ENUM - The bridge between the switched telephony network and the Internet

ENUM (E.164 Number to URI Mapping) translates telephone numbers into Internet addresses. You can dial a telephone number and reach a SIP, H.323 or any other Internet Telephony user. This all happens in the background; you do need to do anything special while calling someone.

A server with ENUM support will lookup a dialled telephone number in the ENUM tree of the DNS to see if there's alternate ways to set up the call instead of just calling out on the PSTN telephone line. ENUM may contain a reference to a SIP URI, a telephone number to dial, a web page or an e-mail address.

ENUM is already supported by SIP Proxies like SER, Kamailio, OpenSIPS or SNOM 4S, VoIP gateways like Asterisk, Swyx, and SIP phones (SNOM).

Enum uses DNS NAPTR resource records.

ENUM RFC 6116 is a protocol developed by the IETF that uses the Internet DNS system to translate E.164 (i.e. ordinary) telephone numbers into IP addressing schemes (like SIP, H323 or Email). To register new Enumservices (or update existing ones) with IANA, RFC 6117 contains all the information you need.


  • ENUMER - Blockchain-based decentralized ENUM technology and implementation is released (11-Sep-2017).
  • New ENUM Standards Published (14. March 2011): RFC 6116, RFC 6117 and RFC 6118 update various older RFCs on ENUM.
  • nrenum.net is now a productive service (Spring 2011). Nrenum.net, a service of the National Research and Education Networks (NRENs), can be used in the countries where the Golden Tree (e164.arpa) is not (yet) available and it is maintained by Terena.

IETF Documents

Selected List of Published RFCs

  • RFC 6117: New process for registering new Enumservices
  • RFC 6116: ENUM Protocol (obsoletes RFC 3761)
  • RFC 5333: Internet Calendaring addresses in ENUM
  • RFC 5076: ENUM Validation Information Mapping for EPP
  • RFC 4725: ENUM Validation Architecture
  • RFC 3761: Old ENUM Protocol (obsoletes RFC 2916, obsolete)
  • RFC 3762: Usage of H323 addresses in ENUM
  • RFC 3764: Usage of SIP addresses in ENUM
  • RFC 3026: Berlin Liaison Statement
  • RFC 2916: ENUM Protocol (obsolete)
  • RFC 2915: NAPTR RR
  • RFC 2870: Root Name Server Operational Requirements

Internet Drafts in the Pipeline

For a complete list of ENUM WG documents, please visit http://datatracker.ietf.org/wg/enum/

ENUM Experts

Various Information on ENUM

Current ENUM deployment status in various countries

ENUM Progress Matrix maintained by RIPE ENUM working group

Software support

Record syntax

Organizations involved with ENUM

  • RIPE - Tier 0 administrator for "official" e164.arpa ENUM top level domain
  • ITU-T TSB - International Telecommunication Union
  • ETSI - European Telecommunications Standards Institute
  • VisionNG - Administrator of ENUM based 878-10 number range
  • Ucom.ch offers Technical Consulting for ENUM

  • E164.org - A free, private validated ENUM service supporting both "real" and "free" 882 numbering and a variety of NAPTR service types including VoIP, mailto and IM.
  • E164.dk - Danish ENUM service
  • ENUM.org is the official web site for NeuStar's ENUM Public Trial.
  • The Voice Peering Fabric ENUM Registry Service/Layer2 peering point - million of numbers reachable at zero cost.
  • IETF Enum page
  • ITU Enum page
  • IANA Enumservice registrations - the list of official ENUM NAPTR service types
  • ENUM Reference: http://www.ngi.org/enum/
  • ENUM Reference: http://www.cybertelecom.org/enum.htm
  • ENUMexchange.org now provides a free seamless ENUM calling service across all major ENUM trees plus approved private ENUM servers added by their operators.
  • enum2go Providing 87810 global ENUM numbers.
  • nemox.net - first ENUM-registrar
  • SIP.edu ENUM and Redirection service Reach the Internet2 / SIP.edu community using ENUM or SIP.
  • enum.at - Austrians ENUM Registry, several ENUM related applications like Softphone, ENUM enabled Gateway ...
  • 43780 - ENUM enabled number range in Austria
  • 3883 - European Telephony Numbering Space
  • Numspark.com - A free and open voip routing platform supporting direct SIP routing and Enum number lookup.
  • SWITCH - ENUM Registry for Switzerland until 2007
  • enum.com.au Site for ENUM trial In Australia using the 0590 0XX XXX Number range
  • NRenum - ENUM tree created by a Terena effort to be used in the countries where the Golden Tree (e164.arpa) is not (yet) available.
  • www.sipbroker.com now provides a free seamless ENUM calling service across the 4 major ENUM trees e164.arpa, e164.org, e164.info and enum.org.
  • StarTel.pt is a free VoIP provider that provides seamless ENUM calling service across 3 major ENUM trees e164.arpa, E164.org and nrenum.net
  • ENUM.nl Enum in the Netherlands
  • ENUM +420 Resources for ENUM in Czech Republic by czech ENUM registry (CZ.NIC)


See also

  • SIP
  • URL SIP: the SIP: url scheme
  • URL SIPS: the SIPS: URL scheme
  • URL TEL: The TEL: URL scheme
  • URL H.323: The H323 URL scheme
  • URL IAX: The IAX: URL scheme
  • DUNDi Peer-to-peer ENUM alternative
Created by: jht2, Last modification: Mon 11 of Sep, 2017 (14:51 UTC) by olegh
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