By far the biggest project to ever hit the telephone industry has been Local Number Portability (LNP). Never before has anything this big been attempted in such a short time frame. There are a lot of questions and issues surrounding LNP, as well as a lot of uncertainties.

Local Number Portability was defined in the Telecommunications Act of 1996 as the "ability of users of telecommunications services to retain, at the same location, existing telecommunications numbers without impairment of quality, reliability, or convenience when switching from one telecommunications carrier to another."

The Telecommunications Act mandated that all telecommunications service providers provide, to the extent technically feasible, number portability in accordance with the requirements prescribed by the Commission. LNP got little attention until the FCC issued a mandate in June of 1996, requiring the implementation of LNP according to a very aggressive schedule. Rather than cite the specifics of the FCC mandate (FCC Docket 95-116), I will leave it to the reader to review the mandate itself, which is being published in three different phases. However, it should be understood that LNP affects everyone involved in wireline and wireless industries.

Following are some highlights from the FCC docket:

• The solution must support existing services and features.
• LNP must use the existing numbering resources efficiently.
• LNP cannot require subscribers to change their telephone numbers.
• There can be no unreasonable degradation in service (such as call setup delays) or network reliability degradation when subscribers switch carriers.
• No carrier can have a proprietary interest.
• The LNP solution must be able to accommodate location and service portability in the future.
• There can be no significant adverse impact outside areas where number portability can be deployed.

The intent of LNP is to open up local telephone service to competition. The authors of the Telecommunications Act feel that the biggest roadblock to competition is the ownership of telephone numbers. Subscribers are reluctant to switch to a new service provider because they have to give up their telephone numbers when they switch to a new service provider. LNP allows subscribers to switch to a new provider while keeping their existing telephone numbers.

This presents a huge challenge to the telephone industry. Until now, routing of telephone calls has been based on the first six digits of the telephone number (NPA NXX, or area code and office code). If a subscriber moves to a new area, or elects to change service providers, this is no longer possible. The telephone switches once identified by the old numbering plan are suddenly faced with servicing numbers from other service providers.

If a subscriber moves across the country, the problem becomes more complex. Telephone equipment and software throughout the network have been designed to use the telephone number to determine the geographical location of subscribers. For example, everyone knows that the 212 area code is Manhattan. However, with Local Number Portability, a subscriber with a 212 area code could live in California. This problem is compounded when one looks at billing systems, operations support systems (OSSs) and other network subsystems which all rely on the numbering plan for determining a caller's geographic location and service provider.

Copied with permission,McGraw-Hill Telecommunications from the book Signaling System #7, Second Edition by Travis Russell, 1998 McGraw-Hill Telecommunications, pages 465-466.