It is common for IM clients to be logged in and 'online' even while the user is not interacting with the application. This protocol allows the client to indicate to the server when the user is not actively using the client, allowing the server to optimise traffic to the client accordingly. This can save bandwidth and resources on both the client and server.
The aim of this specification is to provide a simple and efficient protocol for the client to report its state to the server. Exactly how the server uses this information is beyond the scope of this document, although some examples are given.
Other extensions exist, such as Stanza Interception and Filtering Technology (XEP-0273) [1], which also aim to optimise the traffic between the client and server. A notable difference is that instead of being client-controlled, CSI shifts the responsibility to the server, and aims to just provide the server with enough information to implement various optimisations itself.
Juliet has an XMPP client on her phone, which is available to receive messages. However most of the time Juliet has her phone screen turned off and is not interested in the status of her contacts unless they are communicating with her.
Juliet's client informs the server when Juliet is not interacting with it. The server uses this information to suppress or reduce stanzas that are unimportant, such as status updates.
When Juliet returns to her IM client, the client again informs the server, this time to report that it is active again. The server then disables its traffic optimisations and restores the stream to its normal state.
When the server knows that the user is not engaging with their client many optimisations become possible. For example a server could:
This list is for example only, a server is not required to implement all or any of these, nor is it prevented from implementing other behaviour not listed here. Regardless of what optimisations a server implements, it SHOULD provide a way for administrators to configure them, and MAY provide such configuration to users also (e.g. through an ad-hoc command).
If the server supports CSI, it advertises it in the stream features after the client has authenticated:
<stream:features>
<bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'/>
<csi xmlns='urn:xmpp:csi'/>
</stream:features>
A stream always begins in 'active' state. If a client wishes to inform the server that it has become inactive, it sends an <inactive/> element in the 'urn:xmpp:csi' namespace:
<inactive xmlns='urn:xmpp:csi'/>
As might be anticipated, when the client is active again it sends an <active/> element:
<active xmlns='urn:xmpp:csi'/>
There is no reply from the server to either of these elements (though they may indirectly cause the server to send stanzas, e.g. to update presence information when the client becomes active after a period of inactivity).
As this protocol is for indication only, clients MUST NOT make assumptions about how the server will use the active/inactive state information.
The server MUST assume all clients to be in the 'active' state until the client indicates otherwise. Also the CSI active/inactive state is unrelated to the user's presence, the server MUST treat the two independently.
This protocol is intended primarily for clients with human interaction. Due to the open-ended nature of the possible optimisations implemented by the server, it may not be suitable for non-IM purposes where the fully standard behaviour of XMPP is required.
To protect the privacy of users, servers MUST NOT reveal the clients active/inactive state to other entities on the network.
This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [3].
This document requires no interaction with XMPP Registrar [4].
<?xml version='1.0' encoding='UTF-8'?>
<xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='urn:xmpp:csi'
xmlns='urn:xmpp:csi'
elementFormDefault='qualified'>
<xs:element name='csi' type='empty'/>
<xs:element name='active' type='empty'/>
<xs:element name='inactive' type='empty'/>
<xs:simpleType name='empty'>
<xs:restriction base='xs:string'>
<xs:enumeration value=''/>
</xs:restriction>
</xs:simpleType>
</xs:schema>
This document in other formats: XML PDF
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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.
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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.
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/community/> for a complete list.
Errata can be sent to <editor@xmpp.org>.
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".
1. XEP-0273: Stanza Interception and Filtering Technology <https://xmpp.org/extensions/xep-0273.html>.
2. XEP-0085: Chat State Notifications <https://xmpp.org/extensions/xep-0085.html>.
3. 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/>.
4. 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/>.
Note: Older versions of this specification might be available at https://xmpp.org/extensions/attic/
First draft.
@report{wild2014xepxxxx,
title = {Client State Indication},
author = {Wild, Matthew},
type = {XEP},
number = {xxxx},
version = {0.0.1},
institution = {XMPP Standards Foundation},
url = {https://xmpp.org/extensions/xep-xxxx.html},
date = {2014-08-14/2014-08-14},
}END