Frequently Asked Questions

Does the CNA give or sell lists of phone numbers?
Did you give my number to a political party?
Is the CNA associated with Canada’s National Do Not Call List?
What are CO Codes?
What are NPAs (Area Codes)?
What is an area code "split"?
What is an area code "overlay"?
What is a "permissive dialling period"?
What is "number pooling"?
What is "boundary realignment"?
What other types of telephony numbering services must be administered?

Does the CNA give or sell lists of phone numbers?

The CNA does not have a listing of any telephone numbers. Regarding dialable telephone numbers, we are only mandated to administer the Area Code and the Central Office Code portion. Central Office (CO) Codes are the 3 digits after the area code. The CNA assigns CO codes to Canadian Carriers in Exchange Areas and we are therefore unaware of which telephone numbers are assigned to their customers. The status listing of CO Codes is available on our website.

Did you give my number to a political party?

The CNA does not have a listing of any telephone numbers. Organizations or political parties who insinuate that they received your number from the CNA are misleading at best.

Is the CNA associated with Canada’s National Do Not Call List?

CNA is not involved with the Do Not Call list in any way. For information about Canada’s National Do Not Call List, please see https://lnnte-dncl.gc.ca.

What are CO Codes?

The term CO Code refers to digits D-E-F of the 10-digit NANP area address (where each digit is identified by an alphabetical character in the order ABC-DEF-GHIJ consisting of a 3-digit NPA (ABC), 3-digit CO Code (DEF) and 4-digit Line Number (GHIJ) in the format NXX-NXX-XXXX where: N = 2 to 9 and X = 0 to 9) (e.g., 702 is the CO Code in 613-702-0016 – see below for a diagram of the parts of a 10-digit North American telephone number).

What are NPAs (Area Codes)?

Numbering Plan Area, also called Area Code. An NPA is the 3-digit code that occupies the A, B, and C positions in the 10-digit NANP format that applies throughout the NANP serving area. NPAs are of the form NXX, where N represents the digits 2-9 and X represents any digit 0-9. In the NANP, NPAs are classified as either geographic or non-geographic. (see below for a diagram of the parts of a 10-digit North American telephone number).

Geographic NPAs are NPAs which correspond to discrete geographic areas within the NANP serving area.
Non-geographic NPAs are NPAs that do not correspond to discrete geographic areas, but which are instead assigned for services with attributes, functionalities, or requirements that transcend specific geographic boundaries.

What is an area code "split"?

The exhausting NPA is split into two geographic areas leaving the existing NPA code to serve, for example, an area with the highest customer density (in order to minimize number changes) and assigning a new NPA code to the remaining area. This method divides areas by jurisdictional, natural or physical boundaries (counties, boroughs, cities, river, etc.) between the old and new NPAs.

This method has been the alternative chosen for practically all NPA relief situations prior to 1995. NPA splits have occurred with enough frequency so that technical aspects have been addressed and established implementation procedures are generally understood. Public education and acceptance of the process has been made easier because of the numerous NPA splits that have occurred. This method generally provides long term relief for an area.

What is an area code "overlay"?

An NPA (or area code) overlay occurs when more than one NPA code serves the same geographic area. In an NPA overlay, code relief is provided by opening up a new NPA code within the same geographic area as the NPA(s) requiring relief. Numbers from this new NPA are assigned to new growth on a carrier neutral basis, i.e., first come, first served. Mandatory customer number changes within the affected overlay relief area are eliminated. In most cases, with the overlay relief method, 10-digit dialling is required for some of the affected customers' calling patterns. Since the overlay relief method could result in unequal dialling for those customers served out of the overlay NPA, mandatory 10-digit dialling is recommended for all NPAs covered by the NPA coincident with the implementation of an overlay.

The overlay method reduces or eliminates the need for customer number changes like those required under the split and realignment methods. It also allows the option to eliminate the permissive dialling period as part of implementation. This method will necessitate ten digit dialling of local calls between the old and new NPAs as central office (NXX) codes are implemented in the new NPA. NPAs have been previously implemented within an area and will vary with the individual characteristics of the area involved. They are listed below:

Distributed Overlay - The distributed overlay strategy may be considered in situations when growth in telephone numbers is expected to be more or less evenly distributed throughout the existing NPA requiring relief. The new NPA is added to the NPA requiring relief and shares exactly the same geographic boundaries. When growth telephone numbers are required, they are assigned from the new NPA.
Concentrated Growth Overlay - A concentrated growth overlay may be considered in situations when the majority of the new telephone numbers are expected to be concentrated in one section of the existing NPA. For example, a fast growing metropolitan area and a sparsely populated rural area could exist within the same NPA. The overlay NPA would be assigned initially to the section of the NPA experiencing the fastest growth, and new phone numbers in that section would be assigned from the new NPA. As more relief is required, the geographic area served by multiple NPAs could expand.
Boundary Extension Overlay - With a boundary extension overlay, the NPA requiring relief is adjacent to an NPA with spare capacity. The boundary between these two NPAs is eliminated, and spare NXX codes from the adjacent NPA are assigned within the original NPA boundary where relief is required. An appropriate use of boundary extension might be in a province consisting of two NPAs, where one NPA has spare capacity. This solution has the advantage of not requiring a new NPA code, but it also shares some of the limitation of boundary realignment in that it provides less long term relief.
Multiple Overlay - The multiple overlay strategy may be considered where relief is required in two or more NPAs. For example, this solution may be appropriate in a metropolitan area where two or more NPAs cover a small geographic area and where it would be difficult to implement another kind of relief, i.e., a split or a distributed overlay. The new NPA would be assigned to overlay the multiple existing NPAs serving the entire metropolitan area. As another example, a new NPA could be assigned for new growth within an entire state or province where more than one NPA exists.

What is a "permissive dialling period"?

The time frame beginning with the introduction of the new NPA whereby both the old and new NPA can be dialed. The beginning of permissive dialling is coincident with the relief date and ends with the mandatory dialling date.

What is "number pooling"?

Number pooling, in the context of current guideline, allows for sharing of central office codes (NXXs) among multiple service providers serving the same rate area. All ten thousand numbers within each NXX code continue to be associated with the same rate area designation, but can be distributed among multiple service providers at the thousand block (NXX-X) level. Examples of uses for blocks for which these guideline apply include plain old telephone service (POTS), Centrex, Direct Inward Dialling (DID), wireless service, facsimile, and coin phones.

What is "boundary realignment"?

In an NPA boundary realignment, the NPA requiring relief is adjacent to an NPA, within the same province, which has spare NXX code capacity. A boundary shift occurs so that spare codes in the adjacent NPA can be used in the NPA requiring relief. As a result, the geographic area of the exhausting NPA shrinks and the geographic area of the NPA with spare capacity expands. Only the customers in the geographic area between the old and new boundaries are directly affected the this change. This method applies to multi-NPA states or provinces only. It could provide for a better balance of central office (NXX) code utilization in the affected NPAs. This method is viewed as an interim measure because it tends to provide a shorter term relief than when providing a new NPA code.

What other types of telephony numbering services must be administered?

Other services include the personal communications services or 500-NXX codes, 900-NXX codes, the international inbound 456 codes, N11 codes (911, 411, etc.), 800-855-XXXX line numbers for the hearing impaired, carrier identification codes (CICs), and vertical service codes and automatic number identification information integers (ANI II).

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