Local Number Portability (LNP) was introduced to the telecom industry as a means of fighting the monopolistic practices of phone service providers. Prior to LNP being developed, switching telecom carriers required obtaining a new phone number. This inconvenience allowed vendors to lock-in clients who did not wish to change their current number. With the advent of wireless telephones, Local Number Portability has proliferated as a feature that consumers expect to be available. It has since become a mandated requirement by the FCC for all landline and wireless common carriers as of November 2003 to be LNP-capable.
Mode of operation
Phone numbers that have been ported are registered in a Number Portability Database (NPDB). A typical routing scenario with a ported number begins with an initiating subscriber (A) placing a call to the terminating subscriber (B). Subscriber (A) contacts their Local Exchange Carrier which subsequently issues a query to the NPDB to determine the Local Routing Number (LRN). Subscriber (A) then communicates via Signaling System 7 (SS7) to determine the servicing Local Exchange Carrier of subscriber (B) using the obtained LRN to alert subscriber B of the impending phone call.
There are several scenarios for which a number can be registered as ported. These scenarios include inter-carrier/competitive, intra-carrier, and number pooling. With inter-carrier porting, a number typically moves from one carrier to the next. This can happen for a number of reasons including upgrading phone device or saving costs associated with the previous carrier. Intra-carrier porting registers a phone number with the National Portability Administration Center (NPAC), however the number remains with the same carrier. This typically happens when moving a customer from Digital (2G) to a Next-Generation (2.5G) network, or vice versa. In the US, numbers are pooled in blocks of 1000 and assigned to a new provider to create an inventory of unassigned numbers. These blocks are registered in the NPAC.
Routing and rate deck
Phone service providers generally provide rate schedules based on the 6 digit combination of Area code and Prefix, referred to by the industry as the NPA-NXX. The NPA-NXX is the address of the switch which serves the telephone number. With Local Number Portability this method is no longer accurate in determining the rate to place a call. If a number has been ported, the NPA-NXX of the 10 digit LRN is used to determine rate.
Line type determination
Previous attempts at determining line type relied heavily on the NPA-NXX of a phone number. With the advent of LNP, a phone number can be moved from switch to switch, thus is no longer an effective method of determining line type.
Penalties and consumer protection
The Telephone Consumer Protection Act (TCPA) of 1991 limits the use of automatic dialing systems, artificial and prerecorded voice messages. This legislation provides compensation for subscribers up to $1500, or recovers actual monetary loss for each violation. This includes SMS text messages and fax machines.
With Local Number Portability, an organization could unknowingly be in violation of this legislation through communication sent to a phone number that has been ported to a wireless carrier. It is strongly advised to prescreen phone numbers for LNP before initiating any type of automated campaign which could be in violation of the TCPA.