<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>
<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>
<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>
<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>
<section1topic='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 cannot be negotiated.</p>
<p>The approach taken in this specification is to use the existing IBB mechanisms described in XEP-0047 for transporting the data, and to define Jingle-specific methods only to start and end the in-band bytestream.</p>
<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>
<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. This adds a roundtrip to the negotiation and could be considered a "no-op", but the extra roundtrip is inconsequential given that the parties are exchanging base64-encoded data in-band.</p>
<p>Now the initiator can begin sending IBB packets using an IQ-set for each chunk as described in XEP-0047, where the responder will acknowledge each IQ-set in accordance with &rfc3920;.</p>
<p>Once the parties have finished using the bytestream (e.g., because a complete file has been sent), either party can send a Jingle session-terminate action.</p>
<examplecaption="Initiator terminates the session"><![CDATA[
<section1topic='Adding a Session to a Bytestream'anchor='session'>
<p>As IBB is defined in XEP-0047, there is one session per bytestream (which can be used in both directions). To extend this idea, it might be useful to run multiple 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.</p>
<examplecaption="Initiator adds a session"><![CDATA[
<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>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>
<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>
<section2topic='Encryption of Media'anchor='security-media'>
<p>A Jingle implementation SHOULD support security preconditions that are enforced before application media is allowed to flow over the bytestream, such as those described in &xtls;.</p>
<p>Upon advancement of this specification from a status of Experimental to a status of Draft, the ®ISTRAR; shall add the foregoing namespace to the registry located at &NAMESPACES;, as described in Section 4 of &xep0053;.</p>
<section2topic='Jingle Transport Methods'anchor='registrar-transports'>
<p>The XMPP Registrar shall add to its registry of Jingle transport methods a definition for the "jingle-ibb" transport method. The registry submission is as follows:</p>