<?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 <open/> and <close/> 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 <open/> 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 <open/> 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 <open/> element, with the same 'block-size' and 'sid' values as for the Jingle <transport/> element it negotiated with the recipient (i.e., if the recipient sent a modified <transport/> 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 <open/>'><![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 <open/>'><![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 <open/> 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 <open/> element, which the responder acknowledges (not shown).</p> <example caption='Initiator sends IBB <open/>'><![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 <close/> 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 <close/> 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 ®ISTRAR; 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>