RFC 5888 [1] defines a framework to group SDP 'm' lines for different purposes. A mapping to Jingle as an extension to Jingle (XEP-0166) [2] is defined in this document.
It is anticipated that the primary use of this is with the draft-ietf-mmusic-sdp-bundle-negotiation [3] framework used in WebRTC.
The SDP format defined in RFC 5888 is shown below.
a=group:semantics identification-tag
An example follows.
a=group:LS voice webcam
This SDP attribute is translated to Jingle as a <group/> element qualified by the 'urn:xmpp:jingle:apps:grouping:0' namespace, as shown below. The semantics is mapped to a 'semantics' attribute. The identification-tags are mapped to content elements whose name attribute is set to the identification-tag.
<group xmlns='urn:xmpp:jingle:apps:grouping:0' semantics='semantics'> <content name='identification-tag 1'/> <content name='identification-tag 2'/> </group>
An example follows.
<group xmlns='urn:xmpp:jingle:apps:grouping:0' semantics='LS'> <content name='voice'/> <content name='webcam'/> </group>
The <group/> element is included as child of the <jingle/> element.
<iq from='romeo@montague.lit/orchard'
id='rg6s5134'
to='juliet@capulet.lit/balcony'
type='set'>
<jingle xmlns='urn:xmpp:jingle:1'
action='session-initiate'
initiator='romeo@montague.lit/orchard'
sid='a73sjjvkla37jfea'>
<group xmlns='urn:xmpp:jingle:apps:grouping:0' semantics='BUNDLE'>
<content name='voice'/>
<content name='webcam'/>
</group>
<content creator='initiator' name='voice'>
[ ... ]
</content>
<content creator='initiator' name='webcam'>
[ ... ]
</content>
</jingle>
</iq>
Note: the identification-tags correspond to the <content/> 'name' attributes. These in turn map to the 'mid' attribute in SDP.
If an entity supports the grouping framework described in RFC 5888, it MUST advertise that fact in its responses to Service Discovery (XEP-0030) [4] information ("disco#info") requests by returning a feature of 'urn:ietf:rfc:5888':
<iq type='get'
from='calvin@usrobots.lit/lab'
to='herbie@usrobots.lit/home'
id='disco1'>
<query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
<iq type='result'
from='herbie@usrobots.lit/home'
to='calvin@usrobots.lit/lab'
id='disco1'>
<query xmlns='http://jabber.org/protocol/disco#info'>
<feature var='urn:xmpp:jingle:1'/>
<feature var='urn:ietf:rfc:5888'/>
</query>
</iq>
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 Entity Capabilities (XEP-0115) [5]. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.
Thanks to Emil Ivov and Lance Stout for their feedback.
The XML format for this specification originates from libjingle [6].
This document introduces no additional security considerations above and beyond those defined in the documents on which it depends.
This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [7].
This specification defines the following XML namespace:
The XMPP Registrar [8] includes the foregoing namespace to the registry located at <https://xmpp.org/registrar/namespaces.html>, as described in Section 4 of XMPP Registrar Function (XEP-0053) [9].
If the protocol defined in this specification undergoes a revision that is not fully backwards-compatible with an older version, the XMPP Registrar shall increment the protocol version number found at the end of the XML namespaces defined herein, as described in Section 4 of XEP-0053.
TODO
This document in other formats: XML PDF
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The following requirements 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".
1. RFC 5888: The Session Description Protocol (SDP) Grouping Framework <http://tools.ietf.org/html/rfc5888>.
2. XEP-0166: Jingle <https://xmpp.org/extensions/xep-0166.html>.
3. Negotiating Media Multiplexing Using the Session Description Protocol (SDP) <https://datatracker.ietf.org/doc/draft-ietf-mmusic-sdp-bundle-negotiation/>. Work in progress.
4. XEP-0030: Service Discovery <https://xmpp.org/extensions/xep-0030.html>.
5. XEP-0115: Entity Capabilities <https://xmpp.org/extensions/xep-0115.html>.
6. libjingle is now part of the WebRTC Native Code Package available from webrtc.org.
7. 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/>.
8. 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 <https://xmpp.org/registrar/>.
9. XEP-0053: XMPP Registrar Function <https://xmpp.org/extensions/xep-0053.html>.
Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/
Initial published version approved by the XMPP Council.
First draft.
END