From b3616112eaba42814ecf0b598a151cd66d7b4f96 Mon Sep 17 00:00:00 2001 From: Peter Saint-Andre Date: Wed, 21 Nov 2007 18:11:22 +0000 Subject: [PATCH] copy edit git-svn-id: file:///home/ksmith/gitmigration/svn/xmpp/trunk@1411 4b5297f7-1745-476d-ba37-a9c6900126ab --- xep-0167.xml | 329 ++++++++++++++++++++++++++++++++------------------- 1 file changed, 207 insertions(+), 122 deletions(-) diff --git a/xep-0167.xml b/xep-0167.xml index 28dc28f8..a6cb3207 100644 --- a/xep-0167.xml +++ b/xep-0167.xml @@ -111,12 +111,12 @@ -

&xep0166; can be used to initiate and negotiate a wide range of peer-to-peer sessions. One session type of interest is audio chat. This document specifies a format for negotiating Jingle audio sessions over the Realtime Transport Protocol (RTP; see &rfc3550;).

+

&xep0166; can be used to initiate and negotiate a wide range of peer-to-peer sessions. One session type of interest is audio chat. This document specifies an application format for negotiating Jingle audio sessions, where the media is exchanged over the Realtime Transport Protocol (RTP; see &rfc3550;).

The Jingle application format defined herein is designed to meet the following requirements:

    -
  1. Enable negotiation of parameters necessary for audio chat over Realtime Transport Protocol (RTP; see &rfc3550;).
    2. +
  2. Enable negotiation of parameters necessary for audio chat over Realtime Transport Protocol (RTP).
  3. Map these parameters to Session Description Protocol (SDP; see &rfc4566;) to enable interoperability.
  4. Define informational messages related to audio chat (e.g., ringing, on hold, on mute).
@@ -127,7 +127,7 @@

  • The application format negotiation process is defined in the Negotiating a Jingle Audio 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 audio session SHOULD use a lossy transport method such as &xep0177; or the "ice-udp" method specified in &xep0176;, but MAY use a reliable transport such as "ice-tcp".

    • +

  • A Jingle audio session SHOULD use a lossy transport method such as &xep0177; or the "ice-udp" method specified in &xep0176;, but MAY use a reliable transport such as "ice-tcp" if a low-bandwidth codec is employed.

  • Content is to be sent and received as follows:

      @@ -138,9 +138,26 @@ -

      A Jingle audio session is described by a content type that contains one application format and one transport method. The application format consists of one or more encodings contained within a wrapper <description/> element qualified by the 'http://www.xmpp.org/extensions/xep-0167.html#ns' namespace &NSNOTE;. In the language of RFC 4566 these encodings are payload-types; therefore, each <payload-type/> element specifies an encoding that can be used for the audio stream. In Jingle Audio, these encodings are used in the context of RTP. The most common encodings for the Audio/Video Profile (AVP) of RTP are listed in &rfc3551; (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 allowable attributes are as follows:

      - +

      A Jingle audio session is described by a content type that contains one application format and one transport method. The application format consists of one or more encodings contained within a wrapper <description/> element qualified by the 'http://www.xmpp.org/extensions/xep-0167.html#ns' namespace &NSNOTE;. 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 audio stream, as illustrated in the following example.

      + + + + + + + + + + + + + ]]> +

      The &DESCRIPTION; element is intended to be a child of a &CONTENT; element as specified in XEP-0166.

      +

      The &CONTENT; element SHOULD possess a 'profile' attribute that specifies the exact protocol in use as would be encapsulated in SDP (e.g., "RTP/AVP" or "UDP/TLS/RTP/AVP").

      +

      The encodings SHOULD be provided in order of preference by placing the most-preferred &PAYLOADTYPE; element as the first child of the &DESCRIPTION; element (etc.).

      +

      The allowable attributes of the &PAYLOADTYPE; element are as follows:

      +
      @@ -184,23 +201,7 @@
      Attribute DescriptionOPTIONAL
      -

      The encodings SHOULD be provided in order of preference.

      - - - - - - - - - - - - - ]]> -

      The &DESCRIPTION; element is intended to be a child of a &JINGLE; element as specified in XEP-0166.

      -

      The encodings SHOULD be provided in order of preference by placing the most-preferred &PAYLOADTYPE; element as the first child of the &DESCRIPTION; element (etc.).

      +

      In Jingle Audio, the encodings are used in the context of RTP. The most common encodings for the Audio/Video Profile (AVP) of RTP are listed in &rfc3551; (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 &rtpspeex;, the "cng", "mode", and "vbr" parameters may be specified in relation to usage of the Speex See <http://www.speex.org/>. codec. Where such parameters are encoded via the "fmtp" SDP attribute, they shall be represented in Jingle via the following format:

      @@ -208,11 +209,11 @@

      Note: The parameter names are effectively guaranteed to be unique, since &IANA; maintains a registry of SDP parameters (see <http://www.iana.org/assignments/sdp-parameters>).

       -

      When the initiator sends a session-initiate stanza to the receiver, the &DESCRIPTION; element includes all of the payload types that the initiator can receive for Jingle audio (each one encapsulated in a separate &PAYLOADTYPE; element):

      +

      When the initiator sends a session-initiate stanza to the responder, the &DESCRIPTION; element includes all of the payload types that the initiator can receive for Jingle audio (each one encapsulated in a separate &PAYLOADTYPE; element):

      action='session-initiate' @@ -231,30 +232,30 @@ ]]> -

      Upon receiving the session-initiate stanza, the receiver determines whether it can provisionally accept the session and proceed with the negotiation. The general Jingle error cases are specified in XEP-0166 and illustrated in the Scenarios section of this document. In addition, the receiver must determine if it supports any of the payload types advertised by the initiator; if it supports none of the offered payload types, it must reject the session by returning a ¬acceptable; error with a Jingle-Audio-specific condition of <unsupported-codecs/>:

      - 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. In addition, the responder must determine if it supports any of the payload types advertised by the initiator; if it supports none of the offered payload types, it must reject the session by returning a ¬acceptable; error with a Jingle-Audio-specific condition of <unsupported-codecs/>:

      + + type='error'> ]]> -

      If there is no error, the receiver provisionally accepts the session:

      - If there is no error, the responder acknowledges the session-initiation request.

      + ]]> -

      The receiver then should send a list of the payload types that it can receive via a Jingle "content-accept" (or "session-accept") action. The list that the receiver sends MAY include any payload types (not a subset of the payload types sent by the initiator) but SHOULD retain the ID numbers specified by the initiator. The order of the &PAYLOADTYPE; elements indicates the receiver's preferences, with the most-preferred types first.

      - The responder then should send a list of the payload types that it can receive via a Jingle "content-accept" (or "session-accept") action. The list that the responder sends MAY include any payload types (not a subset of the payload types sent by the initiator) but SHOULD retain the ID numbers specified by the initiator. The order of the &PAYLOADTYPE; elements indicates the responder's preferences, with the most-preferred types first.

      + action='content-accept' @@ -278,20 +279,31 @@

      The initiator acknowledges the 'content-accept' with an empty IQ result:

      ]]> -

      After successful transport negotiation (not shown here), the receiver then accepts the session:

      - +

      After successful transport negotiation (not shown here), the responder then accepts the session:

      + - + + + + + + + + + ]]>

      And the initiator acknowledges session acceptance:

      - ]]>

      Note: Because a "session-accept" action implicitly indicates acceptance of the application format (i.e., "content-accept"), it is not necessary to send a separate "content-accept" action. This flow is shown for completeness only.

      The following sections show a number of Jingle audio scenarios, in relative order of complexity.

      - +

      In this scenario, Romeo initiates a voice chat with Juliet but she is otherwise engaged.

      The session flow is as follows:

      ]]> - @@ -413,16 +425,16 @@ Romeo Juliet ]]> - ]]> -

      For each candidate received, the other party acknowledges receipt or returns an error:

      + - + - + ]]> -

      At the same time (i.e., immediately after provisionally accepting the session, not waiting for the initiator to begin or finish sending candidates), the responder also begins sending candidates that may work for it. As above, the initiator acknowledges receipt of the candidates.

      +

      At the same time (i.e., immediately after acknowledging the session-initation request, not waiting for the initiator to begin or finish sending candidates), the responder also begins sending candidates that may work for it. As above, the initiator acknowledges receipt of the candidates.

      As the initiator and responder receive candidates, they probe the various candidate transports for connectivity. In performing these connectivity checks, the parties follow the procedure specified in Section 7 of draft-ietf-mmusic-ice.

      -

      If one of the candidate transports is found to work, the receiver accepts the session.

      - +

      If one of the candidate transports is found to work, the responder accepts the session.

      +

      If the payload types and transport candidate can be successfully used by both parties, then the initiator acknowledges the session-accept.

      + ]]>

      The parties now begin to exchange media. In this case they would exchange audio using the Speex codec at a clockrate of 8000 since that is the highest-priority codec for the responder (as determined by the XML order of the &PAYLOADTYPE; children).

      The parties may continue the session as long as desired.

      Eventually, one of the parties terminates the session.

      -       -

      In this scenario, Romeo initiates a combined audio and video chat with Juliet using a transport method of ICE. Juliet at first refuses the video portion, then later offers to add video, which Romeo accepts. The parties also exchange various informational messages

      +

      In this scenario, Romeo initiates a combined audio and video chat with Juliet using a transport method of ICE-UDP. Juliet at first refuses the video portion, then later offers to add video, which Romeo accepts. The parties also exchange various informational messages

      The session flow is as follows:

      The protocol flow is as follows.

      + ]]> - + ]]> - ]]>

      However, Juliet doesn't want to do video because she is having a bad hair day, so she sends a "content-remove" request to Romeo.

      - +

      Romeo then acknowledges the content-remove request and, if it is acceptable, returns a content-accept:

      + ]]> + - - - - + ]]>

      The other party then acknowledges the acceptance.

      - + ]]>

      As in the previous scenario, the parties exchange ICE candidates (see above for examples).

      -

      Once the parties find candidate transports that work, the receiver accepts the session.

      - +

      Once the parties find candidate transports that work, the responder accepts the session.

      +

      As above, if the payload types and transport candidate can be successfully used by both parties, then the initiator acknowledges the session-accept.

      + ]]>

      The parties now begin to exchange media. In this case they would exchange audio using the Speex codec at a clockrate of 8000 since that is the highest-priority codec for the responder (as determined by the XML order of the &PAYLOADTYPE; children).

      -

      Juliet wants to get her hair in order so she puts Romeo on hold.

      - The parties chat for a while. Eventually Juliet wants to get her hair in order so she puts Romeo on hold.

      + ]]>

      Juliet returns so she informs Romeo that she is actively engaged in the call again.

      -

      The parties now continue the audio chat.

      Finally Juliet decides that she is presentable for a video chat so she sends a content-add request to Romeo.

      - +

      The entity receiving the content-add request then acknowledges the request and, if it is acceptable, returns a content-accept:

      + ]]> + ]]>

      The other party then acknowledges the acceptance.

      - + ]]>

      The media session proceeds. Now they would exchange both audio and video, where the audio is exchanged the Speex codec at a clockrate of 8000 and the video is exchanged using the Theora codec with a height of 720 pixels, a width of 1280 pixels, and so on.

      The parties may continue the session as long as desired.

      @@ -861,7 +921,7 @@ Romeo Juliet sid='a73sjjvkla37jfea'/> ]]>       -

      The protocol flow is as follows.

      + ]]> - ]]> - ]]>

      However, Juliet wants to make sure that the communications are encrypted, so she sends a "content-modify" request to Romeo.

      - + - + ]]>

      Romeo then acknowledges the content-modify request and, if it is acceptable, returns a content-accept:

      + ]]> + ]]>

      The other party then acknowledges the acceptance.

      - + ]]>

      As in the previous scenario, the parties exchange ICE candidates (see above for examples).

      -

      If one of the candidate transports is found to work, the receiver accepts the session.

      - +

      If one of the candidate transports is found to work, the responder accepts the session.

      +

      If the payload types and transport candidate can be successfully used by both parties, then the initiator acknowledges the session-accept.

      + ]]>

      The parties now begin to exchange media. In this case they would exchange audio using the Speex codec at a clockrate of 8000 since that is the highest-priority codec for the responder (as determined by the XML order of the &PAYLOADTYPE; children).

      The parties may continue the session as long as desired.

      Eventually, one of the parties terminates the session.

      - ]]>       -

      In the context of Jingle audio sessions, the <media> is "audio", the <port> is the preferred port for such communications (which may be determined dynamically), the <transport> is whatever profile is negotiated via the 'profile' attribute of the &CONTENT; element in the Jingle negotiation (e.g., "RTP/AVT"), and the <fmt list> is the payload-type ID.

      +

      In the context of Jingle audio sessions, the <media> is "audio", the <port> is the preferred port for such communications (which may be determined dynamically), the <transport> is whatever profile is negotiated via the 'profile' attribute of the &CONTENT; element in the Jingle negotiation (e.g., "RTP/AVP"), and the <fmt list> is the payload-type ID.

      For example, consider the following static payload-type:

      @@ -1056,7 +1139,7 @@ m=audio 9999 RTP/AVP 13 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 <payload-type/> element of the child <parameter/> element, as in the following example.

      +

      As noted, if additional parameters are to be specified, they shall be represented as attributes of the <parameter/> child of the &PAYLOADTYPE; element, as in the following example.

      @@ -1098,10 +1181,10 @@ a=fmtp:96 vbr=on;cng=on

      Note: Because the informational message is sent in an IQ-set, the receiving party MUST return either an IQ-result or an IQ-error (normally only an IQ-result to acknowledge receipt; no error flows are defined or envisioned at this time).

      - action='session-info' @@ -1111,10 +1194,10 @@ a=fmtp:96 vbr=on;cng=on ]]> - ]]> - ]]> -

      The Jingle-Audio-specific error conditions are as follows:

      - +
      @@ -1192,6 +1275,7 @@ a=fmtp:96 vbr=on;cng=on ]]> +

      Naturally, support may also be discovered by the dynamic, presence-based profile of service discovery defined in &xep0115;.

      @@ -1202,12 +1286,12 @@ a=fmtp:96 vbr=on;cng=on

      If it is necessary to send Dual Tone Multi-Frequency (DTMF) tones, it is REQUIRED to use the XML format specified &xep0181;.

      -

      When the Jingle Audio content is accepted via a 'content-accept' action, both initiator and responder SHOULD start listening for audio as defined by the negotiated transport method and audio application format. For interoperability with telephony systems, each entity SHOULD both play any audio received and send a ringing tone at this time (i.e., before the receiver sends a 'session-accept' action).

      +

      When the Jingle Audio content type is accepted via a "content-accept" action, both initiator and responder SHOULD start listening for audio as defined by the negotiated transport method and audio application format. For interoperability with telephony systems, after the responder acknowledges the session-initiate request, the responder SHOULD send a "ringing" message and both parties SHOULD play any audio received.

             -

      In order to secure the data stream, implementations SHOULD use encryption methods appropriate to the transport method and media being exchanged; for example, in the case of UDP, that would include Datagram Transport Layer Security (DTLS) as specified in &rfc4347;. draft-fishl-mmusic-sdp-dtls defines such methods for the Session Description Protocol; the relevant RTP profile (e.g., "UDP/TLS/RTP/AVP" for transporting the RTP stream over DTLS with UDP) shall be specified as the value of the &CONTENT; element's 'profile' attribute.

      +

      In order to secure the data stream, implementations SHOULD use encryption methods appropriate to the transport method and media being exchanged; for example, in the case of UDP, that would include Datagram Transport Layer Security (DTLS) as specified in &rfc4347;. The work-in-progress draft-fishl-mmusic-sdp-dtls defines such methods for the Session Description Protocol; the relevant RTP profile (e.g., "UDP/TLS/RTP/AVP" for transporting the RTP stream over DTLS with UDP) shall be specified as the value of the &CONTENT; element's 'profile' attribute.

       @@ -1252,8 +1336,9 @@ a=fmtp:96 vbr=on;cng=on - - + + +
      Jingle Audio Condition XMPP Condition