Article published in NARTE News, Vol.15, No. 2, Apr-Jun 1997
LOCAL NUMBER PORTABILITY (LNP)
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
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
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
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 "www.atis.com".
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
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
"www.cameos.com/lmp? and "www.ported.com". 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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