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Reachability Addresses This document defines an XMPP protocol extension for communicating reachability information related to non-XMPP devices. &LEGALNOTICE; 0152 Experimental Standards Track Standards Council XMPP Core XMPP IM reach &hildjj; &stpeter; 0.3 2008-10-06 psa
  • Modified namespaces to incorporate namespace versioning.
  • Removed IQ request-response method.
  • Corrected PEP examples.
  • Corrected XML schema.
0.2 2006-09-17 psa

Defined PEP transport.

0.1 2005-06-16 psa

Initial version.

0.0.1 2005-06-07 psa/jjh

First draft.

Sometimes it is desirable or necessary to switch from instant messaging (IM) to another real-time communications medium, such as a telephone conversation conducted over the traditional public switched telephone network (PSTN) or more recent Voice over Internet Protocol (VoIP) applications. In order to facilitate switching from IM to telephony or some other medium, a user needs to advertise the address(es) at which they can be reached. There are several possible ways to do this:

This document addresses the following requirements:

The following is an example of the basic data format for reachability addresses:

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When publishing reachability addresses, the <reach/> element MUST contain at least one <addr/> element. Each <addr/> element MUST possess a 'uri' attribute, whose value MUST be the Uniform Resource Identifier (&rfc3986;) or Internationalized Resource Identifier (&rfc3987;) of an alternate communications method for reaching the user.

The <addr/> element MAY contain one or more <desc/> children whose XML character data is a natural-language description of the address; this element SHOULD possess an 'xml:lang' attribute whose value is a language tag that conforms to &rfc4646; (although the default language MAY be specified at the stanza level; see Section 9.1.5 of &rfc3920;). In order to preserve bandwidth, the <desc/> element SHOULD NOT be included when sending reachbility data via presence broadcast, but MAY be included when using the personal eventing protocol.

New conference room number My softphone ]]>

As described below, this document specifies two methods of advertising reachability addresses:

This document does not recommend one transport method over the other.

In addition, a contact MAY request a user's reachability addresses using an &IQ; request-response sequence.

In order to broadcast reachability addresses in presence information, a user's client includes the <reach/> element in the &PRESENCE; stanza it sends to its server:

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The user's server then broadcasts that presence stanza to all entities who are subscribed to the user's presence:

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In order to publish reachability addresses via the personal eventing protocol (XEP-0163), the entity simply publishes data to the "urn:xmpp:reach:0" node.

My mobile number My softphone ]]> My mobile number My softphone ]]>

If an entity supports reachability addresses, it MUST advertise that fact by returning a feature of "urn:xmpp:reach:0" &VNOTE; in response to a &xep0030; information request. The response MUST also include features for the application formats and transport methods supported by the responding entity, as described in the relevant specifications.

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In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined in &xep0115;. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.

To preserve network bandwidth, the sender SHOULD NOT include the <desc/> element unless that information is deemed necessary to enable communication.

A recipient SHOULD attempt communications with reachability addresses in the order that the <addr/> elements appear within the <reach/> element.

If included, the <desc/> element SHOULD possess an 'xml:lang' attribute specifying the language of the human-readable descriptive text for a particular address.

This document introduces no security considerations above and beyond those described in RFC 3920, RFC 3921, and (for the personal eventing transport) XEP-0163.

This document requires no interaction with &IANA;.

This specification defines the following XML namespaces:

  • urn:xmpp:reach:0

Upon advancement of this specification from a status of Experimental to a status of Draft, the ®ISTRAR; shall add the foregoing namespaces to the registry located at &NAMESPACES;, as described in Section 4 of &xep0053;.

If the protocol defined in this specification undergoes a major revision that is not fully backward-compatible with an older version, or that contains significant new features, the XMPP Registrar shall increment the protocol version number found at the end of the XML namespaces defined herein, as described in Section 4 of XEP-0053.

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