This document defines a framework for initiating and managing peer-to-peer multimedia sessions (e.g., voice and video chat) between two Jabber/XMPP endpoints in a way that is interoperable with existing Internet standards.
WARNING: This Standards-Track document is Experimental. Publication as an XMPP Extension Protocol does not imply approval of this proposal by the XMPP Standards Foundation. Implementation of the protocol described herein is encouraged in exploratory implementations, but production systems should not deploy implementations of this protocol until it advances to a status of Draft.
Series: XEP
Number: 0166
Publisher: XMPP Standards Foundation
Status:
Experimental
Type:
Standards Track
Version: 0.16
Last Updated: 2007-06-06
Approving Body: XMPP Council
Dependencies: XMPP Core
Supersedes: None
Superseded By: None
Short Name: TO BE ASSIGNED
Wiki Page: <http://wiki.jabber.org/index.php/Jingle (XEP-0166)>
Email:
scottlu@google.com
JabberID:
scottlu@google.com
Email:
jbeda@google.com
JabberID:
jbeda@google.com
Email:
stpeter@jabber.org
JabberID:
stpeter@jabber.org
Email:
robert.mcqueen@collabora.co.uk
JabberID:
robert.mcqueen@collabora.co.uk
Email:
seanegan@google.com
JabberID:
seanegan@google.com
Email:
jhildebrand@jabber.com
JabberID:
hildjj@jabber.org
This XMPP Extension Protocol is copyright 1999 - 2007 by the XMPP Standards Foundation (XSF) and is in full conformance with the XSF's Intellectual Property Rights Policy <http://www.xmpp.org/extensions/ipr-policy.shtml>. This material may be distributed only subject to the terms and conditions set forth in the Creative Commons Attribution License (<http://creativecommons.org/licenses/by/2.5/>).
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. Requirements
3. Glossary
4. Concepts and Approach
4.1. Overall Session Management
5. Session Flow
5.1. Resource Determination
5.2. Initiation
5.3. Receiver Response
5.4. Decline
5.5. Negotiation
5.6. Acceptance
5.7. Modifying an Active Session
5.8. Termination
5.9. Informational Messages
6. Error Handling
7. Determining Support
8. Conformance by Using Protocols
8.1. Application Types
8.2. Transport Methods
9. Security Considerations
9.1. Denial of Service
9.2. Communication Through Gateways
10. IANA Considerations
11. XMPP Registrar Considerations
11.1. Protocol Namespaces
11.2. Jingle Content Description Formats Registry
11.3. Jingle Content Transport Methods Registry
11.4. Jingle Reason Codes Registry
11.4.1. Process
11.4.2. Initial Registration
12. XML Schemas
12.1. Jingle
12.2. Jingle Errors
13. History
14. Acknowledgements
Notes
Revision History
The purpose of Jingle is to enable one-to-one, peer-to-peer media sessions between XMPP entities, with the negotiation occurring over XMPP and the media being exchanged outside the XMPP band using technologies such as the Real-time Transport Protocol (RTP; RFC 3550 [1]), the User Datagram Protocol (UDP; RFC 768 [2]), and Interactive Connectivity Establishment (ICE) [3].
One target application for Jingle is simple voice chat (see Jingle Audio via RTP [4]). We stress the word "simple". The purpose of Jingle is not to build a full-fledged telephony application that supports call waiting, call forwarding, call transfer, hold music, IVR systems, find-me-follow-me functionality, conference calls, and the like. These features are of interest to some user populations, but building in support for these features would introduce unnecessary complexity into a technology that is designed for basic multimedia interaction.
The purpose of Jingle is not to supplant or replace technologies based on Session Initiation Protocol (SIP; RFC 3261 [5]). Because dual-stack XMPP+SIP clients are difficult to build, Jingle was designed as a pure XMPP signalling protocol. However, Jingle is at the same time designed to interwork with SIP so that the millions of deployed XMPP clients can be added onto existing Voice over Internet Protocol (VoIP) networks, rather than limiting XMPP users to a separate and distinct network.
Jingle is designed in a modular way so that developers can easily add support for multimedia session types other than voice chat, such as video chat (see Jingle Video via RTP [6]), application sharing, file sharing, collaborative editing, whiteboarding, and torrent broadcasting. The transport methods are also modular, so that Jingle implementations can use any appropriate media transport (including proprietary methods not standardized through the XMPP Standards Foundation).
The protocol defined herein is designed to meet the following requirements:
This document defines the signalling protocol only. Additional documents specify the following:
Various content description formats (audio, video, etc.) and, where possible, mapping those types to the Session Description Protocol (SDP; see RFC 4566 [7]); examples include XEP-0167 and XEP-0180.
Various content transport methods; examples include Jingle ICE Transport Method [8] and Jingle Raw UDP Transport Method [9].
Procedures for mapping the Jingle signalling protocol to existing signalling standards such as the IETF's Session Initiation Protocol (SIP) and the ITU's H.323 protocol (see H.323 [10]); these documents are forthcoming.
Table 1: Glossary
| Term | Definition |
|---|---|
| Session | A number of pairs of negotiated content transport methods and content description formats connecting two entities. It is delimited in time by an initiate request and session ending events. During the lifetime of a session, pairs of content descriptions and content transport methods can be added or removed. A session consists of at least one active negotiated content type at a time. |
| Content Type | The combination of one content description and one content transport method. |
| Content Description | The format of the content type being established, which formally declares one purpose of the session (e.g., "voice" or "video"). This is the 'what' of the session (i.e., the bits to be transferred), such as the acceptable codecs when establishing a voice conversation. In Jingle XML syntax the content type is the namespace of the <description/> element. |
| Transport Method | The method for establishing data stream(s) between entities. Possible transports might include ICE-TCP, Raw UDP, inband data, etc. This is the 'how' of the session. In Jingle XML syntax this is the namespace of the <transport/> element. The content transport method defines how to transfer bits from one host to another. Each transport method must specify whether it is lossy (thus suitable for applications where some packet loss is tolerable) or reliable (thus suitable for applications where packet loss is not tolerable). |
| Component | A component is a numbered stream of data which needs to be transmitted between the endpoints for a given content type in the context of a given session. It is up to the transport to negotiate the details of each component. Depending on the content type and the content description, one content description may require multiple components to be communicated (e.g., the audio content type might use two components: one to transmit an RTP stream and another to transmit RTCP timing information). |
Jingle consists of three parts, each with its own syntax, semantics, and state machine:
This document defines the semantics and syntax for overall session management. It also provides pluggable "slots" for content description formats and content transport methods, which are specified in separate documents; however, for the sake of completeness, this document also includes examples for all of the actions related to description formats and transport methods.
At the most basic level, the process for negotiating a Jingle session is as follows:
If the parties later discover a better candidate, they perform a "content-modify" negotiation and then switch to the better candidate. Naturally they can also modify various other parameters related to the session (e.g., adding video to a voice chat).
The state machine for overall session management (i.e., the state per Session ID) is as follows:
o
|
| session-initiate
|
| +-----------------------+
|/ |
PENDING o---------------------+ |
| | content-accept, | |
| | content-modify, | |
| | content-remove, | |
| | session-info, | |
| | transport-info | |
| +------------------+ |
| |
| session-accept |
| |
ACTIVE o---------------------+ |
| | content-accept, | |
| | content-add, | |
| | content-modify, | |
| | content-remove, | |
| | session-info, | |
| | transport-info | |
| +------------------+ |
| |
+-------------------------+
|
| session-terminate
|
o ENDED
There are three overall session states:
The actions related to management of the overall Jingle session are as follows:
Table 2: Jingle Actions
| Action | Description |
|---|---|
| content-accept | Accept a content-add or content-remove action received from another party. |
| content-add | Add one or more new content types to the session. This action MUST NOT be sent while the session is in the PENDING state. When a party sends a content-add, it MUST ignore any actions received from the other party until it receives acknowledgement of the content-add. [11] |
| content-modify | Change an existing content type. The recipient MUST NOT reply to a content-modify action with another content-modify action. |
| content-remove | Remove one or more content types from the session. [12] |
| session-accept | Definitively accept a session negotiation. Implicitly this action also serves as a content-accept (which in turn serves as a description-accept and transport-accept). |
| session-info | Send session-level information / messages, such as (for Jingle audio) a ringing message. |
| session-initiate | Request negotiation of a new Jingle session. |
| session-terminate | End an existing session. |
| transport-info | Exchange transport candidates; it is mainly used in XEP-0176 but may be used in other transport specifications. |
In order to initiate a Jingle session, the initiator must determine which of the receiver's XMPP resources is best for the desired content description format. There are several possible scenarios:
If the intended responder shares presence with the initiator (see XMPP IM [13]) and has only one available resource, this task SHOULD be completed using Service Discovery [14] or the presence-based profile of service discovery specified in Entity Capabilities [15]. [16]
If the intended responder shares presence with the initiator and has more than one available resource but only one of the resources supports Jingle and the desired content description format, the initiator SHOULD MUST initiate the Jingle signalling with that resource.
If the intended responder shares presence with the initiator and has more than one available resource but more than one of the resources supports Jingle and the desired content description format, the initiator SHOULD use Resource Application Priority [17] in order to determine which is the best resource with which to initiate the desired Jingle session.
If the intended responder does not share presence with the initiator, the initiator SHOULD first send a Stanza Session Negotiation [18] request to the responder in order to initiate the exchange of XMPP stanzas. The request SHOULD include a RAP routing hint as specified in XEP-0168 and the <message/> stanza containing the request SHOULD be of type "headline" so that (typically) it is not stored offline for later delivery.
Once the initiator has discovered which of the receiver's XMPP resources is ideal for the desired content description format, it sends a session initiation request to the receiver. This request is an IQ-set containing a <jingle/> element qualified by the 'http://www.xmpp.org/extensions/xep-0166.html#ns' namespace. The <jingle/> element MUST possess the 'action', 'initiator', and 'sid' attributes (the latter two uniquely identify the session). For initiation, the 'action' attribute MUST have a value of "session-initiate" and the <jingle/> element MUST contain one or more <content/> elements, each of which defines a content type to be transferred during the session; each <content/> element in turn contains one <description/> child element that specifies a desired content description format and one <transport/> child element that specifies a potential content transport method. If either party wishes to propose the use of multiple transport methods for the same content description, it must send multiple <content/> elements.
The following example shows a Jingle session initiation request for a session that contains both audio and video content:
<iq from='romeo@montague.net/orchard' to='juliet@capulet.com/balcony' id='jingle1' type='set'>
<jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
action='session-initiate'
initiator='romeo@montague.net/orchard'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='this-is-the-audio-content'>
<description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
...
</description>
<transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'/>
</content>
<content creator='initiator' name='this-is-the-video-content'>
<description xmlns='http://www.xmpp.org/extensions/xep-0180.html#ns'>
...
</description>
<transport xmlns='http://www.xmpp.org/extensions/xep-0176.html#ns'/>
</content>
</jingle>
</iq>
Note: The syntax and semantics of the <description/> and <transport/> elements are out of scope for this specification, but are defined in related specifications.
The attributes of the <jingle/> element are as follows:
The attributes of the <content/> element are as follows:
Note: In order to expedite session establishment, the initiator MAY send transport candidates (e.g., for negotiation of the ICE transport) 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).
Unless an error occurs, the receiver MUST acknowledge receipt of the initiation request:
Example 2. Receiver Acknowledges Receipt of Initiation Request
<iq type='result' from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' id='jingle1'/>
If the receiver acknowledges receipt of the initation request, both parties must consider the session to be in the PENDING state.
There are several reasons why the receiver might return an error instead of acknowledging receipt of the initiation request:
If the initiator is unknown to the receiver (e.g., via presence subscription) and the receiver has a policy of not communicating via Jingle with unknown entities, it SHOULD return a <service-unavailable/> error.
Example 3. Initiator Unknown to Receiver
<iq type='error' from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' id='jingle1'>
<error type='cancel'>
<service-unavailable xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
If the receiver wishes to redirect to another address, it SHOULD return a <redirect/> error.
Example 4. Receiver Redirection
<iq type='error' from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' id='jingle1'>
<error type='cancel'>
<redirect xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>xmpp:voicemail@capulet.com</redirect>
</error>
</iq>
If the receiver does not support Jingle, it MUST return a <service-unavailable/> error.
Example 5. Receiver Does Not Support Jingle
<iq type='error' from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' id='jingle1'>
<error type='cancel'>
<service-unavailable xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
If the receiver does not support any of the specified content description formats, it MUST return a <feature-not-implemented/> error with a Jingle-specific error condition of <unsupported-content/>.
Example 6. Receiver Does Not Support Any Content Description Formats
<iq type='error' from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' id='jingle1'>
<error type='cancel'>
<feature-not-implemented xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
<unsupported-content xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns-errors'/>
</error>
</iq>
If the receiver does not support any of the specified content transport methods, it MUST return a <feature-not-implemented/> error with a Jingle-specific error condition of <unsupported-transports/>.
Example 7. Receiver Does Not Support Any Transport Methods
<iq type='error' from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' id='jingle1'>
<error type='cancel'>
<feature-not-implemented xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
<unsupported-transports xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns-errors'/>
</error>
</iq>
If the initiation request was malformed, the receiver MUST return a <bad-request/> error.
Example 8. Initiation Request Malformed
<iq type='error' from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' id='jingle1'>
<error type='cancel'>
<bad-request xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
In order to decline the session initiation request, the receiver MUST acknowledge receipt of the session initiation request, then terminate the session as described under Termination.
In general, negotiation will be necessary before the parties can agree on an acceptable set of content types, content description formats, and content transport methods. The potential combinations of parameters to be negotiated are many, and not all are shown herein (some are shown in the relevant specifications for various content description formats and content transport methods).
One session-level negotiation is to remove a content types. For example, let us imagine that Juliet is having a bad hair day. She certainly does not want to include video in her Jingle session with Romeo, so she sends a "content-remove" request to Romeo:
Example 9. Content Type Removal
<iq from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' id='reduce1' type='set'>
<jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
action='content-remove'
initiator='romeo@montague.net/orchard'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='this-is-the-video-content'/>
</jingle>
</iq>
The entity receiving the session reduction request then acknowledges the request:
<iq from='romeo@montague.net/orchard' to='juliet@capulet.com/balcony' id='reduce1' type='result'/>
If the reduction results in no more content types for the session, the entity that receives the session-reduce SHOULD send a session-terminate action to the other party (since a session with no content types is void).
Another session-level negotiation is to add a content type; however, this MUST NOT be done while the session is in the PENDING state and is allowed only while the session is in the ACTIVE state.
If (after negotiation of content transport methods and content description formats) the receiver determines that it will be able to establish a connection, it sends a definitive acceptance to the initiator:
Example 11. Receiver Definitively Accepts the Call
<iq type='set' from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' id='accept1'>
<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'>
<description xmlns='http://www.xmpp.org/extensions/xep-0167.html#ns'>
...
</description>
<transport xmlns='http://www.xmpp.org/extensions/xep-0177.html#ns'>
<candidate .../>
</transport>
</content>
</jingle>
</iq>
The <jingle/> element in the accept stanza MUST contain one or more <content/> elements, each of which MUST contain one <description/> element and one <transport/> element. The <jingle/> element SHOULD possess a 'responder' attribute that explicitly specifies the full JID of the responding entity, and the initiator SHOULD send all future commmunications about this Jingle session to the JID provided in the 'responder' attribute.
The initiator then acknowledges the receiver's definitive acceptance:
Example 12. Initiator Acknowledges Definitive Acceptance
<iq type='result' to='juliet@capulet.com/balcony' from='romeo@montague.net/orchard' id='accept1'/>
Now the initiator and receiver can begin sending content over the negotiated connection.
If one of the parties cannot find a suitable content transport method, it SHOULD terminate the session as described below.
In order to modify an active session, either party may send a "content-remove", "content-add", "content-modify", "description-modify", or "transport-modify" action to the other party. The receiving party then sends an appropriate "-accept" or "-decline" action, and may first send an appropriate "-info" action.
If both parties send modify messages at the same time, the modify message from the session initiator MUST trump the modify message from the recipient and the initiator SHOULD return an <unexpected-request/> error to the other party.
One example of modifying an active session is to add a content type. For example, let us imagine that Juliet gets her hair in order and now wants to add video. She now sends a "content-add" request to Romeo:
Example 13. Adding a Content Type
<iq from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' id='add1' type='set'>
<jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
action='content-add'
initiator='romeo@montague.net/orchard'
sid='a73sjjvkla37jfea'>
<content creator='responder' name='video-is-back'>
<description xmlns='http://www.xmpp.org/extensions/xep-0180.html#ns'>
...
</description>
<transport xmlns='http://www.xmpp.org/extensions/xep-0177.html#ns'>
<candidate .../>
</transport>
</content>
</jingle>
</iq>
The entity receiving the session extension request then acknowledges the request and, if it is acceptable, returns a content-accept:
<iq from='romeo@montague.net/orchard' to='juliet@capulet.com/balcony' id='add1' type='result'/>
Example 15. Content Acceptance
<iq from='romeo@montague.net/orchard' to='juliet@capulet.com/balcony' id='add2' type='set'>
<jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
action='content-accept'
initiator='romeo@montague.net/orchard'
sid='a73sjjvkla37jfea'>
<content creator='responder' name='video-is-back'>
<description xmlns='http://www.xmpp.org/extensions/xep-0180.html#ns'>
...
</description>
<transport xmlns='http://www.xmpp.org/extensions/xep-0177.html#ns'>
<candidate .../>
</transport>
</content>
</jingle>
</iq>
The other party then acknowledges the acceptance.
<iq from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' id='add2' type='result'/>
In order to gracefully end the session (which MAY be done at any point after acknowledging receipt of the initiation request, including immediately thereafter in order to decline the request), either the receiver or the initiator MUST a send a "terminate" action to the other party:
Example 17. Receiver Terminates the Session
<iq from='juliet@capulet.com/balcony'
id='term1'
to='romeo@montague.net/orchard'
type='set'>
<jingle xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
action='session-terminate'
initiator='romeo@montague.net/orchard'
reason='Sorry, gotta go!'
sid='a73sjjvkla37jfea'/>
</iq>
The other party (in this case the initiator) MUST then acknowledge termination of the session:
Example 18. Initiator Acknowledges Termination
<iq type='result' to='juliet@capulet.com/balcony' from='romeo@montague.net/orchard' id='term1'/>
Note: As soon as an entity sends a "session-terminate" action, it MUST consider the session to be ended (even before receiving acknowledgement from the other party). If the terminating entity receives additional IQ-sets from the other party after sending the "session-terminate" action, it MUST reply with an <unknown-session/> error.
Unfortunately, not all sessions end gracefully. In applications of Jingle that also involve the exchange of presence information, receipt of <presence type='unavailable'/> from the other party MAY be a considered session-ending event. However, in this case there is nothing for the party to acknowledge.
At any point after initiation of a Jingle session, either entity MAY send an informational message to the other party, for example to change a content transport method or content description format parameter, inform the other party that a session initiation request is queued, that a device is ringing, or that a scheduled event has occurred or will occur. An information message MUST be an IQ-set containing a <jingle/> element whose 'action' attribute is set to a value of "session-info", "description-info", or "transport-info"; the <jingle/> element MUST further contain a payload child element (speciific to the session, content description format, or content transport method) that specifies the information being communicated. If either party receives an empty "session-info" message for an active session, it MUST send an empty IQ result; this way, an empty "session-info" message may be used as a "ping" to determine session vitality. (A future version of this specification may define payloads related to the "session-info" action.)
The Jingle-specific error conditions are as follows.
Table 3: Other Error Conditions
| Jingle Condition | XMPP Condition | Description |
|---|---|---|
| <out-of-order/> | <unexpected-request/> | The request cannot occur at this point in the state machine (e.g., initiate after accept). |
| <unknown-session/> | <bad-request/> | The 'sid' attribute specifies a session that is unknown to the recipient (e.g., no longer live according to the recipient's state machine because the recipient previously terminated the session). |
| <unsupported-content/> | <not-acceptable/> | The recipient does not support any of the desired content description formats. |
| <unsupported-transports/> | <not-acceptable/> | The recipient does not support any of the desired content transport methods. |
If an entity supports Jingle, it MUST advertise that fact by returning a feature of "http://www.xmpp.org/extensions/xep-0166.html#ns" (see Protocol Namespaces regarding issuance of one or more permanent namespaces) in response to Service Discovery [20] 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-0166.html#ns'/>
...
</query>
</iq>
A document that specifies a Jingle application type (e.g., audio via RTP) MUST define:
A document that specifies a Jingle transport method (e.g., Raw UDP) MUST define:
Jingle sessions may be resource-intensive. Therefore, it is possible to launch a denial-of-service attack against an entity by burdening it with too many Jingle sessions. Care must be taken to accept content sessions only from known entities and only if the entity's device is able to process such sessions.
Jingle communications may be enabled through gateways to non-XMPP networks, whose security characteristics may be quite different from those of XMPP networks. (For example, on some SIP networks authentication is optional and "from" addresses can be easily forged.) Care must be taken in communicating through such gateways.
This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [21].
Until this specification advances to a status of Draft, its associated namespaces shall be "http://www.xmpp.org/extensions/xep-0166.html#ns" and "http://www.xmpp.org/extensions/xep-0166.html#ns-errors"; upon advancement of this specification, the XMPP Registrar [22] shall issue permanent namespaces in accordance with the process defined in Section 4 of XMPP Registrar Function [23].
The XMPP Registrar shall maintain a registry of Jingle content description formats. All content description format registrations shall be defined in separate specifications (not in this document). Content description formats defined within the XEP series MUST be registered with the XMPP Registrar, resulting in protocol URNs of the form "urn:xmpp:jingle:description:name" (where "name" is the registered name of the content description format).
In order to submit new values to this registry, the registrant must define an XML fragment of the following form and either include it in the relevant XMPP Extension Protocol or send it to the email address <registrar@xmpp.org>:
<content>
<name>the name of the content description format</name>
<desc>a natural-language summary of the content description format</desc>
<transport>whether the content should be sent over a "reliable" or "lossy" transport</transport>
<doc>the document in which this content description format is specified</doc>
</content>
The XMPP Registrar shall maintain a registry of Jingle content transport methods. All content transport method registrations shall be defined in separate specifications (not in this document). Content transport methods defined within the XEP series MUST be registered with the XMPP Registrar, resulting in protocol URNs of the form "urn:xmpp:jingle:transport:name" (where "name" is the registered name of the content transport method).
In order to submit new values to this registry, the registrant must define an XML fragment of the following form and either include it in the relevant XMPP Extension Protocol or send it to the email address <registrar@xmpp.org>:
<transport>
<name>the name of the content transport method</name>
<desc>a natural-language summary of the content transport method</desc>
<type>whether the transport method is "reliable" or "lossy"</type>
<doc>the document in which this content transport method is specified</doc>
</transport>
The XMPP Registrar shall maintain a registry of reasons for Jingle actions.
In order to submit new values to this registry, the registrant must define an XML fragment of the following form and either include it in the relevant XMPP Extension Protocol or send it to the email address <registrar@xmpp.org>:
<reason>
<code>the value of the 'reasoncode' attribute</name>
<desc>a natural-language summary of the reason code</desc>
<doc>the document in which this reason code is specified</doc>
</reason>
The following submission registers reasoncodes in use as of April 2007. Refer to the registry itself for a complete and current list of reasoncodes.
<reason>
<code>connectivity-error</code>
<desc>the action (e.g., session-terminate) is related to connectivity problems</desc>
<doc>XEP-0166</doc>
</reason>
<reason>
<code>general-error</code>
<desc>the action (e.g., session-terminate) is related to a non-specific application error</desc>
<doc>XEP-0166</doc>
</reason>
<reason>
<code>media-error</code>
<desc>the action (e.g., session-terminate) is related to media processing problems</desc>
<doc>XEP-0166</doc>
</reason>
<reason>
<code>no-error</code>
<desc>the action is generated during the normal course of state management</desc>
<doc>XEP-0166</doc>
</reason>
<?xml version='1.0' encoding='UTF-8'?>
<xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='http://www.xmpp.org/extensions/xep-0166.html#ns'
xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns'
elementFormDefault='qualified'>
<xs:element name='jingle'>
<xs:complexType>
<xs:sequence minOccurs='1' maxOccurs='unlimited'>
<xs:element ref='content'/>
</xs:sequence>
<xs:attribute name='action' use='required'>
<xs:simpleType>
<xs:restriction base='xs:NCName'>
<xs:enumeration value='content-accept'/>
<xs:enumeration value='content-add'/>
<xs:enumeration value='content-modify'/>
<xs:enumeration value='content-remove'/>
<xs:enumeration value='session-accept'/>
<xs:enumeration value='session-info'/>
<xs:enumeration value='session-initiate'/>
<xs:enumeration value='session-terminate'/>
<xs:enumeration value='transport-info'/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
<xs:attribute name='initiator' type='xs:string' use='required'/>
<xs:attribute name='reasoncode' type='xs:string' use='optional'/>
<xs:attribute name='reasontext' type='xs:string' use='optional'/>
<xs:attribute name='responder' type='xs:string' use='optional'/>
<xs:attribute name='sid' type='xs:NMTOKEN' use='required'/>
</xs:complexType>
</xs:element>
<xs:element name='content'>
<xs:complexType>
<xs:choice minOccurs='0'>
<xs:sequence>
<xs:any namespace='##other' minOccurs='0' maxOccurs='unbounded'/>
</xs:sequence>
</xs:choice>
<xs:attribute name='creator' use='required'>
<xs:simpleType>
<xs:restriction base='xs:NCName'>
<xs:enumeration value='initiator'>
<xs:enumeration value='responder'/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
<xs:attribute name='name' use='required' type='xs:string'/>
<xs:attribute name='profile' use='optional' type='xs:string'/>
<xs:attribute name='senders' use='optional' default='both'>
<xs:simpleType>
<xs:restriction base='xs:NCName'>
<xs:enumeration value='both'>
<xs:enumeration value='initiator'>
<xs:enumeration value='responder'/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
</xs:complexType>
</xs:element>
</xs:schema>
<?xml version='1.0' encoding='UTF-8'?>
<xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='http://www.xmpp.org/extensions/xep-0166.html#ns-errors'
xmlns='http://www.xmpp.org/extensions/xep-0166.html#ns-errors'
elementFormDefault='qualified'>
<xs:element name='out-of-order' type='empty'/>
<xs:element name='unknown-session' type='empty'/>
<xs:element name='unsupported-content' type='empty'/>
<xs:element name='unsupported-transports' type='empty'/>
<xs:simpleType name='empty'>
<xs:restriction base='xs:string'>
<xs:enumeration value=''/>
</xs:restriction>
</xs:simpleType>
</xs:schema>
Until Jingle was developed, there existed no widely-adopted standard for initiating and managing peer-to-peer interactions between XMPP entities. Although several large service providers and Jabber client teams had written and implemented their own proprietary XMPP extensions for peer-to-peer signalling (usually only for voice), those technologies were not open and did not always take into account requirements to interoperate with SIP-based technologies. The only existing open protocol was A Transport for Initiating and Negotiating Sessions [24], which made it possible to initiate and manage peer-to-peer sessions, but which did not provide enough of the key signalling semantics to be easily implemented in Jabber/XMPP clients. [25]
The result was an unfortunate fragmentation within the XMPP community regarding signalling protocols. Essentially, there were two possible approaches to solving the problem:
Implementation experience indicates that a dual-stack approach may not be feasible on all the computing platforms for which Jabber clients have been written, or even desirable on platforms where it is feasible. [26] Therefore, it seemed reasonable to define an XMPP signalling protocol that could provide the necessary session management semantics while also making it relatively straightforward to interoperate with existing Internet standards.
As a result of feedback received on XEP-0111, the original authors of this document (Joe Hildebrand and Peter Saint-Andre) began to define such a signalling protocol, code-named Jingle. Upon communication with members of the Google Talk team, [27] it was discovered that the emerging Jingle approach was conceptually (and even syntactically) quite similar to the signalling protocol used in the Google Talk application. Therefore, in the interest of interoperability and adoption, we decided to harmonize the two approaches. The signalling protocol specified herein is, therefore, substantially equivalent to the original Google Talk protocol, with several adjustments based on feedback received from implementors as well as for publication within the XMPP Standards Foundation's standards process.
The authors would like to thank Rohan Mahy for his valuable input on early versions of this document. Thiago Camargo, Dafydd Harries, Antti Ijäs, Lauri Kaila, Justin Karneges, Jussi Laako, Anthony Minessale, Matt O'Gorman, Rob Taylor, Matt Tucker, Saku Vainio, Brian West, and others have also provided helpful input. Thanks also to those who have commented on the Standards SIG [28] and (earlier) Jingle [29] mailing lists.
1. RFC 3550: RTP: A Transport Protocol for Real-Time Applications <http://tools.ietf.org/html/rfc3550>.
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. XEP-0167: Jingle Audio via RTP <http://www.xmpp.org/extensions/xep-0167.html>.
5. RFC 3261: Session Initiation Protocol (SIP) <http://tools.ietf.org/html/rfc3261>.
6. XEP-0180: Jingle Video via RTP <http://www.xmpp.org/extensions/xep-0180.html>.
7. RFC 4566: SDP: Session Description Protocol <http://tools.ietf.org/html/rfc4566>.
8. XEP-0176: Jingle ICE Transport Method <http://www.xmpp.org/extensions/xep-0176.html>.
9. XEP-0177: Jingle Raw UDP Transport Method <http://www.xmpp.org/extensions/xep-0177.html>.
10. ITU Recommendation H.323: Packet-based Multimedia Communications Systems (September 1999).
11. In the event that a session contains two unidirectional streams of the same type because a content-add was issued simultaneously by both parties, it is RECOMMENDED that participants close the duplicate stream in favour of that created by the session initiator, which should be made bidirectional with a 'content-modify' action by the responder.
12. A client MUST NOT return an error upon receipt of a 'content-remove' action for a content description that is received after a 'content-remove' action has been sent but before the action has been acknowledged by the peer.
13. RFC 3921: Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence <http://tools.ietf.org/html/rfc3921>.
14. XEP-0030: Service Discovery <http://www.xmpp.org/extensions/xep-0030.html>.
15. XEP-0115: Entity Capabilities <http://www.xmpp.org/extensions/xep-0115.html>.
16. Naturally, instead of sending service discovery requests to every contact in a user's roster, it is more efficient to use Entity Capabilities, whereby support for Jingle and various Jingle content description formats and content transport methods is determined for a client version in general (rather than on a per-JID basis) and then cached. Refer to XEP-0115 for details.
17. XEP-0168: Resource Application Priority <http://www.xmpp.org/extensions/xep-0168.html>.
18. XEP-0155: Stanza Session Negotiation <http://www.xmpp.org/extensions/xep-0155.html>.
19. See <http://www.w3.org/TR/2000/WD-xml-2e-20000814#NT-Nmtoken>
20. XEP-0030: Service Discovery <http://www.xmpp.org/extensions/xep-0030.html>.
21. 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/>.
22. 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/>.
23. XEP-0053: XMPP Registrar Function <http://www.xmpp.org/extensions/xep-0053.html>.
24. XEP-0111: A Transport for Initiating and Negotiating Sessions <http://www.xmpp.org/extensions/xep-0111.html>.
25. It is true that TINS made it relatively easy to implement an XMPP-to-SIP gateway; however, in line with the long-time Jabber philosophy of "simple clients, complex servers", it would be better to force complexity onto the server-side gateway and to keep the client as simple as possible.
26. For example, one large ISP decided to switch to a pure XMPP approach after having implemented and deployed a dual-stack client for several years.
27. Google Talk is a messaging and voice chat service and client provided by Google; see <http://www.google.com/talk/>.
28. The Standards SIG is a standing Special Interest Group devoted to development of XMPP Extension Protocols. The discussion list of the Standards SIG is the primary venue for discussion of XMPP protocol extensions, as well as for announcements by the XMPP Extensions Editor and XMPP Registrar. To subscribe to the list or view the list archives, visit <http://mail.jabber.org/mailman/listinfo/standards/>.
29. Before this specification was accepted as a XMPP Extension Protocol specification, it was discussed on the semi-private <jingle@jabber.org> mailing list; although that list is no longer used (the Standards list is the preferred discussion venue), for historical purposes it is publicly archived at <http://mail.jabber.org/pipermail/jingle/>.
Clarified resource determination process and updated text to reflect modifications to XEP-0168.
(psa)Rewrote introduction and moved historical text to separate section.
(psa)Clarified session lifetime; defined reason attribute and associated registry; further specified conformance requirements.
(psa)Simplified signalling process and state chart; Removed session-redirect action (use redirect error instead); removed content-decline action; removed transport-* actions (except transport-info for ICE negotiation); removed description-* actions; simplified syntax to allow only one transport per content type; corrected syntax of creator attribute to be either initiator or responder (not JIDs); added profile attribute to content element in order to specify RTP profile in use.
(psa/ram)Added creator attribute to content element for prevention of race condition; modified spec to use provisional namespace before advancement to Draft (per XEP-0053).
(psa/ram)Completed clarifications and corrections throughout; added section on Jingle Actions.
(psa)Made several corrections to the state machines and examples.
(ram/psa)Further cleaned up state machines and state-related actions.
(ram/psa)Changed channels to components in line with ICE; changed various action names for consistency; added session-extend and session-reduce actions to add and remove description/transport pairs; added description-modify action; added sender attribute to specify directionality.
(ram/psa)Added implementation note about handling multiple content types.
(psa)Changed media type to content type.
(se/psa)Further clarified state machine diagrams; specified that session accept must include agreed-upon media format and transport description; moved deployment notes to appropriate transport spec.
(psa/jb)Added glossary; clarified state machines; updated to reflect publication of XEP-0176 and XEP-0177.
(psa/jb)Provided more detail about modify scenarios; defined media-specific and transport-specific actions and adjusted state machine accordingly.
(psa/jb)Per agreement among the co-authors, moved transport definition to separate specification, simplified state machine, and made other associated changes to the text, examples, and schemas; also harmonized redirect, decline, and terminate processes.
(psa/jb)Initial version.
(psa)More fully documented burst mode, connectivity checks, error cases, etc.
(psa)Restructured document flow; provided example of burst mode.
(psa)Distinguished between dribble mode and burst mode, including mode attribute, service discovery features, and implementation notes; provided detailed resource discovery examples; corrected state chart; specified session termination; specified error conditions; specified semantics of informational messages; began to define security considerations; added Joe Beda as co-author.
(psa/sl/jb)Added more detail to basic session flow; harmonized candidate negotiation process with ICE.
(psa)Added XMPP Registrar considerations; defined schema; completed slight syntax cleanup.
(psa)Separated methoddescription formats from signalling protocol.
(psa/sl)Harmonized basic session flow with Google Talk protocol; added Scott Ludwig as co-author.
(psa/sl)Added more detail to basic session flow.
(psa)Protocol cleanup.
(psa/jjh)First draft.
(psa/jjh)END