ENUM in Short

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 or SNOM 4S, VoIP gateways like Asterisk,Swyx Cisco) and SIP phones (SNOM 200).

Enum uses DNS NAPTR resource records.

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

ENUM RFC 3761 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). RFC 3761 replaced RFC 2916 in May 2004.

The IETF ENUM Working Group has been working on an update of RFC 3761 as well as a new process for registering new Enumservices, which are expected to be published as RFC soon.

IETF Documents

Published RFCs

• RFC 5333: Internet Calendaring addresses in ENUM
• RFC 5076: ENUM Validation Information Mapping for EPP
• RFC 4725: ENUM Validation Architecture
• RFC 3761: ENUM Protocol (obsoletes RFC 2916)
• 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 Pipe:

• 3761bis: Update of RFC 3761
• Enumservices Guide: New process for registering new Enumservices
• IAX Enumservice Registration: Usage of IAX2 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: A company based in Zurich, Switzerland, owned by the long-standing ENUM Expert and co-chair of the IETF ENUM Working Group.
  • Ucom.ch offers technical consulting for ENUM
  • Contact: bernhard.hoeneisen(a)ucom.ch

Various Information on ENUM

Current ENUM deployment status in various countries

ENUM Progress Matrix maintained by RIPE ENUM working group

News

• A Terena effort creates NRenum, to be used in the countries where the Golden Tree (e164.arpa) is not (yet) available.
• The lastest ENUM plugtest was held 30 May - 3 June 2005, the first at ETSI was in Nov-Dec 2004 http://www.etsi.org/plugtests/ENUM.htm
• The Voice Peering Forum - All about VoIP Peering, Routing, Interconnection and ENUM

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.
  • 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.
• 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

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

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
• enum2go Providing 87810 global ENUM numbers.
• ENUM Forum
• 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
• VoXaLot is a free service provider that provides seamless ENUM calling.
• ENUM.nl Enum in the Netherlands
• ENUM +420 Resources for ENUM in Czech Republic by czech ENUM registry (CZ.NIC)

Articles

• 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