless service providers.


Integrated Services Digital Network. This is defined as communication standards that allow the simultaneous transmission of voice, data, and video over the Public Switched Telephone Network (PSTN).


Local Access Transport Area. The region where LECs can't transport a call without involving an interexchange carrier (IXC).


Local Exchange Carrier. This is one of many terms to identify an organization offering local telephone services.


Local Exchange Routing Guide. A database owned by Telcordia which provides information regarding owned NPA-NXX at the block level.


Line Information DataBase. The database where specific CNAM provisioning, collect call acceptance, and 3rd party billing are identified.


Local Number Portability. The process of porting a number from one carrier to another.


Letter of Agency or Letter of Authorization. A signed agreement indicating that the end user wishes to switch service to a different provider.


Local Routing Number. A 10-digit number used to identify a switch that holds ported or pooled numbers. Calls to ported or pooled numbers are routed based on the NPA-NXX of the number's associated LRN.


Local Service Provider. A company that provides local telephone service, and generally describes the company that has the relationship with the actual end user.


Local Service Request. This is the order that carriers submit to other carriers in order to port a number.


North American Numbering Council. Adopted by the FCC in 1995, NANC provides advice and recommendations to the FCC regarding numbering issues.


New Network Service Provider / Old Network Service Provider. These are fields on a standard LSR for porting used to identify which carrier SPID will be the new provider of services, and which will be the old provider of services.


The first 3 digits (in the case of NPA) or first 6 digits (in the case of NPA-NXX) of a telephone number or LRN.


Number Portability Administration Center. Operated by Neustar, the NPAC is the central mediation center for all LNP activity.


Operating Company Number. Used similarly to a SPID, each carrier has an OCN used to identify intercarrier transactions.

Pooling / Pooled Numbers

Pooling allows the assignment of numbers in blocks of 1,000 to a requesting carrier.


Public Switched Telephone Network. The network of the world's public circuit-switched telephone networks. In short, this is what allows any telephone in the world to communicate with any other telephone.


Remote Call Forwarding. This is a feature an end user might put on their line that allows a number to be remotely forwarded. Most carriers require this feature to be disabled/removed prior to porting.


Responsible Organization. In relation to toll-free telephone numbers, this means the current carrier of record.


Service Provider ID. A 4-digit alphanumeric code that identifies the owner of record in NPAC. The Alt SPID (Alternate SPID) is a 4-digit alphanumeric code that identifies a second service provider associated with the telephone number.


Telephone Number.

Trading Agreement / Partner

Sometimes referred to as TPA/TP. A trading agreement is similar to an ICA (Interconnection Agreement) in that it allows LEC/CLECs to determine conditions in which they'll conduct the exchange of porting information. Trading Agreements are generally easier and quicker to set up than ICAs; they don't require as much legal language and are less expensive. Some carriers require these, while others don't.


Working Telephone Number. This is a number on the end user's account that's not the main (BTN) number, but an additional number on the account.

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