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Network Working Group                                          S. LoretoRequest for Comments: 5509                                      EricssonCategory: Standards Track                                     April 2009Internet Assigned Numbers Authority (IANA) Registrationof Instant Messaging and Presence DNS SRV RRsfor the Session Initiation Protocol (SIP)Status of this Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Copyright Notice   Copyright (c) 2009 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents in effect on the date of   publication of this document (http://trustee.ietf.org/license-info).   Please review these documents carefully, as they describe your rights   and restrictions with respect to this document.Abstract   This document registers with IANA two new DNS SRV protocol labels for   resolving Instant Messaging and Presence services with SIP.Loreto                       Standards Track                    [Page 1]

RFC 5509                 IANA SRV Label for SIP               April 2009Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .32.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . .33.  DNS SRV Usage of SIP with 'im' and 'pres' URIs  . . . . . . . .34.  Security Considerations . . . . . . . . . . . . . . . . . . . .45.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .45.1.  Instant Messaging SRV Protocol Label Registration . . . . .55.2.  Presence SRV Protocol Label Registration  . . . . . . . . .56.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . .57.  Normative References  . . . . . . . . . . . . . . . . . . . . .6   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . .6Loreto                       Standards Track                    [Page 2]

RFC 5509                 IANA SRV Label for SIP               April 20091.  Introduction   The Service Record (SRV) [RFC2782] identifies the host(s) that will   support particular services.  The DNS is queried for SRV RR in the   general form:   _Service._Proto.Name      Service: the symbolic name of the desired service      Proto: the protocol of the desired service      Name: the domain name for which this record is valid   "Address Resolution for Instant Messaging and Presence" [RFC3861]   provides guidance for locating the services associated with URIs that   employ the following two URI schemes [RFC3986]: 'im' for INSTANT   INBOXes [RFC3860] and 'pres' for PRESENTITIES [RFC3859].   In order to ensure that the association between "_im" and "_pres" and   their respective underlying services are deterministic, the IANA has   created two independent registries: the Instant Messaging SRV   Protocol Label registry and the Presence SRV Protocol Label registry.   This document defines and registers the "_sip" protocol label in both   registries so that computer programs can resolve 'im:' and 'pres:'   URIs down to SIP addresses.   Moreover, this document explains how the use of SIP for Presence and   Instant Messaging uses SRV.2.  Terminology   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described inRFC 2119 [RFC2119].3.  DNS SRV Usage of SIP with 'im' and 'pres' URIs   Although there are standard procedures for resolving 'im' and 'pres'   URIs (Section 3 of [RFC3861]), the labels for SIP are not registered.Section 5 of [RFC3428] states that if a user agent (UA) is presented   with an IM URI (e.g., "im:fred@example.com") as the address for an   instant message, it SHOULD resolve it to a SIP URI, and place the   resulting URI in the Request-URI of the MESSAGE request beforeLoreto                       Standards Track                    [Page 3]

RFC 5509                 IANA SRV Label for SIP               April 2009   sending.   Following the procedures defined in [RFC3861], in order to resolve   the IM URI, the UA performs a SRV lookup for:   _im._sip.example.com   Assuming that the example.com domain offers a SIP service for instant   messaging at simple.example.com, this will result in a resolution of   _im._sip.example.com. to simple.example.com.  Thus, the instant   messaging URI im:fred@example.com would resolve to a SIP URI of   sip:fred@simple.example.com.   SIP supports both pager [RFC3428] and session [RFC4975] IM mode.   However, a DNS SRV lookup does not specify which SIP IM mode a domain   offer.  If the user agent client (UAC) supports both session mode and   pager mode, it is then suggested to try session mode first; if that   mode is rejected, the UAC has to be ready to fall back to pager mode.Section 5 of [RFC3856] states that procedures defined in [RFC3861]   are also used to resolve the protocol-independent PRES URI for a   presentity (e.g., "pres:fred@example.com") into a SIP URI.   Following the procedures defined in [RFC3861], in order to resolve   the PRES URI, the UA performs a SRV lookup for:   _pres._sip.example.com   Assuming that the example.com domain offers a SIP presence service at   simple.example.com, this will result in a resolution of   _pres._sip.example.com. to simple.example.com.  Thus, the protocol-   independent PRES URI pres:fred@example.com would resolve to a SIP URI   of sip:fred@simple.example.com.4.  Security Considerations   This document merely serves for the registration of DNS SRV labels in   the appropriate IANA registry.  The document does not specify a   protocol; therefore, there are no security issues associated with it.5.  IANA Considerations   This specification registers a new SRV protocol label in both the   Instant Messaging SRV Protocol Label registry and the Presence SRV   Protocol Label registry.Loreto                       Standards Track                    [Page 4]

RFC 5509                 IANA SRV Label for SIP               April 20095.1.  Instant Messaging SRV Protocol Label Registration   "Address Resolution for Instant Messaging and Presence" [RFC3861]   defines an Instant Messaging SRV Protocol Label registry for   protocols that can provide services that conform to the "_im" SRV   Service label.  Because SIP is one such protocol, IANA registers the   "_sip" protocol label in the "Instant Messaging SRV Protocol Label   Registry", as follows:   Protocol label:  _sip   Specification:RFC 5509   Description:  Instant messaging protocol label for the use of SIP for                 Presence and Instant Messaging protocol as defined by                 [RFC3428].   Registrant Contact:  Salvatore Loreto <salvatore.loreto@ericsson.com>5.2.  Presence SRV Protocol Label Registration   "Address Resolution for Instant Messaging and Presence" [RFC3861]   defines a Presence SRV Protocol Label registry for protocols that can   provide services that conform to the "_pres" SRV Service label.   Because the use of SIP for Presence and Instant Messaging is one such   protocol, the IANA registers the "_sip" protocol label in the   "Presence SRV Protocol Label Registry", as follows:   Protocol label:  _sip   Specification:RFC 5509   Description:  Presence protocol label for the use of SIP for Presence                 and Instant Messaging protocol as defined by [RFC3856].   Registrant Contact:  Salvatore Loreto <salvatore.loreto@ericsson.com>6.  Acknowledgments   The need for this registration was discussed with Jon Peterson and   Peter Saint-Andre.   Miguel Garcia reviewed this document on behalf of the Real-time   Applications and Infrastructure (RAI) Area Review Team (ART).Loreto                       Standards Track                    [Page 5]

RFC 5509                 IANA SRV Label for SIP               April 20097.  Normative References   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC2782]  Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for              specifying the location of services (DNS SRV)",RFC 2782,              February 2000.   [RFC3428]  Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C.,              and D. Gurle, "Session Initiation Protocol (SIP) Extension              for Instant Messaging",RFC 3428, December 2002.   [RFC3856]  Rosenberg, J., "A Presence Event Package for the Session              Initiation Protocol (SIP)",RFC 3856, August 2004.   [RFC3859]  Peterson, J., "Common Profile for Presence (CPP)",RFC 3859, August 2004.   [RFC3860]  Peterson, J., "Common Profile for Instant Messaging              (CPIM)",RFC 3860, August 2004.   [RFC3861]  Peterson, J., "Address Resolution for Instant Messaging              and Presence",RFC 3861, August 2004.   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform              Resource Identifier (URI): Generic Syntax", STD 66,RFC 3986, January 2005.   [RFC4975]  Campbell, B., Mahy, R., and C. Jennings, "The Message              Session Relay Protocol (MSRP)",RFC 4975, September 2007.Author's Address   Salvatore Loreto   Ericsson   Hirsalantie 11   Jorvas  02420   Finland   Email: Salvatore.Loreto@ericsson.comLoreto                       Standards Track                    [Page 6]