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: tel:

With ENUM, Only One tel: tel: tel: Give this number to friends: 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 turn into domain name e164.arpa. return list of URI’s ask the DNS

Step 1 Take an E.164 number and create a fully qualified domain name in a single highly defined and structured domain e164.arpa. The input to the NAPTR 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 algorithm e164.arpa. !^+46(.*)$!ldap://ldap.telco.se/cn=0\1! Use rewrite rules using regular expressions which operate on the E.164 number ( )

Regular Expressions For ENUM, the NAPTR regexp field may yield an (unchanged) URL ! ! ! –“Match on original E.164, and apply rewrite rule ” ^ - Match beginning $ - Match end. - Match any character.* - Match any number of any character () - Grouping, \n in is replaced with group number ‘n’ in

Step 2 in detail $ORIGIN e164.arpa. IN NAPTR ”U” ”mailto+E2U” IN NAPTR ”U” ”ldap+E2U” ”!^+46(.*)$!ldap://ldap.telco.se/cn=0\1” Note that no line break should be in the records

Tier 0 Tier 1 Tier 2 Domain Name System Application Service Provider Registrar Registry ENUM Enabled Applications Provisioning voice fax messaging & presence web pages Authentica tion & Validation Entities

The Public ENUM Infrastructure $ORIGIN e164.arpa IN NS nsnanp.enum.com. 4.4 IN NS sweden_enum.com. … $ORIGIN e164.arpa IN NS e164.att.net IN NS e164.xyz.com. … $ORIGIN e164.arpa. IN NAPTR "u" "sip+E2U" e164.arpa Tier 0 (Country Code Registry) nsnanp.enum.com ( 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 Code in 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 Delegations as of 23 May 2003

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 1 Registry Tier 0 Root Tier 2 Provider Registrant Registrar

Reference Architecture Registrar Registrant Tier 1 Registry oDoes not address non geographic numbers Tier 2 Service Provider oTier 2 contains the NAPTR records or delegations Interfaces Issue: oOne or More Tier 1 Providers – Delegation at Tier 0 by NPA

Tier 1 Aspects Tier 1 Operations oZone Information (aka zone files) oContactInfo (aka WhoIs) oReporting, backup, escrow & performance requirements Performance Aspects oDNS Performance oEPP Interfaces Tier 1 Security Administrative Aspects oDispute Resolution oData 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 2 Nameserver Registrar Tier 1 Registry Registrant Application Service Provider Authentication & Validation Entities

Provisioning Aspects Registrar Requirements oRegistrant Validation & Authentication oDispute Resolution oRegistrar Infrastructure Requirements oRecommended Practices & Requirements oVarious Scenarios -Information Flows Tier 2 Some oMostly Guidelines – Some Requirements oTier 2 may be self-provided or from a commercial 3 rd party oInterfaces & Interactions oPerformance Recommendations

Examples DNS-Server Internet PSTN Called party Calling party SIP-Server Gateway

“Call setup” PSTN to VoIP Call via SIP Sip Query e164.arpa.? Dial DNS-Server Sip serverGateway Response

VoIP via SIP to VoIP DNS-Server “ENUM” SIP-Server Gateway

VoIP via PSTN to PSTN DNS-Server “ENUM” SIP-Server 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