Glossary of Telecom Terms

Access Charges

The fees long distance companies and other network users pay to local telephone companies to originate and terminate calls on their networks.

Access Line

A communications facility extending from a customer’s premises to a serving central office switch, sometimes referred to as a subscriber loop, local loop, or the “last mile.”


The four-digit identifier of a second service provider associated with a telephone number or thousand block. It identifies the wholesale service provider customer to which the PSTN service provider has assigned the number. The second service provider in turn may either assign the number to its retail customer or to another service
provider for its use.

AOCN Administrative Operating Company Number.

A company that has access to update Telecom Routing Administration (TRA) databases, specifically the Business Input Routing and Rating Database System (BIRRDS).


Alliance for Telecommunications Industry Solutions

Average ScheduleCompanies

NECA members that receive pool revenues, or settlements, for interstate telecommunications services based on a series of statistical formulas, approved by the FCC, that approximate the amounts received by a similar cost company.


BIRRDS is the iconectiv (Telcordia) Business Integrated Routing and Rating Database System. Service Providers (SPs) and/or their agents enter their information into BIRRDS which is the information source for the Local Exchange Routing Guide (LERG).


A Bell Operating Company was a company owned or controlled by AT&T prior to the 1984 AT&T divestiture action

CLASS (Custom Local Area Signaling Services)

Identifies a group of vertical service features such as Caller ID (calling number delivery), Calling Name delivery, and call filtering (either to accept or to reject calls from specified numbers). (See also DPC.)

CLEC Competitive Local Exchange Carrier

The land line carrier entrant to a market where there is already an incumbent LEC providing local phone service.


Common Language Location Identifier – identifies a switch in the Public Switched Telephone Network (PSTN)


Caller ID with name


Central Office Codes (NXX) Assignment Guidelines

Common Line Pool

The pool NECA administers for its local exchange carrier members’ non-traffic sensitive costs of providing interstate access associated with subscriber loop plant. Pool members apply the end user common line (EUCL) charge rate element and others as tariffed in NECA’s FCC Tariff No. 5.

Cost Companies

NECA members that receive pool revenues, or settlements, for interstate telecommunications services based on their actual interstate investment and expenses, calculated each year from detailed cost studies.


Canadian Radio-television and Telecommunications Commission. The CRTC regulates and supervises the broadcasting and
telecommunications systems in Canada.


The Dash-X is shorthand for the NPA-NXX-X that represents the 1,000 numbers in a thousand block in the NPAC/SMS network data. Similarly, an NPA-NXX code is a network data level representation of 10,000 numbers.

Digital subscriber line (DSL)

A technology that brings high-bandwidth information services to the home or small business over telephone loop plant. DSL technology enables a loop to simultaneously carry voice, which takes little bandwidth, and high speed data.

DPC (Destination Point Code)

An address of a device on the Common Channel Signaling (SS7) network. The DPCs shown in the NPAC data refer to addresses components such as the databases used in the provision of Collect/Third Party Billing and Calling Name Delivery services and central office switches, for which the address is needed to facilitate inter-switch voice mail system operation (used to route the Call Waiting indicator signal from the voice mail system to the called parties serving the switch) and to accommodate AutoRecall/Auto-Call Return services.


A local area network technology that connects computers, printers, servers, etc., in a physical location. Carrier ethernet equipment provides reliable ethernet connectivity beyond the LAN through the telecommunications network. Ethernet uses twisted pair (copper), fiber optic, and coaxial cable and may also use wireless connectivity or transport.

FCC (Federal Communications Commission)

U.S. government entity endowed with the responsibility to direct the U.S. national telecommunications regulatory environment.


Firm Order Confirmation from a wireline service provider. It is the verification/acknowledgment from one Service Provider (SP) to another of receipt of a valid Service Request. (The service request is an LSR if from wireline carrier; a WPR if from a wireless carrier.)


FCC Registration Number: A unique registration number that identifies any party registered to do business with the FCC.

High cost loop (HCL) support

This Federal USF fund provides support to offset high unseparated local loop costs for rural study areas.

ILEC (Incumbent Local Exchange Carrier)

The local wireline service provider, either an RBOC or an Independent LEC, that served a market prior to the market being opened to competition.


Industry Numbering Committee of ATIS (Alliance for Telecommunications Industry Solutions)

Incumbent local exchange carrier (ILEC)

The telephone company that, on the date of enactment of the Telecommunications Act of 1996 (February 8, 1996), provided telephone exchange service in a specific area and was deemed to be a member of NECA pursuant to section 69.601(b) of the Commission’s regulations (47 C.F.R. 69.601(b)).

Intercarrier compensation

Flows of payments among telecommunications carriers that result from the interconnection of telecommunications networks under current systems of regulation.

Internet protocol (IP)

The method by which packet data is sent from one computer to another. Every server, router, and switch in an IP network is uniquely identified by at least one IP address.

Internet service provider (ISP)

Business entity that provides Internet service to the end user customer.

Interstate common line support (ICLS)

This USF fund supports the interstate common line costs of rate-ofreturn ILECs by funding the residual between the ILEC’s interstate common line costs or revenue requirement and the revenue collected from the common line rate elements charged pursuant to NECA’s FCC Tariff No. 5.

IXC (Inter-Exchange Carrier)

A carrier that provides connections between local service providers when they do not have connection arrangements appropriate for a call. In particular, used when regulatory restrictions preclude delivery of a call across LATA
boundaries. A LEC also may function as an IXC.


The four-digit identifier of the last service provider associated with the telephone number. It identifies the last reseller in the service provider chain, i.e., the one that has the retail sales relationship with
the consumer.

LATA (Local Access Transport Area)

The geographic region beyond which a former BOC, and certain independent LECs, cannot transport a call without involving an IXC.

LEC (Local Exchange Carrier)

A company that provides local wireline telephone service.

LERG (Local Exchange Routing Guide)

A database owned by Telcordia (iconectiv) and providing information at the NPA-NXX and block level.

LIDB (Line Information Database)

One of the original uses is to allow a toll operator to determine whether a telephone number may be billed for a call (Collect or Third Number) by indicating whether the billed number is a public phone. Other uses include an indication that a number will accept all Collect calls, so it is not necessary to have an operator obtain agreement from the billed party on each call. (See also DPC).


Letter of Authorization required by NPAC as evidence that a carrier will allow its telephone numbers to ported to another service provider.

Local number portability (LNP)

The ability to transfer an existing telephone number assigned by a local exchange carrier (LEC) and reassign it to another carrier.

Local switching support (LSS)

This USF fund supports high local switching costs of small ILECs. LRN (Location Routing Number): A 10-digit number used to uniquely identify a switch that has ported or pooled numbers. The first six digits of the LRN is a valid NPA-NXX assigned to the switch that is serving the ported or pooled number. An LNP-enabled switch
interrupts processing of an originating call to determine whether the called number is ported and to obtain the called number’s LRN if the number is ported (or pooled). Calls to a non-ported number are routed based on the NPA-NXX of the called number. Calls to a ported or pooled number are routed instead based on the NPA-NXX of the
number’s associated LRN.

LSMS (Local Service Management System)

The system owned by a service provider and which receives data broadcast from the NPAC/SMS. The LSMS provisions the service provider’s downstream systems, such as its LNP call routing database. The LSMS is a mechanized system used
(primarily) to receive data broadcasts from the NPAC/SMS


The service request to port a number, sent from one SP to another. (LSR if sent from a wireline carrier; WPR if sent from a wireless carrier).

Minutes of use

A total of all premium and non-premium originating and terminating interstate traffic sensitive switched access minutes which are switched in a Class 5 (local) end office.


(“N minus 1”): The next to last network involved in a particular call. In the case of an inter-LATA toll call, for example, the next to last network is the IXC network.The determination of the destination network (and switch) for a ported number is expected to be performed before the call is delivered to the network containing the switch serving the called number. If not already performed, the determination is made by the N-1 network.

NANP (North American Numbering Plan)

The NANP is the plan for telephone numbers in Canada, the US and its territories, and the Caribbean. Telephone number addresses in the NANP are in the form NXX-NXX-XXXX, where N is any digit from 2-9 and X is any digit from
0-9. (The format often is expressed as NPA-NXX-XXXX to reflect the fact that the first three digits of the telephone number represent the area code.) The first six digits (NPA-NXX) of the telephone number identify the local serving switch. The NPA-NXX of a telephone number also indicates the geographic area (“rate area”) associated with the
number. There are exceptions to the meaning of a number’s NXX, such as for “toll-free” numbers and those in certain specially designated NPA-NXXs.

NANPA (North American Numbering Plan Administrator)

The entity selected by the FCC to administer the NANP.


National Exchange Carrier Association, Inc. (NECA), a membership association of U.S. local telecommunications companies.

NPA (Number Plan Area)

The first three digits of the 10-digit NANP telephone number. An NPA is always contained within the boundaries of a single state.

NPAC (Number Portability Administration Center)

The term NPAC refers to the entire operation: both personnel and equipment.

NPAC SPID (Number Portability Administration Center Service Provider Identification Number)

A four-digit alpha-numeric value that identifies the owner of a record in the NPAC/SMS. The SPID is an NPAC account number and in most cases is drawn from the NPAC User’s OCN. The SPID of the owner of a record is included in the data broadcast to the LSMSs

NPAC/SMS (Number Portability Administration Center/Service Management System)

The system used by the NPAC to manage number portability processes and information. The term “NPAC/SMS” is used to refer specifically just to the NPAC hardware/software.


The first six digits of a NANP telephone number (or of an LRN). The NPA-NXX is the PSTN address of the switch serving the telephone number. In a non-pooling area, the NPA-NXX code and the associated 10,000 numbers are assigned by the NANPA. In a pooling area, the NPA-NXX code is assigned by the Pool Administrator along with one
or more thousand blocks drawn from the NPA-NXX. Other thousand blocks drawn from the NPA-NXX are assigned by the PA and can be used in switches other than the one to which the NPA-NXX itself is assigned.


The NPA-NXX-X represents a pooled thousand block drawn from theNPA-NXX


Numbering Resource Utilization Forecast NXX Term used typically to represent the 4th-6th digits of the ten-digit telphone number (N = any digit 2-9, X = any digit 0-9).

OCN (Operating Company Number)

The OCN is assigned by The National Exchange Carrier Association, Inc. ( NECA) and is used as an identifier
for inter-carrier transactions. The OCN of a service provider is used as its NPAC SPID.


National Number Pooling Administrator Phantom traffic Traffic that is terminated but is not billable because the originating source is not identified.


Point of Interconnection – place where two telephone networks interconnect


Point of Presence – Place where a telephone network is available for interconnection


Public Safety Access Poin

PSC Public Service Commission

A state level agency that regulates telephone companies.

Pseudo LRN

A valid LRN is required when a number cannot be routed based on its dialed digits, so an NPAC record is created to show the LRN for that ported (or pooled) number. However, some number records are established in the NPAC/SMS for reasons other than a need for LRNbased routing. Some service providers find in such cases that the use of an intra-SP port to create a conventional NPAC/SMS record, i.e., one containing a valid LRN, is not feasible operationally. Instead a record is created containing a pseudo-LRN – an LRN with a value of 000-000-0000 in the LRN field in lieu of a valid LRN. The digit string in the LRN field of pseudo-LRN records means only that the number should be routed on dialed digits; that is, it is an instruction, not a route choice.

PSTN (Public Switched Telephone Network)

The closed network consisting of interconnections between voice switching nodes identified by
national number plans such as the NANP (the plan used for telephone numbers in Canada, the United States and its territories, and the Caribbean). Other network arrangements such as the internet and private networks also interact with PSTN traffic, but rely on the PSTN switching nodes for their access to PSTN traffic.


Public Utility Commision - A state level agency that regulates telephone companies.


Regional Bell Operating Company. In 1984 AT&T was broken up by the US Justice department in AT&T which provided long distance services and seven Regional Bell Operating Companies that provide local telephone service. The original RBOCs were Ameritech, Bell Atlantic, BellSouth, Nynex, PacTel, SouthWestern Bell and US New Vector. As of 2013, the remants of the seven RBOCs have been consolidated into AT&T, Verizon and CenturyLink.


Service Control Point. Transaction processor-based system that provides common channel signaling network interface to database services.


A settlement is calculated for each pooling company based on their individual expense and tax amounts, including a share of the pool’s calculated rate of return. Each company then receives its settlement minus the access revenue it has already collected.


Switch Homing Arrangement. Homing arrangements include such situations as mapping, to a switch, any appropriate Feature Group B, C, and/or D tandems; STPs; in the case of remotes, their Hosts; in the case of Points of Interfaces (POIs), their ACTUAL SWITCH; etc. This information is defined in LERG7SHA.


Service Provider Identification Number. (See NPAC SPID.)


Signaling System 7. An internationally standardized, general-purpose Common Channel Signaling protocol. It defines the signalingbackbone for the public switched telephone network.


Service Switching Point or service switch point. A switching office that has the SSP features, enabling interactions with SCPs


Signal Transfer Point. A Signaling point in the Common Channel Signaling network with the function of transferring signaling messages from one signaling link to another. A packet switch that transmits messages between switches and other network components. Also transmits messages between switches in the process of normal call set-up and routing. Its function is analogous to a tandem switch in the PSTN.

Tariff 4

NECA’s F.C.C. Tariff No. 4 describes the location and technical capabilities of wire centers providing interstate access telecommunications service. It also provides information to support the ordering and billing of jointly provided (meet point or billing percent) interstate access service. Tariff 5 NECA’s F.C.C. Tariff No. 5 contains the rates, regulations, service terms and conditions that apply to interstate access services offered
by local member telephone companies participating in the tariff.


Thousands-Block Number (NXX-X) Pooling Administration Guidelines


Transaction Capabilities Application Part. TCAP is the application layer of the Transaction Capabilities protocol that is used for messages between end offices and remote databases. (The switch uses TCAP messages over the Common Channel Signaling network to query its LNP call routing database, but uses ISUP messages over the CCS network to set up voice paths to other switches.)

Telecommunications Relay Services (TRS)

The interstate Telecommunications Relay Service Fund, established by the FCC on July 26, 1993, helps speech and hearing impaired individuals use telecom services.

Traffic sensitive pool

The pool NECA administers for the portion of the network where costs vary according to usage. Pool members apply the TS tariff rate elements: Traffic Sensitive – Switched, including charges to interexchange carriers (IXCs) for long distance traffic and Traffic Sensitive – Special Access, including DSL and other broadband services.

Universal Service Fund (USF)

A group of federal funding programs that promote universal service goals created by the FCC to provide support for high cost telcos, low income consumers, rural health care initiatives, and schools and libraries.

Voice over Internet protocol (VoIP)

A technology that allows users to make telephone calls using a broadband Internet connection instead of a regular (or analog) phone line.


Voice over Internet Protocol