JEP-0152: Reachability Addresses

This JEP defines an XMPP protocol extension for communicating reachability information.


WARNING: Consideration of this JEP has been Deferred by the Jabber Software Foundation. Implementation of the protocol described herein is not recommended.


JEP Information

Status: Deferred
Type: Standards Track
Number: 0152
Version: 0.1
Last Updated: 2005-06-16
JIG: Standards JIG
Approving Body: Jabber Council
Dependencies: XMPP Core, XMPP IM
Supersedes: None
Superseded By: None
Short Name: reach
Wiki Page: <http://wiki.jabber.org/index.php/Reachability Addresses (JEP-0152)>

Author Information

Joe Hildebrand

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

Peter Saint-Andre

Email: stpeter@jabber.org
JID: stpeter@jabber.org

Legal Notice

This Jabber Enhancement Proposal is copyright 1999 - 2006 by the Jabber Software Foundation (JSF) and is in full conformance with the JSF's Intellectual Property Rights Policy <http://www.jabber.org/jsf/ipr-policy.shtml>. This material may be distributed only subject to the terms and conditions set forth in the Creative Commons Attribution License (<http://creativecommons.org/licenses/by/2.5/>).

Discussion Venue

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

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 Jabber Software 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 JEP 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 keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.


Table of Contents

1. Introduction
2. Requirements
3. Data Format
4. Data Transport
4.1. Presence Broadcast
4.2. Publish-Subscribe Transport
4.3. IQ Request
5. Implementation Notes
6. Internationalization Considerations
7. Security Considerations
8. IANA Considerations
9. Jabber 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 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 media, 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 JEP addresses the following requirements:

3. Data Format

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

<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'/>
</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 3066 [7] (although the default language MAY be specified at the stanza level; see Section 9.1.5 of RFC 3920 [8]).

4. Data Transport

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

This JEP 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 1. 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'>
      <desc xml:lang='en'>My mobile number</desc>
    </addr>
    <addr uri='sip:romeo@sipspeare.lit'>
      <desc xml:lang='en'>My softphone</desc>
    </addr>
  </reach>
</presence>
    

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

Example 2. 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'>
      <desc xml:lang='en'>My mobile number</desc>
    </addr>
    <addr uri='sip:romeo@sipspeare.lit'>
      <desc xml:lang='en'>My softphone</desc>
    </addr>
  </reach>
</presence>
.
.
.
    

4.2 Publish-Subscribe Transport

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

Example 3. 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='n48ad4fj78zn38st734'>
      <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 4. Subscriber receives event with payload

<message from='pubsub.shakespeare.lit'
         to='juliet@capulet.com'>
  <event xmlns='http://jabber.org/protocol/pubsub#event'>
    <items node='n48ad4fj78zn38st734'>
      <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 5. 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 6. 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>
    

Note: IQ requests are NOT RECOMMENDED; instead, it is RECOMMENDED to use either presence broadcast or publish-subscribe transport as described above.

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 JEP introduces no security considerations above and beyond those described in RFC 3920, RFC 3921, and (for the pubsub transport) JEP-0060.

8. IANA Considerations

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

9. Jabber Registrar Considerations

9.1 Protocol Namespaces

The Jabber 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. JEP-0054: vcard-temp <http://www.jabber.org/jeps/jep-0054.html>.

2. JEP-0115: Entity Capabilities <http://www.jabber.org/jeps/jep-0115.html>.

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

4. JEP-0060: Publish-Subscribe <http://www.jabber.org/jeps/jep-0060.html>.

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

6. RFC 3987: Internationalized Resource Identifiers (IRIs) <http://www.ietf.org/rfc/rfc3987.txt>.

7. RFC 3066: Tags for the Identification of Languages <http://www.ietf.org/rfc/rfc3066.txt>.

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

9. JEP-0030: Service Discovery <http://www.jabber.org/jeps/jep-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 Jabber Registrar maintains a list of reserved Jabber protocol namespaces as well as registries of parameters used in the context of protocols approved by the Jabber Software Foundation. For further information, see <http://www.jabber.org/registrar/>.


Revision History

Version 0.1 (2005-06-16)

Initial JEP version. (psa)

Version 0.0.1 (2005-06-07)

First draft. (psa)


END