?? rfc 3343 the application exchange (apex) presence service.htm
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<TD vAlign=top align=left>Network Working Group<BR>Request for Comments:
3343<BR>Category: Experimental<BR>
<TD vAlign=top align=right>M. Rose<BR>Dover Beach Consulting, Inc.<BR>G.
Klyne<BR>Nine by Nine<BR>D. Crocker<BR>Brandenburg
InternetWorking<BR>April 2003<BR></TD></TR></TBODY></TABLE><EM><A
name=page-1>Page 1</A></EM>
<P>
<H3 align=center>The Application Exchange (APEX) Presence Service</H3>
<P>
<DL>
<DT>Status of this Memo
<DD>
<P>This memo defines an Experimental Protocol for the Internet community. It
does not specify an Internet standard of any kind. Discussion and suggestions
for improvement are requested. Distribution of this memo is unlimited.
<P></P>
<DT>Copyright Notice
<DD>
<P>Copyright © The Internet Society (2003). All Rights Reserved.
<P></P>
<DT>Abstract
<DD>
<P>This memo describes the Application Exchange (APEX) presence service,
addressed as the well-known endpoint "apex=presence". The presence service is
used to manage presence information for APEX endpoints.
<P></P>
<DT>Table of Contents
<DD>
<P><A href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-1">1. Introduction
</A><BR><A href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-2">2. Use and
Management of Presence Information </A><BR><A
href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-2.1">2.1 Update of
Presence Information </A><BR><A
href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-2.2">2.2 Distribution of
Presence Information </A><BR><A
href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-2.3">2.3 Distribution of
Watcher Information </A><BR><A
href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-3">3. Format of Presence
Entries </A><BR><A href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-4">4.
The Presence Service </A><BR><A
href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-4.1">4.1 Use of XML and
MIME </A><BR><A href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-4.2">4.2
The Subscribe Operation </A><BR><A
href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-4.3">4.3 The Watch
Operation </A><BR><A
href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-4.4">4.4 The Publish
Operation </A><BR><A
href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-4.5">4.5 The Terminate
Operation </A><BR><A
href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-4.6">4.6 The Notify
Operation </A><BR><A
href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-4.7">4.7 The Reply
Operation </A><BR><A href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-5">5.
Registration: The Presence Service </A><BR><A
href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-6">6. The Presence Service
DTD </A><BR><A href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-7">7.
Security Considerations </A><BR><A
href="http://www.apps.ietf.org/rfc/rfc3343.html#page-21">References </A>
<P></P>
<DT>
<HR>
<EM><A name=page-2>Page 2</A></EM>
<DD>
<P><A
href="http://www.apps.ietf.org/rfc/rfc3343.html#page-22">Acknowledgements
</A><BR><A href="http://www.apps.ietf.org/rfc/rfc3343.html#page-22">Authors'
Addresses </A><BR><A
href="http://www.apps.ietf.org/rfc/rfc3343.html#page-23">Full Copyright
Statement </A><BR></P>
<DT><STRONG><A name=sec-1>1</A> Introduction</STRONG>
<DD>
<P>This memo describes a presence service that is built upon the APEX [1]
"relaying mesh". The APEX presence service is used to manage presence
information for APEX endpoints.
<P>APEX, at its core, provides a best-effort datagram service. Within an
administrative domain, all relays must be able to handle messages for any
endpoint within that domain. APEX services are logically defined as endpoints,
but given their ubiquitous semantics they do not necessarily need to be
associated with a single physical endpoint. As such, they may be provisioned
co-resident with each relay within an administrative domain, even though they
are logically provided on top of the relaying mesh, i.e.,
<P><PRE> +----------+ +----------+ +----------+ +---------+
| APEX | | APEX | | APEX | | |
| access | | presence | | report | | ... |
| service | | service | | service | | |
+----------+ +----------+ +----------+ +---------+
| | | |
| | | |
+----------------------------------------------------------------+
| |
| APEX core |
| |
+----------------------------------------------------------------+
</PRE>
<P>That is, applications communicate with an APEX service by exchanging data
with a "well-known endpoint" (WKE).
<P>APEX applications communicate with the presence service by exchanging data
with the well-known endpoint "apex=presence" in the <BR>corresponding
administrative domain, e.g., <BR>"apex=presence@example.com" is the endpoint
associated with the presence service in the "example.com" administrative
domain.
<P>Note that within a single administrative domain, the presence service makes
use of the APEX access [3] service in order to determine if an originator is
allowed to view or manage presence information.
<P></P>
<DT>
<HR>
<EM><A name=page-3>Page 3</A></EM>
<DD>
<P></P>
<DT><STRONG><A name=sec-2>2</A> Use and Management of Presence
Information</STRONG>
<DD>
<P>Management of presence information falls into three categories:
<P>
<UL>
<LI>applications may update the presence information associated with an
endpoint;
<P></P>
<LI>applications may subscribe to receive presence information associated
with an endpoint; and,
<P></P>
<LI>applications may find out who is subscribed to receive presence
information. </LI></UL>
<P>Each is now described in turn.
<P></P>
<DT><STRONG><A name=sec-2.1>2.1</A> Update of Presence Information</STRONG>
<DD>
<P>When an application wants to modify the presence information associated
with an endpoint, it sends a publish operation to the service, e.g.,
<P><PRE> +-------+ +-------+
| | -- data -------> | |
| appl. | | relay |
| | <--------- ok -- | |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='fred@example.com' />
<recipient identity='apex=presence@example.com' />
<data-content Name='Content'>
<publish publisher='fred@example.com' transID='1'
timeStamp='2000-05-14T13:30:00-08:00'>
<presence publisher='fred@example.com'
lastUpdate='2000-05-14T13:02:00-08:00'
publisherInfo='<A href="http://www.example.com/fred/'">http://www.example.com/fred/'</A>>
<tuple
destination='apex:fred/appl=im@example.com'
availableUntil='2000-05-14T14:02:00-08:00' />
<tuple destination='mailto:fred@flintstone.com'
availableUntil='2525-12-31T23:59:59-08:00' />
</presence>
</publish>
</data-content>
</data>
S: <ok />
</PRE>
<P></P>
<DT>
<HR>
<EM><A name=page-4>Page 4</A></EM>
<DD>
<P>Note that this example uses the "subaddress" convention specified in
Section 2.2 of [1] (e.g., "fred/appl=im") to denote multiplexing of traffic
for a particular endpoint. Of course, popular applications may have their own
URI method assigned to them (e.g., <BR>"im:fred@example.com").
<P>The service immediately responds with a reply operation containing the same
transaction-identifier, e.g.,
<P><PRE> +-------+ +-------+
| | <------- data -- | |
| relay | | pres. |
| | -- ok ---------> | svc. |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='apex=presence@example.com' />
<recipient identity='fred@example.com' />
<data-content Name='Content'>
<reply code='250' transID='1' />
</data-content>
</data>
S: <ok />
</PRE>
<P></P>
<DT><STRONG><A name=sec-2.2>2.2</A> Distribution of Presence
Information</STRONG>
<DD>
<P>When an application wants to (periodically) receive the presence
information associated with an endpoint, it sends a subscribe operation to the
service, e.g.,
<P><PRE> +-------+ +-------+
| | -- data -------> | |
| appl. | | relay |
| | <--------- ok -- | |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='wilma@example.com' />
<recipient identity='apex=presence@example.com' />
<data-content Name='Content'>
<subscribe publisher='fred@example.com' duration='86400'
transID='100' />
</data-content>
</data>
S: <ok />
</PRE>
<P></P>
<DT>
<HR>
<EM><A name=page-5>Page 5</A></EM>
<DD>
<P>The service immediately responds with a publish operation containing the
same transaction-identifier, e.g.,
<P><PRE> +-------+ +-------+
| | <------- data -- | |
| relay | | pres. |
| | -- ok ---------> | svc. |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='apex=presence@example.com' />
<recipient identity='wilma@example.com' />
<data-content Name='Content'>
<publish publisher='fred@example.com' transID='100'
timeStamp='2000-05-14T13:30:00-08:00'>
<presence publisher='fred@example.com'
lastUpdate='2000-05-14T13:02:00-08:00'
publisherInfo='<A href="http://www.example.com/fred/'">http://www.example.com/fred/'</A>>
<tuple
destination='apex:fred/appl=im@example.com'
availableUntil='2000-05-14T14:02:00-08:00' />
</presence>
</publish>
</data-content>
</data>
S: <ok />
</PRE>
<P>Subsequently, for up to the specified "duration", the service sends new
publish operations whenever there are any changes to the endpoint's presence
information. If the "duration" is zero-valued, a one time poll of the presence
information is achieved; otherwise, at the end of the "duration", a terminate
operation is sent.
<P>Note that Step 5 of <A
href="http://www.apps.ietf.org/rfc/rfc3343.html#sec-4.4">Section 4.4</A>
requires that the "lastUpdate" attribute of a presence entry be supplied in
order to update that entry; accordingly, applications must successfully
retrieve a presence entry prior to trying to update that entry. This is
usually accomplished by subscribing with a zero-valued duration.
<BR>(Regardless, administrators should ensure that applications authorized to
update a presence entry are also authorized to retrieve that entry.)
<P></P>
<DT>
<HR>
<EM><A name=page-6>Page 6</A></EM>
<DD>
<P>Either the subscriber or the service may cancel a subscription by sending a
terminate operation, e.g.,
<P><PRE> +-------+ +-------+
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