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Versions: 00 01 02 03 draft-ietf-stox-im

Network Working Group                                     P. Saint-Andre
Internet-Draft                                       Cisco Systems, Inc.
Intended status: Standards Track                                A. Houri
Expires: October 06, 2013                                            IBM
                                                           J. Hildebrand
                                                     Cisco Systems, Inc.
                                                          April 04, 2013


   Interworking between the Session Initiation Protocol (SIP) and the
  Extensible Messaging and Presence Protocol (XMPP): Instant Messaging
                    draft-saintandre-sip-xmpp-im-03

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 October 06, 2013.

Copyright Notice

   Copyright (c) 2013 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.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  XMPP to SIP . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  SIP to XMPP . . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Content Types . . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   In order to help ensure interworking between instant messaging
   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, as developed within the SIP for Instant
      Messaging and Presence Leveraging Extensions (SIMPLE) Working
      Group; the relevant specification for instant messaging is
      [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-aware SIP systems enable entities to exchange
   "instant messages".  The term "instant message" usually refers to
   messages sent between two entities for delivery in close to real time
   (rather than messages that are stored and forwarded to the intended
   recipient upon request).  This document covers single messages only



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   (sometimes called "pager-mode" messaging), since they form the lowest
   common denominator for instant messaging.  One-to-one chat sessions
   and multi-party groupchat are covered in separate documents.

   The architectural assumptions underlying such direct mappings are
   provided in [I-D.saintandre-sip-xmpp-core], including mapping of
   addresses and error condisions.  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.

   The discussion venue for this document is the mailing list of the
   DISPATCH WG; visit https://www.ietf.org/mailman/listinfo/dispatch for
   subscription information and discussion archives.

2.  Terminology

   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].

3.  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
   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 a bot-controlled client, a component such as a
   workflow application, a server, etc.).  Continuing the tradition of
   Shakespeare examples in XMPP documentation, we will say that the XMPP
   user has an XMPP address of <juliet@example.com>.

   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].  The following is
   an example of such a stanza:

   Example: XMPP user sends message:





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


   Upon receiving such a stanza, the XMPP server to which Juliet has
   connected either delivers it to a local recipient (if the hostname in
   the 'to' attribute matches one of the hostnames serviced by the XMPP
   server) or attempts to route it to the foreign domain that services
   the hostname in the 'to' attribute.  Naturally, in this document we
   assume that the hostname in the 'to' attribute is an IM-aware SIP
   service hosted by a separate server.  As specified in [RFC6121], the
   XMPP server needs to determine the identity of the foreign domain,
   which it does by performing one or more DNS SRV lookups [RFC2782].
   For message stanzas, the order of lookups recommended by [RFC6121] is
   to first try the "_xmpp-server" service as specified in [RFC6120] and
   to then try the "_im" service as specified in [RFC3861].  Here we
   assume that the first lookup will fail but that the second lookup
   will succeed and return a resolution "_im._simple.example.net.",
   since we have already assumed that the example.net hostname is
   running a SIP instant messaging service.  (Note: The XMPP server may
   have previously determined that the foreign domain is a SIMPLE
   server, in which case it would not need to perform the SRV lookups;
   the caching of such information is a matter of implementation and
   local service policy, and is therefore out of scope for this
   document.)

   Once the XMPP server has determined that the foreign domain is
   serviced by a SIMPLE server, it must determine how to proceed.  We
   here assume that the XMPP server contains or has available to it an
   XMPP-SIMPLE gateway (such an architecture is described in
   [I-D.saintandre-sip-xmpp-core]).  The XMPP server would then deliver
   the message stanza to the XMPP-SIMPLE gateway.

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

   Example: XMPP user sends message (SIP transformation):











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   |  MESSAGE sip:romeo@example.net SIP/2.0
   |  Via: SIP/2.0/TCP x2s.example.com;branch=z9hG4bK776sgdkse
   |  Max-Forwards: 70
   |  From: sip:juliet@example.com;gr=balcony
   |  To: sip:romeo@example.net
   |  Call-ID: Hr0zny9l3@example.com
   |  CSeq: 1 MESSAGE
   |  Content-Type: text/plain
   |  Content-Length: 35
   |
   |  Art thou not Romeo, and a Montague?


   The mapping of XMPP syntax elements to SIP syntax elements SHOULD be
   as shown in the following table.  (Mappings for elements not
   mentioned are undefined.)

   Table 4: 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                    |
   |  id                         |  (no mapping)            |
   |  to                         |  To                      |
   |  type                       |  (no mapping)            |
   |  xml:lang                   |  Content-Language        |
   +-----------------------------+--------------------------+


4.  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 may 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:




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   Example: 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
   |  From: sip:romeo@example.net;gr=orchard
   |  To: sip:juliet@example.com;gr=balcony
   |  Call-ID: M4spr4vdu@example.net
   |  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 To header of a request received by a SIMPLE-XMPP
   gateway will contain a sip: or sips: URI.  The gateway SHOULD resolve
   that address to an im: URI for SIP MESSAGE requests, then follow the
   rules in [RFC3861] regarding the "_im" SRV service for the target
   domain contained in the To header.  If SRV address resolution fails
   for the "_im" service, the gateway MUST either attempt a lookup for
   the "_xmpp-server" service as specified in [RFC6120] or return an
   error to the sender (the SIP "502 Bad Gateway" error seems most
   appropriate; see [I-D.saintandre-sip-xmpp-core] for details).  If SRV
   address resolution succeeds, the gateway is 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:

   Example: SIP user sends message (XMPP transformation):

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


   The mapping of SIP syntax elements to XMPP syntax elements SHOULD be
   as shown in the following table.  (Mappings for elements not
   mentioned in the foregoing table are undefined.)

   Table 5: Message syntax mapping from SIP to XMPP








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


   Note: When transforming SIP pager-mode messages, a SIMPLE-XMPP
   gateway SHOULD specify no XMPP 'type' attribute or, equivalently, a
   'type' attribute whose value is "normal".

   Note: See Section 5 of this document about the handling of SIP
   message bodies that contain content types other than plain text.

5.  Content Types

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

   A SIMPLE-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.

   A SIMPLE-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
   1.0 Integration Set specified in [XEP-0071].

   Although a SIMPLE-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.

6.  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]).





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   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 a SIMPLE-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.

7.  IANA Considerations

   This document requests no actions of IANA.

8.  References

8.1.  Normative References

   [I-D.saintandre-sip-xmpp-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-saintandre-sip-xmpp-core-04 (work in
              progress), April 2013.

   [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.

   [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.

   [RFC3861]  Peterson, J., "Address Resolution for Instant Messaging
              and Presence", RFC 3861, August 2004.





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   [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.

8.2.  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.

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

   [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.

Authors' Addresses

   Peter Saint-Andre
   Cisco Systems, Inc.
   1899 Wynkoop Street, Suite 600
   Denver, CO  80202
   USA

   Phone: +1-303-308-3282
   Email: psaintan@cisco.com










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   Avshalom Houri
   IBM
   Building 18/D, Kiryat Weizmann Science Park
   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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