XEP-0152: Reachability Addresses

This document defines an XMPP protocol extension for communicating reachability information related to non-XMPP devices.


WARNING: Consideration of this document has been Deferred by the XMPP Standards Foundation. Implementation of the protocol described herein is not recommended.


Document Information

Series: XEP
Number: 0152
Publisher: XMPP Standards Foundation
Status: Deferred
Type: Standards Track
Version: 0.2
Last Updated: 2006-09-17
Approving Body: XMPP Council
Dependencies: XMPP Core, XMPP IM
Supersedes: None
Superseded By: None
Short Name: reach
Wiki Page: <http://wiki.jabber.org/index.php/Reachability Addresses (XEP-0152)>


Author Information

Joe Hildebrand

Email: jhildebrand@jabber.com
JabberID: hildjj@jabber.org

Peter Saint-Andre

JabberID: stpeter@jabber.org
URI: https://stpeter.im/


Legal Notices

Copyright

This XMPP Extension Protocol is copyright (c) 1999 - 2008 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. In no event shall the XMPP Standards Foundation or the authors of this Specification be liable for any claim, damages, or other liability, whether in an action of contract, tort, or otherwise, arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification. ##

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 out of the use or inability to use 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 may be found at <http://www.xmpp.org/extensions/ipr-policy.shtml> or obtained by writing to XSF, P.O. Box 1641, Denver, CO 80201 USA).

Discussion Venue

The preferred venue for discussion of this document is the Standards discussion list: <http://mail.jabber.org/mailman/listinfo/standards>.

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

Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 3920) and XMPP IM (RFC 3921) 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.

Conformance Terms

The following 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".


Table of Contents


1. Introduction
2. Requirements
3. Data Format
4. Data Transport
    4.1. Presence Broadcast
    4.2. Personal Eventing
    4.3. IQ Request
5. Implementation Notes
6. Internationalization Considerations
7. Security Considerations
8. IANA Considerations
9. XMPP Registrar Considerations
    9.1. Protocol Namespaces
10. XML Schema
Notes
Revision History


1. Introduction

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:

2. Requirements

This document addresses the following requirements:

3. Data Format

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

Example 1. Basic Data Format for Reachability Addresses

<reach xmlns='http://jabber.org/protocol/reach'>
  <addr uri='tel:+1-303-555-1212'/>
  <addr uri='sip:romeo@sipspeare.lit'/>
</reach>
  

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 (RFC 3986 [5]) or Internationalized Resource Identifier (RFC 3987 [6]) 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 RFC 4646 [7] (although the default language MAY be specified at the stanza level; see Section 9.1.5 of RFC 3920 [8]). 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 personal eventing.

Example 2. Reachability Addresses With Descriptions

<reach xmlns='http://jabber.org/protocol/reach'>
  <addr uri='tel:+1-303-555-1212'>
    <desc xml:lang='en'>New conference room number</desc>
  </addr>
  <addr uri='sip:romeo@sipspeare.lit'>
    <desc xml:lang='en'>My softphone</desc>
  </addr>
</reach>
  

4. Data Transport

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.

4.1 Presence Broadcast

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:

Example 3. User's Client Includes Reachability Addresses in Presence Broadcast

<presence from='romeo@montague.net'>
  <reach xmlns='http://jabber.org/protocol/reach'>
    <addr uri='tel:+1-303-555-1212'/>
    <addr uri='sip:romeo@sipspeare.lit'/>
  </reach>
</presence>
    

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

Example 4. User's Server Broadcasts Presence Information

<presence from='romeo@montague.net' to='juliet@capulet.com'>
  <reach xmlns='http://jabber.org/protocol/reach'>
    <addr uri='tel:+1-303-555-1212'/>
    <addr uri='sip:romeo@sipspeare.lit'/>
  </reach>
</presence>
.
.
.
    

4.2 Personal Eventing

In order to publish reachability via the publish-subscribe transport, an entity MUST first create the appropriate node as explained in XEP-0060. Here we assume that the node already exists.

Example 5. Entity publishes reachability addresses

<iq type='set'
    from='romeo@montague.net'
    to='pubsub.shakespeare.lit'
    id='publish1'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <publish node='http://jabber.org/protocol/reach'>
      <item id='a1s2d3f4g5h6bjeh936'>
        <reach xmlns='http://jabber.org/protocol/reach'>
          <addr uri='tel:+1-303-555-1212'>
            <desc xml:lang='en'>My mobile number</desc>
          </addr>
          <addr uri='sip:romeo@sipspeare.lit'>
            <desc xml:lang='en'>My softphone</desc>
          </addr>
        </reach>
      </item>
    </publish>
  </pubsub>
</iq>
    

Example 6. Subscriber receives event with payload

<message from='pubsub.shakespeare.lit'
         to='juliet@capulet.com'>
  <event xmlns='http://jabber.org/protocol/pubsub#event'>
    <items node='http://jabber.org/protocol/reach'>
      <item id='a1s2d3f4g5h6bjeh936'>
        <reach xmlns='http://jabber.org/protocol/reach'>
          <addr uri='tel:+1-303-555-1212'>
            <desc xml:lang='en'>My mobile number</desc>
          </addr>
          <addr uri='sip:romeo@sipspeare.lit'>
            <desc xml:lang='en'>My softphone</desc>
          </addr>
        </reach>
      </item>
    </items>
  </event>
</message>
    

4.3 IQ Request

If a client supports the reachability addresses protocol described herein, it SHOULD include a Service Discovery [9] feature of 'http://jabber.org/protocol/reach' in its replies to disco#info requests:

Example 7. Service Discovery Interaction

<iq from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' id='disco1'>
  <query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>

<iq to='romeo@montague.net/orchard' from='juliet@capulet.com/balcony' id='disco1'>
  <query xmlns='http://jabber.org/protocol/disco#info'>
    ...
    <feature var='http://jabber.org/protocol/reach'/>
    ...
  </query>
</iq>
    

If desired, the contact then MAY query the user for any reachability addresses:

Example 8. Reachability Request-Response

<iq from='juliet@capulet.com/balcony' to='romeo@montague.net/orchard' id='reach1'>
  <reach xmlns='http://jabber.org/protocol/reach'/>
</iq>

<iq to='romeo@montague.net/orchard' from='juliet@capulet.com/balcony' id='reach1'>
  <reach xmlns='http://jabber.org/protocol/reach'>
    <addr uri='tel:+1-303-555-1212'>
      <desc xml:lang='en'>My mobile number</desc>
    </addr>
    <addr uri='sip:romeo@sipspeare.lit'>
      <desc xml:lang='en'>My softphone</desc>
    </addr>
  </reach>
</iq>
    

5. Implementation Notes

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.

6. Internationalization Considerations

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

7. Security Considerations

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

8. IANA Considerations

This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [10].

9. XMPP Registrar Considerations

9.1 Protocol Namespaces

The XMPP Registrar [11] shall include 'http://jabber.org/protocol/reach' in its registry of protocol namespaces.

10. XML Schema

<?xml version='1.0' encoding='UTF-8'?>

<xs:schema
    xmlns:xs='http://www.w3.org/2001/XMLSchema'
    targetNamespace='http://jabber.org/protocol/reach'
    xmlns='http://jabber.org/protocol/reach'
    elementFormDefault='qualified'>

  <xs:element name='reach'>
    <xs:complexType>
      <xs:sequence>
        <xs:element ref='addr' minOccurs='0' maxOccurs='unbounded'/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:element name='address'>
    <xs:complexType>
      <xs:sequence>
        <xs:element ref='desc' minOccurs='0' maxOccurs='unbounded'/>
      </xs:sequence>
      <xs:attribute name='uri' use='required' type='xs:anyURI'/>
    </xs:complexType>
  </xs:element>

  <xs:element name='desc' type='xs:string'/>

</xs:schema>
  

Notes

1. XEP-0054: vcard-temp <http://www.xmpp.org/extensions/xep-0054.html>.

2. XEP-0115: Entity Capabilities <http://www.xmpp.org/extensions/xep-0115.html>.

3. RFC 3921: Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence <http://tools.ietf.org/html/rfc3921>.

4. XEP-0163: Personal Eventing via Pubsub <http://www.xmpp.org/extensions/xep-0163.html>.

5. RFC 3986: Uniform Resource Identifiers (URI): Generic Syntax <http://tools.ietf.org/html/rfc3986>.

6. RFC 3987: Internationalized Resource Identifiers (IRIs) <http://tools.ietf.org/html/rfc3987>.

7. RFC 4646: Tags for Identifying Languages <http://tools.ietf.org/html/rfc4646>.

8. RFC 3920: Extensible Messaging and Presence Protocol (XMPP): Core <http://tools.ietf.org/html/rfc3920>.

9. XEP-0030: Service Discovery <http://www.xmpp.org/extensions/xep-0030.html>.

10. 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/>.

11. 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 <http://www.xmpp.org/registrar/>.


Revision History

Version 0.2 (2006-09-17)

Defined PEP transport.

(psa)

Version 0.1 (2005-06-16)

Initial version.

(psa)

Version 0.0.1 (2005-06-07)

First draft.

(psa/jjh)

END