XEP-xxxx: Call Invites

Abstract
This document defines how to invite someone to a call and how to respond to the invite.
Authors
  • Natalie Wirth
  • Marvin Wissfeld
Copyright
© 1999 – 2021 XMPP Standards Foundation. SEE LEGAL NOTICES.
Status

ProtoXEP

WARNING: This document has not yet been accepted for consideration or approved in any official manner by the XMPP Standards Foundation, and this document is not yet an XMPP Extension Protocol (XEP). If this document is accepted as a XEP by the XMPP Council, it will be published at <https://xmpp.org/extensions/> and announced on the <standards@xmpp.org> mailing list.
Type
Standards Track
Version
0.0.1 (2022-01-01)
Document Lifecycle
  1. Experimental
  2. Proposed
  3. Stable
  4. Final

1. Introduction

A call can take place between two or more parties and can be initiated and conducted via various protocols. This specification defines a way to invite someone to a call providing one or more ways in which to join.

Jingle Message Initiation (XEP-0353) [1] provides partially overlapping functionality. It allows to initiate any kind of Jingle session, for example calls but also file transfers. However, it is not suitable for inviting someone to any kind of call, since a call can also be established through other means than a simple Jingle session-initiate.

This specification defines a way to invite someone to a call. The call can for example be initiated via Jingle RTP Sessions (XEP-0167) [2] or via an external URI. It also allows to define multiple ways to join the same call. Furthermore, it defines how to retract, accept and reject the call invite and how to indicate that a client left the call.

2. Use Cases

2.1 Proposing a call

To invite someone to a call, a message containing an <invite> element in the urn:xmpp:call-invites:0 namespace is sent. The element has an optional 'video' attribute that indicates if the call is intended to be joined with participants sending video ("true") or not ("false", default). An 'audio' attribute is defined analogously, defaulting to "true". The <invite> element contains one sub-element for each way to join the call.

In order to invite someone to a Jingle RTP Sessions (XEP-0167) [2] call, a <jingle> element is placed in the <invite> element. The <jingle> element has a 'sid' attribute specifying the ID of the Jingle session. It can optionally also contain a 'jid' element, to indicate the JID the Jingle session will be initiated from. If no 'jid' element is provided, the default is the sender of the message stanza.

Example 1. Invite to a Jingle video call
<message to='mara@example.com' id='id1' type='chat'>
  <invite video='true' xmlns='urn:xmpp:call-invites:0'>
    <jingle sid='sid1'/>
  </invite>
</message>

External ways to join the call can be specified via an <external> element placed in the <invite> element with an 'uri' attribute that contains a URI. The URI can for example contain a URL to a browser webclient or a dial-in telephone number.

Example 2. Invite to a mixer groupcall with webclient and dial-in fallback
<message to='mara@example.com' id='id2' type='chat'>
  <invite xmlns='urn:xmpp:call-invites:0'>
    <jingle sid='sid2' jid='mixer@example.com/uuid' />
    <external uri='https://example.com/uuid' />
    <external uri='tel:+12345678' />
  </invite>
</message>

Specifications that describe further ways to join a call define their own sub-elements to the <invite> element containing all necessary information for joining.

2.2 Retracting a call

A call invite can be retracted by sending a message containing a <retract> element with an 'id' attribute containing the id of the invite message qualified by the urn:xmpp:call-invites:0 namespace.

Example 3. Retracting a call
<message to='mara@example.com' type='chat'>
  <retract id='id1' xmlns='urn:xmpp:call-invites:0' />
</message>

2.3 Accepting a call

A call invite can be accepted by sending a message containing an <accept> element with an 'id' attribute containing the id of the invite message and qualified by the urn:xmpp:call-invites:0 namespace.

The element describing the connection method used by the accepting client (e.g. <jingle> or <external>) including all of its attributes and children is placed in the <accept> element.

Example 4. Accepting a call
<message to='mara@example.com' type='chat'>
  <accept id='id1' xmlns='urn:xmpp:call-invites:0'>
    <jingle sid='sid1' jid='mixer@example.com/uuid' />
  </accept>
</message>

After the <accept> was sent, the initiating or accepting client continues to establish the call depending on the selected connection method: If an <external> method was selected, the accepting client handles the URI. The exact behaviour of opening the URI is implementation specific. If a <jingle> method was selected, the initiating client triggers a Jingle session-initiate from the JID and with the session ID specified in the 'jid' and 'sid' attributes of the <jingle> element, respectively.

2.4 Rejecting a call

A call invite can be rejected by sending a message containing a <reject> element with an 'id' attribute containing the id of the invite message and qualified by the urn:xmpp:call-invites:0 namespace.

Example 5. Rejecting a call
<message to='mara@example.com' type='chat'>
  <reject id='id1' xmlns='urn:xmpp:call-invites:0' />
</message>

2.5 Leaving a call

When a client leaves a call, it sends a message containing a <left> element with an 'id' attribute containing the id of the invite message and qualified by the urn:xmpp:call-invites:0 namespace.

Example 6. Leaving a call
<message to='mara@example.com' type='chat'>
  <left id='id1' xmlns='urn:xmpp:call-invites:0' />
</message>

3. Business Rules

Clients must ensure that they will receive the accept or reject responses of other resources by the same user (if any) when implementing this specification. This can be achieved by implementing Message Carbons (XEP-0280) [3].

3.1 Using the correct ID

For messages of type 'groupchat', the stanza's 'id' attribute MUST NOT be used for call retracts, accepts, rejects or lefts. Instead, in group chat situations, the ID assigned to the stanza by the group chat itself must be used. This is discovered in a <stanza-id> element with a 'by' attribute that matches the bare JID of the group chat, as defined in Unique and Stable Stanza IDs (XEP-0359) [4].

This implies that invite messages should only be sent in group chats that attach a Unique and Stable Stanza IDs (XEP-0359) [4] stanza-id.

For other message types the sender should use the 'id' from a Unique and Stable Stanza IDs (XEP-0359) [4] <origin-id> if present, or the value of the 'id' attribute on the <message> otherwise.

4. Security Considerations

None.

5. IANA Considerations

This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [5].

6. XMPP Registrar Considerations

This document requires no interaction with XMPP Registrar [6].


Appendices

Appendix A: Document Information

Series
XEP
Number
xxxx
Publisher
XMPP Standards Foundation
Status
ProtoXEP
Type
Standards Track
Version
0.0.1
Last Updated
2022-01-01
Approving Body
XMPP Council
Dependencies
None
Supersedes
None
Superseded By
None
Short Name
call-invites

This document in other formats: XML  PDF

Appendix B: Author Information

Natalie Wirth
Email
nataliew@laposte.net
Marvin Wissfeld
Email
xsf@larma.de
JabberID
jabber@larma.de

Copyright

This XMPP Extension Protocol is copyright © 1999 – 2020 by the XMPP Standards Foundation (XSF).

Permissions

Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.

Disclaimer of Warranty

## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. ##

Limitation of Liability

In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.

IPR Conformance

This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which can be found at <https://xmpp.org/about/xsf/ipr-policy> or obtained by writing to XMPP Standards Foundation, P.O. Box 787, Parker, CO 80134 USA).

Visual Presentation

The HTML representation (you are looking at) is maintained by the XSF. It is based on the YAML CSS Framework, which is licensed under the terms of the CC-BY-SA 2.0 license.

Appendix D: Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) 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.

Appendix E: Discussion Venue

The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.

Discussion on other xmpp.org discussion lists might also be appropriate; see <https://xmpp.org/about/discuss.shtml> for a complete list.

Errata can be sent to <editor@xmpp.org>.

Appendix F: Requirements Conformance

The following requirements 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".

Appendix G: Notes

1. XEP-0353: Jingle Message Initiation <https://xmpp.org/extensions/xep-0353.html>.

2. XEP-0167: Jingle RTP Sessions <https://xmpp.org/extensions/xep-0167.html>.

3. XEP-0280: Message Carbons <https://xmpp.org/extensions/xep-0280.html>.

4. XEP-0359: Unique and Stable Stanza IDs <https://xmpp.org/extensions/xep-0359.html>.

5. 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/>.

6. 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 <https://xmpp.org/registrar/>.

Appendix H: Revision History

Note: Older versions of this specification might be available at https://xmpp.org/extensions/attic/

  1. Version 0.0.1 (2022-01-01)

    First draft.

    nw/mw

Appendix I: Bib(La)TeX Entry

@report{wirth2022call-invites,
  title = {Call Invites},
  author = {Wirth, Natalie and Wissfeld, Marvin},
  type = {XEP},
  number = {xxxx},
  version = {0.0.1},
  institution = {XMPP Standards Foundation},
  url = {https://xmpp.org/extensions/xep-xxxx.html},
  date = {2022-01-01/2022-01-01},
}

END