diff --git a/xep-0176.xml b/xep-0176.xml index 4a3eaa33..7ee368c0 100644 --- a/xep-0176.xml +++ b/xep-0176.xml @@ -8,7 +8,7 @@
- Jingle ICE Transport + Jingle ICE Transport Methods This document defines a Jingle transport method that results in sending data between two entities using the Interactive Connectivity Establishment (ICE) methodology. &LEGALNOTICE; 0176 @@ -28,6 +28,12 @@ &scottlu; &hildjj; &seanegan; + + 0.11 + 2007-11-27 + psa +

Further editorial review; also added sections on modification of existing candidates and exchange of subsequent candidates.

 + 0.10 2007-11-15 @@ -90,14 +96,20 @@
-

Note: This document depends on the IETF's specifications for &ice; and &ice-tcp; (the former has been approved but the latter is still a work in progress). Every effort has been made to keep this document synchronized with draft-ietf-mmusic-ice and draft-ietf-mmusic-ice-tcp. The interested reader is referred to &icecore; for a detailed description of the ICE methodology, which for the most part this document merely maps to XMPP syntax.

-

&xep0166; defines a framework for negotiating and managing out-of-band 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 two transport methods (ice-udp and ice-tcp) for establishing and managing data connections between XMPP entities, using the ICE methodology developed within the IETF. The ice-udp method results in a lossy transport suitable for use in media applications where some packet loss is tolerable (e.g., audio and video), whereas the ice-tcp method results in a reliable transport suitable for use in applications where packet loss is not tolerable (e.g., file transfer).

+

&xep0166; defines a framework for negotiating and managing out-of-band 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 two transport methods for establishing and managing data connections between XMPP entities, using the ICE methodology developed within the IETF:

+
    +

  1. The ice-udp method is an XMPP profile of the core ICE methodology specified in &ice;. The IETF specification in question, hereafter referred to as &icecore;, has been approved for publication as an RFC but has not yet been so published. Use of the ice-udp method results in a lossy transport suitable for media applications where some packet loss is tolerable (e.g., audio and video).

    2. +

  2. The ice-tcp method is an XMPP profile of the ICE methodology as applied to TCP and specified in &ice-tcp;, hereafter referred to as &icetcp;. The IETF specification in question is still a work in progress. Use of the ice-tcp method results in a reliable transport suitable applications where packet loss is not tolerable (e.g., file transfer).

    3. +

The process for ICE negotiation is largely the same in Jingle as it is in ICE. There are several differences:

+

Note: This document depends the &icecore; and &icetcp; specifications developed by the IETF. While every effort has been made to keep this document synchronized with &icecore; and &icetcp;, the interested reader is referred to &icecore; for a detailed description of the ICE methodology.

The reader is referred to &icecore; and &icetcp; for a description of various terms used in the context of ICE. Those terms are not reproduced here.

@@ -124,12 +136,12 @@

In order for the initiator in a Jingle exchange to start the negotiation, it MUST send a Jingle "session-initiate" stanza as described in XEP-0166. A content type MUST include one transport method. If the initiator wishes to negotiate the ice-udp or ice-tcp transport for an application format, it MUST include an empty &TRANSPORT; child element qualified by the 'http://www.xmpp.org/extensions/xep-0176.html#ns-udp' or 'http://www.xmpp.org/extensions/xep-0176.html#ns-tcp' namespace &NSNOTE;.

- @@ -142,47 +154,33 @@ ]]> - -

As described in XEP-0166, to provisionally accept the session initiation request, the responder returns an IQ-result:

- +

As described in XEP-0166, to acknowledge receipt of the session initiation request, the responder returns an IQ-result:

+ ]]> -

If the responder provisionally accepts the session initiation request as shown above, both initiator and responder MUST immediately negotiate connectivity over the ICE transport by exchanging XML-formatted candidate transports for the channel. This negotiation proceeds immediately in order to maximize the possibility that media can be exchanged as quickly as possible. Concurrent with negotiation of the ICE candidates, it is possible for the initiator and responder to negotiate which content types the session will include, which transport methods will be tried for each content type, etc. Those negotiation flows are shown in XEP-0166. This document specifies only negotiation of the ICE transport method.

-

Note: In order to expedite session establishment, the initiator MAY send transport candidates immediately after sending the "session-initiate" message and before receiving acknowledgement from the receiver (i.e., the initiator MUST consider the session to be live even before receiving acknowledgement). Given in-order delivery, the receiver should receive such "transport-info" messages after receiving the "session-initiate" message; if not, it is appropriate for the receiver to return <unknown-session/> errors since it according to its state machine the session does not exist. If either party receives an <unknown-session/> from the other party, it MUST terminate the negotiation and the session.

+

Once the responder acknowledges receipt of the session initiation request as shown above, both initiator and responder MUST immediately negotiate connectivity over the ICE transport by exchanging XML-formatted candidate transports for the channel. This negotiation proceeds immediately in order to maximize the possibility that media can be exchanged as quickly as possible. Concurrent with negotiation of the ICE candidates, it is possible for the initiator and responder to negotiate which content types the session will include, which transport methods will be tried for each content type, etc. Those negotiation flows are shown in other specifications, such as XEP-0166. This document specifies only negotiation of the ICE transport method.

+

Note: In order to expedite session establishment, the initiator MAY send transport candidates immediately after sending the "session-initiate" message and before receiving acknowledgement from the responder (i.e., the initiator MUST consider the session to be live even before receiving acknowledgement). Given in-order delivery, the responder should receive such "transport-info" messages after receiving the "session-initiate" message; if not, it is appropriate for the responder to return <unknown-session/> errors since it according to its state machine the session does not exist. If either party receives an <unknown-session/> from the other party, it MUST terminate the negotiation and the session.

The candidate syntax and negotiation flow are described below. (This document shows negotiation for the ice-udp transport method, but the same principles apply to the ice-tcp transport method.)

The following is an example of the candidate format:

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

The attributes of the <candidate/> element are described in the following table:

@@ -266,14 +264,14 @@

The first step in negotiating connectivity is for both parties to immediately begin sending candidate transport methods to the other client. The fact that both parties send candidates means that Jingle requires each party to be a full implementation of ICE, not a "lite" implementation as specified in &icecore;. These candidates SHOULD be gathered by following the procedure specified in Section 4.1.1 of &icecore; and prioritized by following the procedure specified in Section 4.1.2 of &icecore;. Each candidate MUST be sent in a &JINGLE; element with an action of "transport-info".

If the responder receives and can successfully process a given candidate, it returns an IQ-result (if not, for example because the candidate data is improperly formatted, it returns an error). Note: The responder is only indicating receipt of the candidate, not telling the initiator that the candidate will be used.

The initiator keeps sending candidates, one after the other (without stopping to receive an acknowledgement of receipt from the responder for each candidate) until it has exhausted its supply of possible or desirable candidate transports. (Because certain candidates may be more "expensive" in terms of bandwidth or processing power, the initiator may not want to advertise their existence unless necessary.) For each candidate, the responder acknowledges receipt.

-

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 receipt of the session-initiate request, not waiting for the initiator to begin or finish sending candidates), the responder also begins sending potential candidates, in order of desirability according to the responder. 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, a client SHOULD follow the procedure specified in Section 7 of &icecore;.

- @@ -281,11 +279,11 @@ ]]> - ]]> -

For each candidate received, the other party MUST acknowledge receipt or return an error:

+ - + - + ]]> -

If, based on STUN connectivity checks, the responder determines that it will be able to establish a connection using a given candidate, it sends a &JINGLE; element with an action of 'content-accept' (or 'session-accept') to the initiator, specifying the candidate that succeeded:

+

If, based on STUN connectivity checks (see &rfc3489; and &rfc3489bis;), the responder determines that it will be able to establish a connection using a given candidate, it sends a &JINGLE; element with an action of 'content-accept' (or 'session-accept') to the initiator, specifying the candidate that succeeded:

+ + [ ... ] + ]]> -

The &JINGLE; element in the content-accept stanza SHOULD possess a 'responder' attribute that explicitly specifies the full JID of the responding entity. If the 'responder' attribute is provided, all future commmunications SHOULD be sent to the JID provided in the 'responder' attribute.

+

The &JINGLE; element in the content-accept or session-accept stanza SHOULD possess a 'responder' attribute that explicitly specifies the full JID of the responding entity. If the 'responder' attribute is provided, all future commmunications SHOULD be sent to the JID provided in the 'responder' attribute.

If the initiator can also send data over that candidate, then it acknowledges the responder's acceptance:

]]>

Now the initiator and responder can begin sending data over the negotiated connection.

If a candidate succeeded for the responder but the initiator cannot send data over that candidate, it MUST return a ¬acceptable; error in response to the responder's acceptance of the successful candidate:

@@ -411,6 +421,161 @@ ]]>

If the responder cannot find a suitable candidate transport or it receives a ¬acceptable; error from the initiator in response to its acceptance of a suitable transport, it SHOULD terminate the session as described in Section 6.8 of XEP-0166.

 + +

The creator of a content type MAY modify an existing, in-use candidate at any time during the session, for example to change the IP address or port. This is done by sending a content-modify action with the changed candidate information, where the value of the 'generation' is incremented to specify that the candidate information is a modification to an existing candidate.

+

An example follows (change to IP address and port).

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

The recipient then acknowledges receipt.

+ + ]]> +

If the modification is acceptable, the recipient then sends a content-accept action.

+ + + + + [ ... ] + + + + + + + + ]]> +

The initiator then acknowledges the responder's acceptance:

+ + ]]> +

The parties then use the modified candidate in subsequent communications.

+ + +

Even after content acceptance or session acceptance, either party MAY continue to send additional candidates to the other party (e.g., because the user agent has become aware of a new media proxy or NIC). As above, such candidates are shared by sending a transport-info action.

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

The receiving party MUST acknowledge receipt of the candidate.

+ + ]]> +

The receiving party SHOULD check the newly-offered candidate for connectivity, as above. If the candidate is acceptable, the receiving party shall send a content-accept action.

+ + + + + [ ... ] + + + + + + + + ]]> +

The other party then acknowledges the content-accept.

+ + ]]> +

The parties then use the new candidate in subsequent communications.

+ @@ -456,10 +621,11 @@ ]]> +

Naturally, support MAY also be determined via the dynamic, presence-based profile of Service Discovery defined in &xep0115;.

 -

In order to speed the negotiation process so that media can flow as quickly as possible, the initiatior should gather and priorities candidates in advance or as soon as the principal begins the process of initiating a session.

+

In order to speed the negotiation process so that media can flow as quickly as possible, the initiatior should gather and prioritize candidates in advance or as soon as the principal begins the process of initiating a session.

 @@ -484,9 +650,9 @@ ice-tcp - A method for negotiation of out-of-band TCP connections with built-in NAT - and firewall traversal, equivalent to the IETF's Interactive Connectivity - Establishment (ICE) methodology when resulting in the use of TCP as the + A method for negotiation of out-of-band TCP connections with built-in NAT + and firewall traversal, equivalent to the IETF's Interactive Connectivity + Establishment (ICE) methodology when resulting in the use of TCP as the transport protocol. reliable @@ -496,8 +662,8 @@ ice-udp - A method for negotiation of out-of-band UDP connections with built-in NAT - and firewall traversal, equivalent to the IETF's Interactive Connectivity + A method for negotiation of out-of-band UDP connections with built-in NAT + and firewall traversal, equivalent to the IETF's Interactive Connectivity Establishment (ICE) methodology when resulting in the use of UDP as the transport protocol.