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Versions: (draft-saintandre-sip-xmpp-im) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 RFC 7572

Network Working Group                                     P. Saint-Andre
Internet-Draft                                                      &yet
Intended status: Standards Track                                A. Houri
Expires: September 12, 2014                                          IBM
                                                           J. Hildebrand
                                                     Cisco Systems, Inc.
                                                          March 11, 2014


   Interworking between the Session Initiation Protocol (SIP) and the
  Extensible Messaging and Presence Protocol (XMPP): Instant Messaging
                         draft-ietf-stox-im-08

Abstract

   This document defines a bidirectional protocol mapping for the
   exchange of single instant messages between the Session Initiation
   Protocol (SIP) and the Extensible Messaging and Presence Protocol
   (XMPP).

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 12, 2014.

Copyright Notice

   Copyright (c) 2014 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Intended Audience . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  XMPP to SIP . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  SIP to XMPP . . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Content Types . . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  Internationalization Considerations . . . . . . . . . . . . .   8
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   In order to help ensure interworking between instant messaging (IM)
   systems that conform to the instant messaging / presence requirements
   [RFC2779], it is important to clearly define protocol mappings
   between such systems.  Within the IETF, work has proceeded on two
   instant messaging technologies:

   o  Various extensions to the Session Initiation Protocol ([RFC3261])
      for instant messaging, in particular the MESSAGE method extension
      [RFC3428]

   o  The Extensible Messaging and Presence Protocol (XMPP), which
      consists of a formalization of the core XML streaming protocols
      developed originally by the Jabber open-source community; the
      relevant specifications are [RFC6120] for the XML streaming layer
      and [RFC6121] for basic presence and instant messaging extensions

   One approach to helping ensure interworking between these protocols
   is to map each protocol to the abstract semantics described in
   [RFC3860]; that is the approach taken by
   [I-D.ietf-simple-cpim-mapping] and [RFC3922].  By contrast, the
   approach taken in this document is to directly map semantics from one
   protocol to another (i.e., from SIP/SIMPLE to XMPP and vice-versa).

   Both XMPP and IM-capable SIP systems enable entities to exchange
   "instant messages".  The term "instant message" usually refers to a
   message sent between two entities for delivery in close to real time
   (rather than a message that is stored and forwarded to the intended



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   recipient upon request).  This document covers single messages only
   (sometimes called "pager-mode" messaging), since they form the lowest
   common denominator for IM.  Separate documents cover one-to-one chat
   sessions [I-D.ietf-stox-chat] and multi-party groupchat
   [I-D.ietf-stox-groupchat].

   The architectural assumptions underlying such direct mappings are
   provided in [I-D.ietf-stox-core], including mapping of addresses and
   error conditions.  The mappings specified in this document cover
   basic instant messaging functionality, i.e., the exchange of a single
   instant message between a SIP user and an XMPP user in either
   direction.  Mapping of more advanced functionality is out of scope
   for this document, but other documents in this "series" cover such
   topics.

2.  Intended Audience

   The documents in this series are intended for use by software
   developers who have an existing system based on one of these
   technologies (e.g., SIP), and would like to enable communication from
   that existing system to systems based on the other technology (e.g.,
   XMPP).  We assume that readers are familiar with the core
   specifications for both SIP [RFC3261] and XMPP [RFC6120], with the
   base document for this series [I-D.ietf-stox-core], and with the
   following IM-related specifications:

   o  Session Initiation Protocol (SIP) Extension for Instant Messaging
      [RFC3428]

   o  Extensible Messaging and Presence Protocol: Instant Messaging and
      Presence [RFC6121]

3.  Terminology

   A number of terms used here are explained in [RFC3261], [RFC3428],
   [RFC6120], and [RFC6121].

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

4.  XMPP to SIP

   As described in [RFC6121], a single instant message is an XML
   <message/> stanza of type "normal" sent over an XML stream (since
   "normal" is the default for the 'type' attribute of the <message/>
   stanza, the attribute is often omitted).  In this document we will



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   assume that such a message is sent from an XMPP client to an XMPP
   server over an XML stream negotiated between the client and the
   server, and that the client is controlled by a human user (this is a
   simplifying assumption introduced for explanatory purposes only; the
   XMPP sender could be an automated client, a component such as a
   workflow application, a server, etc.).

   When Juliet wants to send an instant message to Romeo, she interacts
   with her XMPP client, which generates an XMPP <message/> stanza.  The
   syntax of the <message/> stanza, including required and optional
   elements and attributes, is defined in [RFC6121] (for single instant
   messages, the value of the 'to' address SHOULD be a "bare JID" of the
   form "localpart@domainpart").  The following is an example of such a
   stanza:

   Example 1: XMPP user sends message

   |  <message from='juliet@example.com/balcony'
   |           to='romeo@example.net'>
   |    <body>Art thou not Romeo, and a Montague?</body>
   |  </message>

   Upon receiving such a message stanza, the XMPP server needs to
   determine the identity of the domainpart in the 'to' address, which
   it does by following the procedures explained in Section 5 of
   [I-D.ietf-stox-core].  If the domain is a SIP domain, the XMPP server
   will hand off the message stanza to an XMPP-to-SIP gateway or
   connection manager that natively communicates with IM-aware SIP
   servers.

   The XMPP-SIP gateway is then responsible for translating the XMPP
   message stanza into a SIP MESSAGE request from the XMPP user to the
   SIP user:

   Example 2: XMPP user sends message (SIP transformation)

   |  MESSAGE sip:romeo@example.net SIP/2.0
   |  Via: SIP/2.0/TCP x2s.example.com;branch=z9hG4bK776sgdkse
   |  Max-Forwards: 70
   |  To: sip:romeo@example.net
   |  From: <sip:juliet@example.com;gr=balcony>;tag=12345
   |  Call-ID: D9AA95FD-2BD5-46E2-AF0F-6CFAA96BDDFA
   |  CSeq: 1 MESSAGE
   |  Content-Type: text/plain
   |  Content-Length: 35
   |
   |  Art thou not Romeo, and a Montague?




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   The destination SIP server is responsible for delivering the message
   to the intended recipient, and the recipient is responsible for
   generating a response (e.g., 200 OK).

   Example 3: SIP user agent indicates receipt of message

   |  SIP/2.0 200 OK
   |  Via: SIP/2.0/TCP x2s.example.com;branch=z9hG4bK776sgdkse
   |  From: sip:romeo@example.net;tag=vwxyz
   |  To: sip:juliet@example.com;tag=12345
   |  Call-ID: D9AA95FD-2BD5-46E2-AF0F-6CFAA96BDDFA
   |  CSeq: 1 MESSAGE
   |  Content-Length: 0

   As described in [RFC3428], a downstream proxy could fork a MESSAGE
   request, but it would return only one 200 OK to the gateway.

      Informational Note: This document does not specify handling of the
      200 OK by the XMPP-SIP gateway (e.g., to enable message
      acknowledgements).  See [I-D.ietf-stox-chat] for a mapping of
      message acknowledgements in the context of one-to-one chat
      sessions.

   The mapping of XMPP syntax to SIP syntax SHOULD be as shown in the
   following table.  (Mappings for several aspects not mentioned here
   are specified in [I-D.ietf-stox-chat].)

   Table 1: Message syntax mapping from XMPP to SIP

      +-----------------------------+--------------------------+
      |  XMPP Element or Attribute  |  SIP Header or Contents  |
      +-----------------------------+--------------------------+
      |  <body/>                    |  body of MESSAGE         |
      |  <subject/>                 |  Subject                 |
      |  <thread/>                  |  Call-ID                 |
      |  from                       |  From (1)                |
      |  id                         |  (no mapping)            |
      |  to                         |  To or Request-URI       |
      |  type                       |  (no mapping) (2)        |
      |  xml:lang                   |  Content-Language        |
      +-----------------------------+--------------------------+

   1.  As shown in the foregoing example and described in
       [I-D.ietf-stox-core], the XMPP-SIP gateway SHOULD map the full
       JID (localpart@domainpart/resourcepart) of the XMPP sender to the
       SIP From header and include the resourcepart as the GRUU portion
       [RFC5627] of the SIP URI.




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   2.  Because there is no SIP header field that matches the meaning of
       the XMPP message 'type' values ("normal", "chat", "groupchat",
       "headline", "error"), no general mapping is possible here.

5.  SIP to XMPP

   As described in [RFC3428], a single instant message is a SIP MESSAGE
   request sent from a SIP user agent to an intended recipient who is
   most generally referenced by an Instant Message URI of the form
   <im:user@domain> but who might be referenced by a SIP or SIPS URI of
   the form <sip:user@domain> or <sips:user@domain>.  Here again we
   introduce the simplifying assumption that the user agent is
   controlled by a human user, whom we shall dub <romeo@example.net>.

   When Romeo wants to send an instant message to Juliet, he interacts
   with his SIP user agent, which generates a SIP MESSAGE request.  The
   syntax of the MESSAGE request is defined in [RFC3428].  The following
   is an example of such a request:

   Example 4: SIP user sends message

   |  MESSAGE sip:juliet@example.com SIP/2.0
   |  Via: SIP/2.0/TCP s2x.example.net;branch=z9hG4bKeskdgs677
   |  Max-Forwards: 70
   |  To: sip:juliet@example.com
   |  From: sip:romeo@example.net;tag=vwxyz
   |  Call-ID: 9E97FB43-85F4-4A00-8751-1124FD4C7B2E
   |  CSeq: 1 MESSAGE
   |  Content-Type: text/plain
   |  Content-Length: 44
   |
   |  Neither, fair saint, if either thee dislike.

   Section 5 of [RFC3428] stipulates that a SIP User Agent presented
   with an im: URI should resolve it to a sip: or sips: URI.  Therefore
   we assume that the Request-URI of a request received by an IM-capable
   SIP-XMPP gateway will contain a sip: or sips: URI.  Upon receiving
   the MESSAGE, the SIP (MSRP) server needs to determine the identity of
   the domain portion of the Request-URI or To header, which it does by
   following the procedures explained in Section 5 of
   [I-D.ietf-stox-core].  If the domain is an XMPP domain, the SIP
   server will hand off the MESSAGE to an associated SIP-XMPP gateway or
   connection manager that natively communicates with XMPP servers.

   The SIP-to-XMPP gateway is then responsible for translating the
   request into an XMPP message stanza from the SIP user to the XMPP
   user and returning a SIP "200 OK" message to the sender:




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   Example 5: SIP user sends message (XMPP transformation)

   |  <message from='romeo@example.net/orchard'
   |           to='juliet@example.com'>
   |    <body>Neither, fair saint, if either thee dislike.</body>
   |  </message>

   Note that the stanza handling rules specified in [RFC6121] allow the
   receiving XMPP server to deliver a message stanza whose 'to' address
   is a bare JID ("localpart@domainpart") to multiple connected devices.
   This is similar to the "forking" of messages in SIP.

   The mapping of SIP syntax to XMPP syntax SHOULD be as shown in the
   following table.  (Mappings for several aspects not mentioned here
   are specified in [I-D.ietf-stox-chat].)

   Table 2: Message syntax mapping from SIP to XMPP

      +--------------------------+-----------------------------+
      |  SIP Header or Contents  |  XMPP Element or Attribute  |
      +--------------------------+-----------------------------+
      |  Call-ID                 |  <thread/>                  |
      |  Content-Language        |  xml:lang                   |
      |  CSeq                    |  (no mapping)               |
      |  From                    |  from (1)                   |
      |  Subject                 |  <subject/>                 |
      |  Request-URI or To       |  to                         |
      |  body of MESSAGE         |  <body/>                    |
      +--------------------------+-----------------------------+

   1.  As shown in the foregoing example and described in
       [I-D.ietf-stox-core], if the IM-capable SIP-XMPP gateway has
       information about the GRUU [RFC5627] of the particular endpoint
       that sent the SIP message then it SHOULD map the sender's address
       to a full JID (localpart@domainpart/resourcepart) in the 'from'
       attribute of the XMPP stanza and include the GRUU as the
       resourcepart.

   When transforming SIP pager-mode messages, an IM-capable SIP-XMPP
   gateway SHOULD specify no XMPP 'type' attribute or, equivalently, a
   'type' attribute whose value is "normal" [RFC6121].

   See Section 6 of this document about the handling of SIP message
   bodies that contain content types other than plain text.







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6.  Content Types

   SIP requests of type MESSAGE are allowed to contain essentially any
   content type.  The recommended procedures for SIP-to-XMPP gateways to
   use in handling these content types are as follows.

   An IM-aware SIP-to-XMPP gateway MUST process SIP messages that
   contain message bodies of type "text/plain" and MUST encapsulate such
   message bodies as the XML character data of the XMPP <body/> element.

   An IM-aware SIP-to-XMPP gateway SHOULD process SIP messages that
   contain message bodies of type "text/html"; if so, a gateway MUST
   transform the "text/html" content into XHTML content that conforms to
   the XHTML-IM Integration Set specified in [XEP-0071].

   Although an IM-aware SIP-to-XMPP gateway MAY process SIP messages
   that contain message bodies of types other than "text/plain" and
   "text/html", the handling of such content types is a matter of
   implementation.

7.  Internationalization Considerations

   Both XMPP and SIP support the UTF-8 encoding [RFC3629] of Unicode
   characters [UNICODE] within messages, and signalling of the language
   for a particular message (in XMPP via the 'xml:lang' attribute and in
   SIP via the Content-Language header).  Several examples follow, using
   the "XML Notation" for Unicode characters outside the ASCII range
   described in [RFC3987].

   Example 6: SIP user sends message

   |  MESSAGE sip:juliet@example.com SIP/2.0
   |  Via: SIP/2.0/TCP s2x.example.net;branch=z9hG4bKeskdgs677
   |  Max-Forwards: 70
   |  To: sip:juliet@example.com
   |  From: sip:romeo@example.net;tag=vwxyz
   |  Call-ID: 9E97FB43-85F4-4A00-8751-1124FD4C7B2E
   |  CSeq: 1 MESSAGE
   |  Content-Type: text/plain
   |  Content-Length: 45
   |  Content-Language: cs
   |
   |  Nic z ob&#xC3A9;ho, m&#xC3A1; d&#xC49B;vo spanil&#xC3A1;,
   |  nenavid&#xC3AD;&#xC5A1;-li jedno nebo druh&#xC3A9;.







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   Example 7: SIP user sends message (XMPP transformation)

   |  <message from='romeo@example.net'
   |           to='juliet@example.com'
   |           xml:lang='cs'>
   |    <body>
   |  Nic z ob&#xC3A9;ho, m&#xC3A1; d&#xC49B;vo spanil&#xC3A1;,
   |  nenavid&#xC3AD;&#xC5A1;-li jedno nebo druh&#xC3A9;.
   |    </body>
   |  </message>

8.  IANA Considerations

   This document requests no actions of IANA.

9.  Security Considerations

   Detailed security considerations for instant messaging protocols are
   given in [RFC2779], for SIP-based instant messaging in [RFC3428] (see
   also [RFC3261]), and for XMPP-based instant messaging in [RFC6121]
   (see also [RFC6120]).  The security considerations provided in
   [I-D.ietf-stox-core] also apply.

   This document specifies methods for exchanging instant messages
   through a gateway that translates between SIP and XMPP.  Such a
   gateway MUST be compliant with the minimum security requirements of
   the instant messaging protocols for which it translates (i.e., SIP
   and XMPP).  The addition of gateways to the security model of instant
   messaging specified in [RFC2779] introduces some new risks.  In
   particular, end-to-end security properties (especially
   confidentiality and integrity) between instant messaging user agents
   that interface through an IM-capable SIP-XMPP gateway can be provided
   only if common formats are supported.  Specification of those common
   formats is out of scope for this document, although it is preferred
   to use [RFC3862] for instant messages.

10.  References

10.1.  Normative References

   [I-D.ietf-stox-chat]
              Saint-Andre, P. and S. Loreto, "Interworking between the
              Session Initiation Protocol (SIP) and the Extensible
              Messaging and Presence Protocol (XMPP): One-to-One Text
              Chat Sessions", draft-ietf-stox-chat-06 (work in
              progress), March 2014.





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   [I-D.ietf-stox-core]
              Saint-Andre, P., Houri, A., and J. Hildebrand,
              "Interworking between the Session Initiation Protocol
              (SIP) and the Extensible Messaging and Presence Protocol
              (XMPP): Core", draft-ietf-stox-core-11 (work in progress),
              February 2014.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              June 2002.

   [RFC3428]  Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C.,
              and D. Gurle, "Session Initiation Protocol (SIP) Extension
              for Instant Messaging", RFC 3428, December 2002.

   [RFC5627]  Rosenberg, J., "Obtaining and Using Globally Routable User
              Agent URIs (GRUUs) in the Session Initiation Protocol
              (SIP)", RFC 5627, October 2009.

   [RFC6120]  Saint-Andre, P., "Extensible Messaging and Presence
              Protocol (XMPP): Core", RFC 6120, March 2011.

   [RFC6121]  Saint-Andre, P., "Extensible Messaging and Presence
              Protocol (XMPP): Instant Messaging and Presence", RFC
              6121, March 2011.

   [XEP-0071]
              Saint-Andre, P., "XHTML-IM", XSF XEP 0071, November 2012.

10.2.  Informative References

   [I-D.ietf-simple-cpim-mapping]
              Rosenberg, J. and B. Campbell, "CPIM Mapping of SIMPLE
              Presence and Instant Messaging", draft-ietf-simple-cpim-
              mapping-01 (work in progress), June 2002.

   [I-D.ietf-stox-groupchat]
              Saint-Andre, P., Corretge, S., and S. Loreto,
              "Interworking between the Session Initiation Protocol
              (SIP) and the Extensible Messaging and Presence Protocol
              (XMPP): Groupchat", draft-ietf-stox-groupchat-02 (work in
              progress), December 2013.





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   [RFC2779]  Day, M., Aggarwal, S., and J. Vincent, "Instant Messaging
              / Presence Protocol Requirements", RFC 2779, February
              2000.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [RFC3860]  Peterson, J., "Common Profile for Instant Messaging
              (CPIM)", RFC 3860, August 2004.

   [RFC3862]  Klyne, G. and D. Atkins, "Common Presence and Instant
              Messaging (CPIM): Message Format", RFC 3862, August 2004.

   [RFC3922]  Saint-Andre, P., "Mapping the Extensible Messaging and
              Presence Protocol (XMPP) to Common Presence and Instant
              Messaging (CPIM)", RFC 3922, October 2004.

   [RFC3987]  Duerst, M. and M. Suignard, "Internationalized Resource
              Identifiers (IRIs)", RFC 3987, January 2005.

   [UNICODE]  The Unicode Consortium, "The Unicode Standard, Version
              6.3", 2013,
              <http://www.unicode.org/versions/Unicode6.3.0/>.

Appendix A.  Acknowledgements

   The authors wish to thank the following individuals for their
   feedback: Mary Barnes, Dave Cridland, Dave Crocker, Adrian Georgescu,
   Christer Holmberg, Saul Ibarra Corretge, Olle Johansson, Paul
   Kyzivat, Salvatore Loreto, Daniel-Constantin Mierla, and Tory Patnoe.

   The authors gratefully acknowledge the assistance of Markus Isomaki
   and Yana Stamcheva as the working group chairs and Gonzalo Camarillo
   and Alissa Cooper as the sponsoring Area Directors.

   Peter Saint-Andre wishes to acknowledge Cisco Systems, Inc., for
   employing him during his work on earlier versions of this document.

Authors' Addresses

   Peter Saint-Andre
   &yet
   P.O. Box 787
   Parker, CO  80134
   USA

   Email: ietf@stpeter.im




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   Avshalom Houri
   IBM
   Rorberg Building, Pekris 3
   Rehovot  76123
   Israel

   Email: avshalom@il.ibm.com


   Joe Hildebrand
   Cisco Systems, Inc.
   1899 Wynkoop Street, Suite 600
   Denver, CO  80202
   USA

   Email: jhildebr@cisco.com



































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