Interworking between the Session Initiation Protocol (SIP) and the Extensible Messaging and Presence Protocol (XMPP): One-to-One Text Chat
draft-ietf-stox-chat-01

Network Working Group                                     P. Saint-Andre
Internet-Draft                                       Cisco Systems, Inc.
Intended status: Standards Track                               S. Loreto
Expires: March 22, 2014                                        E. Gavita
                                                              N. Hossain
                                                                Ericsson
                                                      September 18, 2013

   Interworking between the Session Initiation Protocol (SIP) and the
Extensible Messaging and Presence Protocol (XMPP): One-to-One Text Chat
                        draft-ietf-stox-chat-01

Abstract

   This document defines a bidirectional protocol mapping for the
   exchange of instant messages in the context of a one-to-one chat
   session between a user of the Session Initiation Protocol (SIP) and a
   user of the Extensible Messaging and Presence Protocol (XMPP).
   Specifically for SIP text chat, this document specifies a mapping to
   the Message Session Relay Protocol (MSRP).

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 22, 2014.

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

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   carefully, as they describe your rights and restrictions with respect
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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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  XMPP to MSRP . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  MSRP to XMPP . . . . . . . . . . . . . . . . . . . . . . . . .  7
   5.  Composing Events . . . . . . . . . . . . . . . . . . . . . . . 10
   6.  Delivery Reports . . . . . . . . . . . . . . . . . . . . . . . 12
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 14
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 14
   Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15

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1.  Introduction

   Both the Session Initiation Protocol [RFC3261] and the Extensible
   Messaging and Presence Protocol [RFC6120] can be used for the purpose
   of one-to-one text chat over the Internet.  To ensure interworking
   between these technologies, it is important to define bidirectional
   protocol mappings.

   The architectural assumptions underlying such protocol mappings are
   provided in [I-D.ietf-stox-core], including mapping of addresses and
   error conditions.  This document specifies mappings for one-to-one
   text chat sessions (sometimes called "session-mode" messaging); in
   particular, this document specifies mappings between XMPP messages of
   type "chat" and the Message Session Relay Protocol [RFC4975].
   Mappings for single instant messages and groupchat are provided in
   separate documents.

   The approach taken here is to directly map syntax and semantics from
   one protocol to another.  The mapping described herein depends on the
   protocols defined in the following specifications:

   o  XMPP chat sessions using message stanzas of type "chat" are
      specified in [RFC6121].
   o  SIP-based chat sessions using the SIP INVITE and SEND request
      types are specified in [RFC4975].

   In SIMPLE, a chat session is formally negotiated just as any other
   session type is using SIP.  By contrast, a one-to-one chat "session"
   in XMPP is an informal construct and is not formally negotiated: a
   user simply sends a message of type "chat" to a contact, the contact
   then replies to the message, and the sum total of such messages
   exchanged during a defined period of time is considered to be a chat
   session.  To overcome the disparity between these approaches, a
   gateway that wishes to map between SIP and XMPP for one-to-one chat
   sessions needs to maintain some additional state, as described below.

   The discussion venue for this document is the mailing list of the
   STOX WG; visit https://www.ietf.org/mailman/listinfo/stox 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].

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3.  XMPP to MSRP

   In XMPP, the "informal session" approach is to simply send someone a
   <message/> of type "chat" without starting any session negotiation
   ahead of time (as described in [RFC6121]).  The XMPP "informal
   session" approach maps very well into a SIP MESSAGE request, as
   described in [I-D.ietf-stox-core].  However, the XMPP informal
   session approach can also be mapped to MSRP if the XMPP-to-SIP
   gateway maintains additional state.

   The order of events is as follows.

   XMPP User                      GW                      SIP User
       |                          |                          |
       |(F1) (XMPP) Chat message  |                          |
       |------------------------->|                          |
       |                          |(F2) (SIP) INVITE         |
       |                          |------------------------->|
       |                          |(F3) (SIP) 200 OK         |
       |                          |<-------------------------|
       |                          |(F4) (SIP) ACK            |
       |                          |------------------------->|
       |                          |(F5) (MSRP) SEND          |
       |                          |------------------------->|
       |                          |(F6) (MSRP) A reply       |
       |                          |<-------------------------|
       |(F7) (XMPP) A reply       |                          |
       |<-------------------------|                          |
       |                          |                          |
       .                          .                          .
       .                          .                          .
       .                          .                          .
       |                          |                          |
       |                          |(F8) (SIP) BYE            |
       |                          |<-------------------------|
       |                          |(F9) (SIP) 200 OK         |
       |                          |------------------------->|
       |                          |                          |

   First the XMPP user would generate an XMPP chat message.

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   Example: (F1) Juliet sends an XMPP message

   | <message from='juliet@example.com/balcony'
   |          to='romeo@example.net'
   |          type='chat'>
   |   <thread>711609sa</thread>
   |   <body>Art thou not Romeo, and a Montague?</body>
   | </message>

   The local SIP-to-XMPP gateway at the SIMPLE server would then
   initiate an MSRP session with Romeo on Juliet's behalf (since there
   is no reliable way for the SIMPLE server to determine if Romeo's user
   agent supports MSRP, it simply needs to guess).

   Example: (F2) Gateway starts a formal session on behalf of Juliet

   | INVITE sip:romeo@example.net SIP/2.0
   | To: <sip:romeo@example.net>
   | From: <sip:juliet@example.com>
   | Contact: <sip:juliet@example.com>;gr=balcony
   | Subject: Open chat with Juliet?
   | Call-ID: 711609sa
   | Content-Type: application/sdp
   |
   | c=IN IP4 x2s.example.com
   | m=message 7654 TCP/MSRP *
   | a=accept-types:text/plain
   | a=lang:en
   | a=lang:it
   | a=path:msrp://x2s.example.com:7654/jshA7weztas;tcp

   Here we assume that Romeo accepts the MSRP session request.

   Example: (F3) Romeo accepts the request

   | SIP/2.0 200 OK
   | To: <sip:juliet@example.com>;gr=balcony
   | From: <sip:romeo@example.net>
   | Contact: <sip:romeo@example.net>;gr=orchard
   | Call-ID: 711609sa
   | Content-Type: application/sdp
   |
   | c=IN IP4 s2x.example.net
   | m=message 12763 TCP/MSRP *
   | a=accept-types:text/plain
   | a=lang:it
   | a=path:msrp://s2x.example.net:12763/kjhd37s2s20w2a;tcp

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   The XMPP-to-SIP gateway then acknowledges the session acceptance on
   behalf of Romeo.

   Example: (F4) Gateway sends ACK to Romeo's UA

   | ACK sip:juliet@example.com SIP/2.0
   | To: <sip:romeo@example.net>;gr=orchard
   | From: <sip:juliet@example.com>
   | Contact: <sip:juliet@example.com>;gr=balcony
   | Call-ID: 711609sa

   The XMPP-to-SIP gateway then transforms the original XMPP chat
   message into MSRP.

   Example: (F5) Gateway transforms XMPP message to MSRP

   | MSRP a786hjs2 SEND
   | From-Path: msrp://x2s.example.com:7654/jshA7weztas;tcp
   | To-Path: msrp://s2x.example.net:12763/kjhd37s2s20w2a;tcp
   | Message-ID: 87652491
   | Byte-Range: 1-25/25
   | Content-Type: text/plain
   |
   | Art thou not Romeo, and a Montague?
   | -------a786hjs2$

   Romeo can then send a reply using his MSRP user agent.

   Example: (F6) Romeo sends a reply

   | MSRP a786hjs2 SEND
   | To-Path: msrp://x2s.example.com:7654/jshA7weztas;tcp
   | From-Path: msrp://s2x.example.net:12763/kjhd37s2s20w2a;tcp
   | Message-ID: 87652491
   | Byte-Range: 1-25/25
   | Failure-Report: no
   | Content-Type: text/plain
   |
   | Neither, fair saint, if either thee dislike.
   | -------a786hjs2$

   The SIP-to-XMPP gateway would then transform that message into
   appropriate XMPP syntax for routing to the intended recipient.

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   Example: (F7) Gateway transforms MSRP message to XMPP

   | <message from='romeo@example.net/orchard'
   |          to='juliet@example.com/balcony'
   |          type='chat'>
   |   <thread>711609sa</thread>
   |   <body>Neither, fair saint, if either thee dislike.</body>
   | </message>

   When the MSRP user wishes to end the chat session, the user's MSRP
   client sends a SIP BYE.

   Example: (F8) Romeo terminates the chat session

   | BYE juliet@example.com sip: SIP/2.0
   | Max-Forwards: 70
   | From: <sip:romeo@example.net>;tag=087js
   | To: <sip:juliet@example.com>;tag=786
   | Call-ID: 711609sa
   | Cseq: 1 BYE
   | Content-Length: 0

   The BYE is then acknowledged by the XMPP-to-SIP gateway.

   Example: (F9) Gateway acknowledges termination

   | SIP/2.0 200 OK
   | From: <sip:juliet@example.com>;tag=786
   | To: <sip:romeo@example.net>;tag=087js
   | Call-ID: 711609sa
   | CSeq: 1 BYE
   | Content-Length: 0

4.  MSRP to XMPP

   When an MSRP client sends messages through a gateway to an XMPP
   client that does not support formal sessinos, the order of events is
   as follows.

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   SIP User                     GW                     XMPP User
      |                         |                          |
      |(F1)(SIP) INVITE         |                          |
      |------------------------>|                          |
      |(F2)(SIP) 200 OK         |                          |
      |<------------------------|                          |
      |(F3)(SIP) ACK            |                          |
      |------------------------>|                          |
      |(F4)(MSRP) SEND          |                          |
      |------------------------>|                          |
      |                         |(F5)(XMPP) A chat message |
      |                         |------------------------->|
      |                         |(F6)(XMPP) A reply        |
      |                         |<-------------------------|
      |                         |                          |
      |(F7)(MSRP) SEND          |                          |
      |<------------------------|                          |
      |                         |                          |
      .                         .                          .
      .                         .                          .
      .                         .                          .
      |                         |                          |
      |(F8)(SIP) BYE            |                          |
      |------------------------>|                          |
      |(F9)(SIP) 200 OK         |                          |
      |<------------------------|                          |
      |                         |                          |

   Example: (F1) SIP user starts the session

   | INVITE sip:juliet@example.com SIP/2.0
   | To: <sip:juliet@example.com>
   | From: <sip:romeo@example.net>
   | Contact: <sip:romeo@example.net>;gr=orchard
   | Subject: Open chat with Romeo?
   | Call-ID: 742507no
   | Content-Type: application/sdp
   |
   | c=IN IP4 s2x.example.net
   | m=message 7313 TCP/MSRP *
   | a=accept-types:text/plain
   | a=lang:en
   | a=lang:it
   | a=path:msrp://s2x.example.net:7313/ansp71weztas;tcp

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   Example: (F2) Gateway accepts session on Juliet's behalf

   | SIP/2.0 200 OK
   | To: <sip:romeo@example.net>;gr=orchard
   | From: <sip:juliet@example.com>
   | Contact: <sip:juliet@example.com>;gr=balcony
   | Call-ID: 742507no
   | Content-Type: application/sdp
   |
   | c=IN IP4 x2s.example.com
   | m=message 8763 TCP/MSRP *
   | a=accept-types:text/plain
   | a=lang:it
   | a=path:msrp://x2s.example.com:8763/lkjh37s2s20w2a;tcp

   Example: (F3) Romeo sends ACK

   | ACK sip:juliet@example.com SIP/2.0
   | To: <sip:juliet@example.com>;gr=balcony
   | From: <sip:romeo@example.net>
   | Contact: <sip:romeo@example.net>;gr=orchard
   | Call-ID: 742507no

   Example: (F4) Romeo sends a message

   | MSRP ad49kswow SEND
   | To-Path: msrp://x2s.example.com:8763/lkjh37s2s20w2a;tcp
   | From-Path: msrp://s2x.example.net:7313/ansp71weztas;tcp
   | Message-ID: 44921zaqwsx
   | Byte-Range: 1-32/32
   | Failure-Report: no
   | Content-Type: text/plain
   |
   | I take thee at thy word ...
   | -------ad49kswow$

   Example: (F5) Romeo sends a message (XMPP translation)

   | <message from='romeo@example.net'
   |          to='juliet@example.com'
   |          type='chat'>
   |   <thread>742507no</thread>
   |   <body>I take thee at thy word ...</body>
   | </message>

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   Example: (F6) Juliet sends a reply

   | <message from='juliet@example.com'
   |          to='romeo@example.net'
   |          type='chat'>
   |   <thread>711609sa</thread>
   |   <body>What man art thou ...?</body>
   | </message>

   Example: (F8) Gateway transforms XMPP message to MSRP

   | MSRP a786hjs2 SEND
   | To-Path: msrp://s2x.example.net:7313/jshA7weztas;tcp
   | From-Path: msrp://x2s.example.com:8763/lkjh37s2s20w2a;tcp
   | Message-ID: 87652491
   | Byte-Range: 1-25/25
   | Failure-Report: no
   | Content-Type: text/plain
   |
   | What man art thou ...?
   | -------a786hjs2$

   Example: (F9) Romeo terminates the session

   | BYE juliet@example.com sip: SIP/2.0
   | Max-Forwards: 70
   | To: <sip:juliet@example.com>;gr=balcony
   | From: <sip:romeo@example.net>
   | Contact: <sip:romeo@example.net>;gr=orchard
   | Call-ID: 742507no
   | Cseq: 1 BYE
   | Content-Length: 0

   Example: (F10) Gateway acknowledges the termination of the session on
   behalf of XMPP user

   | SIP/2.0 200 OK
   | To: <sip:juliet@example.com>;gr=balcony
   | From: <sip:romeo@example.net>
   | Contact: <sip:romeo@example.net>;gr=orchard
   | Call-ID: 742507no
   | CSeq: 1 BYE

5.  Composing Events

   Both XMPP and MSRP enable a user agent to receive notifications when
   a person's conversation partner is composing an instant message

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   within the context of a chat session.

   For XMPP, the Chat State Notifications specification [XEP-0085]
   defines five states: active, inactive, gone, composing, and paused.
   Some of these states are related to the act of message composition
   (composing, paused), whereas others are related to the sender's
   involvement with the chat session (active, inactive, gone).

   For MSRP (and SIMPLE in general), the Indication of Message
   Composition for Instant Messaging specification [RFC3994] defines two
   states: idle and active.  Here the idle state indicates that the
   sender is not actively composing a message, and the active state
   indicates that the sender is indeed actively composing a message (the
   sending user agent simply toggles between the two states, changing to
   active if the user is actively composing a message and changing to
   idle if the user is no longer actively composing a message).

   Because the XEP-0085 states can represent information that is not
   captured in RFC 3994, gateways can either (a) map only the composing-
   related states or (b) map all the XEP-0085 states.

   The following mappings are suggested.

   Table 1: Mapping of SIMPLE isComposing events to XMPP chat states

   +-------------------+--------------------+
   | isComposing Event |  Chat State        |
   +-------------------+--------------------+
   | active            |  composing         |
   | idle              |  active            |
   +-------------------+--------------------+

   Table 2: Mapping of XMPP chat states to SIMPLE isComposing events

   +-------------------+--------------------+
   | Chat State        | isComposing Event  |
   +-------------------+--------------------+
   | active            |  idle              |
   | inactive          |  idle              |
   | gone              |  [none, see note]  |
   | composing         |  active            |
   | paused            |  idle              |
   +-------------------+--------------------+

   Note: Although there is no mapping for the "gone" chat state, receipt
   of the "gone" state can be used as a trigger for terminating the
   formal chat session within MSRP.

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6.  Delivery Reports

   Both XMPP and MSRP enable a user agent to receive notifications when
   a message has been received by the intended recipient.

   For XMPP, the Message Receipts specification [XEP-0184] defines a
   method and XML namespace for requesting and returning indications
   that a message has been received by a client controlled by the
   intended recipient.

   For MSRP, a native reporting feature is included, in the form of
   report chunks (see Sections 7.1.2 and 7.1.3 of [RFC4975]).

   Examples follow.

   First, the XMPP user sends a message containing a request for
   delivery notification.

   Example: Juliet sends a message with a receipt request

   | <message from='juliet@example.com'
   |          id='87652491'
   |          to='romeo@example.net'
   |          type='chat'>
   |   <thread>711609sa</thread>
   |   <body>What man art thou ...?</body>
   |   <request xmlns='urn:xmpp:receipts'/>
   | </message>

   Example: Gateway transforms XMPP message to MSRP

   | MSRP a786hjs2 SEND
   | To-Path: msrp://s2x.example.net:7313/jshA7weztas;tcp
   | From-Path: msrp://x2s.example.com:8763/lkjh37s2s20w2a;tcp
   | Message-ID: 87652491
   | Byte-Range: 1-25/25
   | Success-Report: yes
   | Failure-Report: no
   | Content-Type: text/plain
   |
   | What man art thou ...?
   | -------a786hjs2$

   Next, the recipient returns a report.

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   Example: Recipient returns receipt

   | MSRP hx74g336 REPORT
   | To-Path: msrp://x2s.example.com:8763/lkjh37s2s20w2a;tcp
   | From-Path: msrp://s2x.example.net:7313/jshA7weztas;tcp
   | Message-ID: 87652491
   | Byte-Range: 1-106/106
   | Status: 000 200 OK
   | -------hx74g336$

   Example: Transformed message receipt

   | <message from='romeo@example.net'
   |          id='87652491'
   |          to='juliet@example.com'>
   |   <received xmlns='urn:xmpp:receipts' id='87652491'/>
   | </message>

7.  IANA Considerations

   This document requests no actions of IANA.

8.  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]).

   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 recommended to use
   [RFC3862] for instant messages.

9.  References

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9.1.  Normative References

   [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-04 (work in progress),
              July 2013.

   [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.

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

   [RFC3994]  Schulzrinne, H., "Indication of Message Composition for
              Instant Messaging", RFC 3994, January 2005.

   [RFC4975]  Campbell, B., Mahy, R., and C. Jennings, "The Message
              Session Relay Protocol (MSRP)", RFC 4975, September 2007.

   [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-0085]
              Saint-Andre, P. and D. Smith, "Chat State Notifications",
              XSF XEP 0085, September 2009.

   [XEP-0184]
              Saint-Andre, P. and J. Hildebrand, "Message Delivery
              Receipts", XSF XEP 0184, March 2011.

9.2.  Informative References

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

   [RFC3428]  Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C.,

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              and D. Gurle, "Session Initiation Protocol (SIP) Extension
              for Instant Messaging", RFC 3428, December 2002.

Appendix A.  Acknowledgements

   Some text in this document was borrowed from [I-D.ietf-stox-core].

   Thanks to Adrian Georgescu, Saul Ibarra, and Tory Patnoe for their
   feedback.

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

   Salvatore Loreto
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   Email: Salvatore.Loreto@ericsson.com

   Eddy Gavita
   Ericsson
   Decarie Boulevard
   Town of Mount Royal, Quebec
   Canada

   Email: eddy.gavita@ericsson.com

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   Nazin Hossain
   Ericsson
   Decarie Boulevard
   Town of Mount Royal, Quebec
   Canada

   Email: Nazin.Hossain@ericsson.com

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