ICANN | Letter from ITU on Telephony-Related TLDs

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Letter from ITU on Telephony-Related TLDs
(1 November 2000)


General Secretariat

1 November 2000


Strategies and Policy Unit

Michael M. Roberts - President and CEO
Internet Corporation for Assigned Names and Numbers (ICANN)
4676 Admiralty Way, Suite 330
Marina del Rey, CA 90292
United States of America


+41 22 730 5214


+41 22 730 6453




Applications to ICANN Concerning Telephony Addressing Top Level Domains

Dear Mr. Roberts,

The International Telecommunication Union (ITU) welcomes the opportunity to comment on applications for new Internet top level domains made to the Internet Corporation for Assigned Names and Numbers (ICANN) that relate to the ITU Telecommunication Standardization Sector's (ITU-T) Recommendation E.164: The international public telecommunication numbering plan.

The ITU is an international intergovernmental organization within which governments and the private sector coordinate global telecom networks and services. The ITU currently has 189 Member States and more than 600 Sector Members who participate in the ITU’s telecommunication standardization, radiocommunication and development activities. ITU Sector Members include telecommunications and Internet infrastructure service providers and operators as well as related equipment manufacturers.

As a result of the rapid growth of the Internet and other Internet Protocol (IP)-based networks, support for IP technologies is now a strategic element in the design, development and use of telecommunication networks. As a direct consequence, there has been a rapid expansion in the scope of ITU's IP-related activities.1 For example, most ITU-T Study Groups have now reorientated their work toward standardization activities related to IP networks and convergence with circuit-switched technologies. In addition, ITU Member States have recently decided to convene the next World Telecommunication Policy Forum on the theme of IP Telephony.2

The ITU membership has a clear interest in the stability and future scalability of the Internet’s critical infrastructure, of which naming and addressing systems play an obvious important role. In this regard, ITU Member States have also adopted Resolution 102 (Minneapolis, 1998) on “Management of Internet Domain Names and Addresses”3 where the ITU Secretary-General has been instructed to “to take an active part in the international discussions and initiatives on the management of Internet domain names and addresses, being led by the private sector….” and to “to report annually to the [ITU] Council on the activities undertaken on this subject”.

We have taken note of multiple applications to ICANN for telephony-related TLDs that involve mapping of the E.164 numbering plan into the DNS. As a general remark, the ITU suggests that careful reflection is given by ICANN as to the advisability of allocating TLDs corresponding to Uniform Resource Locator (URL) scheme names as defined in various RFCs and assigned by IANA.4 As URL scheme names are typically associated with widely-deployed protocols or existing naming/addressing resources, control over a corresponding TLD may suggest control over the corresponding protocol or naming/addressing resource.

Even if this were considered to be acceptable practice, the ITU would suggest that particularly careful reflection is warranted as to the global long-term benefits to the Internet community in allocating certain TLDs at this time—especially considering both the irreversibility of such a decision, and that it may preclude, perhaps other, more beneficial, future uses. One example is .tel, which has an obvious mnemonic link to telephony, and particularly IP Telephony services.

IP Telephony has rapidly reached the top of the agenda for the telecommunication industry worldwide. The promise of voice over IP-based networks, with its challenges and associated opportunities, such as voice and data integration, represents a major milestone in the convergence of the communications sector. A great deal of work on technical standards for IP Telephony is currently underway in many forums and standardization bodies such as the European Telecommunications Standards Institute (ETSI), the Internet Engineering Task Force (IETF) and the ITU Telecommunication Standardization Sector (ITU-T). For example, the ITU has produced the H.323 series of Recommendations, which have been widely adopted by the IP telephony service provider market. The ITU has also jointly produced, in collaboration with the IETF, the H.248/Megaco protocol,5 for controlling media gateways that can pass voice, video, facsimile and data traffic between Public Switched Telephone Networks (PSTN) and IPbased networks.

One of the important challenges raised by the ever-closer integration between circuit-switched and packet-switched networks concerns how to address calls that pass from one to the other. Generally, it is widely accepted that it is desirable that an integrated global subscriber access plan exists. For example, the same ITU-T E.164 telephone number would reach a subscriber regardless of whether IP-based or PSTN network technologies are used.

It is now widely possible to originate calls from IP address-based networks to other networks, but it is currently rare to terminate calls from other networks to IP address-based networks. Rather, calls are generally terminated on the PSTN, so the called party can only use a terminal device connected to these networks. In order to access a subscriber on an IP address-based network, some sort of global numbering/addressing scheme across both PSTN and IP address-based networks needs to be developed and implemented.

ITU-T Study Group 2 (SG2) is currently studying a number of possible options whereby users in IP address-based networks can be accessed from/to PSTN users. As one option, SG2 has temporarily reserved, for test purposes, a part of the E.164 numbering plan (+878 878), as an IP-based implementation of Universal Personal Telecommunication (UPT) services. However, a final solution has yet to emerge but could involve a DNS-based mapping solution.

The issues surrounding the intersection between telephone numbering and the DNS are very complex and currently under discussion between experts in the IETF and ITU as well as with governments responsible for numbering plans. As I am sure you are aware, the E.164 international public telecommunication numbering plan is a politically significant numbering resource with direct implications of national sovereignty. It is subject to a multitude of national approaches, regulatory provisions, and, in some cases, multilateral treaty provisions.6 Considering this, governments should be given the opportunity to fully reflect upon how their particular numbering resource responsibilities relate to DNS-based telephony resources.

In this regard, the ITU is working with the IETF to progress a careful exploration of these complicated issues in the context of its joint work concerning the ENUM protocol.7 As there are still considerable areas of coordination work needed at this time, until there is an opportunity to further explore the issues within the context of joint work underway and with national governments,8; it is the view of ITU that it would be premature for ICANN to grant any E.164-related TLD application as this may jeopardize these cooperative activities or prejudice future DNS IP Telephony addressing requirements.

Yours sincerely,




[1] A recent report on ITU activities related to IP-based networks can be found at http://www.itu.int/infocom/ip/

[2] In March 2001, see http://www.itu.int/wtpf/


[4] http://www.isi.edu/in-notes/iana/assignments/url-schemes

[5] Approved in June 2000.

[6] The ITU Constitution and Convention, which are recognized as binding treaty instruments, set forth the functions and role of the ITU Telecommunication Standardization Sector, the World Telecommunication Standardization Assemblies, as well as the Director of the Telecommunication Standardization Bureau (TSB).

The role of the TSB Director as well as that of ITU Member States with respect to the allocation and management of numbering resources is defined in Resolution 20: “Procedures for allocation and management of international numbering resources”, adopted by ITU Member States at the World Telecommunication Standardization Conference (Geneva, 1996). Resolution 20 states, “that the assignment of international numbering and addressing resources is a responsibility of the Director of the TSB and the relevant Administrations.” The term “Administration” is a term of art defined in the Constitution as “Any governmental department or service responsible for discharging the obligations undertaken in the Constitution of the International Telecommunication Union, in the Convention of the International Telecommunication Union and in the Administrative Regulations.”. Related documents include, inter alia, ITU-T Recommendation E.164/I.331 (05/97): “The international public telecommunication numbering plan”, ITU-T Recommendation E.164.1 (03/98): “Criteria and procedures for the reservation, assignment and reclamation of E.164 country codes and associated Identification Codes (ICs)”, and ITU-T Recommendation E.190 (05/97): “Principles and responsibilities for the management, assignment and reclamation of E-series international numbering resources”.

[7] http://www.itu.int/infocom/enum/. For a view of SG2 collaborators, see http://www.ietf.org/internet-drafts/draft-blane-sg2-liason-enum-00.txt

[8] For an example of different national regulatory approaches to IP telephony, see Table B.1 in Annex B of http://www.itu.int/wtpf/sgreport/version1-sgreport-iptel.pdf


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