Article published in NARTE News, Vol.15, No. 2, Apr-Jun 1997



By William T. Belshaw, NCE


LNP is rapidly becoming one of the high tech, high profile acronyms of the

1990s in telecommunications. Within the next few years this term and the

associated technology will impact all wireline and wireless services that

have a telephone number assigned.


The deployment of this technology solicits a variety of responses. Some find

it difficult to accept LNP because it will change the competitive face of the

local market. The cost of implementation is a major issue, and how the costs

will be recouped is of utmost interest to the existing Local Exchange

Carriers (LECs). And because markets have functioned for over a hundred years

in basically the same manner as today, the changes brought by LNP also

produces a level of discomfort for some.


LNP has three components: Provider Portability, Geographic Portability and

Service Portability. The Industry Numbering Committee (INC) agreed on the

following definitions for the three distinct types of Number Portability.


Service Portability is a cafeteria type offering where different services can

be obtained from different carriers. Service Portability, thus allows end

users to change the type of service they receive from a service provider to

another service from that same service provider, without changing their

telephone number. Consequently, telephone numbers may terminate outside the

normal area.


Geographic Portability, is also often referred to as location portability.

Geographic Portability permits end users to move from one permanent

geographic location to another while retaining their telephone number.


Provider Portability is the type of LNP which is critical to the success of

local competition. Provider portability is used and defined by the FCC as

"the term 'number portability' means 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.?

Simply stated, subscribers can select their carriers without changing their

telephone number.


Advantages of LNP

LNP is being implemented to respond to the FCC orders requiring equal access

in the local markets. The FCC has identified the initial 100 Market Service

Areas (MSAs) to implement portability. Many markets have implementation

dates before the end of 1997. It is not surprising that the local state

utility commissions affected by the FCC order are in favor of deploying this

technology because it paves the way for equal access. LNP is also the

long-term solution for number portability, which exists now on an interim

basis using switch-based features such as remote call forwarding. Interim

portability limits the features a customer can have when their numbers are



The various types of LNP open many opportunities in the expanding

telecommunications arenas. Interexchange Carriers (IXCs) will be allowed to

provide dial tone and not be required to pay the access charges currently in

effect. The local carriers will be permitted to enter the long distance

markets as they meet the FCC criteria of allowing competitive access in the

local market.


Sharing Knowledge

The interface specifications for Service Provider portability have been

identified throughout the US in seven regions, which have been established to

make the implementation of LNP more efficient. The original implementation

was being done on a per state basis, which proved to be inefficient, both in

cost and resource allocation. These regions have been identified as having a

foot print that matches the seven Regional Bell Operating Companies. The

regions have established a Limited Liability Corporation (LLC) to provide the

interface for the service providers within the regions. The LLC will be the

owner of the Number Portability Administration Center (NPAC) in each region.


The efforts of the participants in LNP, although regional, have evolved into

a national telecommunications industry effort. The first application of LNP

is being done in Chicago, where inter-network testing will start on July 24th

and ported services will be available for customers by September 29th. The

Chicago efforts have been related to all the other regions. This sharing of

information among the regions has proven time-, cost-, and functionally

effective. The various regions have chosen what they feel is needed to

enhance the Chicago committee?s findings and has similarly provided input to

Chicago. The various participants have sent their Subject Matter Experts

(SMEs) to the regions to provide input. This has truly become an industry

effort with more cooperation between the participants than initially



National forums have rallied to support the industry efforts. The Network

Internetwork/interoperability Forum (NIIF formerly NOF) is committed to the

testing effort and Interconnection issues. The Ordering and Billing Forum

(OBF) has developed new Local Service Request (LSR) forms to be used for

interfacing. North American Numbering Council (NANC) has developed the

process flows for how the companies will interact. All these activities stem

from the various state and regional efforts, much of which may be located on

the web in "".


Technology Behind LNP

The technology used to provide the service is called the Local Routing Number

(LRN). The LRN solution is a database solution, which is an Advanced

Intelligent Network (AIN) application. LRN is a number that replaces the

telephone number dialed in the SS7 message. The LRN must be a routable number

through the existing networks. An existing NPA/NXX in a Central Office is

normally used to replace the NPA/NXX of a called number. The exchange is

found in the database of the SCP. The design is similar to the 800/888

database now being used throughout the country. Other technological solutions

were proposed and examined to determine the most feasible solution. The

Carrier Portability Code (CPC), another database solution, underwent an FCC

sanction trial in New York City where it was quite successful.


Designing the basic interconnection architecture will be helpful when

following the call flow description. The information on ported numbers is

distributed within regions using a Number Portability Administration Center

(NPAC). Carriers providing porting services in a region are connected to the

NPAC via a link identified as Service Order Administration (SOA). The NPAC

accepts the porting information and distributes the information to the Local

Service Management Systems (LSMS) within each carriers' organization. The

NPACs have been designed and implemented throughout the country to meet

similar standards.


The LSMS serves as the connection to the carrier?s Service Control Point

(SCP) from the NPAC. The LSMS is the generic term applied to the

interconnection into the Service Providers network. Many Service Providers

use the LSMS to interact with their internal operating systems. Again, the

LSMS interfaces are defined at the regional level, based on shared

information between the regions. The internal workings of the individual LSMS

are determined by the individual Service Provider.


When a ported number is dialed from within the same central office or from

across the country, it will be identified as belonging to a ported NPA/NXX on

its interaction with the SS7 signaling network. Being identified as ported

establishes the requirement for a database look-up within an SCP, to identify

where the number should be routed. It also sets a bit within the SS7 message

indicating the dip is required.


LRN utilizes a database contained in the SCP for each Service Provider. The

exact architecture and configuration of these SCPs will vary with the

manufacturer of the equipment and the software applications used by the

Service Provider. While each region has identified the interconnection

requirements for the SCPs, the sharing and cooperation fostered throughout

the industry has spawned many of the same specifications.


The SS7 message contains the called number, when SS7 elements in the networks

screen the number, the NPA/NXX of a ported number is identified as ported

and routed to the appropriate database. The database examines the called

number in the SS7 message, and re-sets the bit in the SS7 message. This

indicates the look-up has been done. If the number is not ported, the call is

routed to the end office that is responsible for the NPA/NXX. If the number

is ported, the called number is replaced with the LRN for the office that is

providing dial tone to the subscriber. The called number is put into a

designated field within the SS7 message. The call to the ported number is

then routed to the appropriate central office using the LRN. Finally, the

end office providing the ported service then retrieves the called number from

the SS7 message and delivers the call to the intended subscriber.


The basic call to ported numbers is a relatively simple process. However, the

interaction with services such as CLASS, ISDN, 911, Operator Service. etc., makes the

deployment of the technology very complex. Other services are going to be

extensively tested in Chicago to ensure they are not negatively affected by

the introduction of LNP.


What the Future Holds

NIIF is preparing an interconnection test plan for future use when providing

LNP. This document will provide the basis for the testing to be performed in

Chicago starting this month. Other MSAs and states have chosen to adapt the

Chicago Test Plan as their base test document when deploying LRN within their

regions and MSAs.


The wireless community is currently planing for their deployment of LNP,

which the FCC has ordered to be completed by the end of 1998.


Location Portability does not have a set deployment schedule at this time.

The Illinois Commerce Commission (ICC) has received recommendations on

possible solutions for the implementation. The application of this technology

is still in the discussion and planning stages. There is concern about the

marketability of the Location Portability. The general feeling at this time

is that, if the technology is applied, it will be confined to a regional or

state basis initially.


Service Portability is still on the horizon and has not been addressed by

anyone at this point.


More on porting can be found on the web. The recommended locations are

" and "". Both sites have links to other

LNP information that is being updated as changes are made.



Bio: Bill Belshaw has over thirty years experience in telecommunications. He

is presently working as a consultant for MCI. He wrote the LNP Test Plan for

the Manhattan LNP Trial, and is the editor and primary contributor for the

Illinois Test Plan. The Illinois Test Plan has been accepted across the

nation for LNP testing. Bill is also directly involved in the implementation

of LNP in the South East, West Coast and Western Regions.







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