ENUM Tutorial

ENUM Tutorial

ENUM Forum

June 3, 2003

Steven D. Lind, AT&T

GEN0075R0

Disclaimer

• Heavily borrowed from:– Patrik Faltström’s IETF presentation to

February 2002 ITU Workshop on ENUM – AT&T/ENUM Forum presentation to

December 2002 SG2 meeting

• Added some telecomm perspective

Assumption

• Use of standard telephone numbers is not going away– PSTN/analog terminals

are going to be around– IP phones use 12-

button keypad– Globally unique

identifier that has established familiarity with end users

Problem statements

• How do network elements (gateways, SIP servers etc) find services on the Internet if you only have a telephone (E.164) number?

• How can subscribers define their preferences for incoming communications?

More Problem Statements

• How do you address an IP-based voice terminal from the PSTN?

• For a call that starts out as VoIP, how do you know to keep the call on the IP-plane (as opposed to the PSTN) for a dialed telephone number if the customer is not yours?

Today, Many Addresses

tel:+46-8-971234

mailto:paf@example.com

tel:+46-706051234

sip:paf@example.com

With ENUM, Only One

tel:+46-8-971234

mailto:paf@example.com

tel:+46-706051234

sip:paf@example.com

tel:+46-706051234

Give this number to friends:+46-8-971234

ENUM

Solution in short

• Put domain names derived from telephone numbers in the global domain name system, DNS

• IETF ENUM Working Group created to solve the problem of using the DNS for:

–domain name in– [Numbers re-formatted as domain names] –URI out– [mailto, sip, tel, http or other URI scheme]

• Solution: NAPTR records• Use the URI’s for the communication

ENUM in a nutshell

• take phone number +46-8-6859131

• turn into domain name 1.3.1.9.5.8.6.8.6.4.e164.arpa.

• return list of URI’ssip:paf@cisco.com

• ask the DNS

mailto:paf@cisco.com

Step 1

• Take an E.164 number and create a fully qualified domain name in a single highly defined and structured domain

• +46-8-971234• +468971234• 4.3.2.1.7.9.8.6.4.e164.arpa.

The input to theNAPTR algorithm

Step 1 - Explanation

• Each digit can become a definable and distributed “zone” in DNS terms

• Delegation can (doesn’t have to) happen at every digit, including at last digit

• Zones such as country codes, area codes or primary delegated blocks of numbers can be delegated as well as individual numbers

• DNS defines authoritative name servers for NAPTR/service resource records

Step 2

• Lookup NAPTR RR’s in DNS, and apply NAPTR/ENUM algorithm4.3.2.1.7.9.8.6.4.e164.arpa.!^.*$!mailto:spam@paf.se!!^+46(.*)$!ldap://ldap.telco.se/cn=0\1!

• Use rewrite rules using regular expressions which operate on the E.164 number (+468971234)

Regular Expressions

• For ENUM, the NAPTR regexp field may yield an (unchanged) URL

• !<regexp>!<string>!– “Match <regexp> on original E.164,

and apply rewrite rule <string>” ^ - Match beginning $ - Match end . - Match any character.* - Match any number of any character() - Grouping, \n in <string> is replaced with group number ‘n’ in <regexp>

Step 2 in detail

• $ORIGIN 4.3.2.1.7.9.8.6.4.e164.arpa.• IN NAPTR 10 10 ”U” ”mailto+E2U”

”!^.*$!mailto:spam@paf.se!”• IN NAPTR 20 10 ”U” ”ldap+E2U”

”!^+46(.*)$!ldap://ldap.telco.se/cn=0\1”

• Note that no line break should be in the records

Tier 0

Tier 1

Tier 2

DomainName

System

ApplicationServiceProvider

Registrar

Registry

ENUMEnabled

Applications

Provisioning

• voice• fax• messaging & presence• email• web pages

Authentication &

ValidationEntities

The Public ENUM Infrastructure

$ORIGIN e164.arpa. 3.7.9.1 IN NS nsnanp.enum.com . 4.4 IN NS sweden_enum.com .…

$ORIGIN 3.7.9.1.e164.arpa. 7.9.7.6.6.3.2 IN NS e164.att.net .8.9.7.6.6.3.2 IN NS e164.xyz.com .…

$ORIGIN 7.9.7.6.6.3.2.3.7.9.1.e164.arpa. IN NAPTR 100 10 "u" "sip+E2U" "!^.*$!sip:19732366797@att.net!" .

e164.arpa

Tier 0 (Country Code Registry)

nsnanp.enum.com(3.7.9.1.e164.arpa)

Tier 1 (Telephone Number Registry)

e164.att.net

Tier 2 (Application Information)

International Implementation worked in IETF and ITU-T

National Implementation worked in ENUM Forum (US)

sweden_enum.com(4.4.e164.arpa)

…

Delegation of Country Codein Tier 0

• Draft Recommendation E.A-ENUM in progress• Interim Procedures in place between IAB/ISOC

and ITU-TSB– Use of e164.arpa pending outcome of Recommendation– Requests must be authenticated by TSB before RIPE-

NCC can act– Country Code must be valid and assigned– Position of National Numbering Administrator must be

known and must opt-in

• Similar situation for shared Network codes and codes for Groups of Countries (e.g., ETNS)

Country Code Delegationsas of 23 May 2003

E.164 Country Code

Country

Delegee Date of TSB Approval dd/mm/yy

246 Diego Garcia Government 12/08/02 247 Ascension Government 12/08/02

290 Saint Helena Government 12/08/02 31 Netherlands Ministry 23/05/02 33 France DiGITIP (Government) 28/03/03 358 Finland Finnish Communications

Regulatory Authority 26/02/03

36 Hungary CHIP/ISzT 15/07/02 40 Romania MinCom 10/12/02

43 Austria Regulator 11/06/02 44 UK DTI/Nominum 16/05/02 46 Sweden NPTA 10/12/02 48 Poland NASK 18/07/02 49 Germany DENIC 16/05/02 55 Brazil Brazilian Internet Registry 19/07/02 86 China (c) CNNIC 02/09/02

878 10 (a) VISIONng 16/05/02 971 United Arab

Emirates Etisalat 13/01/03

991 001 (b) NeuStar 02/02/01

Notes: (a) This is a Universal Personal Telephony (UPT) code. (b) This is a trial code granted to NeuStar for a limited period. The period expires on 2 November

2003. (c) This is a temporary authorization for ENUM global TLD trial and evaluation. This delegation

will end on 30 June 2003. If the ITU Interim Procedure is discontinued before then, or if the Recommendation E.A-ENUM is approved before 30 June 2003, the delegation will be turned into an objection.

National Implementation in the US• ENUM Forum organized in August 2001 to

address technical specifications• “ENUM Forum Specifications for US

Implementation of ENUM” (6000_1_0) approved and reviewed with USG in February, 2003– Requirements for Tier 1 Registry

– Specifications and guidelines for Registrar & Tier 2 nameserver

• Need mechanism for contracting with Tier 1 operators

Requirements Document

• Reference Architecture• Tier 1 Registry Operations, Security, & Admin• Tier 1 Performance Specifications• Privacy Considerations• Provisioning• Registrar Requirements• Authentication & Authorization• Tier 2 Requirements & Guidelines• Conflict Resolution• Issues Out of Scope

Reference Architecture

Tier 1Registry

Tier 0

Root

Tier 2Provider

RegistrantRegistrant RegistrarRegistrar

Reference Architecture

• Registrar• Registrant• Tier 1 Registry

o Does not address non geographic numbers• Tier 2 Service Provider

o Tier 2 contains the NAPTR records or delegations • Interfaces• Issue:

o One or More Tier 1 Providers– Delegation at Tier 0 by NPA

Tier 1 Aspects

• Tier 1 Operationso Zone Information (aka zone files)o ContactInfo (aka WhoIs)o Reporting, backup, escrow & performance

requirements• Performance Aspects

o DNS Performanceo EPP Interfaces

• Tier 1 Security• Administrative Aspects

o Dispute Resolutiono Data Collection and Privacy

Privacy Considerations

• Registrant Choice• Privacy Analysis• Open Disclosure of Registrant Information in DNS• Information Handling During Registration and

Provisioning• Contact Info• Fair Information Practices

Provisioning

Tier 2Nameserver

RegistrarRegistrarTier 1

RegistryRegistrantRegistrant

Application ServiceProvider

Application ServiceProvider

Authentication & Validation Entities

Provisioning Aspects

• Registrar Requirementso Registrant Validation & Authenticationo Dispute Resolutiono Registrar Infrastructure Requirementso Recommended Practices & Requirementso Various Scenarios

- Information Flows

• Tier 2o Mostly Guidelines – SomeSome Requirementso Tier 2 may be self-provided or from a commercial 3rd partyo Interfaces & Interactionso Performance Recommendations

ExamplesDNS-Server

InternetPSTN

Cal

led

par

ty

Cal

ling

par

ty

SIP-Server

SIP-Server

Gateway

Gateway

“Call setup”

PSTN to VoIP Call via SIP

Sipsip:paf@cisco.com

Query1.3.1.9.5.8.6.8.6.4.e164.arpa.?

Dial+4686859131

DNS-Server

Sip serverGateway

Responsesip:paf@cisco.com

VoIP via SIP to VoIPDNS-Server

“ENUM”

SIP-Server

SIP-Server

Gateway

Gateway

VoIP via PSTN to PSTN

DNS-Server

“ENUM”

SIP-Server

SIP-Server

Gateway

Gateway

Future Actions

• Address implementation issues– Contracting model

– Integration/separation of North American countries

– Number of Tier 1 operators

• Address Non-geographic numbers (specifically 8YY Toll Free)– Can’t be cleanly separated by North American country

– Has unique provisioning requirements