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Entity Time This document defines an XMPP protocol extension for communicating the local time of an entity. &LEGALNOTICE; 0202 Experimental Standards Track Standards Council XMPP Core XEP-0082 XEP-0090 Not yet assigned &stpeter; Maciej Niedzielski machekku@uaznia.net machekku@uaznia.net 0.1 2006-12-20 psa

Initial version; further specified security considerations; per Council feedback, removed tz and display elements.

0.0.2 2006-12-19 psa

Clarified text; adjusted protocol definition; corrected schema.

0.0.1 2006-12-05 mn

First draft.

Although the XMPP protocol extension defined in &xep0090; provides a way to discover the time at another entity, it has several limitations:

To overcome these limitations, this document defines a replacement for XEP-0090 which enables communication of an entity's UTC time and numeric time zone offset while adhering to XEP-0082.

The namespace defined herein provides a standard way for XMPP entities to exchange information about the local time. The information is communicated in a request/response pair using an &IQ; element that contains a <time/> element qualified by an XML namespace to be issued when this specification advances to a status of Draft (see Protocol Namespace). The following children of the <time/> element are defined for use in IQ stanzas of type 'result':

Element Definition Inclusion
<tzo/> The entity's numeric time zone offset from UTC. The format MUST conform to Time Zone Definition (TZD) in XEP-0082. REQUIRED
<utc/> The UTC time according to the responding entity. The format MUST conform to the dateTime profile specified in XEP-0082 and MUST be expressed in UTC. REQUIRED
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The standard error conditions described in &xep0086; apply (e.g., &unavailable; if the entity does not support the namespace).

This protocol was designed in a way that makes migration from XEP-0090 straightforward. This document specifies a different format for the XML character data of the <utc> element (compliant with XEP-0082) and specifies a new <tzo> element for the numeric offset from UTC, while removing the formerly optional and effectively useless <display/> and <tz/> elements.

Implementations that support XEP-0090 should support the protocol defined herein as soon as possible, but should continue to support the protocol defined in XEP-0090 for backwards compatibility until the status of that specification is changed to Obsolete.

Revealing an entity's numeric time zone offset may leak limited information about the entity's current location. If the entity's understanding of UTC is far off from actual UTC, revealing that discrepancy may make it possible for an attacker to send XML stanzas that appear to be in the past or future even though they are not; therefore an entity should use the Network Time Protocol (&rfc0958;) or a similar technology to stay synchronized with actual UTC.

This document requires no interaction with &IANA;.

Until this specification advances to a status of Draft, its associated namespace shall be "http://www.xmpp.org/extensions/xep-0202.html#ns"; upon advancement of this specification, the XMPP Registrar shall issue a permanent namespace in accordance with the process defined in Section 4 of &xep0053;.

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