This document defines a Jingle transport method that results in sending data between two XMPP entities via the User Datagram Protocol (UDP) as negotiated using the Interactive Connectivity Establishment (ICE) methodology.
NOTICE: This document is currently within Last Call or under consideration by the XMPP Council for advancement to the next stage in the XSF standards process.
Series: XEP
Number: 0176
Publisher: XMPP Standards Foundation
Status:
Proposed
Type:
Standards Track
Version: 0.12
Last Updated: 2007-11-28
Approving Body: XMPP Council
Dependencies: XMPP Core, XEP-0166
Supersedes: None
Superseded By: None
Short Name: TO BE ASSIGNED
Wiki Page: <http://wiki.jabber.org/index.php/Jingle ICE-UDP Transport Method (XEP-0176)>
Email:
jbeda@google.com
JabberID:
jbeda@google.com
Email:
scottlu@google.com
JabberID:
scottlu@google.com
JabberID:
stpeter@jabber.org
URI:
https://stpeter.im/
Email:
jhildebrand@jabber.com
JabberID:
hildjj@jabber.org
Email:
seanegan@google.com
JabberID:
seanegan@google.com
The preferred venue for discussion of this document is the Standards discussion list: <http://mail.jabber.org/mailman/listinfo/standards>.
The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 3920) and XMPP IM (RFC 3921) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.
The following 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. Introduction
2. Glossary
3. Requirements
4. Jingle Conformance
5. Protocol Description
5.1. Transport Initiation
5.2. Response
5.3. ICE Negotiation
5.3.1. Syntax of Candidate Element
5.3.2. Negotiation Flow
5.4. Acceptance of Successful Candidate
5.5. Modifying an Existing Candidate
5.6. Negotiating a New Candidate
6. Determining Support
7. Implementation Notes
8. Deployment Notes
9. Security Considerations
10. IANA Considerations
11. XMPP Registrar Considerations
11.1. Protocol Namespaces
11.2. Jingle Transport Methods
12. XML Schema
Notes
Revision History
Jingle [1] 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 over the User Datagram Protocol (see RFC 768 [2]), using the ICE methodology developed within the IETF and specified in Interactive Connectivity Establishment (ICE) [3] (hereafter referred to as ICE-CORE). 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).
Note: ICE-CORE has been approved for publication as an RFC but has not yet been published as an RFC. While every effort has been made to keep this document synchronized with ICE-CORE, the interested reader is referred to ICE-CORE for a detailed description of the ICE methodology.
The process for ICE negotiation is largely the same in Jingle as it is in ICE. There are several differences:
The reader is referred to ICE-CORE for a description of various terms used in the context of ICE. Those terms are not reproduced here.
The Jingle transport method defined herein are designed to meet the following requirements:
In accordance with Section 8 of XEP-0166, this document specifies the following information related to the Jingle ice-udp transport method:
The transport negotiation process is defined in the Protocol Description section of this document.
The semantics of the <transport/> element are defined in the ICE Negotiation section of this document.
Successful negotiation of the ice-udp method results in use of a lossy transport that is suitable for applications where some packet loss is tolerable, such as audio and video.
If multiple components are to be communicated over the transport in the context of the Real-time Transport Protocol (RTP; see RFC 3550 [6]), the component numbered "1" shall be associated with RTP and the component numbered "2" shall be associated with the Real Time Control Protocol (RTCP).
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 transport method for an application format, it MUST include an empty <transport/> child element qualified by the 'http://www.xmpp.org/extensions/xep-0176.html#ns' namespace (see Protocol Namespaces regarding issuance of one or more permanent namespaces).
<iq from='romeo@montague.net/orchard'
id='jingle1'
to='juliet@capulet.com/balcony'
type='set'>
<jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
action='session-initiate'
initiator='romeo@montague.net/orchard'
sid='a73sjjvkla37jfea'>
<content name='this-is-the-audio-content' profile='RTP/AVP'>
<description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
[ ... ]
</description>
<transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'/>
</content>
</jingle>
</iq>
As described in XEP-0166, to acknowledge receipt of the session initiation request, the responder returns an IQ-result:
Example 2. Responder acknowledges receipt of session-initiate request
<iq from='juliet@capulet.com/balcony'
id='jingle1'
to='romeo@montague.net/orchard'
type='result'/>
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. [7]
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.
The following is an example of the candidate format:
Example 3. A candidate transport
<candidate component='1'
foundation='1'
generation='0'
ip='10.0.1.1'
network='0'
port='8998'
priority='2114978302'
protocol='udp'
pwd='asd88fgpdd777uzjYhagZg'
type='host'
ufrag='8hhy'/>
The attributes of the <candidate/> element are described in the following table:
| Name | Description | SDP Syntax | Example |
|---|---|---|---|
| component | A Component ID as defined in ICE-CORE. | Component ID value in a=candidate line | 1 |
| foundation | A Foundation as defined in ICE-CORE. | Foundation value in a=candidate line | 1 |
| generation | An index, starting at 0, that enables the parties to keep track of updates to the candidate throughout the life of the session. | N/A | 0 |
| ip | The Internet Protocol (IP) address for the candidate transport mechanism; this may be either an IPv4 address or an IPv6 address. | IP Address value in a=candidate line | 10.0.1.1 |
| network | An index, starting at 0, referencing which network this candidate is on for a given peer (used for diagnostic purposes if the calling hardware has more than one Network Interface Card). | N/A | 0 |
| port | The port at the candidate IP address. | Port value in a=candidate line | 8998 |
| priority | A Priority as defined in ICE-CORE [8] | Priority value in a=candidate line | 1678246398 |
| protocol | The protocol to be used. The only allowable value is "udp". | Transport protocol field in a=candidate line | udp |
| pwd | A Password as defined in ICE-CORE. | a=ice-pwd line | asd88fgpdd777uzjYhagZg |
| type | A Candidate Type as defined in ICE-CORE. The allowable values are "host" for host candidates, "prflx" for peer reflexive candidates, "relay" for relayed candidates, and "srflx" for server reflexive candidates. | Typ field in a=candidate line | srflx |
| ufrag | A User Fragment as defined in ICE-CORE. | a=ice-ufrag line | 8hhy |
The first step in negotiating connectivity is for both parties to immediately begin sending transport candidates methods to the other client. [9] These candidates SHOULD be gathered by following the procedure specified in Section 4.1.1 of ICE-CORE and prioritized by following the procedure specified in Section 4.1.2 of ICE-CORE. 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 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 ICE-CORE.
Example 4. Initiator sends a candidate
<iq from='romeo@montague.net/orchard'
id='info1'
to='juliet@capulet.com/balcony'
type='set'>
<jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
action='transport-info'
initiator='romeo@montague.net/orchard'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
<transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
<candidate component='1'
foundation='1'
generation='0'
ip='10.0.1.1'
network='1'
port='8998'
priority='2114453759'
protocol='udp'
pwd='asd88fgpdd777uzjYhagZg'
type='host'
ufrag='8hhy'/>
</transport>
</content>
</jingle>
</iq>
Example 5. Initiator sends a second candidate
<iq from='romeo@montague.net/orchard'
id='info2'
to='juliet@capulet.com/balcony'
type='set'>
<jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
action='transport-info'
initiator='romeo@montague.net/orchard'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
<transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
<candidate component='1'
foundation='1'
generation='0'
ip='192.0.2.3'
network='1'
port='45664'
priority='1678246398'
protocol='udp'
pwd='asd88fgpdd777uzjYhagZg'
type='srflx'
ufrag='8hhy'/>
</transport>
</content>
</jingle>
</iq>
Example 6. Initiator sends a third candidate
<iq from='romeo@montague.net/orchard'
id='info3'
to='juliet@capulet.com/balcony'
type='set'>
<jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
action='transport-info'
initiator='romeo@montague.net/orchard'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
<transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
<candidate component='1'
foundation='1'
generation='0'
ip='208.245.212.67'
network='2'
port='53267'
priority='1677984254'
protocol='udp'
pwd='asd88fgpdd777uzjYhagZg'
type='srflx'
ufrag='8hhy'/>
</transport>
</content>
</jingle>
</iq>
For each candidate received, the other party MUST acknowledge receipt or return an error:
Example 7. Responder acknowledges receipt
<iq from='juliet@capulet.com/balcony'
id='info1'
to='romeo@montague.net/orchard'
type='result'/>
<iq from='juliet@capulet.com/balcony'
id='info2'
to='romeo@montague.net/orchard'
type='result'/>
<iq from='juliet@capulet.com/balcony'
id='info3'
to='romeo@montague.net/orchard'
type='result'/>
If, based on STUN connectivity checks (see RFC 3489 [10] and draft-ietf-behave-rfc3489bis [11]), 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:
Example 8. Responder definitively accepts the successful candidate
<iq from='juliet@capulet.com/balcony'
id='accept1'
to='romeo@montague.net/orchard'
type='set'>
<jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
action='session-accept'
initiator='romeo@montague.net/orchard'
responder='juliet@capulet.com/balcony'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
<description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
[ ... ]
</description>
<transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
<candidate component='1'
foundation='1'
generation='0'
ip='192.0.2.3'
network='1'
port='45664'
priority='1678246398'
protocol='udp'
pwd='asd88fgpdd777uzjYhagZg'
type='srflx'
ufrag='8hhy'/>
</transport>
</content>
</jingle>
</iq>
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:
Example 9. Initiator acknowledges acceptance of successful candidate
<iq from='romeo@montague.net/orchard'
id='accept1'
to='juliet@capulet.com/balcony'
type='result'/>
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 <not-acceptable/> error in response to the responder's acceptance of the successful candidate:
Example 10. Initiator returns error in response to acceptance of successful candidate
<iq from='romeo@montague.net/orchard'
id='accept1'
to='juliet@capulet.com/balcony'
type='error'>
<error type='cancel'>
<not-acceptable xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
If the responder cannot find a suitable candidate transport or it receives a <not-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).
Example 11. Initiator modifies the in-use candidate
<iq from='romeo@montague.net/orchard'
id='modify1'
to='juliet@capulet.com/balcony'
type='set'>
<jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
action='content-modify'
initiator='romeo@montague.net/orchard'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
<transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
<candidate component='1'
foundation='1'
generation='1'
ip='192.0.2.4'
network='1'
port='45665'
priority='1678246398'
protocol='udp'
pwd='asd88fgpdd777uzjYhagZg'
type='srflx'
ufrag='8hhy'/>
</transport>
</content>
</jingle>
</iq>
The recipient then acknowledges receipt.
Example 12. Recipient acknowledges content-modify
<iq from='juliet@capulet.com/balcony'
id='modify1'
to='romeo@montague.net/orchard'
type='result'/>
If the modification is acceptable, the recipient then sends a content-accept action.
Example 13. Responder definitively accepts the modified candidate
<iq from='juliet@capulet.com/balcony'
id='accept2'
to='romeo@montague.net/orchard'
type='set'>
<jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
action='content-accept'
initiator='romeo@montague.net/orchard'
responder='juliet@capulet.com/balcony'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
<description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
[ ... ]
</description>
<transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
<candidate component='1'
foundation='1'
generation='1'
ip='192.0.2.4'
network='1'
port='45665'
priority='1678246398'
protocol='udp'
pwd='asd88fgpdd777uzjYhagZg'
type='srflx'
ufrag='8hhy'/>
</transport>
</content>
</jingle>
</iq>
The initiator then acknowledges the responder's acceptance:
Example 14. Initiator acknowledges content-accept
<iq from='romeo@montague.net/orchard'
id='accept2'
to='juliet@capulet.com/balcony'
type='result'/>
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.
Example 15. Initiator sends a fourth candidate
<iq from='romeo@montague.net/orchard'
id='info4'
to='juliet@capulet.com/balcony'
type='set'>
<jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
action='transport-info'
initiator='romeo@montague.net/orchard'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
<transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
<candidate component='1'
foundation='1'
generation='0'
ip='10.0.1.2'
network='0'
port='9001'
priority='21149780477'
protocol='udp'
pwd='asd88fgpdd777uzjYhagZg'
type='host'
ufrag='8hhy'/>
</transport>
</content>
</jingle>
</iq>
The receiving party MUST acknowledge receipt of the candidate.
Example 16. Recipient acknowledges receipt
<iq from='juliet@capulet.com/balcony'
id='info4'
to='romeo@montague.net/orchard'
type='result'/>
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.
Example 17. Responder definitively accepts the new candidate
<iq from='juliet@capulet.com/balcony'
id='accept3'
to='romeo@montague.net/orchard'
type='set'>
<jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
action='content-accept'
initiator='romeo@montague.net/orchard'
responder='juliet@capulet.com/balcony'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='this-is-the-audio-content' profile='RTP/AVP'>
<description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
[ ... ]
</description>
<transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'>
<candidate component='1'
foundation='1'
generation='0'
ip='10.0.1.2'
network='0'
port='9001'
priority='21149780477'
protocol='udp'
pwd='asd88fgpdd777uzjYhagZg'
type='host'
ufrag='8hhy'/>
</transport>
</content>
</jingle>
</iq>
The other party then acknowledges the content-accept.
Example 18. Initiator acknowledges content-accept
<iq from='romeo@montague.net/orchard'
id='accept3'
to='juliet@capulet.com/balcony'
type='result'/>
The parties then use the new candidate in subsequent communications.
If an entity supports the Jingle ice-udp transport, it MUST return a feature of "http://www.xmpp.org/extensions/xep-0176.html#ns" (see Protocol Namespaces regarding issuance of one or more permanent namespaces) in response to Service Discovery [12] information requests.
Example 19. Service discovery information request
<iq from='romeo@montague.net/orchard'
id='disco1'
to='juliet@capulet.com/balcony'
type='get'>
<query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
Example 20. Service discovery information response
<iq from='juliet@capulet.com/balcony'
id='disco1'
to='romeo@montague.net/orchard'
type='result'>
<query xmlns='http://jabber.org/protocol/disco#info'>
...
<feature var='http://www.xmpp.org/extensions/xep-0176.html#ns'/>
...
</query>
</iq>
Naturally, support MAY also be determined via the dynamic, presence-based profile of Service Discovery defined in Entity Capabilities [13].
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.
This specification applies exclusively to Jabber/XMPP clients and places no additional requirements on Jabber/XMPP servers. However, service administrators may wish to deploy a STUN server in order to ease the client-to-client negotiation process. See External Service Discovery [14] for related information.
In order to secure the data stream that is negotiated via the Jingle ICE transport, implementations SHOULD use encryption methods appropriate to the transport method and media being exchanged (for details regarding audio and video exchanges via RTP, refer to XEP-0167 and XEP-0180).
This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [15].
Until this specification advances to a status of Draft, its associated namespaces shall be:
Upon advancement of this specification, the XMPP Registrar [16] shall issue permanent namespaces in accordance with the process defined in Section 4 of XMPP Registrar Function [17].
The following namespaces are requested, and are thought to be unique per the XMPP Registrar's requirements:
The XMPP Registrar shall include "ice-udp" in its registry of Jingle transport methods. The registry submission is as follows:
<transport>
<name>ice-udp</name>
<desc>
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.
</desc>
<type>lossy</type>
<doc>XEP-0176</doc>
</transport>
<?xml version='1.0' encoding='UTF-8'?>
<xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='http://www.xmpp.org/extensions/xep-0176.html#ns'
xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'
elementFormDefault='qualified'>
<xs:element name='transport'>
<xs:complexType>
<xs:choice>
<xs:sequence>
<xs:element ref='candidate' minOccurs='0' maxOccurs='1'/>
</xs:sequence>
</xs:choice>
</xs:complexType>
</xs:element>
<xs:element name='candidate'>
<xs:complexType>
<xs:simpleContent>
<xs:extension base='empty'>
<xs:attribute name='component' type='xs:unsignedByte' use='required'/>
<xs:attribute name='foundation' type='xs:unsignedByte' use='required'/>
<xs:attribute name='generation' type='xs:unsignedByte' use='required'/>
<xs:attribute name='ip' type='xs:string' use='required'/>
<xs:attribute name='network' type='xs:unsignedByte' use='required'/>
<xs:attribute name='port' type='xs:unsignedShort' use='required'/>
<xs:attribute name='priority' type='xs:positiveInteger' use='required'/>
<xs:attribute name='protocol' type='xs:NCName' use='required'/>
<xs:attribute name='pwd' type='xs:string' use='required'/>
<xs:attribute name='type' use='required'>
<xs:simpleType>
<xs:restriction base='xs:NCName'>
<xs:enumeration value='host'/>
<xs:enumeration value='prflx'/>
<xs:enumeration value='relay'/>
<xs:enumeration value='srflx'/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
<xs:attribute name='ufrag' type='xs:string' use='required'/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:simpleType name='empty'>
<xs:restriction base='xs:string'>
<xs:enumeration value=''/>
</xs:restriction>
</xs:simpleType>
</xs:schema>
1. XEP-0166: Jingle <http://www.xmpp.org/extensions/xep-0166.html>.
2. RFC 768: User Datagram Protocol <http://tools.ietf.org/html/rfc0768>.
3. Interactive Connectivity Establishment (ICE): A Methodology for Network Address Translator (NAT) Traversal for Offer/Answer Protocols <http://tools.ietf.org/html/draft-ietf-mmusic-ice>. Work in progress.
4. This approach takes advantage of the request-response semantics of the XMPP <iq/> stanza type and enables the parties to send higher-priority candidates earlier in the negotiation, but implies that Jingle is not exactly an offer-answer protocol as specified in RFC 3264.
5. RFC 4566: SDP: Session Description Protocol <http://tools.ietf.org/html/rfc4566>.
6. RFC 3550: RTP: A Transport Protocol for Real-Time Applications <http://tools.ietf.org/html/rfc3550>.
7. 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.
8. In accordance with the rules specified in Section 4.1.1 of ICE-CORE, the priority values shown in the examples within this document have been calculated as follows. The "type preference" for host candidates is stipulated to be "126" and for server reflexive candidates "100". The "local preference" for network 0 is stipulated to be "4096", for network 1 "2048", and for network 2 "1024".
9. 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 ICE-CORE.
10. RFC 3489: STUN - Simple Traversal of User Datagram Protocol (UDP) Through Network Address Translators (NATs) <http://tools.ietf.org/html/rfc3489>.
11. Session Traversal Utilities for NAT (STUN) <http://tools.ietf.org/html/draft-ietf-behave-rfc3489bis>.
12. XEP-0030: Service Discovery <http://www.xmpp.org/extensions/xep-0030.html>.
13. XEP-0115: Entity Capabilities <http://www.xmpp.org/extensions/xep-0115.html>.
14. XEP-0215: External Service Discovery <http://www.xmpp.org/extensions/xep-0215.html>.
15. 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/>.
16. 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 <http://www.xmpp.org/registrar/>.
17. XEP-0053: XMPP Registrar Function <http://www.xmpp.org/extensions/xep-0053.html>.
Moved ice-tcp definition to a separate specification.
(psa)Further editorial review; also added sections on modification of existing candidates and exchange of subsequent candidates.
(psa)Editorial review and consistency check.
(psa)Updated to track ICE-16.
(psa)Separately defined ice-tcp and ice-udp transport methods to enable clearer definition of transport methods and reuse by application types; specified Jingle conformance, including definition of ice-udp as lossy and ice-tcp as reliable.
(psa)Updated to track ICE-14 and ICE-TCP-03; moved text on discovery of STUN servers to separate specification.
(psa)Modified spec to use provisional namespace before advancement to Draft (per XEP-0053).
(psa)Updated to track ICE-12; corrected service discovery process; completed editorial review; removed mention of DTMF, which is for audio only.
(psa)Updated to track ICE-10; added section on service discovery.
(psa)Specified that DTMF must use in-band signalling (XEP-0181).
(se/psa)Recommended use of RTP-native methods for DTMF.
(psa)Initial version (split from XEP-0166).
(psa/jb)END