Updated to reflect new XMPP RFCs; strengthened security considerations.
Initial version.
Initial published version.
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:
+Sometimes it is desirable to augment instant messaging (IM) with another real-time communications medium, such as a voice conversation conducted over the traditional public switched telephone network (PSTN) or more recent Voice over Internet Protocol (VoIP) applications. In order to facilitate this functionality, a user needs to advertise the address(es) at which they can be reached. There are several possible ways to do this:
Publish the reachability address(es) in the user's vCard (see &xep0054;); this is convenient, but is not very dynamic (e.g., reachability addresses might change when the user moves to a new conference room in an office building).
Send the reachability address(es) within a &PRESENCE; stanza; this option is described in the Presence Broadcast section of this document and is consistent with &rfc6121; since reachability is one aspect of a user's availability for communication.
Send reachability address(es) to the appropriate &xep0163; node; this option is described in the PEP Transport section of this document but may not be available at all service providers.
Publish the address(es) in the user's vCard (see &xep0054; and &xep0292;); this is convenient, but is not very dynamic (e.g., reachability addresses might change when the user moves to a new conference room in an office building).
Send the address(es) within a &PRESENCE; stanza; this option is described in the Presence Transport section of this document and is consistent with &rfc6121; since reachability is one aspect of a user's availability for communication.
Send address(es) to the appropriate &xep0060; node; this option is described in the PEP Transport section of this document but might not be available at all service providers.
The following is an example of the basic data format for reachability addresses:
-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 &rfc6120;). 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.
+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 &rfc6120;). 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 directed presence or the personal eventing protocol.
As described below, this document specifies two methods of advertising reachability addresses:
+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:
-To broadcast reachability addresses in presence information, a user's client includes the <reach/> element in the &PRESENCE; stanza it sends to its server:
+Naturally, a reachability address MAY alternatively be included in directed presence.
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.
-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.
+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.
This document introduces no security considerations above and beyond those described in RFC 6120, RFC 6121, and (for the personal eventing transport) XEP-0163.
+Security considerations for XMPP presence and PEP publication are described in RFC 6120, RFC 6121, XEP-0060, and XEP-0163.
+