Summary - ENUM functions that maps telephone numbers to Internet based addresses - A description and the possible introduction to Sweden

Transcription

1 DATE REFERENCE NO. 30 March Summary - ENUM functions that maps telephone numbers to Internet based addresses - A description and the possible introduction to Sweden AUTHOR Joakim Strålmark

2 Summary Introduction PTS 1 has been given the assignment by the Government to submit a proposal on how the Government may collaborate with the implementation of ENUM in Sweden. When using ENUM, PTS refers to that stated in IETF s 2 technical specification RFC [1], which was produced by a working group of the same name. ENUM is a protocol and a database that maps telephone numbers to Internet domain names. The domain name that corresponds to the telephone number will be written in reverse order and is included under a specially allocated second-level domain. For the telephone number of PTS (+46 (0) ) the corresponding ENUM domain name would be e164.arpa. As can be seen, both the trunk code (area code without the first zero) and the country code 46 for Sweden form part of the domain name. The trunk code and the country code appear closest to the special second-level domain.e164.arpa. The ENUM domain name is mapped further to other kinds of addresses (e.g. e- mail addresses, SIP URL 4 for IP telephony, mobile telephone numbers, web addresses stored in special records, so-called NAPTR 5 records) which can thereby facilitate various communication solutions where telephone numbers are used as the only call identity. With this mapping function in the telecommunications systems, ENUM can be used for various applications. Application means in the computer world a concept corresponding to the expression telecommunications service as expressed according to the terminology of the Telecommunications Act. The acronym ENUM stands for Telephone Number Mapping, but also Electronic Numbering, Electronic NUMber and Telephone Number URI Mapping exist as explanations. The benefits of ENUM ENUM has promoted great interest among public telecommunications operators, Internet service providers, ITU-T 6, IETF, the EU, together with commercial actors, which today provide various top-level domains on the Internet. One of the reasons for the attention surrounding ENUM may be that it solves a problem that exists today in obtaining real speed with IP telephony. ENUM transforms the end users communications identities 7 in real time in connection with, for 1 National Post & Telecom Agency 2 Internet Engineering Task Force Session Initiation Protocol Uniform Resource Locators 5 Naming Authority Pointer 6 International Telecommunication Union - Telecommunication Standardisation Bureau 7 Communications identity is a generic term including both a name, a number or an address. For explanation of these three terms refer to ITU-T Recommendation E.191 [2]. This new english term is introduced in this report in absence of a suitable well-known generic english term covering both a name, a number and an address for use in electronic communications networks (e.g. PSTN, ISDN, PLMN, Internet and PSPDN) National Post and Telecom Agency 1

3 example, calls from the circuit switched telephone network (PSTN) to the Internet or another IP network. Communications identities are obtained from the numbering plan for E.164 numbers and the name plan for the Internet domain names. ENUM can be viewed as a means for service and network convergence. ENUM should be an interesting function for end users who wish to be able to be reached via various means of communication where various kinds of communications identities are called. Here some similarities with the today somewhat dormant concept UPT (Universal Personal Telecommunications) can exist. For Internet service providers that have not been allocated an E.164 number by PTS, ENUM may offer an interesting functionality. They could, with the assistance of ENUM, be able to connect customers that have E.164 numbers directly to their IP network and with the assistance of these numbers arrange IP telephony calls for their customers, although these E.164 numbers really belong to another public telecommunications operator, the so-called access network operator. It is not yet possible to assess the consequences of an introduction of ENUM or whether the use would be a marketable success. One or more second-level domains According to IETF s specification for ENUM, it is stated that those ENUM domain names that correspond to telephone numbers shall be located under the top-level domain.arpa. This was established when IESG 8 decided to publish the specification in August Originally,.arpa comprised the only top-level domain in the Internet domain name system (DNS), but by a decision of IAB 9 year 2000.arpa has been rearranged as a domain for infrastructure related purposes. The responsible administrative organization for the top-level domain.arpa is IETF and the responsible technical organization (registry) is IANA 10 in accordance with an agreement between ICANN 11 and IETF. IANA is now a part of ICANN. IAB is the responsible administrative organization for the secondlevel domain.e164.arpa and has for a limited period delegated the technical responsibility for this second-level domain to RIPE NCC 12 in Amsterdam. As regards ENUM, the intention is that every country should notify ITU that they wish to execute delegation of country code zones, i.e. the level which for Sweden corresponds to.6.4.e164.arpa. ITU shall subsequently notify RIPE NCC so that delegation can be executed. This procedure will thereby be able to safeguard that the respective Member State in ITU, on the part of Sweden the Ministry of Industry, Employment and Communications has authorised the introduction of the information for its country code in DNS. 8 Internet Engineering Steering Group 9 Internet Architecture Board 10 Internet Assigned Numbers Authority 11 Internet Corporation for Assigned Numbers and Names 12 Reseaux IP Europeens Network Coordination Centre National Post and Telecom Agency 2

4 The choice of top-level domain.arpa. for the ENUM function has not been completely free from controversy. The issue is indeed still considered to be open and not finally resolved in the ITU, while in the Internet world (IETF/IAB) it s decided that.arpa should be used for ENUM. There are in particular three different matters worthy of mention as regards appropriate second-level domain for ENUM. From the very first there were discussions within, among others, the ITU, and also inside the IETF, about whether ENUM should be located under the second-level domain.e164.int. ITU has the ambition of becoming the registry for the top-level domain.int. Secondly, some countries consider that the current choice of.arpa., to place in parts of their national E.164 plans, feels less satisfactory as it is still really the U.S. Department of Commerce, which through its agreements with ICANN, has the ultimate right to decide as regards some parts of the domain name system for Internet as the U.S. ultimately can control the authoritative root name server in DNS. Thirdly, the commercially created parallel second-level domains for ENUM-like functions will undermine the thought behind ENUM according to IETF s intentions. It is primarily the two American companies, VeriSign and NetNumber, which intend to offer ENUMlike functions under their own second-level domains (.enumworld.com for VeriSign and.e164.com for NetNumber). VeriSign has already today a special status in the domain name market as the sole registry for the popular top-level domains.com,.net and.org, and surely views its involvement with its own ENUM function as a possibility to acquire for itself market advantages before ITU s 189 Member States have decided on ENUM under the second-level domain.e164.arpa. Besides the above-mentioned selection of commercial ENUM-like functions, one can in DNS find other second-level domains that could be aimed at similar purposes. Among others, NeuStar has registered.enum.org and Lucent.e164.org. However, these companies state that they do not at present have any plans to launch commercial ENUM-like functions, but they have mostly used the domains for various information and testing purposes. Knowledge that there are now several second-level domains intended for ENUM creates some problems. First and foremost, the question arises for the national regulatory authorities, which administer the E.164 plan, of in which domain name branch the support of ENUM shall occur. Shall IETF s intentions with ENUM under the.e164.arpa branch be supported, or should other second-level domains also be possible for ENUM? It may with several domain name branches be difficult for the final customer to know in which such branch he should have his ENUM information stored. There is in the domain name system only an opportunity to make direct searches for a particular domain name. There are thus no search functions between several branch structures under different secondlevel domains, to identify a final customer s stored ENUM information. Responsibility in Sweden At the national level, many reasons speak to PTS being appointed as the responsible administrative organization (the designated manager) for the sub- National Post and Telecom Agency 3

5 domain regarding ENUM, as the authority today has similar responsibility for the E.164 plan. In order for this to be realised, the Government must adopt a position and delegate powers to PTS the initial country code zone to enable the authority to be able to select an appropriate organisational structure on matters concerning administrative and technical responsibility for, among other things, the allocation of ENUM domain names, and also the operation of DNS respectively. The choice of permanent delegation of Sweden s country code zone in RIPE NCC s DNS under the second-level domain.e164.arpa should be further considered taking into account the current global debate. PTS considers that one domain name branch should be supported for ENUM and that it is most appropriate to follow that which will be determined through ITU. As mentioned previously, this has not been finally determined within the ITU work. However the IETF already consider this decided and that.arpa should be used for ENUM. PTS considers that if several domain name branches for ENUM are supported, this will probably only create uncertainty about which ENUM is the one with the most reliable final customer data concerning stored E.164 numbers. Provided ENUM is supported under the.arpa branch, or under another domain name branch that is recommended by ITU, such a delegation will entail a choice of organisation that is responsible for the country code zone. As ENUM, among other things, is aimed at ensuring the correctness of address information stored in DNS of an E.164 number, some procedures must be laid down. As the party ultimately responsible for country code 46 and the national implementation of the E.164 plan, it is up to the Ministry of Industry, Employment and Communications to determine to whom delegation shall be made of the country code zone for ENUM. Alternatively, it may be PTS which has today been given responsibility for the E.164 plan through an authorisation by the Government, or the II-stiftelsen that is responsible for the top-level domain.se by delegation from ICANN, or another organisation considered appropriate by the Government. PTS at present has experience of the E.164 plan and its management, while the II-stiftelsen and its company in NIC-SE have knowledge of domain name management. The actor identified for the level.6.4.e164.arpa, or the equivalent, will operate as the registry (responsible technical organization) for the Swedish part of ENUM. It is normal to have only one registry per second-level domain when the domain comprises a country code zone. In the context of ENUM, this level has been termed Tier-1. This level will not contain any final customer data, but only contains a reference to the DNS which contains such data. The term registry also includes the role of being DNS operator for the country code zone. PTS proposes that PTS is appointed as the responsible administrative organization for the sub-domain regarding ENUM and that the Government National Post and Telecom Agency 4

6 authorises PTS to request delegation from ITU for the relevant domain corresponding to country code 46. The level containing the final customer data of an E.164 number has been given the title Tier-2 and can be said to correspond to the registrar if a comparison is made with other domain name branches such as.se. An internationally much discussed issue is which actor should be able to act as registrar for ENUM. In the draft of various documents that have been produced in the framework of IETF s work, one can distinguish two main approaches. One is that the Tier-2 role is held by the public telecommunications operator that holds the E.164 number that the ENUM data will exist for. The other main approach is that Tier-2 is held by an independent service provider. The first-mentioned alternative has the advantage that the public telecommunications operator can easily control that it really is the subscriber, who has been assigned an E.164 number, who wishes to insert ENUM information. However, one disadvantage is that the public telecommunications operator may be unwilling to include communications identities for services that it does not itself provide to the final customer. One way of overcoming this conflict of interest may be that Tier-2 is provided by an independent ENUM service provider. However, with this scenario, the issue arises of how verifications can be conducted to ensure that it really is the E.164 subscriber that is requesting the inclusion of ENUM data. One solution may comprise the ENUM service provider verifying with the public telecommunications operator that it is the correct subscriber that is involved. This procedure involves the public telecommunications operator, and it could possibly be viewed as valuable as it will also be this operator that knows when a subscription is terminated or if a telephone number is ported to another public telecommunications operator in connection with number portability. The interest of the subscriber in being protected against unauthorised loading of ENUM data can thereby be safeguarded in a simple manner. Number portability means a such that an allocated number block of, for example, 10,000 E.164 numbers, will be fragmented when individual subscribers choose to port their E.164 numbers to another public telecommunications operator from the operator, which was originally allocated the block. If DNS at Tier-1 level is also pointed to a public telecommunications operator s DNS ( Tier-2 ) relying solely on information about to whom a number block was originally allocated, this may result in a query for the ported number (in the form of a ENUM domain name) being wrong. One way of resolving this problem may be that DNS for Tier-1 collects information about to which public telecommunications operator a telephone number has been ported. As of August 2001, there will be a central reference database (SNPAC) containing information about all ported telephone numbers in Sweden. Alternatively, the public telecommunications operator can directly provide information to DNS at Tier-1 level when an E.164 number is ported to another public telecommunications operator. Another way to resolve this situation would be that ENUM service provider may have the Tier-2 role. National Post and Telecom Agency 5

7 In preparation for a permanent introduction of ENUM in Sweden, the issue of whom may hold a Tier-2 role must be considered in detail 13. Furthermore, the financing principles for registration of ENUM domain names and operation of DNS at Tier-1 level should be determined. Outcome of consultations PTS has consulted 15 interested parties in the course of the investigation relating to ENUM. Responses were received from Telia, II-stiftelsen, Tele2, Netnod, NIC-SE, Stokab and Ericsson. Generally, there is an interest for ENUM in accordance with the replies received. The instances consulted consider that the Government should cooperate with the introduction and the country code zone.6.4.e164.arpa being delegated to PTS. DNS corresponding to this level should be run by a neutral instance. Telia considers that the choice of the.arpa branch for ENUM should be considered in detail. Furthermore, it is considered unfortunate if there are several competing ENUM-like functions under various domain name branches. This is so, primarily due to the difficulties of the domain name system with searches over several parallel top-level domains. It has also been stated that some kind of trial activity should be implemented in order that Sweden may gain more practical experience pending a possible permanent introduction of ENUM with the collaboration of the Government. Recommendations to the Government ENUM may develop into a function important to society for convergence between circuit switched and packet switched telecommunications network. Links to the E.164 plan will require the collaboration of the Government in the future. Recommendation 1 A national decision on ENUM should be taken at an early stage to avoid several ENUM-like functions being developed, which could make the future use more difficult, both within Sweden and globally. However, PTS considers that adopting a position on a permanent introduction of ENUM under the second-level domain.e164.arpa 14 should not be made before discussions have been concluded within ITU. Recommendation 2 In order to gain experience of ENUM, a trial activity should be implemented under the supervision of PTS. The choice of second-level domain for this trial activity should be determined by PTS and the sector in consensus. The primary indications at present suggest that.6.4.e164.arpa 15 should be used in order to bring 13 Within ITU-T, a Supplement for ITU-T Recommendation E.164 concerning ENUM is being produced. The intention is that this document may provide guidance for the Member States in connection with a possible introduction of ENUM. The objective is to approve the Supplement in September According to information, the ITU has been starting discussions with the IAB concerning an appropriate second-level domain e164.se or.6.4.enum.se are conceivable alternatives. National Post and Telecom Agency 6

8 about a complete trial with the involvement of ITU and RIPE NCC. For.6.4.e164.arpa, it is required that the Ministry of Industry, Employment and Communications assists, as delegation must be requested from ITU for the time the trial should be conducted. The Government should also authorise PTS to be the responsible administrative organization for the country code zone regarding ENUM as it is PTS that has today been appointed as responsible for the E.164 plan. As regard the trial activity, the Government should give PTS the assignment of conducting such trials in collaboration with actors within the sector (IIstiftelsen, NIC-SE, Netnod, telecommunications operators and Internet service providers). Recommendation 3 PTS should be given powers to enter into a contract concerning about the technical responsibility (registry), including the operation of DNS at a level corresponding to the country code zone ( Tier-1 ) for the trial period in question. An appropriate time period for the operational trial may be 12 months. In addition to this, time is required to initiate the operational trials and to produce suitable administrative routines, etc. Recommendation 4 The choice of whom should have the Tier-2 role in Sweden should be evaluated during the trial period. Two alternatives are possible, either the public telecommunications operator that has a subscription relationship with the final customer who has an E.164 number, or an independent ENUM service provider that is independent of the public telecommunications operator. Recommendation 5 It is desirable that the sector during the trial period resolves an appropriate form of financing pending the permanent introduction of ENUM. PTS proposes that the trial is financed by those who participate, i.e. the telecommunications operators and Internet service providers affected. PTS considers that public funds cannot be appropriated for the trial activity. Recommendation 6 PTS should be given the assignment to produce, at the end of a fixed trial period, a follow-up report for the Government containing the following main points: the interest for ENUM among customers in Sweden how the division of responsibilities will function between the various actors in the sector operational experience of DNS for ENUM financing form in connection with a permanent introduction of ENUM need for legislations in connection with permanent introduction of ENUM resolution of the issue concerning appropriate second-level domain for ENUM how the parallel commercial ENUM-like functions have developed international development of ENUM. the ITU s and EU s further involvement in ENUM recommendation to the Government on the permanent introduction of ENUM in Sweden. National Post and Telecom Agency 7