Internet Assigned Numbers Authority (IANA) Registration of Instant Messaging and Presence DNS SRV RRs for the Session Initiation Protocol (SIP)
RFC 5509

• Status
• IESG evaluation record
• IESG writeups
• Email expansions
• History

• Versions
• 03

Network Working Group                                          S. Loreto
Request for Comments: 5509                                      Ericsson
Category: Standards Track                                     April 2009

        Internet Assigned Numbers Authority (IANA) Registration
             of Instant Messaging and Presence DNS SRV RRs
               for 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 to BCP 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 2009

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  DNS SRV Usage of SIP with 'im' and 'pres' URIs  . . . . . . . . 3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
     5.1.  Instant Messaging SRV Protocol Label Registration . . . . . 5
     5.2.  Presence SRV Protocol Label Registration  . . . . . . . . . 5
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5
   7.  Normative References  . . . . . . . . . . . . . . . . . . . . . 6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 6

Loreto                       Standards Track                    [Page 2]
RFC 5509                 IANA SRV Label for SIP               April 2009

1.  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 in RFC 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 before

Loreto                       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.