Voip numbering Issues Prepared by: BellSouth Qwest Verizon Voip numbering Issues

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VoIP Numbering Issues

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VoIP Numbering Issues

  1. Purpose and Format

The purpose of this paper is to examine, from a numbering perspective only, the impact of Voice over Internet Protocol (VoIP). This paper will provide background information on VoIP service but the primary focus is intended to examine how the service uses telephone numbers from the PSTN and how this use potentially impacts the life and present assignment and administration of NANP numbers.

  1. Description of Service

      1. Many companies who provide VoIP service will and already are competing with service providers in the PSTN. In the October 2002 issue, of ISPWORLD the CEO of one VoIP provider, states that his company is not selling their specific brand of service to customers as VoIP phone service, but they “are selling it to them as a replacement to their existing phone service.” 1

      1. VoIP service is described as a way for end users to get local, regional, and long distance nationwide calling. Many VoIP service providers offer features such as Call Waiting Caller ID, Personalized Voice Mail, Call Forwarding, Caller ID Block (*67), Repeat Dialing.

The specific feature offerings that directly impact numbering are the ability of the customer to have:

  • A telephone number in any area code of their choice;

  • The ability to take their telephone number with them when they move outside of their current rate center.

      1. Many VoIP providers’ services are based on Internet Session Initiation Protocol (SIP)2.

      1. A high-speed Internet connection, such as a Cable Modem or DSL connection is required. In addition, a phone adaptor is required. One such VoIP service provider provides the customer with a Cisco ATA 186 Analog Telephone Adaptor, which converts the traditional analog phone into a SIP VoIP phone The adaptor converts analog voice into digitized voice signals and then into IP data packets. The adaptor is installed at the customer’s premise(s).3

  1. Conceptual Diagram

Figure 1 is a conceptual diagram of architecture used to support VoIP service. The diagram illustrates when a customer is assigned a TN from a non-home rate center. In this diagram, the customer who resides in the Atlanta rate center is assigned a number from a New York NPA/NXX. A call that originates from the PSTN to this Atlanta customer would be routed via the PSTN to New York. The call then is placed on the Internet via a Gateway server. The call is routed to the Atlanta customer via the Internet. It should be noted that the customer can subscribe to this service without changing their existing NPA or rate center.

Figure 1.






Class 5 End Office Or Tandem






Atlanta Customer with NY TN

New York

(212 NPA)

  1. Examples of Numbering Selection Currently Offered by Two VoIP Providers

    1. VoIP providers do not obtain numbers directly from NANPA. It appears they obtain numbers from LECs that have received numbers from NANPA. Today, the LEC service provider that provides the numbers to VoIP providers must report these numbers on NRUF as “Intermediate” numbers. The VoIP provider in turn re-assigns these numbers to their VoIP customers.

In the previously cited example of service, the VoIP service provider allows customers to obtain and keep telephone numbers from any of the area codes where the VoIP service provider has received Intermediate numbers as long as they remain with that VoIP company. The following list includes some of the area codes served by one VoIP service provider:

California: 213 310 323 408 510 619 626 650 707 714 760 805 818 831 858 909 925 949

Delaware: 302

Florida: 305 561 786 954

Georgia: 404 678 706

Illinois: 312 630 708 773 815 847

Indiana: 219

Massachusetts: 508 617 781 978

New Jersey: 201 609 732 856 908 973

New York: 212 347 516 631 646 718 845 914 917

Pennsylvania: 215 267 412 484 610

Texas: 409 832 936 979 214 254 469 817 903 940
At least one VoIP provider advertises that by subscribing to their service the customer is no longer tied to their "local area code". The customer can select any area code they want from the list of available area codes where they operate. For example if a subscriber lives in New York, they can have a telephone number in a California Area Code. Their advertisement goes on to state their service gives an appearance of a local presence without having to be physically located in that area.
Two features that one VoIP provider presents as unique features of their service include allowing customers to keep their telephone number as long as they want and allowing customers to keep their numbers even if the customer changes location regardless of the their new location. Their website explains these features as follows:
“Keep your ________telephone number for as long as you’d like. As long as you are a ________customer, you can keep your telephone number. Even if you move across the state, or across the country, you never have to change your telephone number again.”
“Never before have you had the ability to take your home phone with you wherever you go. With _________, you can travel with your home phone or even move (emphasis added) without skipping a beat. Whether you’re traveling across the United States or anywhere else or you’re moving into a dorm, or another town; all you need is a high speed internet connection and the phone adapter (that we provide for free). It’s home phone service that goes with you.” This, in fact, is the same as maintaining a wireless telephone number and service when moving.
It should be noted however that in this VoIP providers Terms and Conditions, they state that the “Customer has no proprietary or ownership rights to or interest in a specific phone number or phone numbers ("Number") assigned to you by _______, and the number is not portable to any other service provider.

    1. A second VoIP service provider allows a customer to get a personal number based on the area code of the customer’s choice. Also, each account includes voicemail that can be accessed from a telephone or from the web. This particular VoIP service provider advertises that customers can select any available area code from the list below, no matter where they live in the world. Their number is not constrained by the city that they live in.

They currently offer numbers from the following area codes:

Arizona: 480

California: 213 415 510

Colorado: 720

Florida: 407

New York: 347 646 718 917

Pennsylvania: 610

Texas: 214 281
The company advertises that the customer should contact them if the above list does not contain the area code from which a customer wishes to request a telephone number.

  1. Numbering Issues

Shown below are excerpts from industry guidelines established by the Industry Numbering Committee, which is sponsored by ATIS. The FCC has plenary authority over the INC’s guidelines. This section contains identified numbering issues with VoIP type service and is divided into three sections: General Issues, Specific Numbering Guideline Issues and Technical Issues.

    1. General Issues

      1. Rate Center Assignment Principle

An assignment principle in the both the Industry Numbering Committee’s (INC) CO-NXX Assignment Guidelines and the Industry Numbering Committee’s Thousands-Block Number Pooling Assignment Guidelines is that service providers are assigned resources on a rate center basis4. This principle applies whether the service provider is applying for initial numbering resources in a rate center or additional numbering resources in a rate center. For initial resources in a rate center, a service provider must show proof of readiness and certification for providing service. For growth numbering resources, the service provider must show proof of need, and must show the months to exhaust and utilization requirement have been met.
Issue Description:

Entities that receive “intermediate” numbers do not have to meet utilization criteria today per the FCC. Many service providers, including VoIP service providers, can obtain any quantity of numbers from LECs anywhere in the country without meeting the requirements applicable to other certified service providers. This is in contrast to current requirements for the more conventional service providers who must track and report their quantities of intermediate numbers and use them in demonstrating their ability to meet the current Months-to-Exhaust requirements for growth numbering resources on a per rate center basis.

Since VoIP service providers are interconnecting with the existing PSTN and using PSTN numbering resources, the primary question is: Should the number assignment rules that apply to conventional service providers apply to VoIP providers?

      1. Impact on NPA Relief & NANP Exhaust

VoIP provider’s current use of telephone numbers will expand the need for telephone numbers, which could advance the exhaust of the NPAs. Assigning telephone numbers from a particular NPA in one area of the country to customers that do not reside in that NPA (i.e. they may actually reside in another state) may accelerate the need for NPA relief. As VoIP service providers begin to obtain and assign numbers in this fashion, it creates additional demand. This issue also arose with the deployment of E-fax services and will continue to be an issue as new technologies are deployed offering alternatives to the traditional use of numbers.
Issue Description:

The impacts on NPA relief and NANP exhaust will no doubt cause concern with some state public utility commissions since NPA exhaust may be accelerated because telephone numbers are assigned to customers outside the NPA or even outside their respective state. For example, New York City residents can potentially be burdened with additional area code relief because subscribers not under New York regulatory jurisdiction could end up taking a large quantity of their numbers for use outside of the state. On the other hand, there is an impact on customers who keep their existing numbers when they move. In the past these numbers went back into a carriers inventory for reassignment to other customers.

One other concern stems from the situation where a typical subscriber may already have a wireline phone, fax, cell phone etc., where they preside. VoIP service may encourage subscribers to add additional numbers from any number of cities. This scenario could lead to a single customer obtaining multiple sets of numbers from multiple cities. Should this concept become popular it could result in an acceleration of the demand for numbers.

      1. Number Resource Utilization and Forecasting (NRUF) Reporting

The definition of Intermediate numbers and how they are treated in utilization calculations and in NRUF reporting is currently under review by the NANC. Numbers obtained and used by VoIP service providers may impact NRUF reporting.
Issue Description:

Should VoIP service providers be accountable for how they use NANPA resources?

The current arrangement requires VoIP providers to obtain individual telephone numbers from existing code holders.
Also, should numbers given to VoIP service providers be reported and tracked using a new FCC numbering category?

    1. Specific Numbering Guidelines Issues

      1. Assumptions of the Industry Numbering Committee (INC) on Use of Numbers

This section will review INC’s assumptions from the Central Office Code (NXX) Assignment Guidelines and the Thousands Block Number (NXX-X) Pooling Assignment Guidelines as adopted by the FCC. The issues address the use of NANPA resources and identify those assumptions, which appear to conflict with existing VoIP use of numbers.

        1. Central Office Code Assignment Guidelines dated September 27, 2002

          1. Assumptions 2.1:

The NANP resources are considered a public resource and are not owned by the assignees. Consequently, the resources cannot be sold, brokered, bartered, or leased by the assignee for a fee or other consideration. Transfer of code(s) due to merger/acquisition is permitted.

If a resource is sold, brokered, bartered, or leased for a fee, the resource is subject to reclamation.
Issue Description:

It should be clear to customers when purchasing service from any service provider that the customer is not purchasing the number and does not own the number.

          1. Assumption 2.2

NANP numbering resources shall be assigned to permit the most effective and efficient use of a finite numbering resource in order to prevent premature exhaust of the NANP and delay the need to develop and implement costly new numbering plans.
Issue Description:

The existing numbering resources have historically been allocated for specific geographic areas. By assigning New York telephone numbers to Georgia residents this geographic association is impacted.

          1. Assumption 2.10:

SPs and numbering resource administrators are responsible for managing numbering resources in accordance with these guidelines and the orders of applicable regulatory authorities.
Issue Description:

INC numbering guidelines will have to be revised to incorporate VoIP applications that use NANP numbers. Is it time for resellers and VoIP service providers to be recognized as service providers subject to the accountability for their use of TNs? Furthermore, the impacts of area code relief measures such as NPA splits must be addressed as this may require changes to the numbers used by VoIP providers.

          1. Assumption 2.14:

It is assumed from a wireline perspective that CO codes/blocks allocated to a wireline service provider are to be utilized to provide service to a customer’s premise physically located in the same rate center that the CO codes/blocks are assigned. Exceptions exist, for example tariffed services such as with the exception of foreign exchange service.5
Issue Description:

Should all providers be afforded the opportunity to be excluded from this existing assumption, permitting the use of numbers beyond rate centers? This is a large issue since existing number assignment guidelines and regulations for the request, use, and reporting of numbers are all rate center based.

    1. Technical Issues

      1. Number Portability

According to the October 2002 issue of ISPWORLD, in September 2002, a VoIP provider planned to introduce number portability using partnerships with local exchange carriers (LECs). As VoIP service providers begin to offer local service, the impact of VoIP service on number portability requires examination.
As background there are three types of portability. They are:

        1. Service Provider Portability

Service provider portability, as defined in the Telecommunications Act of 1996, is “the ability of end users to retain, at the same location, existing telephone numbers as they change from one service provider to another”.
This is the type of portability that has been ordered by the FCC and implemented by LECs and will soon be implemented by wireless service providers.

        1. Location Portability

Location portability, as defined in the First Report & Order, Docket No. 95-116, is “the ability of users of telecommunications services to retain existing telephone numbers without impairment of quality, reliability, or convenience when moving from one physical location to another”.
Location portability allows customers to take their telephone when they move to another geographic location outside of the original rate center.6

        1. Service Portability

Service portability, as defined in the First Report & Order in Docket No. 95-116, is “the ability of users of telecommunications services to retain existing telephone numbers without impairment of quality, reliability, or convenience when switching from one service to another service provided by the same telecommunications carrier7.
Issue Description:

The implementation of service provider portability was very complex and time consuming. The technical requirements and standards ordered by the FCC and adopted by the industry were developed by the industry after lengthy periods of analysis and discussion. The FCC adopted the industry recommendations and standards.

From a service provider portability viewpoint, some questions that arise are:

  • How will “porting” be done with a VoIP service provider? For example:

  • If VoIP service providers are going to complete calls to and from the PSTN, should they also be required to have to implement LNP using LRN?

  • If VoIP service providers offer number portability will they need to interact with the NPAC?

  • Will a new subscriber that is assigned a PSTN telephone number from a VoIP provider be able to port their number to a PSTN service provider if requested? If so, will that port be limited to a specific geographic area? Should compatible system interfaces be developed to port numbers between VoIP providers and PSTN providers?

  • Does the definition or the role of N-1 carrier apply or change?

  • Should the process of “snap back” be used when a number is ported from a PSTN service provider to a VoIP service provider or is it correct to leave it with the VoIP provider who has obtained the number form another type of carrier?

These are just some of the portability issues that should be addressed when VoIP service providers begin to offer local service. In the end, the concept of location portability as it is known today may need to be revisited. For example, as other VoIP providers enter the market and offer limited location portability, an issue of standards may arise.8 Do standard bodies need to ensure that location portability is developed in a consistent manner and is compatible with the PSTN? Will location probability need to be offered by traditional LECs? Should there be a limitation to the geographic area for which location portability applies? These are just some of the issues that require examination.

    1. Other Issues

      1. Number Jurisdictional Issues

With VoIP service providers offering local service with NANP resources, concerns regarding jurisdictional authority over numbering resources become a key issue. The FCC has plenary jurisdiction over the use of NANP resources. Specific aspects of that jurisdiction have been delegated to state regulatory bodies. As such, any concerns as to the ability of VoIP providers to use NANP numbers are to be guided by the intentions of the FCC. As technology continues to advance and the integration of IP telephony and the existing PSTN develops, it becomes necessary for the industry as a whole, (wireline, wireless, VoIP, CLEC, DLEC, etc.) to provide the FCC with solid data and facts to permit the FCC to make its decision on the appropriate use and applications for NANP numbering resources.
Embedded within the jurisdictional issue is the matter of how the cost of NANP number administration is paid and prorated. With VoIP service offerings, VoIP is obtaining numbers that were originally allocated to LECs. Therefore the LEC pays for the administration of that number. In the future, the question will become should the VoIP providers also pay for the numbering resources administration under the required guidelines. These administrative issues should be dealt with, once the jurisdiction issues are addressed.
Finally, 911 and other N11 dialing capabilities and requirements may vary from State to State. These must be clearly evaluated as a to if and how VoIP will support these dialing capabilities and requirements.

  1. Summary

One of the major challenges resulting from the integration of the PSTN and Internet is the status of calls that pass from one network service provider to another service provider between the PSTN and the Internet. Due to multiple architectural configurations for VoIP, a lack of existing all-encompassing industry standards, and an indeterminate regulatory landscape, the current numbering paradigm as applied to numbering responsibilities and obligations needs to change in this developing environment. The change is a complex problem to solve. Today’s rules and regulations address number assignment, number use and the responsibilities of both regulators and Industry only in a PSTN environment. These rules and regulations have been formulated to maximize the use and life of the existing NANP numbering resources. VoIP service represents a new element and application that will have an impact on the life of the NANP. In the past the introduction of cell phones, CLEC entry, pagers and other services have impacted NANP numbering resources and consequently changes were adopted.
It will be necessary to address the constraints that PSTN service providers must operate under in order to obtain and use NANP resources when incorporating the VoIP service providers use of numbers into the rules and regulations.
In order to support PSTN and Internet integration it is necessary that all numbering issues be thoroughly examined. Thus, as new implementations of VoIP are introduced (e.g. ENUM), or for that matter any future use of the numbering resources, issues involving numbering in VoIP environments need to be identified and examined to determine their impact on the North American Numbering Plan (NANP).
It’s recommended that the NANC assist the FCC in addressing these numbering issues to prevent any disparities that are arising based on existing regulations to achieve true NANP resource optimization.

1 Erickson, Todd Judd, “VoIP Finally Flexes Some Market Muscle”, :ISPWORLD, October 2002

2 The Session Initiation Protocol (SIP) is based on the protocols used for emails and web pages, which follow a client-host model.

Users in a SIP network are identified by unique SIP addresses. A SIP address is similar to an e-mail address and is in the format of sip:userID@gateway.com. The user ID can be either a user name or an E.164 address.

3 The Cisco ATA 186 Analog Telephone Adaptor is a handset-to-Ethernet adaptor that interfaces regular analog phones with IP-based telephony networks. The ATA 186 has two voice ports that can only support legacy analog touchtone telephones.

4 The Industry Numbering Committee (INC) is an ATIS forum provides and provides a forum for customers and providers in the telecommunications industry to identify, discuss and resolve national issues that affect numbering.

5 Foreign Exchange differs in that it uses a dedicated facility from the customer premise located in a foreign rate center to a switch of a code holder in the serving rate center.

6 In the Second Memorandum Opinion and Order on Reconsideration in CC Docket 95-116, the FCC concluded that nothing in the Act precludes them from mandating location portability; however, they had plans to address location portability.

7 The FCC is not addressing service portability at this time and requirements for service portability are still undefined

8 Limited location portability in IP telephony is implemented by the use of redirect servers and proxy servers. It is similar to call forwarding in the PSTN


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