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

ENUM RFC 3761 is a protocol 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.

Current ENUM deployment status in various countries

ENUM Progress Matrix maintained by RIPE ENUM working group

Applicable RFCs

• RFC 2915: NAPTR RR
• RFC 2916: ENUM Protocol (obsolete)
• RFC 3761: ENUM Protocol (obsoletes RFC 2916)
• RFC 3762: Usage of H323 addresses in ENUM Protocol
• RFC 3764: Usage of SIP addresses in ENUM Protocol
• RFC 3026: Berlin Liaison Statement
• RFC 2870: Root Name Server Operational Requirements

ENUM is already supported by SIP Proxies like SER or SNOM 4S, VoIP gateways like Asterisk,Swyx Cisco) and SIP phones (SNOM 200).

From the RFC abstract:



In short, a server with ENUM support will lookup a dialled telephone number in 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 URL, a telephone number to dial, a web page or an e-mail address.

Enum uses DNS NAPTR resource records.

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
• Good overview here: http://www.enum.info/
• 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, information related to ENUM and ENUM provisioning
• 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.

Articles

• 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