ENUM stands for "“telephones NUMBER Mapping"” and is an application of the Domain Name of system for the translation of telephone numbers in Internet addresses. ENUM is defined in the RFC 3761. The need for such a solution arose from the availability of VoIP services and the need of the user to be attainable both in the Internet and in the classical telephone network under the same number.

ENUM and world-wide telephone numbers

Classical telephone numbers in the world-wide telephone network follow a number plan of the International Telecommunication Union, in the International Telecommunication Union recommendation E.164 is fixed to which. Since it with ENUM Mappings of world-wide telephone numbers Internet resources (contrary to the telephone numbers themselves, which can be regarded as resources under the administration of the International Telecommunication Union) concerns, for it the classical Top level Domain for Internet resources of the IETF, was used ARPA. As Subdomain - there it around Mappings of the E.164 of number plan acts - e164 was selected. Since ENUM Mappings are finally nothing else as simple DNS entries, it is however naturally just as possible thereby to illustrate own number plans under other Domains (e.g. see. http://www.e164.org/).

Conversion and inquiry

The conversion of a telephone number to the corresponding ENUM Domain (in this case the IETF Mapping) happens thereby as follows:

1. +44 1 2345 6789 - writing the complete E.164-Nummer down
2. 44123456789 - Remove all indications, which do not represent numbers
3. 4.4.1.2 .3.4.5.6.7.8.9 - Insert from points between the individual numbers
4. 9.8.7.6 .5.4.3.2.1.4.4 - Turn around the sequence of the numbers
5. 9.8.7.6 .5.4.3.2.1.4.4.e164.arpa - Adds the ENUM Domain suffix .e164.arpa

This conversion happens in most ENUM Clients automatically, so that only the input of the telephone number is necessary.

The out above conversion resulting Domainnamen over the resolver for NAPTR resource record one scans. The evaluation of this resource record results in or several uniform resource Identifier, under which/those the desired service of the indicated Domain and/or telephone number can be addressed.

Administration

The international ENUM Top level Domain e164.arpa is administered at present on behalf the International Telecommunication Union by RIPE. On request the individual are delegated after consultation with representatives of the International Telecommunication Union to local land organizations. The further organization of the national Domainraumes is determined autonomously by the land organization, whereby this happens usually under close co-operation with the national responsible authority.

The assignment and Provisionierung of these new Domainnamen are tested since at the beginning of of 2002 in some countries in ENUM Trials so mentioned. This Trials serves for usually to the research of ENUM and related technologies as well as preparation of a possible commercial enterprise.

In Germany ENUM of entries under 9.4.e164.arpa is available in the context Trials since 2002 over some the IC members. The transition to the effect enterprise was originally for December 2005 planned, however on 26 January 2006 finally was then only taken up.

As world-wide the first country in Austria after one over two-year Trial on 24 August 2004 a contract was signed to the commercial enterprise of ENUM. In the present Treaty delegates the Austrian modulator, the RTR GmbH, which enterprise enum.at limited to at the end of on of 2007. The production enterprise was taken up through enum.at on 9 December 2004.

Expiration

If one calls with a ENUM Look UP terminal or over a Provider, which supports ENUM Look UP, a telephone number on, for which there is a ENUM Domain, then queries the own terminal or the Provider by means of the ENUM Domain the goal. There is another deposited goal, e.g. A VoIP goal, Handynummer or fixed net number, are preferred this for the connection establishment. Also several goals can be deposited, which are queried after priorities. Otherwise the indicated telephone number is called. The moreover one also the telephone number can be deposited a E-Mail address or the web page.

In order to register to a German call number the ENUM Domain, several conditions must be fulfilled:

• The call number must possess a correspondence in the German call number plan
• The Registrant of the ENUM Domains must possess the right to use at the call number
• The call number must come of from a call number lane for ENUM the available
  • Local area networks
  • Portable radio 015, 016, 017
  • Services free of charge 0800
  • Personal call numbers 0700
  • National participant call numbers (NTR, nomadische use for VoIP) 032

The caller pays extra costs, which arise by rerouting over ENUM. Example: One selected a fixed net number, was led however by the ENUM Lookup on a portable radio number or an increase in value service number (0900 in former times 0190). But: Since the ENUM Lookup on user side is implemented, it is because of the hard and software of the user whether such a forwarding without note for the user is accomplished. ENUM "“distributed"” only the information, which is made from it, is because of the user and its hard and software.

Related links

Further information

• http://www.denic.de/de/enum/ - information of the German Registry DENIC
• - information of the Austrian ENUM Registry

Registration places (Registries)

• http://ripe.net/ - animal 0 Registry (e164.arpa)
• http://www.denic.de/ - animal 1 Registry of the German ENUM zone (9.4.e164.arpa)

Offerer and alternative projects

• e164.org - project for the setting up an alternative ENUM registration
• e164.info - "“carrier ENUM"” project of a German VoIP of offerer
• http://www.enum-center.de/ - ENUM portal, .de
• - side enum test.at for examining the ENUM Lookups
• www.sipbroker.com - manual ENUM Lookup with different ENUM service providern

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