XEP-0234: Jingle File Transfer

This specification defines a Jingle application type for transferring files between two entities. The protocol provides a modular framework that enables the exchange of information about the file to be transferred as well as the negotiation of parameters such as the transport to be used.

WARNING: This Standards-Track document is Experimental. Publication as an XMPP Extension Protocol does not imply approval of this proposal by the XMPP Standards Foundation. Implementation of the protocol described herein is encouraged in exploratory implementations, but production systems should not deploy implementations of this protocol until it advances to a status of Draft.

Document Information

Series: XEP
Number: 0234
Publisher: XMPP Standards Foundation
Status: Experimental
Type: Standards Track
Version: 0.4
Last Updated: 2008-06-04
Approving Body: XMPP Council
Dependencies: XMPP Core, XEP-0047, XEP-0096, XEP-0166
Supersedes: None
Superseded By: None
Short Name: NOT_YET_ASSIGNED
Wiki Page: <http://wiki.jabber.org/index.php/Jingle File Transfer (XEP-0234)>

Author Information

Peter Saint-Andre

JabberID: stpeter@jabber.org
URI: https://stpeter.im/

Legal Notices

Copyright

This XMPP Extension Protocol is copyright (c) 1999 - 2008 by the XMPP Standards Foundation (XSF).

Permissions

Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.

Disclaimer of Warranty

## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. In no event shall the XMPP Standards Foundation or the authors of this Specification be liable for any claim, damages, or other liability, whether in an action of contract, tort, or otherwise, arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification. ##

Limitation of Liability

In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising out of the use or inability to use the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.

IPR Conformance

This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which may be found at <http://www.xmpp.org/extensions/ipr-policy.shtml> or obtained by writing to XSF, P.O. Box 1641, Denver, CO 80201 USA).

Discussion Venue

The preferred venue for discussion of this document is the Standards discussion list: <http://mail.jabber.org/mailman/listinfo/standards>.

Errata may be sent to <editor@xmpp.org>.

Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 3920) and XMPP IM (RFC 3921) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.

Conformance Terms

The following keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".

Table of Contents


1. Introduction
2. How It Works
3. Scenarios
    3.1. Transport Selection
    3.2. Fallback
4. Implementation Notes
    4.1. Mandatory to Implement Technologies
    4.2. Preference Order of Transport Methods
    4.3. Migration from XEP-0096
5. Security Considerations
6. IANA Considerations
7. XMPP Registrar Considerations
    7.1. Protocol Namespaces
    7.2. Jingle Application Formats
    7.3. Jingle Transport Methods
8. XML Schema
Notes
Revision History

1. Introduction

SI File Transfer [1] defines the current XMPP protocol extension for file transfer. However, that protocol has several drawbacks, most related to the Stream Initiation [2] protocol on which it depends:

  1. It does not enable a true, bidirectional negotiation; instead, the initiator sets the terms for the file transfer and the responder either accepts the terms or cancels the negotiation.
  2. It is the only technology in the Jabber/XMPP protocol "stack" that uses XEP-095: Stream Initiation. More modern technologies such as voice and video session negotiation use Jingle [3], and it would be helpful if implementors could use the same code for all negotiation use cases.

To overcome these drawbacks, this specification defines a file transfer negotiation method that meets the following requirements:

Jingle file transfer is only as reliable as the transports on which it depends. In particular, SOCKS5 Bytestreams does not always result in NAT or firewall traversal. To work around that problem, this specification requires all implementations to support In-Band Bytestreams, which tends to result in a successful (if slow) file transfer. A future version of this specification will also recommend implementation of a Jingle transport method that emulates the IETF's ICE-TCP technology, which is currently a work in progress (see TCP Candidates with Interactive Connectivity Establishment (ICE) [4]).

2. How It Works

This section provides a friendly introduction to Jingle file transfer.

First, the party that wishes to initiate the file transfer determines the responder's capabilities (via Service Discovery [5] or Entity Capabilities [6]). Here we assume that the responder supports the following service discovery features (note: these features may not reflect final namespace assignments):

The initiator then sends a Jingle session-initiation request to a potential responder. The content-type of the request specifies two things:

  1. An application type of "urn:xmpp:tmp:jingle:apps:file-transfer" (see Protocol Namespaces regarding issuance of one or more permanent namespaces). In particular, the <description/> element contains an <offer/> or <request/> element that in turn contains a <file/> element qualified by the existing 'http://jabber.org/protocol/si/profile/file-transfer' namespace from XEP-0096.
  2. An appropriate transport method. Because the existing transport methods used in XEP-0096 (i.e., SOCKS5 Bytestreams [7] and In-Band Bytestreams [8]) are not yet defined as Jingle transport methods, this specification registers those definitions.

In this example, the initiator is <kingclaudius@shakespeare.lit>, the responder is <laertes@shakespeare.lit>, and the initiation request specifies a file offer and a transport method of bytestreams (i.e., XEP-0065).

The flow is as follows.

Claudius                      Laertes
   |                             |
   |   session-initiate          |
   |---------------------------->|
   |   ack                       |
   |<----------------------------|
   |   [ SOCKS5 negotiation ]    |
   |<--------------------------->|
   |   session-accept            |
   |<----------------------------|
   |   ack                       |
   |---------------------------->|
   |   [ file transfer ]         |
   |---------------------------->|
   |   terminate                 |
   |<----------------------------|
   |   ack                       |
   |---------------------------->|
   |                             |

First the initiator sends a Jingle session-initiate.

Example 1. Initiator sends session-initiate

<iq from='kingclaudius@shakespeare.lit/castle'
    id='jingle1'
    to='laertes@shakespeare.lit/castle'
    type='set'>
  <jingle xmlns='urn:xmpp:tmp:jingle'
          action='session-initiate'
          initiator='kingclaudius@shakespeare.lit/castle'
          sid='851ba2'>
    <content creator='initiator' name='a-file-offer'>
      <description xmlns='urn:xmpp:tmp:jingle:apps:file-transfer'>
        <offer>
          <file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
                name='test.txt'
                size='1022'
                hash='552da749930852c69ae5d2141d3766b1'
                date='1969-07-21T02:56:15Z'>
            <desc>This is a test. If this were a real file...</desc>
          </file>
        </offer>
      </description>
      <transport xmlns='urn:xmpp:tmp:jingle:transports:bytestreams'/>
    </content>
  </jingle>
</iq>

The responder immediately acknowledges receipt of the Jingle session-initiate.

Example 2. Responder acknowledges session-initiate

<iq from='laertes@shakespeare.lit/castle'
    id='jingle1'
    to='kingclaudius@shakespeare.lit/castle'
    type='result'/>

The initiator then attempts to initiate a SOCKS5 Bytestream with the responder.

Example 3. Initiation of Interaction

<iq type='set' 
    from='kingclaudius@shakespeare.lit/castle' 
    to='laertes@shakespeare.lit/castle' 
    id='initiate'>
  <query xmlns='http://jabber.org/protocol/bytestreams' 
         sid='mySID' 
	 mode='tcp'>
    <streamhost 
        jid='kingclaudius@shakespeare.lit/castle' 
        host='192.168.4.1' 
        port='5086'/>
    <streamhost 
        jid='streamhostproxy.example.net' 
        host='24.24.24.1' 
        zeroconf='_jabber.bytestreams'/>
  </query>
</iq>

If the responder is willing to accept the bytestream, it MUST attempt to open a standard TCP socket on the network address of the StreamHost communicated by the initiator. If the initiator provides more than one StreamHost, the responder SHOULD try to connect to them in the order they occur.

If the responder is able to open a TCP socket on a StreamHost, it MUST utilize the SOCKS5 protocol specified in RFC 1928 [9] to establish the connection with the StreamHost.

Example 4. Responder Connects to StreamHost

CMD = X'01'
ATYP = X'03'
DST.ADDR = SHA1 Hash of: (SID + Initiator JID + Responder JID)
DST.PORT = 0

Example 5. StreamHost Acknowledges Connection

STATUS = X'00'

After the responder has authenticated with the StreamHost, it MUST send an IQ-result to the initiator indicating which StreamHost was used.

Example 6. Responder Notifies Initiator of Connection

<iq type='result' 
    from='laertes@shakespeare.lit/castle' 
    to='kingclaudius@shakespeare.lit/castle' 
    id='initiate'>
  <query xmlns='http://jabber.org/protocol/bytestreams'>
    <streamhost-used jid='streamhostproxy.example.net'/>
  </query>
</iq>

The responder then sends a Jingle session-accept.

Example 7. Responder sends session-accept

<iq from='laertes@shakespeare.lit/castle'
    id='accept1'
    to='kingclaudius@shakespeare.lit/castle'
    type='set'>
  <jingle xmlns='urn:xmpp:tmp:jingle'
          action='session-accept'
          initiator='kingclaudius@shakespeare.lit/castle'
          sid='851ba2'>
    <content creator='initiator' name='a-file-offer'>
      <description xmlns='urn:xmpp:tmp:jingle:apps:file-transfer'>
        <offer>
          <file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
                name='test.txt'
                size='1022'
                hash='552da749930852c69ae5d2141d3766b1'
                date='1969-07-21T02:56:15Z'>
            <desc>This is a test. If this were a real file...</desc>
          </file>
        </offer>
      </description>
      <transport xmlns='urn:xmpp:tmp:jingle:transports:bytestreams'/>
    </content>
  </jingle>
</iq>

The initiator acknowledges the Jingle session-accept.

Example 8. Initiator acknowledges session-accept

<iq from='laertes@shakespeare.lit/castle'
    id='accept1'
    to='kingclaudius@shakespeare.lit/castle'
    type='result'/>

Now the parties exchange the file using SOCKS5 Bytestreams.

Once the transfer is completed, either party can terminate the Jingle session.

More detailed scenarios follow.

3. Scenarios

3.1 Transport Selection

XEP-0096 enables the initiator to offer more than one transport and for the receiving party to choose its desired transport. This flow can be emulated in Jingle negotiation if the initiator includes more than one <content/> element (each with a different proposed transport method) and the responder removes all but its desired transport method before the session is accepted.

The protocol flow is as follows:

Claudius                      Laertes
   |                             |
   |   session-initiate          |
   |   ( S5B + IBB )             |
   |---------------------------->|
   |   ack                       |
   |<----------------------------|
   |   content-remove (S5B)      |
   |<----------------------------|
   |   ack                       |
   |---------------------------->|
   |   [ IBB negotiation ]       |
   |<--------------------------->|
   |   session-accept            |
   |<----------------------------|
   |   ack                       |
   |---------------------------->|
   |   [ file transfer ]         |
   |---------------------------->|
   |   terminate                 |
   |<----------------------------|
   |   ack                       |
   |---------------------------->|
   |                             |

First the initiator sends a Jingle session-initiate, in this case with multiple transports (SOCKS5 Bytestreams and IBB).

Example 9. Initiator sends session-initiate with multiple transports

<iq from='kingclaudius@shakespeare.lit/castle'
    id='jingle1'
    to='laertes@shakespeare.lit/castle'
    type='set'>
  <jingle xmlns='urn:xmpp:tmp:jingle'
          action='session-initiate'
          initiator='kingclaudius@shakespeare.lit/castle'
          sid='851ba2'>
    <content creator='initiator' name='first-transport'>
      <description xmlns='urn:xmpp:tmp:jingle:apps:file-transfer'>
        <offer>
          <file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
                name='test.txt'
                size='1022'
                hash='552da749930852c69ae5d2141d3766b1'
                date='1969-07-21T02:56:15Z'>
            <desc>This is a test. If this were a real file...</desc>
          </file>
        </offer>
      </description>
      <transport xmlns='urn:xmpp:tmp:jingle:transports:bytestreams'/>
    </content>
    <content creator='initiator' name='second-transport'>
      <description xmlns='urn:xmpp:tmp:jingle:apps:file-transfer'>
        <offer>
          <file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
                name='test.txt'
                size='1022'
                hash='552da749930852c69ae5d2141d3766b1'
                date='1969-07-21T02:56:15Z'>
            <desc>This is a test. If this were a real file...</desc>
          </file>
        </offer>
      </description>
      <transport xmlns='urn:xmpp:tmp:jingle:transports:ibb'/>
    </content>
  </jingle>
</iq>

The responder immediately acknowledges receipt of the Jingle session-initiate.

Example 10. Responder acknowledges session-initiate

<iq from='laertes@shakespeare.lit/castle'
    id='jingle1'
    to='kingclaudius@shakespeare.lit/castle'
    type='result'/>

The responder then sends a Jingle content-remove (deleting SOCKS5 Bytestreams) in order to choose the desired transport, which in this case is IBB.

Example 11. Responder sends content-remove

<iq from='laertes@shakespeare.lit/castle'
    id='remove1'
    to='kingclaudius@shakespeare.lit/castle'
    type='set'>
  <jingle xmlns='urn:xmpp:tmp:jingle'
          action='content-remove'
          initiator='kingclaudius@shakespeare.lit/castle'
          sid='851ba2'>
    <content creator='initiator' name='first-transport'>
      <description xmlns='urn:xmpp:tmp:jingle:apps:file-transfer'>
        <offer>
          <file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
                name='test.txt'
                size='1022'
                hash='552da749930852c69ae5d2141d3766b1'
                date='1969-07-21T02:56:15Z'>
            <desc>This is a test. If this were a real file...</desc>
          </file>
        </offer>
      </description>
      <transport xmlns='urn:xmpp:tmp:jingle:transports:bytestreams'/>
    </content>
  </jingle>
</iq>

The initiator acknowledges receipt of the Jingle content-remove action.

Example 12. Responder acknowledges content-remove

<iq from='laertes@shakespeare.lit/castle'
    id='remove1'
    to='kingclaudius@shakespeare.lit/castle'
    type='result'/>

The initiator then sends an IBB initiation request to the responder.

Example 13. Initiation of Interaction

<iq from='kingclaudius@shakespeare.lit/castle'
    id='inband_1'
    to='laertes@shakespeare.lit/castle'
    type='set'>
  <open sid='mySID' 
        block-size='4096'
        xmlns='http://jabber.org/protocol/ibb'/>
</iq>

Example 14. Success Response

<iq from='laertes@shakespeare.lit/castle'
    id='inband_1'
    to='kingclaudius@shakespeare.lit/castle'
    type='result'/>

The responder then sends a Jingle session-accept.

Example 15. Responder sends session-accept

<iq from='laertes@shakespeare.lit/castle'
    id='accept1'
    to='kingclaudius@shakespeare.lit/castle'
    type='set'>
  <jingle xmlns='urn:xmpp:tmp:jingle'
          action='session-accept'
          initiator='kingclaudius@shakespeare.lit/castle'
          sid='851ba2'>
    <content creator='initiator' name='a-file-offer'>
      <description xmlns='urn:xmpp:tmp:jingle:apps:file-transfer'>
        <offer>
          <file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
                name='test.txt'
                size='1022'
                hash='552da749930852c69ae5d2141d3766b1'
                date='1969-07-21T02:56:15Z'>
            <desc>This is a test. If this were a real file...</desc>
          </file>
        </offer>
      </description>
      <transport xmlns='urn:xmpp:tmp:jingle:transports:bytestreams'/>
    </content>
  </jingle>
</iq>

The initiator acknowledges the Jingle session-accept action.

Example 16. Initiator acknowledges session-accept

<iq from='laertes@shakespeare.lit/castle'
    id='accept1'
    to='kingclaudius@shakespeare.lit/castle'
    type='result'/>

Now the initiator sends the file using In-Band Bytestreams as defined in XEP-0047.

3.2 Fallback

Currently, XEP-0096 does not enable the parties to fall back to a second method (e.g., In-Band Bytestreams) if the first method tried (e.g., SOCKS5 Bytestreams) does not work. This problem is addressed by Jingle. Such a fallback scenario is especially helpful when re-using the existing SOCKS5 Bytestreams ("S5B") method, since that method does not necessarily result in NAT or firewall traversal and therefore often results in a failed transfer attempt. However, because In-Band Bytestreams ("IBB") almost always succeeds (except if the parties violate rate-limiting policies at their servers), it provides a reliable transfer method of last resort. To provide seamless fallback, the initiator or responder can counter-propose IBB if S5B fails.

The protocol flow is as follows:

Claudius                      Laertes
   |                             |
   |   session-initiate          |
   |---------------------------->|
   |   ack                       |
   |<----------------------------|
   |   [ SOCKS5 failure! ]       |
   |x---------------------------x|
   |   session-accept            |
   |<----------------------------|
   |   ack                       |
   |---------------------------->|
   |   content-replace (IBB)     |
   |<----------------------------|
   |   ack                       |
   |---------------------------->|
   |   content-accept            |
   |---------------------------->|
   |   ack                       |
   |<----------------------------|
   |   [ IBB negotiation ]       |
   |<--------------------------->|
   |   [ file transfer ]         |
   |---------------------------->|
   |   terminate                 |
   |<----------------------------|
   |   ack                       |
   |---------------------------->|
   |                             |

First the initiator sends a Jingle session-initiate, in this case with a transport of SOCKS5 Bytestreams.

Example 17. Initiator sends session-initiate

<iq from='kingclaudius@shakespeare.lit/castle'
    id='jingle1'
    to='laertes@shakespeare.lit/castle'
    type='set'>
  <jingle xmlns='urn:xmpp:tmp:jingle'
          action='session-initiate'
          initiator='kingclaudius@shakespeare.lit/castle'
          sid='851ba2'>
    <content creator='initiator' name='a-file-offer'>
      <description xmlns='urn:xmpp:tmp:jingle:apps:file-transfer'>
        <offer>
          <file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
                name='test.txt'
                size='1022'
                hash='552da749930852c69ae5d2141d3766b1'
                date='1969-07-21T02:56:15Z'>
            <desc>This is a test. If this were a real file...</desc>
          </file>
        </offer>
      </description>
      <transport xmlns='urn:xmpp:tmp:jingle:transports:bytestreams'/>
    </content>
  </jingle>
</iq>

The responder immediately acknowledges receipt of the session-initiate.

Example 18. Responder acknowledges session-initiate

<iq from='laertes@shakespeare.lit/castle'
    id='jingle1'
    to='kingclaudius@shakespeare.lit/castle'
    type='result'/>

The initiator then attempts to initiate a SOCKS5 Bytestream with the responder.

Example 19. Initiation of Interaction

<iq from='kingclaudius@shakespeare.lit/castle' 
    id='initiate'
    to='laertes@shakespeare.lit/castle' 
    type='set'>
  <query xmlns='http://jabber.org/protocol/bytestreams' 
         sid='mySID' 
	 mode='tcp'>
    <streamhost 
        jid='kingclaudius@shakespeare.lit/castle' 
        host='192.168.4.1' 
        port='5086'/>
    <streamhost 
        jid='streamhostproxy.example.net' 
        host='24.24.24.1' 
        zeroconf='_jabber.bytestreams'/>
  </query>
</iq>

If the responder is willing to accept the bytestream, it MUST attempt to open a standard TCP socket on the network address of the StreamHost communicated by the initiator. If the initiator provides more than one StreamHost, the responder SHOULD try to connect to them in the order they occur.

If the responder tries but is unable to connect to any of the StreamHosts and it cannot or does not wish to attempt a connection from its side, it returns a <item-not-found/> error to the initiator.

Example 20. Target Is Unable to Connect to Any StreamHost and Wishes to End Transaction

<iq from='laertes@shakespeare.lit/castle'
    id='initiate'
    to='kingclaudius@shakespeare.lit/castle' 
    type='error'>
  <error code='404' type='cancel'>
    <item-not-found xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
  </error>
</iq>

At this point the file transfer has failed using SOCKS5 Bytestreams. However, all is not lost, because the parties can attempt to fall back to In-Band Bytestreams. Therefore the responder sends a session-accept to the initiator but immediately sends a Jingle content-replace action to propose the fallback.

Example 21. Responder sends session-accept

<iq from='laertes@shakespeare.lit/castle'
    id='accept1'
    to='kingclaudius@shakespeare.lit/castle'
    type='set'>
  <jingle xmlns='urn:xmpp:tmp:jingle'
          action='session-accept'
          initiator='kingclaudius@shakespeare.lit/castle'
          sid='851ba2'>
    <content creator='initiator' name='a-file-offer'>
      <description xmlns='urn:xmpp:tmp:jingle:apps:file-transfer'>
        <offer>
          <file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
                name='test.txt'
                size='1022'
                hash='552da749930852c69ae5d2141d3766b1'
                date='1969-07-21T02:56:15Z'>
            <desc>This is a test. If this were a real file...</desc>
          </file>
        </offer>
      </description>
      <transport xmlns='urn:xmpp:tmp:jingle:transports:bytestreams'/>
    </content>
  </jingle>
</iq>

The initiator acknowledges the Jingle session-accept action.

Example 22. Initiator acknowledges session-accept

<iq from='laertes@shakespeare.lit/castle'
    id='accept1'
    to='kingclaudius@shakespeare.lit/castle'
    type='result'/>

However, this session-accept is just a placeholder, and the initiator MUST NOT send the file using SOCKS5 Bytestreams because the initiator received a notification that the SOCKS5 negotiation failed. The responder immediately sends a content-replace action including a transport of IBB and a request for the file originally offered (note the use of the <request/> element instead of the <offer/> element, since the responder wants the initiator to send the previously-offered file).

Example 23. Responder requests content-replace

<iq from='laertes@shakespeare.lit/castle'
    id='replace1'
    to='kingclaudius@shakespeare.lit/castle'
    type='set'>
  <jingle xmlns='urn:xmpp:tmp:jingle'
          action='content-replace'
          initiator='kingclaudius@shakespeare.lit/castle'
          sid='851ba2'>
    <content creator='responder' name='a-file-request'>
      <description xmlns='urn:xmpp:tmp:jingle:apps:file-transfer'>
        <request>
          <file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
                hash='552da749930852c69ae5d2141d3766b1'
                name='test.txt'/>
          </file>
        </request>
      </description>
      <transport xmlns='urn:xmpp:tmp:jingle:transports:ibb'/>
    </content>
  </jingle>
</iq>

The initiator then acknowledges the content-replace action.

Example 24. Initiator acknowledges content-replace

<iq from='kingclaudius@shakespeare.lit/castle'
    id='replace1'
    to='laertes@shakespeare.lit/castle'
    type='result'/>

If the content definition is acceptable, the initiator then sends a content-accept action to the responder.

Example 25. Initiator sends content-accept

<iq to='kingclaudius@shakespeare.lit/castle'
    id='accept2'
    to='laertes@shakespeare.lit/castle'
    type='set'>
  <jingle xmlns='urn:xmpp:tmp:jingle'
          action='content-accept'
          initiator='kingclaudius@shakespeare.lit/castle'
          sid='851ba2'>
    <content creator='responder' name='a-file-request'>
      <description xmlns='urn:xmpp:tmp:jingle:apps:file-transfer'>
        <request>
          <file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
                hash='552da749930852c69ae5d2141d3766b1'
                name='test.txt'/>
          </file>
        </request>
      </description>
      <transport xmlns='urn:xmpp:tmp:jingle:transports:ibb'/>
    </content>
  </jingle>
</iq>

The responder then acknowledges the content-accept action.

Example 26. Responder acknowledges content-accept

<iq from='laertes@shakespeare.lit/castle'
    id='accept2'
    to='kingclaudius@shakespeare.lit/castle'
    type='result'/>

The initiator then sends an IBB initiation request to the responder.

Example 27. Initiation of Interaction

<iq from='kingclaudius@shakespeare.lit/castle'
    id='inband_1'
    to='laertes@shakespeare.lit/castle'
    type='set'>
  <open sid='mySID' 
        block-size='4096'
        xmlns='http://jabber.org/protocol/ibb'/>
</iq>

Example 28. Success Response

<iq from='laertes@shakespeare.lit/castle'
    id='inband_1'
    to='kingclaudius@shakespeare.lit/castle'
    type='result'/>

Now the initiator sends the file using In-Band Bytestreams as defined in XEP-0047.

4. Implementation Notes

4.1 Mandatory to Implement Technologies

All implementations MUST support the In-Band Bytestreams transport method as a reliable method of last resort. An implementation SHOULD support other transport methods as well.

4.2 Preference Order of Transport Methods

An application MAY present transport methods in any order, except that the In-Band Bytestreams method MUST be the lowest preference.

4.3 Migration from XEP-0096

Support for Jingle file transfer can be determined through discovery of the 'urn:xmpp:tmp:jingle:apps:file-transfer' namespace (see Protocol Namespaces regarding issuance of one or more permanent namespaces), via either service discovery (XEP-0030) or entity capabilities (XEP-0115). If the initiator knows that the responder supports Jingle file transfer, it SHOULD first attempt negotiation using XEP-0166 rather than XEP-0095.

5. Security Considerations

In order to secure the data stream, implementations SHOULD use encryption methods appropriate to the transport method being used. For details, refer to the specifications for those transport methods.

6. IANA Considerations

No interaction with the Internet Assigned Numbers Authority (IANA) [10] is required as a result of this document.

7. XMPP Registrar Considerations

7.1 Protocol Namespaces

Until this specification advances to a status of Draft, its associated namespaces shall be:

Upon advancement of this specification, the XMPP Registrar [11] shall issue permanent namespaces in accordance with the process defined in Section 4 of XMPP Registrar Function [12].

The following namespaces are requested, and are thought to be unique per the XMPP Registrar's requirements:

7.2 Jingle Application Formats

The XMPP Registrar shall include "file-transfer" in its registry of Jingle application formats. The registry submission is as follows:

<application>
  <name>file-transfer</name>
  <desc>Jingle sessions for the transfer of a file</desc>
  <transport>reliable</transport>
  <doc>XEP-xxxx</doc>
</application>

7.3 Jingle Transport Methods

The XMPP Registrar shall add to its registry of Jingle transport methods definitions for the reliable transport methods defined in XEP-0047 and XEP-0065. The registry submissions are as follows:

<transport>
  <name>bytestreams</name>
  <desc>A method for exchanging data over SOCKS5 Bytestreams.</desc>
  <type>reliable</type>
  <doc>XEP-0065</doc>
</transport>
<transport>
  <name>ibb</name>
  <desc>A method for exchanging data over In-Band Bytestreams.</desc>
  <type>reliable</type>
  <doc>XEP-0047</doc>
</transport>

8. XML Schema

<?xml version='1.0' encoding='UTF-8'?>

<xs:schema
    xmlns:xs='http://www.w3.org/2001/XMLSchema'
    targetNamespace='urn:xmpp:tmp:jingle:apps:file-transfer'
    xmlns='urn:xmpp:tmp:jingle:apps:file-transfer'
    elementFormDefault='qualified'>

  <xs:import 
      namespace='http://jabber.org/protocol/si/profile/file-transfer'
      schemaLocation='http://www.xmpp.org/schemas/file-transfer.xsd'/>

  <xs:element name='description'>
    <xs:complexType>
      <xs:choice>
        <xs:element ref='offer'/>
        <xs:element ref='request'/>
      </xs:choice>
    </xs:complexType>
  </xs:element>

  <xs:element name='offer'>
    <xs:complexType>
      <xs:sequence xmlns:ft='http://jabber.org/protocol/si/profile/file-transfer'>
        <xs:element ref='ft:file'/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:element name='request'>
    <xs:complexType>
      <xs:sequence xmlns:ft='http://jabber.org/protocol/si/profile/file-transfer'>
        <xs:element ref='ft:file'/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

</xs:schema>

Notes

1. XEP-0096: SI File Transfer <http://www.xmpp.org/extensions/xep-0096.html>.

2. XEP-0095: Stream Initiation <http://www.xmpp.org/extensions/xep-0095.html>.

3. XEP-0166: Jingle <http://www.xmpp.org/extensions/xep-0166.html>.

4. TCP Candidates with Interactive Connectivity Establishment (ICE) <http://tools.ietf.org/html/draft-ietf-mmusic-ice-tcp>. Work in progress.

5. XEP-0030: Service Discovery <http://www.xmpp.org/extensions/xep-0030.html>.

6. XEP-0115: Entity Capabilities <http://www.xmpp.org/extensions/xep-0115.html>.

7. XEP-0065: SOCKS5 Bytestreams <http://www.xmpp.org/extensions/xep-0065.html>.

8. XEP-0047: In-Band Bytestreams <http://www.xmpp.org/extensions/xep-0047.html>.

9. RFC 1928: SOCKS Protocol Version 5 <http://tools.ietf.org/html/rfc1928>.

10. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.

11. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <http://www.xmpp.org/registrar/>.

12. XEP-0053: XMPP Registrar Function <http://www.xmpp.org/extensions/xep-0053.html>.

Revision History

Version 0.4 (2008-06-04)

Harmonized negotiation flows with other Jingle application types.

(psa)

Version 0.3 (2008-05-29)

Corrected and more clearly explained negotiation flows for consistency with XEP-0166 and other Jingle specifications.

(psa)

Version 0.2 (2008-03-20)

Added transport negotiation scenario.

(psa)

Version 0.1 (2008-03-05)

Initial published version.

(psa)

Version 0.0.3 (2008-02-29)

Corrected use of content-replace action; specified that the In-Band Bytestreams transport method is mandatory-to-implement but must have the lowest preference order.

(psa)

Version 0.0.2 (2008-02-28)

Modified negotiation flow to use new content-replace action. (psa)

Version 0.0.1 (2008-01-29)

First draft. (psa)

END