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ENUM Technical issues / DNS Patrik Fältström Area Director, Applications Area, IETF [email protected] ENUM 1 Agenda • Background • Problem we want to solve • Technical solution • Conclusion ENUM 2 Background ENUM 3 The Domain Name System • It is a distributed database • It is a protocol • Often the two get mixed up ENUM 4 DNS as distributed database Central server, “root server” Server for “com” Server for “se” Local resolver Client ENUM Server for “jp” 5 Recursion Root-server Query a.paf.se? Query a.paf.se? Server “se” Query a.paf.se? Ask “paf.se”! Query a.paf.se? 192.168.1.11 Local resolver ENUM Ask “se”! 192.168.1.11 Server “paf.se” 6 Domains and zones "root" se c ns zone "a.se." b domain "a.se." domain/zone "b.a.se." ENUM a ns ns 7 Delegations Root server se. IN NS ns.nic-se.se ns.nic-se.se. IN A 192.168.0.1 ns.nic-se.se ns.se. IN NS ns.nic-se.se. a.se. IN NS ns.a.se. c.se. IN NS ns.c.se. ns.nic-se.se. IN A 192.168.0.1 ns.a.se. IN A 192.168.1.1 ns.c.se. IN A 192.168.3.1 ns.a.se a.se. IN NS ns.c.se. b.a.se. IN NS ns.b.se. ns.a.se. IN A 192.168.1.1 ns.b.se. IN A 192.168.2.1 ns.c.se. c.se. IN NS ns.c.se. ns.c.se. IN A 192.168.3.1 ns.b.a.se. b.a.se. IN N S ns.b.a.se. ns.b.a.se. IN A 192.168.3.1 ENUM 8 E.164 numbers • Allocation at CC level by the ITU, SG2/WP1/2 (from an IETF perspective) • E.164 provides the number structure and functionality of numbers used for international public • telecommunicationsHierarchically allocated ENUM 9 Structure of E.164 • Structure to use for geographic areas CC NDC SN 1-3 digits N digits Max (15-N) digits National (significant) number International public telecommunication Number for geographical areas ENUM 10 Problem we want to solve ENUM 11 Problem statements 1(2) • How do network elements find services on the Internet if you only have a telephone (E.164) number? • How can subscribers (as opposed to carriers) define their preferences for incoming communications? • How can we (IETF/ITU) enable new services while enabling competition, consumer choice and consumer protection? ENUM 12 Problem statements 2(2) • How can consumers, carriers and new players have equal access to these new opportunities? • How do we (IETF/ITU) make this simple and easy to use without reinventing the wheel? ENUM 13 Technical solution ENUM 14 Solution in short • Put telephone numbers* in the global domain name system, DNS • ENUM Working Group created to solve the problem of using the DNS for: Domainname in [Numbers reformatted as domain names] URI out [mailto, sip, tel, http or other URI scheme] • Solution was to use NAPTR records * Maybe not in the original E.164 format ENUM 15 Example • $ORIGIN 4.3.2.1.7.9.8.6.4.e164.arpa. IN NAPTR 10 10 "U" "sip+E2U" "!^.*$!sip:[email protected]!" IN NAPTR 20 10 "U" "ldap+E2U" "!^.*$!mailto:[email protected]!" ENUM 16 Why DNS? • It’s there It works… It’s global… It scales… It’s fast… It’s open… • Grandfather existing DNS delegation mechanisms, which looks like delegation in E.164 world • ENUM enabled DNS provides a low cost, shared SCP-like infrastructure for IP infrastructure • ENUM facilitates PSTN/IP convergence ENUM 17 Step 1 • Take an E.164 number and create a fully qualified domain name in a single highly defined and structured domain • +46-8-971234 • +468971234 The input to the NAPTR algorithm • 4.3.2.1.7.9.8.6.4.e164.arpa. ENUM 18 Step 1 Explanation • Each digit becomes a definable and distributed “zone” in DNS terms • Delegation can (doesn’t have to) happen at every digit, including at last digit • Zones such as country codes, area codes or primary delegated blocks of numbers can be delegated as well as individual numbers • DNS defines authoritative nameservers for NAPTR/service resource records (RR’s) ENUM 19 Step 2 • Lookup NAPTR RR’s in DNS, and apply NAPTR/ENUM algorithm • 4.3.2.1.7.9.8.6.4.e164.arpa. • !^.*$!mailto:[email protected]! !^+46(.*)$!ldap://ldap.telco.se/cn=0\1! • Use rewrite rules using regular expressions which operate on the E.164 number (+468971234) ENUM 20 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> ENUM 21 Step 2 in detail • $ORIGIN 4.3.2.1.7.9.8.6.4.e164.arpa. • IN NAPTR 10 10 “U” “mailto+E2U” “!^.*$!mailto:[email protected]!” • 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 ENUM 22 ENUM DNS Hierarchy Alternative 2 1 e164.arpa 6.4.e164.arpa 7.9.8.6.4.e164.arpa 4.3.2.1.7.9.8.6.4.e164.arpa ENUM 23 +46-8-976123 Root server e164.arpa. IN NS. ns.ripe.net ns.ripe.net. IN A 193.0.0.193 ns.ripe.net e164.arpa. IN NS ns.ripe.net. 6.4.e164.arpa. IN NS ns.e164.se. ns.ns.e164.se. IN A 192.168.0.1 ns.e164.se 6.4.e164.arpa IN NS ns.e164.se. 7.9.8.6.4.e164.se. IN NS e164.telco.se. e164.telia.se. IN A 192.168.1.1 e164.telco.se. 7.9.8.6.4.e164.se. IN NS e164.telco.se. 3.2.1.6.7.9.8.6.4.e164.arpa. IN NS ns.eservice.net. ns.eservice.net. 3.2.1.6.7.9.8.6.4.e164.arpa. IN NS eservice.net. 3.2.1.6.7.9.8.6.4.e164.arpa. IN NAPTR ……. ENUM 24 DNS Hierarchy • Strictly delegated • One authoritative server for each name, and only one Have led to the registry/registrar model • One responsible registry, but many registrars which talk with customers ENUM 25 Registry/registrar Root server Server for .com Verisign Global Registry Server for .se NIC-SE AB Registrar for .com interQ Incorporated Registrar for .se Tele2 Registrars for .se Today 227 ENUM Registrar for .com Network Solutions Registrar for .com Active ISP Registrars for .com Today 77 26 Conclusion ENUM 27 ENUM example flow/usage DNS-Server Query 4.3.2.1.7.9.8.6.4.e164.arpa? Response sip:[email protected] “Call setup” Dial +468971234 Sip sip:[email protected] Sip proxy ENUM Sip proxy 28 ENUM and VoIP • ENUM allows VoIP proxies and servers to find each other Intra and inter domain call setup Only for declaring ability to accept certain applications • ENUM is an opt-in system (also on country code level) ENUM 29 ENUM in Universal Messaging • IETF Voice Profile for Internet Mail • ENUM enables carrier and enterprise voice mail systems to find each other, interoperate and exchange messages • Linkage to directory gives access to “spoken name” as well as authenticated access to sensitive information (privacy) ENUM 30 ENUM in Internet Fax • IETF RFC 2305 / ITU-T Rec. T.37 • ENUM enables internet aware fax machines to find each other, interoperate and exchange messages ENUM 31 Detailed example of Fax • Person X wants to send a fax to Person Y; she knows Y's E.164 number. • Person Y has many IP applications tied to her own (Y's) E.164 number. • Device C became responsible for delivering the fax. Device C is Internet Aware, is ENUM-enhanced, can do SMTP and SIP, but can't do H.323 yet. • Device C does a DNS query on the E.164 number. Device C discovers from the response that Person Y prefers real-time to store-and-forward fax delivery, likes SIP and H.323 equally, and has SMTP, too. • Device C tries SIP first. If SIP fails, Device C does not try H.323. Instead, Device C then tries SMTP. • Note: Device C uses ENUM in its application selection logic. ENUM is an enabler and not the same sort of thing as SMTP, SIP, H.323, voice/fax/data, etc. ENUM 32 From RFC 2916 • 4. IANA Considerations • This memo requests that the IANA delegate the E164.ARPA domain following instructions to be provided by the IAB. Names within this zone are to be delegated to parties according to the ITU recommendation E.164. The names allocated should be hierarchic in accordance with ITU Recommendation E.164, and the codes should assigned in accordance with that Recommendation. • Delegations in the zone e164.arpa (not delegations in delegated domains of e164.arpa) should be done after Expert Review, and the IESG will appoint a designated expert. ENUM 33 Status as of Jan 10, 2001 (done) • Base spec published as RFC 2916 • e164.arpa delegated to RIPE-NCC • ITU SG2/WP1/2 liaison statement: Member state can inform ITU on entry of numbers in DNS, provision of E.164 information ENUM 34 Status as of Jan 10, 2001 (not done) • Delegation of domains below e164.arpa to managing entities that are appointed by member states • National issues ENUM 35 Resources • NAPTR Resource Records (RFC 2915) http://www.ietf.org/rfc/rfc2915.txt • ENUM Specification (RFC 2916) http://www.ietf.org/rfc/rfc2916.txt • Liaison Statement (RFC 3026) http://www.ietf.org/rfc/rfc3026.txt • IAB on need for unique root (RFC 2826) http://www.ietf.org/rfc/rfc2826.txt • IAB Statement on ARPA http://www.iab.org/iab/DOCUMENTS/statement-on-infrastructuredomains.txt • My email address: [email protected] ENUM 36