&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 a transport method for establishing and managing data exchanges between XMPP entities by means of the Interactive Connectivity Establishment (ICE) methodology specified in &rfc5245;. The Jingle usage of ICE was also the first technology to send ICE candidates incrementally, a technique that has since become known as "Trickle ICE" &trickle;.
-The process for ICE negotiation is largely the same in Jingle as it is in RFC 5245. There are several differences:
+The current document defines a transport method for establishing and managing data exchanges between XMPP entities by means of the Interactive Connectivity Establishment (ICE) methodology specified in &rfc8445;. The Jingle usage of ICE was also the first technology to send ICE candidates incrementally, a technique that has since become known as "Trickle ICE" &trickle;.
+The process for ICE negotiation is largely the same in Jingle as it is in &rfc8445;. There are several differences:
As originally defined in XEP-0166 and then &xep0176; the use of ICE in Jingle applied only to negotiations that established a User Datagram Protocol association (see &rfc0768;) and thus resulted in a Jingle datagram transport suitable for media applications where some packet loss is tolerable (e.g., audio and video). However, since the publication of &rfc6544; in 2012 it has also been possible to exchange Transmission Control Protocol (see &rfc0793;) candidates during ICE negotiation. Therefore this document expands the use of ICE in Jingle to also establish a TCP connection and thus result in a Jingle stream transport suitable for media applications where packet loss cannot be tolerated (e.g., file transfer). To reduce the possibility of confusion, the expanded definition provided here is specified in a new XEP, which is intended to supersede XEP-0176.
The reader is referred to RFC 5245 and draft-ietf-ice-trickle for a description of various terms used in the context of ICE. Those terms are not reproduced here.
+The reader is referred to &rfc8445; and draft-ietf-ice-trickle for a description of various terms used in the context of ICE. Those terms are not reproduced here.
The Jingle transport method defined herein is designed to meet the following requirements:
@@ -134,7 +150,7 @@ INITIATOR RESPONDER |<------------------------------------>| | | ]]> -Note: The examples in this document follow the scenario described in Section 17 of RFC 5245, except that we substitute the Shakespearean characters "Romeo" and "Juliet" for the generic entities "L" and "R".
+Note: The examples in this document follow the scenario described in Section 15 of &rfc8445;, except that we substitute the Shakespearean characters "Romeo" and "Juliet" for the generic entities "L" and "R".
In order for the initiator in a Jingle exchange to start the negotiation, it sends a Jingle "session-initiate" stanza that includes at least one content type, as described in XEP-0166. If the initiator wishes to negotiate the ICE transport method for an application format, it MUST include a &TRANSPORT; child element qualified by the 'urn:xmpp:jingle:transports:ice:0' namespace &VNOTE;. This element SHOULD in turn contain one &CANDIDATE; element for each of the initiator's higher-priority transport candidates as determined in accordance with the ICE methodology, but MAY instead be empty (with each candidate to be sent as the payload of a transport-info message).
@@ -158,7 +174,8 @@ INITIATOR RESPONDERThe &TRANSPORT; element's 'pwd' and 'ufrag' attributes MUST be included whenever sending one or more candidates to the other party, e.g., in a session-initiate, session-accept, transport-info, content-add, or transport-replace message. The values for these attributes are separately generated for both the initiator and the responder, in accordance with RFC 5245 and as shown in the examples. The attributes of the <transport/> element are as follows.
+The &TRANSPORT; element's 'pwd' and 'ufrag' attributes MUST be included whenever sending one or more candidates to the other party, e.g., in a session-initiate, session-accept, transport-info, content-add, or transport-replace message. The values for these attributes are separately generated for both the initiator and the responder, in accordance with &rfc8445; and as shown in the examples.
+'ice2' attribute tells about compliancy with &rfc8445;. If the attribute is not set or set to 'false' in &TRANSPORT; element, the recipient can assume &rfc5245;. The value of the attribute may not be changed during lifetime of the transport instance, but it's not an error to skip the attribute in consequent transport-info updates.
+The attributes of the <transport/> element are as follows.
| Name | @@ -198,16 +217,22 @@ INITIATOR RESPONDER||||
|---|---|---|---|---|
| pwd | -A Password as defined in RFC 5245. | +A Password as defined in &rfc8445;. | a=ice-pwd line | asd88fgpdd777uzjYhagZg |
| ufrag | -A User Fragment as defined in RFC 5245. | +A Username Fragment as defined in &rfc8445;. | a=ice-ufrag line | 8hhy |
| ice2 | +ice2 option as defined in &rfc8445;. | +a=ice-options:ice2 | +true | +
The attributes of the <candidate/> element are as follows.
| component | -A Component ID as defined in RFC 5245. | +A Component ID as defined in &rfc8445;. | Component ID value in a=candidate line | 1 |
| foundation | -A Foundation as defined in RFC 5245. (Note that version 1.0 of this specification container an error, whereby the data type for the Jingle 'foundation' attribute was defined as xs:unsignedByte; in version 1.1 this was corrected to xs:string, however some existing implementations might not use or expect strings.) | +A Foundation as defined in &rfc8445;. (Note that version 1.0 of this specification container an error, whereby the data type for the Jingle 'foundation' attribute was defined as xs:unsignedByte; in version 1.1 this was corrected to xs:string, however some existing implementations might not use or expect strings.) | Foundation value in a=candidate line | 2B78DADC1A9E |
| priority | -A Priority as defined in RFC 5245.
- | A Priority as defined in &rfc8445;.
+ |
Priority value in a=candidate line | 2130706431 |
| protocol | -The protocol to be used. The values allowed by this specification are "udp" (see RFC 5245) and "tcp" (see RFC 6455). | +The protocol to be used. The values allowed by this specification are "udp" (see &rfc8445;) and "tcp" (see &rfc6544;). | Transport protocol field in a=candidate line | udp |
| rel-addr | -A related address as defined in RFC 5245. | +A related address as defined in &rfc8445;. | Value of raddr attribute in a=candidate line | 10.0.1.1 |
| rel-port | -A related port as defined in RFC 5245. | +A related port as defined in &rfc8445;. | Value of rport attribute in a=candidate line | 8998 |
| tcptype | -A TCP candidate type as defined in RFC 6455. The allowable values are "active" for TCP active candidates, "passive" for TCP passive candidates, and "so" for TCP simultaneous-open candidates. | +A TCP candidate type as defined in &rfc6544;. The allowable values are "active" for TCP active candidates, "passive" for TCP passive candidates, and "so" for TCP simultaneous-open candidates. | Value of tcptype attribute in a=candidate line | so |
| type | -An ICE candidate type as defined in RFC 5245. The allowable values are "host" for host candidates, "prflx" for peer reflexive candidates, "relay" for relayed candidates, and "srflx" for server reflexive candidates. Note that TCP candidate types (RFC 6455) are handled via the 'tcptype' attribute. | +An ICE candidate type as defined in &rfc8445;. The allowable values are "host" for host candidates, "prflx" for peer reflexive candidates, "relay" for relayed candidates, and "srflx" for server reflexive candidates. Note that TCP candidate types (&rfc6544;) are handled via the 'tcptype' attribute. | Value of typ attribute in a=candidate line | srflx |
Note this specification does not provide an equivalent of the "ice-options" attribute defined in Section 15.5 of RFC 5245, since it is not needed in XMPP given the existence of the Service Discovery extension (XEP-0030).
As described in XEP-0166, to acknowledge receipt of the session initiation request, the responder immediately returns an IQ-result.
@@ -346,90 +370,153 @@ INITIATOR RESPONDERThe initiator and responder negotiate connectivity over ICE by exchanging XML-formatted transport candidates for the channel. This negotiation proceeds immediately in order to maximize the possibility that connectivity can be established (and therefore media can be exchanged) as quickly as possible. In order to expedite session establishment, the initiator SHOULD include transport candidates in its session-initiate message but MAY also send additional transport candidates as soon as it learns of them, even before receiving the IQ-result that acknowledges the session-initiate message (i.e., the initiator MUST consider the session to be live as soon as it sends the session-initiate message).
The first step in negotiating connectivity is for each party to send transport candidates to the other party.
The first step in negotiating connectivity is for each party to send transport candidates to the other party.
Each candidate shall be sent as a <candidate/> child of a &TRANSPORT; element qualified by the 'urn:xmpp:jingle:transports:ice:0' namespace. The &TRANSPORT; element is sent via a Jingle message of type session-initiate, session-accept, or transport-info.
Either party MAY include multiple <candidate/> elements in one &TRANSPORT; element, especially in the session-initiate and session-accept messages sent at the beginning of the session negotiation. Including multiple candidates in the session-initiate and session-accept messages can help to ensure interoperability with entities that implement the SDP offer/answer model described in RFC 3264; in particular, an entity SHOULD include multiple candidates in its session-initiate or session-accept message if the other party advertises support for the "urn:ietf:rfc:3264" service discovery feature as described in the SDP Offer / Answer Support section of this document. However, including one candidate per subsequent transport-info message typically results in a faster negotiation because the candidates most likely to succeed are sent first (in the session-info and session-accept messages) and it is not necessary to gather all candidates before beginning to send any candidates; furthermore, because certain candidates can be more "expensive" in terms of bandwidth or processing power, either party might not want to advertise the existence of such candidates unless it is necessary to do so after other candidates have failed.
If the party that receives a candidate in a Jingle message can successfully process a given candidate or set of candidates, it returns an IQ-result (if not, for example because the candidate data is improperly formatted, it returns an IQ-error). At this point, the receiving entity is only indicating receipt of the candidate or set of candidates, not telling the other party that the candidate will be used.
The initiator can keep sending candidates (without stopping to receive an acknowledgement of receipt from the responder for each candidate) until it has exhausted its supply of possible or desirable transport candidates. The responder can also keep sending potential candidates, which the initiator will acknowledge.
As the initiator and responder receive candidates, they probe the candidates for connectivity. In performing these connectivity checks, each party SHOULD follow the procedure specified in Section 7 of RFC 5245. The following business rules apply:
+As the initiator and responder receive candidates, they probe the candidates for connectivity. In performing these connectivity checks, each party SHOULD follow the procedure specified in Section 7 of &rfc8445;. The following business rules apply:
When it receives a STUN Binding Request, each party MUST return a STUN Binding Response, which indicates either an error case or the success case. As described in Section 7.1.2.2 of RFC 5245, a connectivity check succeeds if all of the following are true:
+When it receives a STUN Binding Request, each party MUST return a STUN Binding Response, which indicates either an error case or the success case. As described in Section 7.2.5.3 of &rfc8445;, a connectivity check succeeds if all of the following are true:
For the candidates exchanged in the previous section, the connectivity checks would be as follows (this diagram mirrors the example in RFC 5245).
+For the candidates exchanged in the previous section, the connectivity checks would be as follows (this diagram mirrors the example from section 15.1 of &rfc8445;).
| |
- | | STUN Binding Request |
- | | from 192.0.2.3:45664 |
- | | to 192.0.2.1:3478 |
- | | USE-CANDIDATE |
- | |======================>|
- | | STUN Binding Response |
- | | from 192.0.2.1:3478 |
- | | to 192.0.2.3:45664 |
- | |<======================|
- | STUN Binding Response | |
- | from 192.0.2.1:3478 | |
- | to 10.0.1.1:8998 | |
- | map 192.0.2.3:45664 | |
- |<======================| |
- | | |
- |<==Media Now Can Flow==| |
- | | |
- | | STUN Binding Request |
- | | from 192.0.2.1:3478 |
- | | to 192.0.2.3:45664 |
- | |<======================|
- | STUN Binding Request | |
- | from 192.0.2.1:3478 | |
- | to 10.0.1.1:8998 | |
- |<======================| |
- | STUN Binding Response | |
- | from 10.0.1.1:8998 | |
- | to 192.0.2.1:3478 | |
- | map 192.0.2.1:3478 | |
- |======================>| |
- | | STUN Binding Response |
- | | from 192.0.2.3:45664 |
- | | to 192.0.2.1:3478 |
- | | map 192.0.2.1:3478 |
- | |======================>|
- | | |
- | |==Media Now Can Flow==>|
- | | |
+ENTITY IP Address Mnemonic name
+ --------------------------------------------------
+ ICE Agent L (Initiator): 10.0.1.1 L-PRIV-1
+ ICE Agent R (Responder): 192.0.2.1 R-PUB-1
+ STUN Server: 192.0.2.2 STUN-PUB-1
+ NAT (Public): 192.0.2.3 NAT-PUB-1
+
+
+ L NAT STUN R
+ |STUN alloc. | | |
+ |(1) STUN Req | | |
+ |S=$L-PRIV-1 | | |
+ |D=$STUN-PUB-1 | | |
+ |------------->| | |
+ | |(2) STUN Req | |
+ | |S=$NAT-PUB-1 | |
+ | |D=$STUN-PUB-1 | |
+ | |------------->| |
+ | |(3) STUN Res | |
+ | |S=$STUN-PUB-1 | |
+ | |D=$NAT-PUB-1 | |
+ | |MA=$NAT-PUB-1 | |
+ | |<-------------| |
+ |(4) STUN Res | | |
+ |S=$STUN-PUB-1 | | |
+ |D=$L-PRIV-1 | | |
+ |MA=$NAT-PUB-1 | | |
+ |<-------------| | |
+ |(5) L's Candidate Information| |
+ |------------------------------------------->|
+ | | | | STUN
+ | | | | alloc.
+ | | |(6) STUN Req |
+ | | |S=$R-PUB-1 |
+ | | |D=$STUN-PUB-1 |
+ | | |<-------------|
+ | | |(7) STUN Res |
+ | | |S=$STUN-PUB-1 |
+ | | |D=$R-PUB-1 |
+ | | |MA=$R-PUB-1 |
+ | | |------------->|
+ |(8) R's Candidate Information| |
+ |<-------------------------------------------|
+ | | (9) Bind Req |Begin
+ | | S=$R-PUB-1 |Connectivity
+ | | D=$L-PRIV-1 |Checks
+ | | <-------------------|
+ | | Dropped |
+ |(10) Bind Req | | |
+ |S=$L-PRIV-1 | | |
+ |D=$R-PUB-1 | | |
+ |------------->| | |
+ | |(11) Bind Req | |
+ | |S=$NAT-PUB-1 | |
+ | |D=$R-PUB-1 | |
+ | |---------------------------->|
+ | |(12) Bind Res | |
+ | |S=$R-PUB-1 | |
+ | |D=$NAT-PUB-1 | |
+ | |MA=$NAT-PUB-1 | |
+ | |<----------------------------|
+ |(13) Bind Res | | |
+ |S=$R-PUB-1 | | |
+ |D=$L-PRIV-1 | | |
+ |MA=$NAT-PUB-1 | | |
+ |<-------------| | |
+ |Data | | |
+ |===========================================>|
+ | | | |
+ | |(14) Bind Req | |
+ | |S=$R-PUB-1 | |
+ | |D=$NAT-PUB-1 | |
+ | |<----------------------------|
+ |(15) Bind Req | | |
+ |S=$R-PUB-1 | | |
+ |D=$L-PRIV-1 | | |
+ |<-------------| | |
+ |(16) Bind Res | | |
+ |S=$L-PRIV-1 | | |
+ |D=$R-PUB-1 | | |
+ |MA=$R-PUB-1 | | |
+ |------------->| | |
+ | |(17) Bind Res | |
+ | |S=$NAT-PUB-1 | |
+ | |D=$R-PUB-1 | |
+ | |MA=$R-PUB-1 | |
+ | |---------------------------->|
+ |Data | | |
+ |<===========================================|
+ | | | |
+ .......
+ | | | |
+ |(18) Bind Req | | |
+ |S=$L-PRIV-1 | | |
+ |D=$R-PUB-1 | | |
+ |USE-CAND | | |
+ |------------->| | |
+ | |(19) Bind Req | |
+ | |S=$NAT-PUB-1 | |
+ | |D=$R-PUB-1 | |
+ | |USE-CAND | |
+ | |---------------------------->|
+ | |(20) Bind Res | |
+ | |S=$R-PUB-1 | |
+ | |D=$NAT-PUB-1 | |
+ | |MA=$NAT-PUB-1 | |
+ | |<----------------------------|
+ |(21) Bind Res | | |
+ |S=$R-PUB-1 | | |
+ |D=$L-PRIV-1 | | |
+ |MA=$NAT-PUB-1 | | |
+ |<-------------| | |
+ | | | |
]]>
- Note: Here the initiator (controlling agent) is using "aggressive nomination" as described in Section 8.1.1.2 of RFC 5245 and therefore includes the USE-CANDIDATE attribute in the STUN Binding Requests it sends.
+Note: aggressive nomination described in RFC 5245 is not used anymore in the updated &rfc8445;. From now on the initiator MUST nominate just one valid candidate pair.
As explained in the Trickle ICE specification, when a party has completed gathering of ICE candidates it will send an "end-of-candidates indication" to the other party. In Jingle, this takes the form of an informational message as described under Informational Messages. This specificaton defines only a standalone "end-of-candidates indication" (i.e., not a way to indicate ICE completion in an offer or answer).
If, based on STUN connectivity checks, the parties determine that they will be able to exchange media between a given pair of local candidates and remote candidates (i.e., the pair is "nominated" and ICE processing is "completed"), they can then begin using that candidate pair to exchange media.
-Once the parties have connectivity and therefore the initiator has completed ICE as explained in RFC 5245, the initiator MAY communicate the in-use candidate pair in the signalling channel by sending a transport-info message that contains a <remote-candidate/> element (this maps to the SDP "remote-candidates" attribute as described in Section B.6 of RFC 5245, i.e., remote candidates are "the actual candidates at R that were selected by the offerer", of which there will be only one at this stage of the ICE negotiation).
+If, based on STUN connectivity checks, the parties determine that they will be able to exchange media (i.e., each component has "nominated" candidate pair and ICE processing is "completed"), they proceed with optional remote-candidate notification after which ICE transport is considered to be established. By this moment the parties may exchange media data already since it's allowed even before the candidate pairs nomination according to &rfc8445;
+Once the parties have connectivity and therefore the initiator has completed ICE for the media stream as explained in &rfc8445;, the initiator MAY communicate the in-use (nominated) candidate pairs in the signalling channel by sending a transport-info message that contains a <remote-candidate/> element for each component of the data stream (this maps to the SDP "remote-candidates" attribute as described in Appendix B of draft-ietf-mmusic-ice-sip-sdp specification, i.e., remote candidates are "the actual candidates at R that were selected by the offerer").
+Note, while in SIP this message is MUST it's just MAY for XMPP. The difference comes from a SIP problem (offer updates) which doesn't exist in XMPP. Basically there is no transport-info or any other message which represents candidates of a valid pair and therefore the race condition is not possible. Even so if the responder advertises "urn:ietf:rfc:3264" disco feature and hence may serve as a Jingle-to-SIP proxy the message MUST be sent.
(In accordance with Jingle core, the responder will also acknowledge the transport-info message.)
-In the unlikely event that one of the parties determines that it cannot establish connectivity even after sending and checking lower-priority candidates, it SHOULD terminate the session as described in XEP-0166.
+In the unlikely event that one of the parties determines that it cannot establish connectivity even after sending and checking lower-priority candidates, it SHOULD terminate the session as described in XEP-0166, or alternatively it may do content-remove or transport-replace.
Even after media has begun to flow, 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 network interface card). Such candidates are shared by sending a transport-info message.
@@ -494,7 +584,7 @@ INITIATOR NAT RESPONDERThe parties would check the newly-offered candidate for connectivity, as described previously. If the parties determine that media can flow over the candidate, they MAY then use the new candidate in subsequent communications.
At any time, either party MAY restart the process of ICE negotiation by sending a candidate with a 'generation' value that is greater than the previous generation of candidates; when it does so, it MUST generate new values for the 'pwd' and 'ufrag' attributes, consistent with the definition of an ICE restart in Section 9.1.1.1 of RFC 5245 (because an ICE restart is signalled by a change in the 'pwd' and 'ufrag' attributes, strictly speaking the 'generation' attribute is not absolutely necessary). As explained in RFC 5245, typically the ICE negotiation would be restarted to change the media target (e.g., an IP address change for one of the parties) and certain third-party-call-control scenarios.
+At any time, either party MAY restart the process of ICE negotiation by sending a candidate with a 'generation' value that is greater than the previous generation of candidates; when it does so, it MUST generate new values for the 'pwd' and 'ufrag' attributes, consistent with the definition of an ICE restart in Section 9 of &rfc8445; (because an ICE restart is signalled by a change in the 'pwd' and 'ufrag' attributes, strictly speaking the 'generation' attribute is not absolutely necessary). As explained in &rfc8445;, typically the ICE negotiation would be restarted to change the media target (e.g., an IP address change for one of the parties) and certain third-party-call-control scenarios.
The parties would then exchange new candidates to renegotiate connectivity and would check the new candidates for connectivity, as described previously. If the parties determine that media can flow over one of the new candidates, they can then use the successful candidate in subsequent communications. However, while ICE is being renegotiated the parties can continue to send media with the existing candidate-in-use.
+Note: If a party has already sent ICE restart and receives any transport-info message before <iq/> stanza of type "result", the transport-info messages have to be acknowledged with <iq/> stanzas of type "result" but dropped afterwards. After the restart was acknowledged, the other party MAY send the same candidates again as a part of the new ICE session. It's also possible both parties will send ICE restart simultaneously. In this case session initiator MUST respond with <tie-break/> error (see &xep0166;).
Informational messages can be sent by either party within the context of Jingle to communicate the status of a Jingle ICE "session". The informational message MUST be an IQ-set containing a &JINGLE; element of type "transport-info", where the informational message is a payload element qualified by the 'urn:xmpp:jingle:transports:ice:info:0' namespace.
+Informational messages can be sent by either party within the context of Jingle to communicate the status of a Jingle ICE "session". The informational message MUST be an IQ-set containing a &JINGLE; element of type "transport-info", where the informational message is a payload element qualified by the 'urn:xmpp:jingle:transports:ice:0' namespace.
The only payload element defined so far is the <gathering-complete/> element. This element is used only to signal that gathering of ICE candidates has been completed (i.e., to send an "end-of-candidates indication"), as in the following example.
The <gathering-complete/> element can be combined with remaining candidates or sent alone.