Abstract: | This specification defines a Jingle application type for negotiating one or more sessions that use the Real-time Transport Protocol (RTP) to exchange media such as voice or video. The application type includes a straightforward mapping to Session Description Protocol (SDP) for interworking with SIP media endpoints. |
Authors: | Scott Ludwig, Peter Saint-Andre, Sean Egan, Robert McQueen, Diana Cionoiu |
Copyright: | © 1999 - 2012 XMPP Standards Foundation. SEE LEGAL NOTICES. |
Status: | Draft |
Type: | Standards Track |
Version: | 1.1 |
Last Updated: | 2009-12-23 |
NOTICE: The protocol defined herein is a Draft Standard of the XMPP Standards Foundation. Implementations are encouraged and the protocol is appropriate for deployment in production systems, but some changes to the protocol are possible before it becomes a Final Standard.
1. Introduction
2. Requirements
3. Jingle Conformance
4. Application Format
5. Negotiating a Jingle RTP Session
6. Mapping to Session Description Protocol
7. Negotiation of SRTP
8. Informational Messages
8.1. Active
8.2. Hold
8.3. Mute
8.4. Ringing
9. Exchanging Application Parameters
10. Determining Support
11. Scenarios
11.1. Responder is Busy
11.2. Jingle Audio via RTP, Negotiated with ICE-UDP
11.3. Jingle Audio via SRTP, Negotiated with ICE-UDP
11.4. Jingle Audio and Video via RTP, Negotiated with ICE-UDP
12. Implementation Notes
12.1. DTMF
12.2. When to Listen for Audio
13. Security Considerations
14. IANA Considerations
15. XMPP Registrar Considerations
15.1. Protocol Namespaces
15.2. Namespace Versioning
15.3. Service Discovery Features
15.4. Jingle Application Formats
16. XML Schemas
16.1. Application Format
16.2. Errors
16.3. Informational Messages
17. Acknowledgements
Appendices
A: Document Information
B: Author Information
C: Legal Notices
D: Relation to XMPP
E: Discussion Venue
F: Requirements Conformance
G: Notes
H: Revision History
Jingle [1] can be used to initiate and negotiate a wide range of peer-to-peer sessions. One session type of interest is media such as voice or video. This document specifies an application format for negotiating Jingle media sessions, where the media is exchanged over the Realtime Transport Protocol (RTP; see RFC 3550 [2]).
The Jingle application format defined herein is designed to meet the following requirements:
In accordance with Section 10 of XEP-0166, this document specifies the following information related to the Jingle RTP application type:
The application format negotiation process is defined in the Negotiating a Jingle RTP Session section of this document.
The semantics of the <description/> element are defined in the Application Format section of this document.
A mapping of Jingle semantics to the Session Description Protocol is provided in the Mapping to Session Description Protocol section of this document.
A Jingle RTP session SHOULD use a datagram transport method (e.g. Jingle Raw UDP Transport Method [4] or the "ice-udp" method specified in Jingle ICE-UDP Transport Method [5]), but MAY use a streaming transport if the end-to-end link has minimal latency and the media negotiated is not unduly heavy (e.g., it might be possible to use a streaming transport for audio, but not for video).
Jingle RTP supports two components: one for RTP itself and one for the Real Time Control Protocol (RTCP). The component numbered "1" MUST be associated with RTP and the component numbered "2" MUST be associated with RTCP. Even if an implementation does not support RTCP, it MUST accept Jingle content types that include component "2" by mirroring the second component in its replies (however, it would simply ignore the RTCP-related data during the RTP session).
Content is to be sent and received as follows:
For datagram transports, outbound content shall be encoded into RTP packets and each packet shall be sent individually over the transport. Each inbound packet received over the transport is an RTP packet.
For streaming transports, outbound content shall be encoded into RTP packets, framed in accordance with RFC 4571 [6], and sent in succession over the transport. Incoming data received over the transport shall be processed as a stream of RTP packets, where each RTP packet boundary marks the location of the next packet.
A Jingle RTP session is described by a content type that contains one application format and one transport method. Each <content/> element defines a single RTP session. A Jingle negotiation MAY result in the establishment of multiple RTP sessions (e.g., one for audio and one for video). An application SHOULD consider all of the RTP sessions that are established via the same Jingle negotiation to be synchronized for purposes of streaming, playback, recording, etc.
RTP as defined in RFC 3550 is used in the context of various "profiles" that are defined by other specifications. Jingle RTP treats RTP profiles as follows:
The application format consists of one or more encodings contained within a wrapper <description/> element qualified by the 'urn:xmpp:jingle:apps:rtp:1' namespace (see Namespace Versioning regarding the possibility of incrementing the version number). In the language of RFC 4566 each encoding is a payload-type; therefore, each <payload-type/> element specifies an encoding that can be used for the RTP stream, as illustrated in the following example.
<description xmlns='urn:xmpp:jingle:apps:rtp:1' media='audio'> <payload-type id='96' name='speex' clockrate='16000'/> <payload-type id='97' name='speex' clockrate='8000'/> <payload-type id='18' name='G729'/> <payload-type id='103' name='L16' clockrate='16000' channels='2'/> <payload-type id='98' name='x-ISAC' clockrate='8000'/> <payload-type id='102' name='iLBC'/> <payload-type id='4' name='G723'/> <payload-type id='0' name='PCMU' clockrate='16000'/> <payload-type id='8' name='PCMA'/> <payload-type id='13' name='CN'/> </description>
The <description/> element is intended to be a child of a Jingle <content/> element as specified in XEP-0166.
The <description/> element MUST possess a 'media' attribute that specifies the media type, such as "audio" or "video", where the media type SHOULD be as registered at IANA MIME Media Types Registry [11].
The <description/> element MAY possess a 'ssrc' attribute that specifies the 32-bit synchronization source for this media stream, as defined in RFC 3550.
After inclusion of one or more <payload-type/> child elements, the <description/> element MAY also contain a <bandwidth/> element that specifies the allowable or preferred bandwidth for use by this application type. The 'type' attribute of the <bandwidth/> element SHOULD be a value for the SDP "bwtype" parameter as listed in the IANA Session Description Protocol Parameters Registry [12]. For RTP sessions, often the <bandwidth/> element will specify the "session bandwidth" as described in Section 6.2 of RFC 3550, measured in kilobits per second as described in Section 5.2 of RFC 4566.
The encodings SHOULD be provided in order of preference by placing the most-preferred payload type as the first <payload-type/> child of the <description/> element and the least-preferred payload type as the last child.
The attributes of the <payload-type/> element are as follows:
Table 1: Payload-Type Attributes
Attribute | Description | Datatype | Inclusion |
---|---|---|---|
channels | The number of channels; if omitted, it MUST be assumed to contain one channel | unsignedByte (defaults to 1) | RECOMMENDED |
clockrate | The sampling frequency in Hertz | unsignedInt | RECOMMENDED |
id | The payload identifier | unsignedByte | REQUIRED |
maxptime | Maximum packet time as specified in RFC 4566 | unsignedInt | OPTIONAL |
name | The appropriate subtype of the MIME type | string | RECOMMENDED for static payload types, REQUIRED for dynamic payload types |
ptime | Packet time as specified in RFC 4566 | unsignedInt | OPTIONAL |
In Jingle RTP, the encodings are used in the context of RTP. The most common encodings for the Audio/Video Profile (AVP) of RTP are listed in RFC 3551 (these "static" types are reserved from payload ID 0 through payload ID 95), although other encodings are allowed (these "dynamic" types use payload IDs 96 to 127) in accordance with the dynamic assignment rules described in Section 3 of RFC 3551. The payload IDs are represented in the 'id' attribute.
Each <payload-type/> element MAY contain one or more child elements that specify particular parameters related to the payload. For example, as described in RFC 5574 [13], the "cng", "mode", and "vbr" parameters can be specified in relation to usage of the Speex [14] codec. Where such parameters are encoded via the "fmtp" SDP attribute, they shall be represented in Jingle via the following format:
<parameter name='foo' value='bar'/>
The order of parameter elements MUST be ignored.
Parameter names MUST be treated as case-sensitive.
Note: Parameter names are effectively guaranteed to be unique, since the Internet Assigned Numbers Authority (IANA) [15] maintains a registry of SDP parameters (see <www.iana.org/assignments/sdp-parameters>).
In general, the process for negotiating a Jingle RTP session is as follows:
Initiator Responder | | | session-initiate | |---------------------------->| | ack | |<----------------------------| | session-accept | |<----------------------------| | ack | |---------------------------->| | [optional further | | negotiation] | |<--------------------------->| | AUDIO (RTP) | |<===========================>| | |
When the initiator sends a session-initiate message to the responder, the <description/> element includes all of the payload types that the initiator can send and/or receive for Jingle RTP, each one encapsulated in a separate <payload-type/> element (the rules specified in RFC 3264 [16] SHOULD be followed regarding inclusion of payload types).
Example 1. Initiation
<iq from='romeo@montague.lit/orchard' id='ih28sx61' 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='voice'> <description xmlns='urn:xmpp:jingle:apps:rtp:1' media='audio'> <payload-type id='96' name='speex' clockrate='16000'/> <payload-type id='97' name='speex' clockrate='8000'/> <payload-type id='18' name='G729'/> <payload-type id='0' name='PCMU'/> <payload-type id='103' name='L16' clockrate='16000' channels='2'/> <payload-type id='98' name='x-ISAC' clockrate='8000'/> </description> <transport xmlns='urn:xmpp:jingle:transports:ice-udp:1' pwd='asd88fgpdd777uzjYhagZg' ufrag='8hhy'> <candidate component='1' foundation='1' generation='0' id='el0747fg11' ip='10.0.1.1' network='1' port='8998' priority='2130706431' protocol='udp' type='host'/> <candidate component='1' foundation='2' generation='0' id='y3s2b30v3r' ip='192.0.2.3' network='1' port='45664' priority='1694498815' protocol='udp' rel-addr='10.0.1.1' rel-port='8998' type='srflx'/> </transport> </content> </jingle> </iq>
Upon receiving the session-initiate stanza, the responder determines whether it can proceed with the negotiation. The general Jingle error cases are specified in XEP-0166 and illustrated in the Scenarios section of this document.
If there is no immediate error, the responder acknowledges the session initiation request.
Example 2. Responder acknowledges session-initiate
<iq from='juliet@capulet.lit/balcony' id='ih28sx61' to='romeo@montague.lit/orchard' type='result'/>
Depending on user preferences or client configuration, a user agent controlled by a human user might need to wait for the user to affirm a desire to proceed with the session before continuing. When the user agent has received such affirmation (or if the user agent can automatically proceed for any reason, e.g. because no human intervention is expected or because a human user has configured the user agent to automatically accept sessions with a given entity), it returns a Jingle session-accept message. The session-accept message SHOULD include a subset of the payload types sent by the initiator, i.e., a list of the offered payload types that the responder can send and/or receive. The list that the responder sends SHOULD retain the ID numbers specified by the initiator. The order of the <payload-type/> elements indicates the responder's preferences, with the most-preferred type first.
In the following example, we imagine that the responder supports Speex at a clockrate of 8000 but not 16000, G729, and PCMA but not PMCU. Therefore the responder returns only two payload types (since PMCA was not offered).
Example 3. Responder definitively accepts the session
<iq from='juliet@capulet.lit/balcony' id='i91fs6d5' to='romeo@montague.lit/orchard' type='set'> <jingle xmlns='urn:xmpp:jingle:1' action='session-accept' initiator='romeo@montague.lit/orchard' responder='juliet@capulet.lit/balcony' sid='a73sjjvkla37jfea'> <content creator='initiator' name='voice'> <description xmlns='urn:xmpp:jingle:apps:rtp:1' media='audio'> <payload-type id='97' name='speex' clockrate='8000'/> <payload-type id='18' name='G729'/> </description> <transport xmlns='urn:xmpp:jingle:transports:ice-udp:1' pwd='YH75Fviy6338Vbrhrlp8Yh' ufrag='9uB6'> <candidate component='1' foundation='1' generation='0' id='or2ii2syr1' ip='192.0.2.1' network='0' port='3478' priority='2130706431' protocol='udp' type='host'/> </transport> </content> </jingle> </iq>
If the responder supports none of the payload-types offered by the initiator, the responder SHOULD terminate the session and include a Jingle reason of <failed-application/>.
If the responder accepts the session, the initiator acknowledges the session-accept message:
Example 4. Initiator acknowledges session acceptance
<iq from='romeo@montague.lit/orchard' id='i91fs6d5' to='juliet@capulet.lit/balcony' type='result'/>
The initiator and responder would then attempt to establish connectivity for the data channel, Once they do, they would exchange media using any of the codecs that meet the following criteria:
The SDP media type for Jingle RTP is "audio" (see Section 8.2.1 of RFC 4566) for audio media, "video" (see Section 8.2.1 of RFC 4566) for video media, etc. The media type is reflected in the Jingle 'media' attribute.
The Jingle <bandwidth/> element SHALL be mapped to an SDP b= line; in particular, the value of the 'type' attribute SHALL be mapped to the SDP <bwtype> parameter and the XML character data of the Jingle <bandwidth/> element SHALL be mapped to the SDP <bandwidth> parameter.
If the payload type is static (payload-type IDs 0 through 95 inclusive), it MUST be mapped to an m= line as defined in RFC 4566. The generic format for this line is as follows:
m=<media> <port> <transport> <fmt list>
The SDP <media> parameter is "audio" or "video" or some other media type as specified by the Jingle 'media' attribute, the <port> parameter is the preferred port for such communications (which might be determined dynamically), the <transport> parameter corresponds to the RTP profile as described under Application Format, and the <fmt list> parameter is the payload-type ID.
For example, consider the following static payload-type:
<description xmlns='urn:xmpp:jingle:apps:rtp:1' media='audio'> <payload-type id="13" name="CN"/> </description>
That Jingle-formatted information would be mapped to SDP as follows:
m=audio 9999 RTP/AVP 13
If the payload type is dynamic (payload-type IDs 96 through 127 inclusive), it SHOULD be mapped to an SDP media field plus an SDP attribute field named "rtpmap".
For example, consider a payload of 16-bit linear-encoded stereo audio sampled at 16KHz associated with dynamic payload-type 96:
<description xmlns='urn:xmpp:jingle:apps:rtp:1' media='audio'> <payload-type id='96' name='speex' clockrate='16000'/> </description>
That Jingle-formatted information would be mapped to SDP as follows:
m=audio 9999 RTP/AVP 96 a=rtpmap:96 speex/16000
As noted, if additional parameters are to be specified, they shall be represented as attributes of the <parameter/> child of the <payload-type/> element, as in the following example.
<description xmlns='urn:xmpp:jingle:apps:rtp:1' media='audio'> <payload-type id='96' name='speex' clockrate='16000' ptime='40'> <parameter name='vbr' value='on'/> <parameter name='cng' value='on'/> </payload-type> </description>
That Jingle-formatted information would be mapped to SDP as follows:
m=audio 9999 RTP/AVP 96 a=rtpmap:96 speex/16000 a=ptime:40 a=fmtp:96 vbr=on;cng=on
The formatting is similar for video parameters, as shown in the following example.
<description xmlns='urn:xmpp:jingle:apps:rtp:1' media='video'> <payload-type id='98' name='theora' clockrate='90000'> <parameter name='height' value='600'/> <parameter name='width' value='800'/> <parameter name='delivery-method' value='inline'/> <parameter name='configuration' value='somebase16string'/> <parameter name='sampling' value='YCbCr-4:2:2'/> </payload-type> </description>
That Jingle-formatted information would be mapped to SDP as follows:
m=video 49170 RTP/AVP 98 a=rtpmap:98 theora/90000 a=fmtp:98 sampling=YCbCr-4:2:2; ; ; delivery-method=inline; configuration=somebase16string;
RFC 3711 [17] defines the Secure Real-time Transport Protocol, and RFC 4568 [18] defines the SDP "crypto" attribute for signalling and negotiating the use of SRTP in the context of offer-answer protocols such as SIP. To enable the use of SRTP and gatewaying to non-XMPP technologies that make use of the "crypto" SDP attribute, we define a corresponding <crypto/> element qualified by the 'urn:xmpp:jingle:apps:rtp:1' namespace.
If the initiator wishes to use SRTP, the session-initiate stanza shall include an <encryption/> element, which MUST contain at least one <crypto/> element and MAY include multiple instances of the <crypto/> element. The <encryption/> element MUST be a child of the <description/> element. If the initiator requires the session to be encrypted, the <encryption/> element MUST include a 'required' attribute whose logical value is TRUE and whose lexical value is "true" or "1" [19], where this attribute defaults to a logical value of FALSE (i.e., a lexical value of "false" or "0").
The <crypto/> element is defined as empty (i.e., not containing any child elements); the XML attributes of the <crypto/> element are as follows:
An example follows.
<encryption required='1'> <crypto crypto-suite='AES_CM_128_HMAC_SHA1_80' key-params='inline:WVNfX19zZW1jdGwgKCkgewkyMjA7fQp9CnVubGVz|2^20|1:32' session-params='KDR=1 UNENCRYPTED_SRTCP' tag='1'/> </encryption>
The mapping of that data to SDP is as follows.
a=crypto:1 AES_CM_128_HMAC_SHA1_80 inline:WVNfX19zZW1jdGwgKCkgewkyMjA7fQp9CnVubGVz|2^20|1:32 KDR=1 UNENCRYPTED_SRTCP
When the responder receives a session-initiate message containing an <encryption/> element, the responder MUST do one of the following:
Which of these the responder does is a matter of personal security policies or client configuration.
Example 5. Responder terminates session because of invalid crypto
<iq from='juliet@capulet.lit/balcony' id='nv71c396' to='romeo@montague.lit/orchard' type='set'> <jingle xmlns='urn:xmpp:jingle:1' action='session-terminate' initiator='romeo@montague.lit/orchard' sid='a73sjjvkla37jfea'> <reason> <security-error/> <invalid-crypto xmlns='urn:xmpp:jingle:apps:rtp:errors:1'/> </reason> </jingle> </iq>
If the responder requires encryption but the initiator did not include an <encryption/> element in its offer, the responder MUST reject the offer by sending a session-terminate message with a Jingle reason of <security-error/> and an RTP-specific condition of <crypto-required/>.
Example 6. Responder terminates session because crypto is required
<iq from='juliet@capulet.lit/balcony' id='nv71c396' to='romeo@montague.lit/orchard' type='set'> <jingle xmlns='urn:xmpp:jingle:1' action='session-terminate' initiator='romeo@montague.lit/orchard' sid='a73sjjvkla37jfea'> <reason> <security-error/> <crypto-required xmlns='urn:xmpp:jingle:apps:rtp:errors:1'/> </reason> </jingle> </iq>
If the initiator requires encryption but the responder does not include an <encryption/> element in its session acceptance, the initiator MUST terminate the session with a Jingle reason of <security-error/> and an RTP-specific condition of <crypto-required/>.
Example 7. Initiator terminates session because crypto is required
<iq from='romeo@montague.lit/orchard' id='ik3hs615' to='juliet@capulet.lit/balcony' type='set'> <jingle xmlns='urn:xmpp:jingle:1' action='session-terminate' initiator='romeo@montague.lit/orchard' sid='a73sjjvkla37jfea'> <reason> <security-error/> <crypto-required xmlns='urn:xmpp:jingle:apps:rtp:errors:1'/> </reason> </jingle> </iq>
Informational messages can be sent by either party within the context of Jingle to communicate the status of a Jingle RTP session, device, or principal. The informational message MUST be an IQ-set containing a <jingle/> element of type "session-info", where the informational message is a payload element qualified by the 'urn:xmpp:jingle:apps:rtp:info:1' namespace. The following payload elements are defined. [20]
Note: Because an informational message is sent in an IQ-set, the receiving party MUST return either an IQ-result or an IQ-error (normally an IQ-result simply to acknowledge receipt).
The <active/> payload indicates that the principal or device is again actively participating in the session after having been on mute or having put the other party on hold. The <active/> element applies to all aspects of the session, and thus does not possess a 'name' attribute.
Example 8. Responder sends active message
<iq from='juliet@capulet.lit/balcony' id='yh3gr714' to='romeo@montague.lit/orchard' type='set'> <jingle xmlns='urn:xmpp:jingle:1' action='session-info' initiator='romeo@montague.lit/orchard' sid='a73sjjvkla37jfea'> <active xmlns='urn:xmpp:jingle:apps:rtp:info:1'/> </jingle> </iq>
The <hold/> payload indicates that the principal is temporarily not listening for media from the other party. It is RECOMMENDED for the parties to handle informational <hold/> messages as follows (where the holdee is the party that receives the hold message and the holder is the party that sends the hold message):
Example 9. Responder sends hold message
<iq from='juliet@capulet.lit/balcony' id='xv39z423' to='romeo@montague.lit/orchard' type='set'> <jingle xmlns='urn:xmpp:jingle:1' action='session-info' initiator='romeo@montague.lit/orchard' sid='a73sjjvkla37jfea'> <hold xmlns='urn:xmpp:jingle:apps:rtp:info:1'/> </jingle> </iq>
When the holder wishes to end the hold state, it sends an informational payload of <unhold/> or <active/>.
Example 10. Responder ends the hold state
<iq from='juliet@capulet.lit/balcony' id='br81gd63' to='romeo@montague.lit/orchard' type='set'> <jingle xmlns='urn:xmpp:jingle:1' action='session-info' initiator='romeo@montague.lit/orchard' sid='a73sjjvkla37jfea'> <unhold xmlns='urn:xmpp:jingle:apps:rtp:info:1'/> </jingle> </iq>
The <mute/> payload indicates that the principal is temporarily not sending media to the other party but continuing to accept media from the other party. The <mute/> element MAY possess a 'name' attribute whose value specifies a particular session to be muted (e.g., muting the audio aspect but not the video aspect of a voice+video chat). If no 'name' attribute is included, the recipient MUST assume that all sessions are to be muted.
Example 11. Responder sends mute message
<iq from='juliet@capulet.lit/balcony' id='hg4891f5' to='romeo@montague.lit/orchard' type='set'> <jingle xmlns='urn:xmpp:jingle:1' action='session-info' initiator='romeo@montague.lit/orchard' sid='a73sjjvkla37jfea'> <mute xmlns='urn:xmpp:jingle:apps:rtp:info:1' creator='responder' name='voice'/> </jingle> </iq>
To end the mute state, the party sends an informational payload of <unmute/> or <active/>.
Example 12. Responder ends the mute state
<iq from='juliet@capulet.lit/balcony' id='ms91g47c' to='romeo@montague.lit/orchard' type='set'> <jingle xmlns='urn:xmpp:jingle:1' action='session-info' initiator='romeo@montague.lit/orchard' sid='a73sjjvkla37jfea'> <unmute xmlns='urn:xmpp:jingle:apps:rtp:info:1' creator='responder' name='voice'/> </jingle> </iq>
The <ringing/> payload indicates that the device is ringing but the principal has not yet interacted with it to answer (this maps to the SIP 180 response code).
Example 13. Responder sends ringing message
<iq from='juliet@capulet.lit/balcony' id='tgr515bt' to='romeo@montague.lit/orchard' type='set'> <jingle xmlns='urn:xmpp:jingle:1' action='session-info' initiator='romeo@montague.lit/orchard' sid='a73sjjvkla37jfea'> <ringing xmlns='urn:xmpp:jingle:apps:rtp:info:1'/> </jingle> </iq>
Before or during an RTP session, either party can share suggested application parameters with the other party by sending a Jingle stanza with an action of "description-info". The stanza shall contain only a <description/> element, which specifies suggested parameters for a given application type (e.g., a change to the height and width for display of a video stream). An example follows.
Example 14. Entity sends application parameters
<iq from='romeo@montague.lit/orchard' id='pq6x5v37' to='juliet@capulet.lit/balcony' type='set'> <jingle xmlns='urn:xmpp:jingle:1' action='description-info' initiator='romeo@montague.lit/orchard' sid='a73sjjvkla37jfea'> <content creator='initiator' name='webcam'> <description xmlns='urn:xmpp:jingle:apps:rtp:1' media='video'> <payload-type id='98' name='theora' clockrate='90000'> <parameter name='height' value='768'/> <parameter name='width' value='1024'/> </payload-type> </description> </content> </jingle> </iq>
The description-info message SHOULD include only the modified codecs, not the complete set of codecs (if those codecs have not changed). Their order is NOT meaningful. Furthermore, the data provided is purely advisory; the session SHOULD NOT fail if the receiving party cannot adjust its parameters accordingly.
To advertise its support for Jingle RTP Sessions and specific media types for RTP, when replying to Service Discovery [21] information requests an entity MUST return the following features:
An example follows.
Example 15. Service discovery information request
<iq from='romeo@montague.lit/orchard' id='bh3vd715' to='juliet@capulet.lit/balcony' type='get'> <query xmlns='jabber.org/protocol/disco#info'/> </iq>
Example 16. Service discovery information response
<iq from='juliet@capulet.lit/balcony' id='bh3vd715' to='romeo@montague.lit/orchard' type='result'> <query xmlns='jabber.org/protocol/disco#info'> <feature var='urn:xmpp:jingle:1'/> <feature var='urn:xmpp:jingle:apps:rtp:0'/> <feature var='urn:xmpp:jingle:apps:rtp:1'/> <feature var='urn:xmpp:jingle:apps:rtp:audio'/> <feature var='urn:xmpp:jingle:apps:rtp:video'/> </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 [23]. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.
The following sections show a number of Jingle RTP scenarios, roughly in order of increasing complexity.
In this scenario, Romeo initiates a voice chat with Juliet but she is otherwise engaged.
The session flow is as follows:
Romeo Juliet | | | session-initiate | |---------------------------->| | ack | |<----------------------------| | terminate | | (reason = busy) | |<----------------------------| | ack | |---------------------------->| | |
The protocol flow is as follows.
Example 17. Initiator sends session-initiate
<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'> <content creator='initiator' name='voice'> <description xmlns='urn:xmpp:jingle:apps:rtp:1' media='audio'> <payload-type id='96' name='speex' clockrate='16000'/> <payload-type id='97' name='speex' clockrate='8000'/> <payload-type id='18' name='G729'/> <payload-type id='103' name='L16' clockrate='16000' channels='2'/> <payload-type id='98' name='x-ISAC' clockrate='8000'/> </description> <transport xmlns='urn:xmpp:jingle:transports:ice-udp:1' pwd='asd88fgpdd777uzjYhagZg' ufrag='8hhy'> <candidate component='1' foundation='1' generation='0' id='el0747fg11' ip='10.0.1.1' network='1' port='8998' priority='2130706431' protocol='udp' type='host'/> <candidate component='1' foundation='2' generation='0' id='y3s2b30v3r' ip='192.0.2.3' network='1' port='45664' priority='1694498815' protocol='udp' rel-addr='10.0.1.1' rel-port='8998' type='srflx'/> </transport> </content> </jingle> </iq>
Example 18. Responder acknowledges session-initiate
<iq from='juliet@capulet.lit/balcony' id='rg6s5134' to='romeo@montague.lit/orchard' type='result'/>
However, the responder immediately terminates the session.
Example 19. R