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<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE xep SYSTEM 'xep.dtd' [
<!ENTITY % ents SYSTEM 'xep.ent'>
%ents;
]>
<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
<xep>
<header>
<title>Jingle In-Band Bytestreams Transport Method</title>
<abstract>This specification defines a Jingle transport method that results in sending data via the In-Band Bytestreams (IBB) protocol defined in XEP-0047. Essentially this transport method reuses XEP-0047 semantics for sending the data and defines native Jingle methods for starting and ending an IBB session.</abstract>
&LEGALNOTICE;
<number>0261</number>
<status>Draft</status>
<type>Standards Track</type>
<sig>Standards</sig>
<dependencies>
<spec>XMPP Core</spec>
<spec>XEP-0047</spec>
</dependencies>
<supersedes/>
<supersededby/>
<shortname>jingle-ibb</shortname>
<schemaloc>
<url>http://xmpp.org/schemas/jingle-transports-ibb.xsd</url>
</schemaloc>
<discuss>jingle</discuss>
&stpeter;
<revision>
<version>1.0</version>
<date>2011-09-23</date>
<initials>psa</initials>
<remark><p>Per a vote of the XMPP Council, advanced specification from Experimental to Draft.</p></remark>
</revision>
<revision>
<version>0.8</version>
<date>2011-08-31</date>
<initials>psa</initials>
<remark><p>Per feedback from the XMPP Council, modified the security considerations to remove the recommendation to use XTLS (since it is not longer being actively developed).</p></remark>
</revision>
<revision>
<version>0.7</version>
<date>2011-05-16</date>
<initials>psa</initials>
<remark><p>Further clarified order of layers, in particular the reuse of IBB &lt;open/&gt; and &lt;close/&gt; elements.</p></remark>
</revision>
<revision>
<version>0.6</version>
<date>2011-03-07</date>
<initials>psa</initials>
<remark><p>Clarified error flows and handling of multiple IBB sessions within the bytestream.</p></remark>
</revision>
<revision>
<version>0.5</version>
<date>2010-04-14</date>
<initials>psa</initials>
<remark><p>Incremented the protocol version from 0 to 1 because the changes in document version 0.4 are backward-incompatible.</p></remark>
</revision>
<revision>
<version>0.4</version>
<date>2010-04-13</date>
<initials>psa</initials>
<remark><p>Added roundtrip for exchange of IBB &lt;open/&gt; element to provide proper layering between Jingle and IBB; defined how to close a single session within the bytestream; defined how to close the bytestream itself.</p></remark>
</revision>
<revision>
<version>0.3</version>
<date>2010-02-16</date>
<initials>psa</initials>
<remark><p>Added negotiation flow for block size; corrected some slight errors.</p></remark>
</revision>
<revision>
<version>0.2</version>
<date>2009-03-09</date>
<initials>psa</initials>
<remark><p>Minor changes to track modifications to XEP-0166; updated security considerations for consistency with other transport methods; added section on service discovery.</p></remark>
</revision>
<revision>
<version>0.1</version>
<date>2009-02-19</date>
<initials>psa</initials>
<remark><p>Initial published version.</p></remark>
</revision>
<revision>
<version>0.0.2</version>
<date>2009-02-11</date>
<initials>psa</initials>
<remark>Defined ability to add more session IDs to a bytestream using Jingle transport-info.</remark>
</revision>
<revision>
<version>0.0.1</version>
<date>2009-02-10</date>
<initials>psa</initials>
<remark>Rough draft.</remark>
</revision>
</header>
<section1 topic='Introduction' anchor='intro'>
<p>&xep0166; defines a framework for negotiating and managing data sessions over XMPP. In order to provide a flexible framework, the base Jingle specification defines neither data transport methods nor application formats, leaving that up to separate specifications. The current document defines a transport method for establishing and managing data exchanges between XMPP entities using the existing In-Band Bytestreams (IBB) protocol specified in &xep0047;. This "jingle-ibb" method results in a streaming transport method suitable for use in Jingle application types where packet loss cannot be tolerated (e.g., file transfer); however, because the "jingle-ibb" transport method sends data over the XMPP channel itself (albeit not the Jingle signalling channel), it is intended as a transport of last resort when other streaming transports (e.g., &xep0260;) cannot be negotiated.</p>
<p>The approach taken in this specification is to use the existing IBB mechanisms described in <cite>XEP-0047</cite> for transporting the data, and to define Jingle-specific methods only to start and end the in-band bytestream.</p>
</section1>
<section1 topic='Protocol' anchor='protocol'>
<section2 topic='Flow' anchor='protocol-flow'>
<p>The basic flow is as follows.</p>
<code><![CDATA[
Initiator Responder
| |
| session-initiate |
| (with IBB info) |
|--------------------------->|
| ack |
|<---------------------------|
| session-accept |
|<---------------------------|
| ack |
|--------------------------->|
| IBB <open/> |
|--------------------------->|
| ack |
|<---------------------------|
| IBB "SESSION" |
|<==========================>|
| IBB <close/> |
|--------------------------->|
| ack |
|<---------------------------|
| session-terminate |
|<---------------------------|
| ack |
|--------------------------->|
| |
]]></code>
<p>This flow is illustrated in the following sections (to prevent confusion these use an "example" description instead of a real application type).</p>
</section2>
<section2 topic='Establishing a Bytestream' anchor='protocol-start'>
<p>First the initiator sends a Jingle session-initiate request.</p>
<example caption="Initiator sends session-initiate"><![CDATA[
<iq from='romeo@montague.lit/orchard'
id='xn28s7gk'
to='juliet@capulet.lit/balcony'
type='set'>
<jingle xmlns='urn:xmpp:jingle:1'
action='session-initiate'
initiator='romeo@montague.lit/orchard'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='ex'>
<description xmlns='urn:xmpp:example'/>
<transport xmlns='urn:xmpp:jingle:transports:ibb:1'
block-size='4096'
sid='ch3d9s71'/>
</content>
</jingle>
</iq>
]]></example>
<p>Note: The default value of the 'stanza' attribute is "iq", signifying use of &IQ; stanzas for data exchange; a value of "message" signifies that &MESSAGE; stanzas are to be used for data exchange. See <cite>XEP-0047</cite> for further discussion regarding use of these stanza types for data exchange.</p>
<p>The responder immediately acknowledges receipt (but does not yet accept the session).</p>
<example caption="Responder acknowledges session-initiate"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
id='xn28s7gk'
to='romeo@montague.lit/orchard'
type='result'/>
]]></example>
<p>If the offer is acceptable, the responder returns a Jingle session-accept. If the responder wishes to use a smaller block-size, the responder can specify that in the session-accept by returning a different value for the 'block-size' attribute.</p>
<example caption="Responder definitively accepts the session"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
id='bsa91h56'
to='romeo@montague.lit/orchard'
type='set'>
<jingle xmlns='urn:xmpp:jingle:1'
action='session-accept'
responder='juliet@capulet.lit/balcony'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='ex'>
<description xmlns='urn:xmpp:example'/>
<transport xmlns='urn:xmpp:jingle:transports:ibb:1'
block-size='2048'
sid='ch3d9s71'/>
</content>
</jingle>
</iq>
]]></example>
<p>The initiator then acknowledges the session-accept.</p>
<example caption="Initiator acknowledges session-accept"><![CDATA[
<iq from='romeo@montague.lit/orchard'
id='bsa91h56'
to='juliet@capulet.lit/balcony'
type='result'/>
]]></example>
<p>In essence, the foregoing Jingle negotiation replaces the &lt;open/&gt; element from <cite>XEP-0047</cite>. However, to provide consistent layering of Jingle on top of IBB (thus enabling separation of existing IBB code from new Jingle code), the initiator now MUST also send the &lt;open/&gt; element, with the same 'block-size' and 'sid' values as for the Jingle &lt;transport/&gt; element it negotiated with the recipient (i.e., if the recipient sent a modified &lt;transport/&gt; element element containing a different block size, the initiator MUST use the negotiated values). This adds a roundtrip to the negotiation and could be considered a "no-op", but the extra roundtrip is inconsequential given that the parties will be exchanging base64-encoded data in-band.</p>
<example caption='Initiator sends IBB &lt;open/&gt;'><![CDATA[
<iq from='romeo@montague.net/orchard'
id='jn3h8g65'
to='juliet@capulet.com/balcony'
type='set'>
<open xmlns='http://jabber.org/protocol/ibb'
block-size='2048'
sid='ch3d9s71'
stanza='iq'/>
</iq>
]]></example>
<p>If no error occurs, the responder returns an IQ-result to the initiator.</p>
<example caption='Responder accepts IBB &lt;open/&gt;'><![CDATA[
<iq from='juliet@capulet.com/balcony'
id='jn3h8g65'
to='romeo@montague.net/orchard'
type='result'/>
]]></example>
<p>However, one of the errors described in <cite>XEP-0047</cite> might occur; in particular, if the value of the IBB 'block-size' attribute sent by the initiator in the &lt;open/&gt; element does not match the value of the 'block-size' attribute communicated by the responder in the Jingle session-accept message then the responder SHOULD return a &constraint; error as described in <cite>XEP-0047</cite>.</p>
</section2>
<section2 topic='Exchanging Data' anchor='protocol-data'>
<p>Now the initiator can begin sending IBB packets using an IQ-set for each chunk as described in <cite>XEP-0047</cite>, where the responder will acknowledge each IQ-set in accordance with &xmppcore;.</p>
<example caption='An IBB packet'><![CDATA[
<iq from='romeo@montague.net/orchard'
id='ls72b58f'
to='juliet@capulet.com/balcony'
type='set'>
<data xmlns='http://jabber.org/protocol/ibb' seq='0' sid='ch3d9s71'>
qANQR1DBwU4DX7jmYZnncmUQB/9KuKBddzQH+tZ1ZywKK0yHKnq57kWq+RFtQdCJ
WpdWpR0uQsuJe7+vh3NWn59/gTc5MDlX8dS9p0ovStmNcyLhxVgmqS8ZKhsblVeu
IpQ0JgavABqibJolc3BKrVtVV1igKiX/N7Pi8RtY1K18toaMDhdEfhBRzO/XB0+P
AQhYlRjNacGcslkhXqNjK5Va4tuOAPy2n1Q8UUrHbUd0g+xJ9Bm0G0LZXyvCWyKH
kuNEHFQiLuCY6Iv0myq6iX6tjuHehZlFSh80b5BVV9tNLwNR5Eqz1klxMhoghJOA
</data>
</iq>
]]></example>
<example caption='An IBB ack'><![CDATA[
<iq from='juliet@capulet.com/balcony'
id='ls72b58f'
to='romeo@montague.net/orchard'
type='result'/>
]]></example>
</section2>
<section2 topic='Managing Multiple IBB Sessions' anchor='protocol-multi'>
<p>As IBB is defined in <cite>XEP-0047</cite>, there is one session per bytestream (which can be used in both directions). However, because Jingle-IBB provides a management layer on top of IBB, it can be used to run multiple IBB sessions over a single bytestream. This can be done by sending a transport-info message that authorizes an additional session, as shown in the following example (although this example shows the initiator adding a session, the responder could just as well do so).</p>
<example caption="Initiator adds a session to the bytestream"><![CDATA[
<iq from='romeo@montague.lit/orchard'
id='znb376s4'
to='juliet@capulet.lit/balcony'
type='set'>
<jingle xmlns='urn:xmpp:jingle:1'
action='transport-info'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='ex'>
<transport xmlns='urn:xmpp:jingle:transports:ibb:1'
block-size='2048'
sid='bt8a71h6'/>
</content>
</jingle>
</iq>
]]></example>
<p>Here the Jingle Session ID is the same ("a73sjjvkla37jfea") but the new IBB Session ID ("bt8a71h6") is different from the old IBB Session ID that is already in use ("ch3d9s71").</p>
<p>The initiator opens the second session by sending an IBB &lt;open/&gt; element, which the responder acknowledges (not shown).</p>
<example caption='Initiator sends IBB &lt;open/&gt;'><![CDATA[
<iq from='romeo@montague.net/orchard'
id='yh3vs613'
to='juliet@capulet.com/balcony'
type='set'>
<open xmlns='http://jabber.org/protocol/ibb'
block-size='2048'
sid='bt8a71h6'
stanza='iq'/>
</iq>
]]></example>
<p>The parties can then exchange data over the second session (see <cite>XEP-0047</cite>).</p>
<p>If a party wishes to close one session within a bytestream, it sends an IBB &lt;close/&gt; element as defined in <cite>XEP-0047</cite> specifying the appropriate IBB SessionID.</p>
<example caption='Ending an IBB session'><![CDATA[
<iq from='romeo@montague.net/orchard'
id='us71g45j'
to='juliet@capulet.com/balcony'
type='set'>
<close xmlns='http://jabber.org/protocol/ibb'
sid='bt8a71h6'/>
</iq>
]]></example>
<p>The receiving party then acknowledges that the IBB session has been closed by returning an IQ-result.</p>
<example caption='Success response'><![CDATA[
<iq from='juliet@capulet.com/balcony'
id='us71g45j'
to='romeo@montague.net/orchard'
type='result'/>
]]></example>
</section2>
<section2 topic='Closing the Bytestream' anchor='protocol-close'>
<p>Whenever a party is finished with a particular session within the bytestream, it SHOULD send an IBB &lt;close/&gt; as shown above. This applies to all sessions, including the last one.</p>
<p>To close the bytestream itself (e.g., because the parties have finished using all sessions associated with the bytestream), a party sends a Jingle session-terminate action as defined in <cite>XEP-0166</cite>.</p>
<example caption="Initiator terminates the session"><![CDATA[
<iq from='romeo@montague.lit/orchard'
id='hz81vf48'
to='juliet@capulet.lit/balcony'
type='set'>
<jingle xmlns='urn:xmpp:jingle:1'
action='session-terminate'
sid='a73sjjvkla37jfea'>
<reason><success/></reason>
</jingle>
</iq>
]]></example>
<p>The other party then acknowledges the session-terminate and the Jingle session is finished.</p>
<example caption="Responder acknowledges session-terminate"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
id='hz81vf48'
to='romeo@montague.lit/orchard'
type='result'/>
]]></example>
</section2>
</section1>
<section1 topic='Processing Rules and Usage Guidelines' anchor='rules'>
<p>The same processing rules and usage guidelines defined in <cite>XEP-0047</cite> apply to the Jingle IBB Transport Method.</p>
</section1>
<section1 topic='Determining Support' anchor='support'>
<p>To advertise its support for the Jingle In-Band Bytestreams Transport Method, when replying to &xep0030; information requests an entity MUST return URNs for any version of this protocol that the entity supports -- e.g., "urn:xmpp:jingle:transports:ibb:1" for this version &VNOTE;.</p>
<example caption="Service discovery information request"><![CDATA[
<iq from='romeo@montague.lit/orchard'
id='uw72g176'
to='juliet@capulet.lit/balcony'
type='get'>
<query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
]]></example>
<example caption="Service discovery information response"><![CDATA[
<iq from='juliet@capulet.lit/balcony'
id='uw72g176'
to='romeo@montague.lit/orchard'
type='result'>
<query xmlns='http://jabber.org/protocol/disco#info'>
<feature var='urn:xmpp:jingle:1'/>
<feature var='urn:xmpp:jingle:transports:ibb:1'/>
</query>
</iq>
]]></example>
<p>In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined in &xep0115;. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.</p>
</section1>
<section1 topic='Security Considerations' anchor='security'>
<section2 topic='Encryption of Media' anchor='security-media'>
<p>This specification, like <cite>XEP-0047</cite> before it, does not directly support end-to-end encryption of the media sent over the transport.</p>
</section2>
<section2 topic='Use of Base64' anchor='security-base64'>
<p>See <cite>XEP-0047</cite> for security considerations related to the use of Base64.</p>
</section2>
</section1>
<section1 topic='IANA Considerations' anchor='iana'>
<p>This document requires no interaction with &IANA;.</p>
</section1>
<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
<section2 topic='Protocol Namespaces' anchor='registrar-ns'>
<p>The &REGISTRAR; includes 'urn:xmpp:jingle:transports:ibb:1' in its registry of protocol namespaces at &NAMESPACES;, as described in Section 4 of &xep0053;.</p>
</section2>
<section2 topic='Protocol Versioning' anchor='registrar-versioning'>
&NSVER;
</section2>
<section2 topic='Jingle Transport Methods' anchor='registrar-transports'>
<p>The XMPP Registrar includes "jingle-ibb" in its registry of Jingle transport methods at &JINGLETRANSPORTS;. The registry submission is as follows.</p>
<code><![CDATA[
<transport>
<name>ibb</name>
<desc>
A method for data exchange over In-Band Bytestreams.
</desc>
<type>streaming</type>
<doc>XEP-0261</doc>
</transport>
]]></code>
</section2>
</section1>
<section1 topic='XML Schema' anchor='schema'>
<code><![CDATA[
<?xml version='1.0' encoding='UTF-8'?>
<xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='urn:xmpp:jingle:transports:ibb:1'
xmlns='urn:xmpp:jingle:transports:ibb:1'
elementFormDefault='qualified'>
<xs:annotation>
<xs:documentation>
The protocol documented by this schema is defined in
XEP-0261: http://www.xmpp.org/extensions/xep-0261.html
</xs:documentation>
</xs:annotation>
<xs:element name='transport'>
<xs:complexType>
<xs:simpleContent>
<xs:extension base='empty'>
<xs:attribute name='block-size'
type='xs:short'
use='required'/>
<xs:attribute name='sid'
type='xs:string'
use='required'/>
<xs:attribute name='stanza'
use='optional'
default='iq'>
<xs:simpleType>
<xs:restriction base='xs:NCName'>
<xs:enumeration value='iq'/>
<xs:enumeration value='message'/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:simpleType name='empty'>
<xs:restriction base='xs:string'>
<xs:enumeration value=''/>
</xs:restriction>
</xs:simpleType>
</xs:schema>
]]></code>
</section1>
<section1 topic='Acknowledgements' anchor='ack'>
<p>Thanks to Paul Aurich, Fabio Forno, and Marcus Lundblad for their feedback.</p>
</section1>
</xep>