Digital Regulation Platform

Numbering: valuation of numbers, portability, and emergency and toll-free numbers



The evolution of the use of the NNAI resources in the digital age brings new opportunities and challenges to existing and established concepts. The development of both over-the-top (OTT) services and machine-to-machine (M2M) and Internet of Things (IoT) capabilities, and the access that providers of these capabilities have to NNAI resources, will have an impact on the governance of such resources. This section outlines three such areas of impact: the valuation of numbers, number portability, and the handling of emergency and toll-free numbers.

Valuation of numbers

The valuation of numbers permits charges to be levied on NNAI resources, and charging for NNAI resources is undertaken for two distinct reasons. One reason is to cover the costs of the regulator or as a revenue stream (taxation) for government. The other reason is to ensure the availability of numbers (or NNAI resources) by charging a premium for those resources that are in demand. In reality, in many instances, charging for NNAI resources is a combination of cost recovery and managing demand.

Though the obvious resource that is impacted the most by charging is numbers, both E.164 numbers (that are part of the national numbering plan and dialable from abroad) as well as national only numbers, charges can also be levied to a lesser extent on the other NNAI resources – the international mobile subscriber identity (IMSI) and the issuer identification number (IIN). Depending upon national infrastructure, other resources can be included in any charging regime, but these are not dealt with here.

The elements for levying charges on numbers for cost recovery is open to interpretation. The elements may include the number of staff involved in managing the NNAI resources (either full time or part time), the running costs of the regulator associated with manging NNAI resources, and time spent on managing NNAI resources. Within this, costs incurred in assigning NNAI resources, as a one-off cost, can also be part of the cost recovery. If full-time staff are considered then then the calculation of costs to be recovered can be simpler than if the staff have other functions and only spend a percentage of their time in managing NNAI resources.

Having agreed the constituents of the costs to be recovered, the next step is to set a time period for which those costs will be valid. In some cases, an annual percentage increase is allowed for to reflect changing economic circumstances or increased activity to support managing NNAI resources.

Developing the valuation for NNAI resources to enable costs to be used to manage demand for NNAI resources reflects the structure of the national numbering plan. National numbering plans contain both E.164 numbers and national-only numbers. In many countries, the vast majority of numbers assigned are geographic numbers, for both residential and commercial use, and they are the base on which the calculations are made. That said, where poor infrastructure exists, the majority of numbers assigned may in fact be mobile numbers. The majority of the assigned numbers are taken to be the base and the value assigned to these numbers are then varied against other numbers and NNAI resources.

What value should be assigned to the base numbers? There is no single answer to this. The basic charge, and the charges that are generated from that base, depends upon what the market will accept. There will always be a premium element to such charges if the driver for the charge is to manage the availability of NNAI resources.

Having established the base charge, it can then be adapted according to the demand for certain types of numbers. National-only numbers of 3, 4, or 5 digits can be charged at higher rate than geographic numbers, often by a factor of 10, if such numbers are allocated to service providers. Non-geographic numbers, such as toll-free and premium-rate and shared-cost numbers, can also attract a premium for pattern recognition, e.g. pairs of numbers or runs of numbers, or alpha mnemonics, where the numbers assigned map to the letters on the keypad and make recognizable words. For example, 0800 3569377 may not seem as valuable as 0800 FLOWERS but, according to ITU Recommendation E.161, the former maps to the latter.

Costs associated with other NNAI resources, such as IMSI and IIN, are likely to be impacted by, on the one hand, the demand being stable, but the use for critical mobile communications. The exact charge for such resources will depend on demand for the resource, the nature of the national market (is the market predominantly fixed or mobile network-based?), the size of that market, and the nature of the service.

As with cost recovery charges, to manage number demand there is a need for charges to be able to be increased. This management of demand will be managed by increasing the charge for NNAI resources. All of the steps need be underpinned by the national regulatory framework

Update on number portability

Number portability has become a central pillar to the provision of telecommunication services. The reliance that consumers had on their telephone numbers became a barrier to the benefits of competition. The introduction of portability removed that barrier in all but a few countries.[1]

Number portability can be introduced in a number of ways. Descriptions of the various technical solutions to implement number portability are described in Supplement 2 to Recommendation E.164. Over recent years, the technology of providing number portability has evolved as the network technology used by operators has changed.

Network operators have moved away from the traditional circuit-switched technology associated with signalling system 7 (SS7) and are utilizing packet-switched technology driven by the flexibility that packet switching can provide. As a consequence, the laborious way that number portability was originally forwarded, through call forwarding, has been replaced by packet-switching databases. As part of the transition to a flexible approach, the packet-switched network has further developed the use of the concept of a central database associated with number portability.

The use of a central database to provide information on number portability allowed a single consistent source of information that is often independent of the incumbent operator. The database allowed for the control, either by the regulator, or an independent third party, to be accessed for each call to determine the recipient operator of a call, or as a source of information shared across all operators and used internally by those operators to determine the recipient operator of the call. The move to packet-switched technology allowed the use of the database to be maintained.

As the technology has evolved and new services, such as M2M/IoT emerge that have introduced new stakeholders, then there are implications for number portability. The NNAI resources for such services are no longer assigned to consumers, or end users directly. Rather, they are assigned to the technology that is used by end users. One example is the allocation of NNAI resources to a vehicle for in-car emergency calling, engine/fleet management, and infotainment, all of which may require their own NNAI resources. In such circumstances, the assignment of the NNAI resources may be to the enterprise and not to the end user and that has implications for number portability. Who, then, can instigate number portability?

Number portability was conceived for an end user, as the assignee, to be able to move between operators to take service, in effect creating choice. In an M2M/IoT environment, the end user may not know which NNAI resource has been assigned to the M2M/IoT service. Choosing an alternative service, perhaps associated with a smart meter, may need to change the NNAI resources associated with the smart meter. Where an end user wants to change service provider, then it could result in a change of meter; when the provider of a smart meter, the enterprise, wants to change service provider or network operator, how does the enterprise change service provider?

In most cases the use of NNAI resources in M2M/IoT is to support wireless communication, and changing these resources in such circumstances is complicated for two reasons. The first is because of the potential volume of NNAI resources used by M2M/IoT that would require changing, and the second is the distance between the end user, where the NNAI resource is deployed, and the assignee of the NNAI resource, the enterprise.

How then are NNAI resources amended to provide number portability in wireless contexts to support M2M/IoT? One way is to physically change the modules associated with mobile communications – the SIM cards. This is costly and requires physical attendance at all points. In some use cases, such as smart meters, this could be time consuming and costly. In other use cases, such as remotely managing static infrastructure, such as traffic lights, it could be cost effective when considering the alternative. The alternative is to amend the NNAI resources that are detailed on, and associated with, the SIM card over the air (OTA). While more efficient than physically changing SIM cards, there are costs involved, not least in putting the equipment in place to support the capability.

In the case of vehicles, where there are potentially three sets of NNAI resources in use, the complexity increases. Setting aside what needs to change when cars are imported into a country, then for engine management and infotainment use cases the requirement to amend NNAI resources emerges. The extent to which number portability similarities would exist is dependent upon the change that is occurring and who has initiated it. It is a different requirement to have a car manufacturer change their service provider for connectivity of the engine management system, to an end user choosing to change their infotainment service provider.

There is currently no clear description of the issues or recognition of best practice for how enterprises can move between service providers. ITU-T SG2 has identified this as an area of study in the future.

Handling emergency and free numbers

Emergency and toll-free numbers are examples of national-only numbers and of E.164 numbers, respectively. Toll-free numbers can be assigned directly to service providers by the ITU, according to ITU-T Recommendation E.152 on International Freephone Service, or from within a national numbering space by a national regulator, the so-called indirect allocation.

The manner by which emergency numbers are handled depends upon the national approach to the provision of public safety access points (PSAPs). There are two broad approaches. The first is to provide each emergency service with its own number and to have the caller decide whom to contact in the case of an emergency. The second is to have a central PSAP through which all calls to emergency services are routed. From a numbering perspective, the impact is clear – the more avenues to access PSAPs, the more numbers are required.

Irrespective of the national approach to the provision of PSAPs, there are common issues, including directing the call to the nearest available PSAP, and providing the PSAP with information about the caller and their location. With fixed networks, providing such information was relatively easy. Use of calling line identification (CLI) was often used to direct the call to the closest available PSAP operator and to provide the details of the geographical location of the number to the PSAP.

The introduction of mobile telephones made that more difficult. The separation of the mobile phone from a physical location made generating information for the PSAP operator difficult. This situation was further complicated as users of mobile phones roamed abroad and wanted to access emergency services because of the different access numbers.

Generating information about the physical location of a mobile phone has evolved. The evolution away from relying upon users to describe or state their location to use of technology, such as triangulation of the location of the phone from radio masts, has automated the generation of location information. The technology that is available is wide ranging. ITU-T Study Group 2 (SG2) agreed a technical report on identifying call location for emergency service that gives further information on technology options.

The ability of consumers to travel overseas (and take their mobile phones with them) created an issue of accessing emergency services as countries used different telephone numbers (often national-only numbers). This was solved by having the technology (a combination of the phone and the network) determine the number and only requiring the consumer to indicate that an emergency call is required.[2]

Access to emergency services from services that are emerging in the digital age varies between country, and between operators and service providers nationally. In many cases emerging services, such as OTT services that are seeking to duplicate voice services may not be able to provide access to emergency services. In such circumstances, this limitation may restrict the OTT service providers access to NNAI resources (and the services that can be deployed), or may require the service provider to make clear to consumers that a specific service cannot be used to call emergency services.

The issue of access to and use of toll-free numbers in a digital age brings its own challenges. Toll-free numbers were established for businesses in the 1980s as a means of attracting calls from potential customers. The use of these numbers was made more attractive to consumers by mapping the numbers to letters on keypads to make the numbers easier to remember by spelling out words. This mapping has been made redundant over time with the introduction of technology on phones that either store numbers or allow access to the Internet from which toll-free numbers can be called.

A further challenge relates to the payment for the communication, recalling that it is the recipient of the call who pays for the call. In a simple fixed-line scenario, it is fairly straightforward to translate the toll-free number to a geographic telephone number to complete the call. This geographic telephone number is also called a “deliver to” number. The cost of the call to the recipient was based on fixed network technology.

The introduction of mobile technology introduced additional costs that had to be addressed. In some countries, access from mobile phones attracted a premium and had to incur a payment at the point of origin to cover the additional costs. As costs associated with mobile communications reduced, through competition, and regulation, so the premium also reduced. This facilitated the use of toll-free numbers from within the mobile environment.

In the digital age where the nature of communications is moving away from voice communication, the use of toll-free numbers is also reducing. Calls associated with M2M/IoT services are likely to be of short duration and, for the most part, data communication. Access to free numbers from OTT service providers is likely to encounter issues similar to the introduction of mobile technology. From a regulatory aspect, interconnection would have to be allowed between the OTT provider and the telephone network, and commercial arrangements would need to exist. In the digital age with the availability of technology (such as smartphones) providing alternative channels of communication, the requirement to use toll-free numbers will continue to be challenged.


  1. Where consumers had multiple mobile handsets, for the operators in a given national environment, the introduction of number portability was deemed to have little or no benefit.
  2. This is detailed in ITU-T SG2 approved Recommendation ITU-T E161.1 Guidelines to Select Emergency Number for public telecommunications networks.
Last updated on: 03.09.2020