1 2 3 4 5 3GPP2 S.R0118-0 6 Version 1.0 7 Version Date: 25 May 2006 8 9 10 11 12 13

14 Telephone Number Mapping (ENUM)

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16 Stage 1 Requirements 17 18 19 20 21 22 23 24 25 COPYRIGHT NOTICE 3GPP2 and its Organizational Partners claim copyright in this document and individual Organizational Partners may copyright and issue documents or standards publications in individual Organizational Partner’s name based on this document. Requests for reproduction of this document should be directed to the 3GPP2 Secretariat at [email protected]. Requests to reproduce individual Organizational Partner’s documents should be directed to that Organizational Partner. See www.3gpp2.org for more information. 26 27

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1 EDITOR 2 Brian G. Egbert (Sprint), +1-913-794-4289 [email protected] 3 4 REVISION HISTORY

5 REVISION HISTORY ver 1.0 Final Draft for WG recommendation to publish May 25, 2006

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1 Table of Contents

2 TELEPHONE NUMBER MAPPING (ENUM)...... I

3 1 INTRODUCTION...... 1

4 2 GENERAL FEATURE DESCRIPTION ...... 1

5 3 SCOPE ...... 2

6 4 REFERENCES...... 2 7 4.1 NORMATIVE REFERENCES ...... 2 8 4.2 INFORMATIVE REFERENCES...... 3 9 5 DEFINITIONS AND ABBREVIATIONS ...... 6 10 5.1 DEFINITIONS...... 6 11 5.2 ABBREVIATIONS...... 6 12 6 DETAILED FUNCTIONALITY REQUIREMENTS ...... 7 13 6.1 GENERAL REQUIREMENTS...... 7 14 6.1.1 ENUM Subscriber...... 8 15 6.1.2 ENUM Client ...... 9 16 6.1.3 ENUM Name Server ...... 9 17 6.2 NORMAL PROCEDURES WITH SUCCESSFUL OUTCOME...... 10 18 6.2.1 SIP Server to PSTN Gateway over ...... 10 19 6.2.2 ENUM Enabled PSTN Gateway to Internet Terminations ...... 11 20

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1 List of Figures 2 Figure 1 Example of the DNS architecture for a Country Code with multiple 3 sovereign entities ...... 1 4 5 6 7

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1 1 INTRODUCTION 2 The Public ENUM implementation is based on a hierarchical tiered 3 architecture. At the top of the authoritative Public ENUM DNS tree is the 4 Tier 0 RIPE NCC root name server which hosts the e164.arpa zone. At 5 the next level of the Public ENUM DNS tree are the authoritative Tier 1 6 name servers. There is an authoritative Tier 1 name server for each 7 country code [see ITU-T Recommendation E.164]. For each 8 that corresponds to a particular country code, the Tier 0 name server 9 points to the proper Tier 1 name server hosting the respective country 10 code. The next level of the Public ENUM DNS tree consists of the Tier 2 11 ENUM name servers. There will be a number of Tier 2 ENUM name 12 servers for each country code. For each E.164 number, the Tier 1 name 13 server maintains a NS resource record that points to the Tier 2 ENUM 14 name server hosting the respective E.164 number. Each Tier 2 ENUM 15 name server maintains the actual ENUM NAPTR resource records for all 16 E.164 numbers that it hosts. For each E.164 number, the associated 17 ENUM NAPTR resource records indicate which communication services 18 are available for the respective E.164 number. 19 For the assignee of the E.164 numbers, the participation in the Public 20 ENUM is optional. Each Public ENUM subscriber chooses to have his or 21 her E.164 number included in the authoritative Public ENUM DNS. Upon 22 deciding to participate in the Public ENUM, the Public ENUM subscriber 23 choose the Tier 2 ENUM provider who will host his or her E.164 number 24 and the associated ENUM NAPTR resource records. 25 Once consenting to the inclusion of its E.164 number and associated 26 ENUM NAPTR resource records into the Public ENUM DNS, the ENUM 27 subscriber will authorize the Tier 2 ENUM name server to provide this 28 information in response to a Public ENUM DNS query that can be 29 initiated by any party. 30 2 GENERAL FEATURE DESCRIPTION 31 This feature will provide an interface for the core network to interwork 32 with Public ENUM which is defined as a DNS-based architecture and 33 protocol [RFC 3761] by which an E.164 number, as defined in ITU 34 Recommendation E.164, can be expressed as a Fully Qualified Domain 35 Name in a specific Internet Infrastructure domain defined for this 36 purpose (e164.arpa). The result of the ENUM query is a series of DNS 37 ENUM NAPTR resource records [RFC 2915] which can be used to 38 contact a resource (e.g.URI) associated with that number. Each ENUM 39 NAPTR resource record contains information that is used to derive an 40 URI, the associated ENUM services, and order and preference fields that 41 determines the sequence in which ENUM NAPTR resource records and 42 the derived URIs should be processed by the ENUM user.

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1 2 3 SCOPE 3 This document specifies the requirements for the development of a 4 specification in support of Public ENUM. The requirements pertain to the 5 content, format and meaning of information included in the ENUM 6 NAPTR resource records associated with an E.164 number, the handling 7 of this information by the Public ENUM name servers and the ENUM 8 clients. 9 10 4 REFERENCES 11

12 4.1 Normative References

13 14 The following standards contain provisions, which, through reference in 15 this text, constitute provisions of this Standard. At the time of 16 publication, the editions indicated were valid. All standards are subject 17 to revision, and parties to agreements based on this Standard are 18 encouraged to investigate the possibility of applying the most recent 19 editions of the standards indicated below. ANSI and TIA maintain 20 registers of currently valid national standards published by them. 21 22 • References are either specific (identified by date of publication, edition 23 number, version number, etc.) or non-specific. 24 • For a specific reference, subsequent revisions do not apply. 25 • For a non-specific reference, the latest version applies. In the case of a 26 reference to a 3GPP2 document, a non-specific reference implicitly 27 refers to the latest version of that document in the same Release as the 28 present document.

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ITU-T Recommendation The international public telecommunication E.164 numbering plan 3GPP2 X.S0013-002-A All-IP Core Network Multimedia Domain IP Multimedia Subsystem – Stage-2 IETF RFC 1035 Domain Names - Implementation and Specification http://www.ietf.org/rfc/rfc1035.txt IETF RFC 1123 Requirements for Internet Hosts -Application and Support http://www.ietf.org/rfc/rfc1123.txt IETF RFC 1591 Structure and Delegation

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http://www.ietf.org/rfc/rfc1591.txt IETF RFC 2181 Clarifications to the DNS Specification http://www.ietf.org/rfc/rfc2181.txt IETF RFC 2182 Selection and Operation of Secondary DNS Servers http://www.ietf.org/rfc/rfc2182.txt IETF RFC 2396 Uniform Resource Identifiers (URI): Generic Syntax http://www.ietf.org/rfc/rfc2396.txt IETF RFC 2671 Extension Mechanisms for DNS (EDNS0) http://www.ietf.org/rfc/rfc2671.txt IETF RFC 3403 Dynamic Delegation Discovery System (DDDS)Part Three: The Domain Name System (DNS) Database http://www.ietf.org/rfc/rfc3403.txt IETF RFC 3761 The E.164 to Uniform Resource Identifiers (URI) Dynamic Delegation Discovery System (DDDS) Application (ENUM) (Replaces RFC 2916) http://www.ietf.org/rfc/rfc3761.txt IETF RFC 3762 Telephone Number Mapping (ENUM) Service Registration for H.323 http://www.ietf.org/rfc/rfc3762.txt IETF RFC 2460 Internet Protocol version 6 http://www.ietf.org/rfc/rfc2460.txt IETF RFC 3263 Session Initiation Protocol (SIP): Locating SIP Servers http://www.ietf.org/rfc/rfc3263.txt IETF RFC 3482 Number Portability in the Global Switched Telephone Network (GSTN) http://www.ietf.org/rfc/rfc3482.txt IETF RFC 3764 enumservice registration for Session Initiation Protocol (SIP) Addresses-of-Record http://www.ietf.org/rfc/rfc3764.txt Mobility Support in IPv6 IETF RFC 3775 http://www.ietf.org/rfc/rfc3775.txt?number=3775 IETF RFC 3824 Using E.164 numbers with the Session Initiation Protocol (SIP) http://www.ietf.org/rfc/rfc3824.txt Telephone Number Mapping (ENUM) Service IETF RFC 3953 Registration for Presence Services http://www.ietf.org/rfc/rfc3953.txt IETF RFC 3966 The tel URI for Telephone Numbers http://www.ietf.org/rfc/rfc3966.txt IANA Registration for Enumservice 'web' and 'ft' IETF RFC 4002 http://www.ietf.org/rfc/rfc4002.txt 1 2 4.2 Informative References 3 4

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draft-draft-ietf-enum-msg- IANA Registration for Enum services email, fax, mms, 04 ems and sms http://www.ietf.org/rfc/rfc4355.txt 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

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1 ENUM Architecture 2 3 Figure 1 – Example of the DNS architecture for a Country Code with 4 multiple sovereign entities: 5

“.” and International Root .arpa

e164.arpa Tier 0

Country Code 1 1.e164.arpa NPA Data Tier 1A

Individual Authentication & E.164 zone(s) Validation Entities

a.p.n.1.e164.arpa

Registrant Registrar Tier 1B Registry

Tier 2 Provider

Application Service Provider

6 7 8

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1 2 3 4 5 DEFINITIONS AND ABBREVIATIONS 5 The terms and abbreviations used within this specification are defined as 6 follows: 7 5.1 Definitions 8 9 For the purposes of the present document, the following terms and 10 definitions apply. 11 12 ENUM subscriber: an assignee of the E.164 number who has consented 13 to insert its E.164 number and associated ENUM NAPTR resource 14 records into the Public ENUM DNS. 15 16 ENUM name server: A Public ENUM DNS server that is providing the 17 information pertaining to the ENUM subscriber in response to a DNS 18 query that can be initiated by any party based on the E.164 number. The 19 response to the query can either point to the next DNS server to be 20 contacted or it contains the ENUM NAPTR resource records associated 21 with the E.164 number. 22 23 ENUM client: a function that retrieves the ENUM NAPTR resource 24 records associated with the E.164 number from the Public ENUM DNS 25 on behalf of the ENUM user. The ENUM client is responsible for hiding 26 the distribution of data among Public ENUM name servers from the 27 ENUM user. 28 29 ENUM user: any entity that is requesting the ENUM NAPTR resource 30 records that reveal the ENUM services associated with the E.164 31 number. The ENUM user requests the information by passing to the 32 ENUM client the query type and the E.164 number. 33 5.2 Abbreviations 34 AUS Application Unique String NAI Network Access Identifier MIPv6 Mobile Internet Protocol version 6 DDDS Dynamic Delegation Discovery System DNS Domain Name System

EMS Enhenced Message Service

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ENUM E.164 Number Mapping FAX Facsimile Service FTP File Transfer Protocol H323 Protocol defined in ITU-Recommendation H.323

IANA Internet Assigned Numbers Authority IETF Internet Engineering Task Force IPv4 Internet Protocol version 4 IPv6 Internet Protocol version 6 ITU-T International Telecommunication Union - Telecommunication Standardization Sector MMS Multimedia Message Service MSCe Mobile Switching Center Emulation NAPTR Naming Authority Pointer NPA Numbering Plan Area NS Name Server PSTN Public Switched Telephone Network RegExp Regular Expression RFC Request For Comment Reseaux IP European Network Control RIPE NCC Center Resource Record RR Session Initiation Protocol SIP Secure Session Initiation Protocol SIPS Short Message Service SMS Temporary Local Directory Number TLDN Uniform Resource Identifier URI 1 2 3 6 DETAILED FUNCTIONALITY REQUIREMENTS 4 Public ENUM for the core network detailed functional requirements are 5 listed in section 6.1 below. 6 6.1 General Requirements 7 ENUM-01 The ENUM DNS operations shall be implemented according to 8 RFC 1035, RFC 1123, RFC 1591, RFC 2181 and 2182.

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1 ENUM-02 The ENUM NAPTR resource records shall be formatted according 2 to RFC 3403 and RFC 3761. 3 ENUM-03 The “ENUMService" field values and associated URI that will be 4 supported by the ENUM shall be the ones listed in the RFC 3762, RFC 5 3764, RFC 3953, and the draft-ietf-enum-msg-04. 6 ENUM-04 The flag field in the ENUM NAPTR resource records shall be set to 7 "U". The flag field shall not be blank. 8 ENUM-05 The Order field for all ENUM NAPTR resource records within a 9 single ENUM domain shall be set to the same value [as recommended in 10 RFC 3761 and RFC 3824]. The value shall be 100. 11 ENUM-06 If a PSTN telephone with an E.164 number can be reached from 12 an IP network via a telephony gateway that converts the SIP signaling 13 to/from the PSTN signaling, then there should be a NAPTR resource 14 record in the public ENUM DNS for the respective E.164 number. If there 15 is such a NAPTR resource record, then the ENUMservice field in the 16 respective NAPTR resource record shall be either "E2U+SIP" or 17 "E2U+SIPS", and the URI generated from the respective NAPTR resource 18 record shall be either SIP URI or SIPS URI, respectively. The user part of 19 either the SIP URI or the SIPS URI shall contain the E.164 number 20 [preceded by a plus sign and without visual separators], and the 21 hostname field of either the SIP URI or the SIPS URI shall contain the 22 domain name of the telephony gateway. Either the SIP URI or SIPS URI 23 shall also contain the user parameter value "phone" ["user=phone"] as 24 specified in RFC 3261. 25 ENUM-07 An MSCe may populate the ENUM DNS with some or all of the 26 TLDNs it supports. For each TLDN that is included in the ENUM DNS, 27 there shall be a NAPTR resource record with ENUMservice field set either 28 to "E2U+SIP" or "E2U+SIPS", and the URI generated from the respective 29 NAPTR resource record shall be either SIP URI or SIPS URI, respectively. 30 The user part of either the SIP URI or the SIPS URI shall contain the 31 TLDN, [i.e., an E.164 number preceded by a plus sign and without 32 visual separators], and the hostname field of either the SIP URI or the 33 SIPS URI shall contain the domain name of the MSCe. The SIP URI or 34 SIPS URI shall also contain the user parameter value "phone" 35 ["user=phone"] as specified in RFC 3261.

36 6.1.1 ENUM Subscriber 37 38 ENUM-08 The Public ENUM subscriber shall decide whether its E.164 39 number and associated ENUM NAPTR resource records will be loaded 40 into, modified, or deleted from the authoritative Public ENUM DNS. 41 ENUM-09 The Public ENUM subscriber shall select the Tier 2 ENUM 42 provider who will host its E.164 number and associated ENUM NAPTR 43 resource records. 44 ENUM-10 The Public ENUM subscriber shall have exclusive control over the 45 information that will be included in their ENUM NAPTR resource records 46 hosted by the authoritative Tier 2 ENUM name server.

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1 ENUM-11 Once consenting to the inclusion of its E.164 number and 2 associated ENUM NAPTR resource records into the Public ENUM DNS, 3 the Public ENUM subscriber shall explicitly authorize the Tier 2 ENUM 4 name server to provide the ENUM NAPTR resource records in response to 5 any DNS query that can be initiated by any party based on the E.164 6 number. 7 ENUM-12 The ENUM subscriber shall recommend the order in which it 8 wants to be contacted by the ENUM user by setting the Preference field 9 as specified in RFC 3761. However, the ENUM user is not required to use 10 the ENUM NAPTR resource records as recommended by the Preference 11 field.

12 6.1.2 ENUM Client 13 14 ENUM-13 The ENUM clients shall support only the "ENUMService" field for 15 the service that they are designed for [e.g. SIP User Agent]. An ENUM 16 client may receive ENUM NAPTR resource records that it doesn't support 17 or understand. In this case the ENUM clients shall ignore the ENUM 18 NAPTR resource records that it doesn't support or understand. 19 ENUM-14 The ENUM clients shall ignore all ENUM NAPTR resource records 20 with the flag field that are different then "U". 21 ENUM-15 The ENUM clients shall assume that the DNS for ENUM is 22 available in the domain e.164.arpa, and query the ENUM when 23 requested by the ENUM user. The ENUM clients shall access the ENUM 24 by using standard technical mechanism as specified in RFC 3761 and 25 RFC1035 for record type NAPTR. 26 ENUM-16 The ENUM clients shall be able to receive the ENUM query 27 responses that are larger than 512 octets. To obtain the ENUM NAPTR 28 resource records that are larger than 512 octets, the ENUM client shall 29 ether use a TCP connection, or use the EDNS "extended length" option 30 with UDP, as specified in RFC 2671. 31 ENUM-17 When sending any ENUM query, the ENUM client that supports 32 the EDNS "extended length" option, shall indicate it supports of this 33 option and also specify the amount of data that it is willing to accept in a 34 UDP query response, as specified in RFC 2671. 35 ENUM-18 The ENUM clients shall be able to receive and recognized the 36 truncated query responses. If the truncated query returned response 37 does not contain the required information, the ENUM clients shall be 38 able to obtain the entire response by either employing the TCP 39 mechanism or using the UDP with EDNS "extended length" option as 40 specified in RFC 2671. 41

42 6.1.3 ENUM Name Server 43 44 ENUM-19 The Tier 2 ENUM name servers shall be able to receive ENUM 45 queries over the UDP and/or the TCP connections.

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1 ENUM-20 When an ENUM query arrives over the UDP and it did not 2 indicate the support for the EDNS "extended length" option, and the 3 query response exceeds 512 bytes, the Tier 2 ENUM name server shall 4 send a truncated query response, and indicate that the query response is 5 a truncated response. 6 ENUM-21 The Tier 2 ENUM name servers shall support the EDNS "extended 7 length" option as specified in RFC 2671. The Tier 2 ENUM name server 8 shall indicate that it supports the EDNS "extended length" option in 9 every query response as specified in RFC 2671. 10 11 6.1.4 ENUM Security 12 13 ENUM-22 The ENUM name server shall ensure that the ENUM subscriber is 14 authorized to add/remove/edit the data held on the server. 15 ENUM-23 Authentication of the ENUM name server by the ENUM client 16 shall be supported. 17 Note: As the ENUM name server responds to all requests (see ENUM-11), there is no 18 requirement for client authentication by the ENUM name server 19 ENUM-24 The integrity of the traffic between the ENUM name server and 20 the ENUM client shall be supported 21 ENUM-25 The ENUM name server should mitigate against Denial of Service 22 attacks. 23 24 6.2 Normal Procedures with Successful Outcome 25 This section gives several examples how the ENUM user processes the 26 information that it has retrieved from the ENUM DNS. The ENUM user 27 may be a subscriber's terminal or any node in the network [e.g., SIP 28 server, VoIP PSTN gateway]. In most cases the ENUM user will support 29 only a particular application. Hence, the ENUM user will be only looking 30 for a particular NAPTR resource record that pertains to the application 31 that it supports [e.g., it retrieves only a SIP URI] while ignoring the other 32 NAPTR resource records, if returned in the EMUM DNS query response 33 6.2.1 SIP Server to PSTN Gateway over Internet 34 When a SIP Server serving the calling party [e.g., the S-CSCF as 35 specified in 3GPP2 X.S0013-002-A] receives an initial SIP request 36 for a dialog that identifies the called subscriber with a tel URI [i.e. 37 the Request-URI in the INVITE request contains a tel URI], the SIP 38 Server may translate the tel URI into a globally routable SIP URI by 39 querying the ENUM DNS. 40 If the SIP server obtains a SIP URI or SIPS URI in the ENUM DNS 41 response, the SIP server resolves and forwards the request as per 42 procedures specified in RFC 3263 and RFC 3261. When forwarding

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1 the INVITE request, the SIP Server replaces the Request-URI with 2 the retrieved SIP URI or SIPS URI. If a telephony gateway in the 3 destination network that converts the SIP signalling to/from the 4 PSTN signalling receives the forwarded INVITE request, the 5 telephony gateway extracts the E.164 number from the user part of 6 the SIP URI or SIPS URI [received in the Request-URI], and 7 forwards the call to the called user over the PSTN using the E.164 8 number. 9 If the SIP server does not obtain a SIP URI or SIPS URI in the 10 ENUM DNS response, the SIP Server may forward the request to a 11 telephony gateway whose IP address and port number are 12 provisioned in the SIP server (e.g., BGCF, MGCF) or it may send an 13 appropriate SIP error response to the calling subscriber.

14 6.2.2 ENUM Enabled PSTN Gateway to Internet Terminations 15 When any ENUM enabled telephony gateway that converts the SIP 16 signalling to/from the PSTN signalling (e.g., a MGCF in the calling 17 subscriber network) receives a call originating from a PSTN 18 telephone that identifies the called SIP subscriber with an E.164, 19 the telephony gateway may translate the E.164 into a globally 20 routable SIP URI or SIPS URI by querying the ENUM DNS. If the 21 telephony gateway obtains a SIP URI or SIPS URI in the ENUM 22 DNS response, the telephony gateway forwards the request as per 23 procedures specified in RFC 3263 and RFC 3261. When forwarding 24 the INVITE request to the SIP Server, the telephony gateway will 25 place the retrieved SIP URI or SIPS URI into the Request-URI of the 26 INVITE request. 27 If the telephony gateway does not obtain a SIP URI or SIPS URI in 28 the ENUM DNS response, the telephony gateway may forward the 29 request to the home network of the called SIP subscriber over the 30 PSTN using the E.164 number. Subsequently, the telephony 31 gateway in the home network of the called SIP subscriber, upon 32 receiving the PSTN call that identifies the called SIP subscriber 33 with an E.164 number, will convert the E.164 number into a tel 34 URI [as specified in RFC 3966] and forward the call to the SIP 35 Server using the SIP signalling. Since, in this case both the 36 telephony gateway and the SIP Server are in the home network of 37 the called SIP subscriber, the port number and the IP address of 38 the SIP Server may be provisioned in the telephony gateway. When 39 forwarding the INVITE request to the SIP Server, the telephony 40 gateway will place the tel URI into the Request-URI of the INVITE 41 request.

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