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Versions: 00 01 02 03 04 draft-ietf-xmpp-websocket

HyBi Working Group                                       J. Moffitt, Ed.
Internet-Draft
Intended status: Standards Track                              E. Cestari
Expires: June 11, 2011                                        ProcessOne
                                                        December 8, 2010


                   An XMPP Sub-protocol for WebSocket
                  draft-moffitt-xmpp-over-websocket-00

Abstract

   This document defines a binding for the XMPP protocol over a
   WebSocket transport layer.  A WebSocket binding for XMPP provides
   higher performance than the current HTTP binding for 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 June 11, 2011.

Copyright Notice

   Copyright (c) 2010 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
   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.




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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  XMPP Sub-Protocol  . . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  Handshake  . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.2.  Messages . . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.3.  XMPP Stream Setup  . . . . . . . . . . . . . . . . . . . .  5
     3.4.  Stream Errors  . . . . . . . . . . . . . . . . . . . . . .  5
     3.5.  Closing the Connection . . . . . . . . . . . . . . . . . .  6
     3.6.  Stanzas  . . . . . . . . . . . . . . . . . . . . . . . . .  6
     3.7.  Stream Restarts  . . . . . . . . . . . . . . . . . . . . .  6
     3.8.  Pings and Keepalives . . . . . . . . . . . . . . . . . . .  6
     3.9.  TLS  . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
   4.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   7.  Informative References . . . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
































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1.  Introduction

   Applications using XMPP (see [RFC3920] and [RFC3921]) on the Web
   currently make use of BOSH (see [XEP-0124] and [XEP-0206]), an XMPP
   binding to HTTP.  BOSH is based on the HTTP long polling technique,
   and it suffers from high transport overhead compared to XMPP's native
   binding to TCP.

   It would be much better in most circumstances to avoid tunneling XMPP
   over HTTP long polled connections and instead use the XMPP protocol
   directly.  However, the APIs and sandbox that browsers have provided
   do not allow this.  The WebSocket protocol
   [I-D.ietf-hybi-thewebsocketprotocol] now exists to solve these kinds
   of problems.  The WebSocket protocol is a bi-directional protocol
   that provides a simple message-based framing layer over raw sockets
   and allows for more robust and efficient communication in web
   applications.

   This document defines a binding of the XMPP protocol over the
   WebSocket protocol transport.  It makes using XMPP within web
   applications simpler and more efficient.






























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2.  Terminology

   The basic unit of framing in the WebSocket protocol is called a
   message.  In XMPP, the basic unit is the stanza, which is a subset of
   the first-level children of each document in an XMPP stream (see
   Section 9 of [RFC3920]).  XMPP also has a concept of messages, which
   are stanzas whose top-level element name is message.  In this
   document, the word "message" will mean a WebSocket message, not an
   XMPP message stanza (see Section 3.2).










































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3.  XMPP Sub-Protocol

3.1.  Handshake

   The xmpp sub-protocol is used to transport XMPP over a WebSocket
   connection.  The client and server agree to this protocol during the
   WebSocket handshake (see Section 1.3 of
   [I-D.ietf-hybi-thewebsocketprotocol]).

   During the WebSocket handshake, the client MUST include the |Sec-
   WebSocket-Protocol| header in its handshake, and the value |xmpp|
   must be included in the list of protocols.  The reply from the server
   MUST also contain |xmpp| in its own |Sec-WebSocket-Protocol| header
   in order for an XMPP sub-protocol connection to be established.

   Once the handshake is complete, WebSocket messages sent or received
   will conform to the protocol defined in the rest of this document.

3.2.  Messages

   Data frame messages in the XMPP sub-protocol MUST be of the text type
   and contain UTF-8 encoded data.  The close control frame's contents
   are specified in Section 3.5.  Control frames other than close are
   not restricted.

   Unless noted in text, the word "message" will mean a WebSocket
   message containing a text data frame.

3.3.  XMPP Stream Setup

   The first message sent after the handshake is complete MUST be an
   XMPP opening stream tag as defined in XMPP [RFC3920] or an XML text
   declaration (see Section 4.3.1 of [W3C.REC-xml-20081126]) followed by
   an XMPP opening stream tag.  The stream tag MUST NOT be closed (i.e.
   the closing </stream:stream> tag should not appear in the message) as
   it is the start of the client's outgoing XML.  The '<' character of
   the tag or text declaration MUST be the first character of the text
   payload.

   The server MUST respond with a message containing an error (see
   Section 3.4), its own opening stream tag, or an XML text declaration
   followed by an opening stream tag.

3.4.  Stream Errors

   Stream level errors in XMPP are terminal.  Should such an error
   occur, the server MUST send the stream error as a complete element in
   a message to the client.  This message MAY include the closing stream



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   tag if a stream is opened.

   If the error occurs during the opening of a stream, the stream error
   message MUST start with an opening stream tag (see Section 4.7.1 of
   [RFC3920]) and end with a closing stream tag.

   After the stream error and closing stream tag have been sent, the
   server MUST close the connection as in Section 3.5.

3.5.  Closing the Connection

   Either the server or the client may close the connection at any time.
   Before closing the connection, the closing party MUST close the XMPP
   stream if it has been established.  To initiate the close, the
   closing party MUST send a normal WebSocket close message with an
   empty body.  The connection is considered closed when a matching
   close message is received (see Section 1.4 of
   [I-D.ietf-hybi-thewebsocketprotocol]).

3.6.  Stanzas

   Each XMPP stanza MUST be sent in its own message.  A stanza MUST NOT
   be split over multiple messages.  All first level children of the
   <stream:stream> element MUST be treated the same as stanzas (e.g.
   <stream:features> and <stream:error>).

3.7.  Stream Restarts

   After successful SASL authentication, an XMPP stream must be
   restarted.  In these cases, as soon as the message is sent (or
   received) containing the success indication, both the server and
   client streams are implicitly closed, and new streams must be opened.
   The client MUST open a new stream as in Section 3.3 and MUST NOT send
   a closing stream tag.

3.8.  Pings and Keepalives

   XMPP servers send whitespace pings as keepalives between stanzas, and
   XMPP clients can do the same thing.  These extra whitespace
   characters are not significant in the protocol.  Servers and clients
   SHOULD use WebSocket ping messages instead for this purpose.

   The XMPP Ping extension [XEP-0199] allows entities to send and
   respond to ping requests.  A client sending a WebSocket ping is
   equivalent to pinging the WebSocket server, which may also be the
   XMPP server.  When the XMPP server is not also the WebSocket server,
   a WebSocket ping may be useful to check the health of the
   intermediary server.



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3.9.  TLS

   TLS cannot be used in The XMPP sub-protocol because the sub-protocol
   does not allow for raw binary data to be sent.  A server MUST NOT
   advertise TLS as a stream feature (see Section 4.6 of [RFC3920]).  A
   client MUST ignore the TLS feature if it is advertised over
   WebSocket.












































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4.  Examples

   Examples will be added as soon as the WebSocket protocol
   specification is more stable.















































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5.  IANA Considerations

   If a registry is created for WebSocket sub-protocols, the xmpp sub-
   protocol will be registered.















































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6.  Security Considerations

   Since application level TLS cannot be used (see Section 3.9),
   applications which need to protect the privacy of the XMPP traffic
   need to do so a the WebSocket level or some other higher level.














































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7.  Informative References

   [I-D.ietf-hybi-thewebsocketprotocol]
              Fette, I., "The WebSocket protocol",
              draft-ietf-hybi-thewebsocketprotocol-03 (work in
              progress), October 2010.

   [RFC3920]  Saint-Andre, P., Ed., "Extensible Messaging and Presence
              Protocol (XMPP): Core", RFC 3920, October 2004.

   [RFC3921]  Saint-Andre, P., Ed., "Extensible Messaging and Presence
              Protocol (XMPP): Instant Messaging and Presence",
              RFC 3921, October 2004.

   [W3C.REC-xml-20081126]
              Sperberg-McQueen, C., Yergeau, F., Maler, E., Paoli, J.,
              and T. Bray, "Extensible Markup Language (XML) 1.0 (Fifth
              Edition)", World Wide Web Consortium Recommendation REC-
              xml-20081126, November 2008,
              <http://www.w3.org/TR/2008/REC-xml-20081126>.

   [XEP-0124]
              Paterson, I., Smith, D., Saint-Andre, P., and J. Moffitt,
              "Bidirectional-streams Over Synchronous HTTP (BOSH)", XSF
              XEP 0124, July 2010.

   [XEP-0199]
              Saint-Andre, P., "XMPP Ping", XSF XEP 0199, June 2009.

   [XEP-0206]
              Paterson, I. and P. Saint-Andre, "XMPP Over BOSH", XSF
              XEP 0206, July 2010.



















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Authors' Addresses

   Jack Moffitt (editor)

   Email: jack@metajack.im


   Eric Cestari
   ProcessOne

   Email: ecestari@process-one.com








































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