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Understanding Local Number Portability

When the 1996 Telecom act mandated that subscribers be allowed to take their phone numbers to other carriers, this had the potential to be a real challenge for the carriers.  This number portability feature is also referred-to as Local Number Portability or LNP.  This is a big liberation for subscribers for so many obvious reasons.  However, the amount of technical changes that would be required every time a user would switch carriers would place a huge burden on profitability (call forwarding, trunk tromboning, etc.).  Fortunately, a simple method was devised that allowed LNP to be put in place that didn’t require the previous carrier to be swamped with technical issues.

In the Old Days

Before LNP, each subscriber number was inextricably tied to a location by the numbering methodology known as NPA-NXX.   This was important because it allowed for both easy routing and accurate billing of subscriber calls.  The NPA-NXX describes the format for phone numbers used in North America.  The “NPA” or “Number Plan Area” is also known as the “Area Code”.  The “NXX” is the local exchange within the area code.  So for example a subscriber phone number of 713-498-xxxx would have a NPA of 713 (Houston’s area code).  Then 498 would be the central office in southwest Houston which handles that exchange.  And lastly the “XXXX” portion of the would be the subscriber’s  number.  This was very important at one time when phone switching equipment was more rudimentary and mechanical than the computerized systems of today.

Switchless in Seattle

So what happens when our example subscriber in Houston we just mentioned decides to “port” (the act of moving a number to another carrier) to a wireless phone?  Moreover, what if that same subscriber has ported that Houston number to a cellular provider in Seattle?  (Because she’s moving there but really values her current number).  After the port, the NPA-NXX will no longer represent the location for our Houston girl who’s moved to Seattle.

Fortunately, a relatively simple system was devised that accommodate this issue.   And, it didn’t require overhauling the PTSN.   They devised a system of associating ported numbers with another number to provide routing information.  This new number is called a “local routing number” or LNR.

NPAC’s Got Your Number!

Since number portability erodes the NPA-NXX value as a routing tool, it was decided that a database could be created to associate the Central Office location with the subscriber’s ported number.  This was made possible by assigning an LNR to every central office.  A LNR looks just like a 10-digit phone number (but it is not a phone number).  The LNR behaves like a phone number to the extent that it allows for routing over the PSTN.

This look-up tool, or database, is called the Number Portability Administration Center or NPAC. United Technologies was originally awarded the task of creating the NPAC  look-up tool.    But after that, the company maintaining the NPAC  is now known as Neustar.

The NPAC  and the LRN system are the keys to making local number portability work.  So, when a call is placed to our example subscriber in Seattle, the PSTN carrier first checks the NPAC to see if the number has been ported.  And if it has, the NPAC tells the carrier what LNR to use to route the call to where the subscriber is now located.  She’s obviously not in Houston anymore.

All Roads lead to VoIP

Voice over IP will eventually become the new PSTN.  At which time, the need for the NPAC will be diminished.   It is possible that at some point in the future NPA-NXX numbers will be nothing more than labels that will serve as easy to remember handles that really just point to IP addresses or SIP URI’s (VoIP addresses).  And, they might be resolved much the way that dot.com addresses are resolved to IP addresses today.  But, so long as there is legacy phone equipment in the network, the NPAC will continue to serve a useful role.

– October 27, 2014 by Steve O’Neal


NANPA Planning Letter 463 – South Carolina – NPA 854 to Overlay NPA 843

Wednesday, February 12, 2014

The South Carolina Public Service Commission has approved an all services overlay to provide relief for the 843 NPA, which serves the coastal communities of Charleston, Florence, Hilton Head Island and Myrtle Beach.

Key implementation dates for the new 854 NPA are:

  • 09/13/2014 – Network preparation begins
  • 03/14/2015 – Permissive 10-digit dialing begins
  • 04/19/2015 – Central office codes in new NPA may be ordered
  • 09/19/2015 – Mandatory 10-digit dialing begins
  • 10/19/2015 – New NPA central office code activation

For test numbers and a map of the affected area, go to www.nanpa.com.


NANPA Planning Letter 462 – Ohio – NPA 220 to Overlay NPA 740

Tuesday, February 4, 2014

The Public Utilities Commission of Ohio has approved an all services overlay to provide relief for the 740 NPA, which serves the southeastern portion of the state. Communities include Athens, Cambridge, Delaware, Jackson, Lancaster, Marion, Newark, Marietta, Portsmouth and Zanesville.

Key implementation dates for the new 220 NPA are:

  • 03/20/2014 – Network preparation begins
  • 09/20/2014 – Permissive 10-digit dialing begins
  • 10/22/2014 – Central office codes in new NPA may be ordered
  • 03/21/2015 – Mandatory 10-digit dialing begins
  • 04/22/2015 – New NPA central office code activation

For test numbers and a map of the affected area, go to www.nanpa.com.


NANPA Planning Letter 461 – California – NPA 628 to Overlay NPA 415

Wednesday, January 29, 2014

The California Public Utilities Commission has approved an all services overlay to provide relief for the 415 NPA, which serves communities in San Francisco, Marin and San Mateo counties.

Key implementation dates for the new 628 NPA are:

  • 08/16/2014 – Permissive 10-digit dialing begins
  • 09/21/2014 – Central office codes in new NPA may be ordered
  • 02/21/2015 – Mandatory 10-digit dialing begins
  • 03/21/2015 – New NPA central office code activation

For test numbers and a map of the affected area, go to www.nanpa.com.

 


NANPA Planning Letter 459 – Tennessee – NPA 629 to Overlay NPA 615

Friday, December 6, 2013

The Tennessee Regulatory Authority has approved an all services overlay to provide relief for the 615 NPA, which serves the Tennessee communities of Franklin, Gallatin, Hendersonville, Lebanon, Murfreesboro, Nashville and Springfield.

Key implementation dates for the new 629 NPA are:

  • 12/19/2013 – Network preparation begins
  • 07/26/2014 – Permissive 10-digit dialing begins
  • 09/28/2014 – Central office codes in new NPA may be ordered
  • 02/28/2015 – Mandatory 10-digit dialing begins
  • 03/28/2015 – New NPA central office code activation

For test numbers and a map of the affected area, go to www.nanpa.com.


All NXX Codes in Connecticut 203 NPA Assigned

Friday, December 6, 2013

NANPA is notifying service providers to now request codes in the CT 475 overlay code. All NXX codes in the 203 NPA have been assigned.


All NXX Codes in Georgia 706 NPA Assigned

Monday, November 11, 2013

NANPA is notifying service providers to now request codes in the GA 762 overlay code. All NXX codes in the 706 NPA have been assigned.


NANPA Planning Letter 458 – Assignment of NPA 577 for Non-Geographic Services

Monday, October 14, 2013

The Industry Numbering Committee (INC) has assigned NPA 577 as the next 5XX NPA.

The 5XX-NXX resource is projected to exhaust in the first half of 2014. From January 1 through October 10, 2013, NANPA had assigned 328 codes. Currently, there are 169 5XX-NXXs available for assignment.

NANPA will send notification when the 577 NPA opens. Meanwhile, the industry will continue to receive updates on the current supply of 500, 533, 544 and 566 NXXs.

Here’s how NANPA describes the 5XX-NXX resource:

 

5XX-NXX codes are used for applications which are non-geographic in nature, are not assigned to rate centers and may or may not traverse the Public Switched Telephone Network (PSTN), but do require an E.164 addressing scheme. The use of this NANP numbering resource is to communicate with both fixed and mobile devices, some of which may be unattended. This resource may also be used for applications enabling machines, which would include but not be limited to wireless devices and appliances, with the ability to share information with back-office control and data base systems and the people that use them. Service is limited only by terminal and network capabilities and restrictions imposed by the service provider

NANPA Opens NXX Codes in Georgia 470 NPA

Monday, October 14, 2013

NANPA is now taking requests for codes in the GA 470 overlay code. All assignable NXX codes in the 404 area code have been assigned.


Exhaust Projection for New Jersey 609 NPA Revised

Friday, October 11, 2013

After recovering central office codes, NANPA has now revised the projected exhaust date for the 609 NPA in New Jersey.

The new projected exhaust date is 1Q2016, changed from 2Q2015.

The revised projections report can be found at www.nanpa.com.