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.

News

• 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

• IAX Enumservice Registration: Usage of IAX2 addresses in ENUM
• RFC 5333bis: Update of Internet Calendaring addresses in ENUM

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

ENUM Experts

• Ucom Standards Track Solutions GmbH (Zurich, Switzerland):
  • A Swiss company owned by Bernie Hoeneisen, co-chair of the IETF ENUM Working Group and Designated Expert of the IESG (Internet Engineering Steering Group).
  • Ucom.ch offers Technical Consulting for ENUM
  • Contact: expert(a)ucom.ch

Various Information on ENUM

Current ENUM deployment status in various countries

ENUM Progress Matrix maintained by RIPE ENUM working group

Software support

• Yate supports querys from enum.com and for e164.org.
• Asterisk has a module that supports ENUM lookups, but returns at most one route even when more are available.
• FreeSWITCH has a module that supports ENUM lookups, with highly flexible routing options.
  • The LCDial.sh AGI script can make use of that limited facility, or, if dig is installed and in the path, use it to retrieve all the available routes.
• SIP Express Router has a ENUM module
• PowerDNS supports NAPTR and many (custom even!) back-ends.
• TekENUM ENUM server for Windows.
• Bind from ISC, version 9. Please note that earlier versions of bind might give you trouble with wildcard records in ENUM.
• AG Projects Managed DNS platform has web management interface for DNS NAPTR and SRV records
• Sentiro's ENUM lookup webpage - Lookup ENUM records worldwide (UK)
• Alex Mayrhofer's ENUM lookup webpage - Lookup ENUM records worldwide (Austria)
• Adrian Georgescu's Managed DNS lookup webpage - (NL)
• The Voice Peering Fabric - ENUM Lookup Page
• cnum.info - Meta-ENUM lookup and LCR. It includes german Call-by-Call rates as tel: entries
• ENUM PUA (Personal User Agent) prototype source code released under an Open Source BSD Licence http://www.internetnz.net.nz/public/enum
• The GNU Gatekeeper support H.323 routing by ENUM
• Voxeo VoipCenter and VoiceCenter IVR, SIP Application Server, and SIP Media Server platforms fully support ENUM
• OpenSER has a module that supports ENUM
• TANDBERG have a degree of ENUM support in their H.323 Gatekeeper and Border Controller products
• TekSIP and TekPhone supports ENUM.
• Turvox Yasin KAPLAN's ENUM Lookup site.
• ENUM Resolver ENUM Resolver software for Windows.

Record syntax

• ENUM syntax: Syntax of ENUM records in the DNS zone

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

Links

• 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
• 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)

Articles

• IESG assigns Designated Expert for ENUM
• How to build an ENUM server based on powerDNS
• Link from Archive Asterisk ENUM HOWTO at Astmasters.net
• IEEE - Carriers and Users Prepare to Midwife ENUM
• Lightreading - Carrier ENUM Gains Ground
• Article at www.SIPCenter.com by Adrian Georgescu http://www.sipcenter.com/sip.nsf/html/ENUM+on+its+way+to+maturity
• Article in NWfusion.com http://www.nwfusion.com/news/2001/0430enum.html
• FIXED Asterisk at Home ENUM HOWTO at http://www.geek-pages.com/articles/asterisk/setting_up_enum_for_outbound_calls_on_asterisk_at_home.html
• Trixbox ENUM HOWTO at http://www.geek-pages.com/articles/asterisk/setting_up_enum_for_outbound_calls_on_trixbox.html

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