GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc3343

Network Working Group M. Rose Request for Comments: 3343 Dover Beach Consulting, Inc. Category: Experimental G. Klyne

                                                          Nine by Nine
                                                            D. Crocker
                                           Brandenburg InternetWorking
                                                            April 2003
          The Application Exchange (APEX) Presence Service

Status of this Memo

 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.

Copyright Notice

 Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

 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.

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
 2.  Use and Management of Presence Information . . . . . . . . . .  3
 2.1 Update of Presence Information . . . . . . . . . . . . . . . .  3
 2.2 Distribution of Presence Information . . . . . . . . . . . . .  4
 2.3 Distribution of Watcher Information  . . . . . . . . . . . . .  7
 3.  Format of Presence Entries . . . . . . . . . . . . . . . . . . 10
 4.  The Presence Service . . . . . . . . . . . . . . . . . . . . . 11
 4.1 Use of XML and MIME  . . . . . . . . . . . . . . . . . . . . . 12
 4.2 The Subscribe Operation  . . . . . . . . . . . . . . . . . . . 13
 4.3 The Watch Operation  . . . . . . . . . . . . . . . . . . . . . 14
 4.4 The Publish Operation  . . . . . . . . . . . . . . . . . . . . 15
 4.5 The Terminate Operation  . . . . . . . . . . . . . . . . . . . 17
 4.6 The Notify Operation . . . . . . . . . . . . . . . . . . . . . 17
 4.7 The Reply Operation  . . . . . . . . . . . . . . . . . . . . . 18
 5.  Registration: The Presence Service . . . . . . . . . . . . . . 18
 6.  The Presence Service DTD . . . . . . . . . . . . . . . . . . . 18
 7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 21
     References . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Rose, et al. Experimental [Page 1] RFC 3343 The Application Exchange (APEX) Presence April 2003

     Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 22
     Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 22
     Full Copyright Statement . . . . . . . . . . . . . . . . . . . 23

1. Introduction

 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.
 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.,
    +----------+     +----------+    +----------+    +---------+
    |   APEX   |     |   APEX   |    |   APEX   |    |         |
    |  access  |     | presence |    |  report  |    |   ...   |
    | service  |     |  service |    | service  |    |         |
    +----------+     +----------+    +----------+    +---------+
         |                |               |               |
         |                |               |               |
 +----------------------------------------------------------------+
 |                                                                |
 |                            APEX core                           |
 |                                                                |
 +----------------------------------------------------------------+
 That is, applications communicate with an APEX service by exchanging
 data with a "well-known endpoint" (WKE).
 APEX applications communicate with the presence service by exchanging
 data with the well-known endpoint "apex=presence" in the
 corresponding administrative domain, e.g.,
 "apex=presence@example.com" is the endpoint associated with the
 presence service in the "example.com" administrative domain.
 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.

Rose, et al. Experimental [Page 2] RFC 3343 The Application Exchange (APEX) Presence April 2003

2. Use and Management of Presence Information

 Management of presence information falls into three categories:
 o  applications may update the presence information associated with
    an endpoint;
 o  applications may subscribe to receive presence information
    associated with an endpoint; and,
 o  applications may find out who is subscribed to receive presence
    information.
 Each is now described in turn.

2.1 Update of Presence Information

 When an application wants to modify the presence information
 associated with an endpoint, it sends a publish operation to the
 service, e.g.,
     +-------+                  +-------+
     |       | -- 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='http://www.example.com/fred/'>
                      <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 />

Rose, et al. Experimental [Page 3] RFC 3343 The Application Exchange (APEX) Presence April 2003

 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.,
 "im:fred@example.com").
 The service immediately responds with a reply operation containing
 the same transaction-identifier, e.g.,
                                +-------+                  +-------+
                                |       | <------- 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 />

2.2 Distribution of Presence Information

 When an application wants to (periodically) receive the presence
 information associated with an endpoint, it sends a subscribe
 operation to the service, e.g.,
     +-------+                  +-------+
     |       | -- 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 />

Rose, et al. Experimental [Page 4] RFC 3343 The Application Exchange (APEX) Presence April 2003

 The service immediately responds with a publish operation containing
 the same transaction-identifier, e.g.,
                                +-------+                  +-------+
                                |       | <------- 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='http://www.example.com/fred/'>
                      <tuple
                        destination='apex:fred/appl=im@example.com'
                        availableUntil='2000-05-14T14:02:00-08:00' />
                  </presence>
              </publish>
          </data-content>
      </data>
   S: <ok />
 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.
 Note that Step 5 of Section 4.4 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.
 (Regardless, administrators should ensure that applications
 authorized to update a presence entry are also authorized to retrieve
 that entry.)

Rose, et al. Experimental [Page 5] RFC 3343 The Application Exchange (APEX) Presence April 2003

 Either the subscriber or the service may cancel a subscription by
 sending a terminate operation, e.g.,
     +-------+                  +-------+
     |       | -- data -------> |       |
     | appl. |                  | relay |
     |       | <--------- ok -- |       |
     +-------+                  +-------+
   C: <data content='#Content'>
          <originator identity='wilma@example.com' />
          <recipient identity='apex=presence@example.com' />
          <data-content Name='Content'>
              <terminate transID='100' />
          </data-content>
      </data>
   S: <ok />
                                +-------+                  +-------+
                                |       | <------- data -- |       |
                                | relay |                  | pres. |
                                |       | -- ok ---------> |  svc. |
                                +-------+                  +-------+
   C: <data content='#Content'>
          <originator identity='apex=presence@example.com' />
          <recipient identity='wilma@example.com' />
          <data-content Name='Content'>
              <reply code='250' transID='100' />
          </data-content>
      </data>
   S: <ok />
 or
                                +-------+                  +-------+
                                |       | <------- data -- |       |
                                | relay |                  | pres. |
                                |       | -- ok ---------> |  svc. |
                                +-------+                  +-------+
   C: <data content='#Content'>
          <originator identity='apex=presence@example.com' />
          <recipient identity='wilma@example.com' />
          <data-content Name='Content'>
              <terminate transID='100' />
          </data-content>
      </data>
   S: <ok />

Rose, et al. Experimental [Page 6] RFC 3343 The Application Exchange (APEX) Presence April 2003

2.3 Distribution of Watcher Information

 When an application wants to (periodically) receive notices about
 endpoints that are subscribed to receive presence information, it
 sends a watch operation to the service, e.g.,
     +-------+                  +-------+
     |       | -- data -------> |       |
     | appl. |                  | relay |
     |       | <--------- ok -- |       |
     +-------+                  +-------+
   C: <data content='#Content'>
          <originator identity='fred@example.com' />
          <recipient identity='apex=presence@example.com' />
          <data-content Name='Content'>
              <watch publisher='fred@example.com' duration='86400'
                     transID='2' />
          </data-content>
      </data>
   S: <ok />
 The service immediately responds with a reply operation containing
 the same transaction-identifier, e.g.,
                                +-------+                  +-------+
                                |       | <------- 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='2' />
          </data-content>
      </data>
   S: <ok />

Rose, et al. Experimental [Page 7] RFC 3343 The Application Exchange (APEX) Presence April 2003

 For each current subscriber, the service immediately sends a notify
 operation containing the same transaction-identifier, e.g.,
                                +-------+                  +-------+
                                |       | <------- data -- |       |
                                | relay |                  | pres. |
                                |       | -- ok ---------> |  svc. |
                                +-------+                  +-------+
   C: <data content='#Content'>
          <originator identity='apex=presence@example.com' />
          <recipient identity='fred@example.com' />
          <data-content Name='Content'>
              <notify subscriber='wilma@example.com' transID='2'
                      duration='86000' action='subscribe' />
          </data-content>
      </data>
   S: <ok />
 Subsequently, for up to the specified "duration", the service sends
 new notify operations whenever an application subscribes successfully
 or a subscription is terminated.  If the "duration" is zero-valued, a
 one time poll of the watcher information is achieved; otherwise, at
 the end of the "duration", a terminate operation is sent.

Rose, et al. Experimental [Page 8] RFC 3343 The Application Exchange (APEX) Presence April 2003

 Either the watcher or the service may cancel the request by sending a
 terminate operation, e.g.,
     +-------+                  +-------+
     |       | -- data -------> |       |
     | appl. |                  | relay |
     |       | <--------- ok -- |       |
     +-------+                  +-------+
   C: <data content='#Content'>
          <originator identity='fred@example.com' />
          <recipient identity='apex=presence@example.com' />
          <data-content Name='Content'>
              <terminate transID='2' />
          </data-content>
      </data>
   S: <ok />
                                +-------+                  +-------+
                                |       | <------- 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='2' />
           </data-content>
      </data>
   S: <ok />
 or
                                +-------+                  +-------+
                                |       | <------- data -- |       |
                                | relay |                  | pres. |
                                |       | -- ok ---------> |  svc. |
                                +-------+                  +-------+
   C: <data content='#Content'>
          <originator identity='apex=presence@example.com' />
          <recipient identity='fred@example.com' />
          <data-content Name='Content'>
              <terminate transID='2' />
           </data-content>
      </data>
   S: <ok />

Rose, et al. Experimental [Page 9] RFC 3343 The Application Exchange (APEX) Presence April 2003

3. Format of Presence Entries

 Each administrative domain is responsible for maintaining a "presence
 entry" for each of its endpoints (regardless of whether those
 endpoints are currently attached to the relaying mesh).
 Section 6 defines the syntax for presence entries.  Each presence
 entry has a "publisher" attribute, a "lastUpdate" attribute, a
 "publisherInfo" attribute, and contains one or more "tuple" elements:
 o  the "publisher" attribute specifies the endpoint associated with
    the presence entry;
 o  the "lastUpdate" attribute specifies the date and time that the
    service last updated the presence entry;
 o  the "publisherInfo" attribute specifies arbitrary information
    about the publisher (using a URI); and,
 o  each "tuple" element specifies information about an entity
    associated with the endpoint.
 Each "tuple" element has a "destination" attribute, an
 "availableUntil" attribute, a "tupleInfo" attribute, and contains
 zero or more "capability" elements:
 o  the "destination" attribute identifies the entity as a URI (e.g.,
    "apex:fred/appl=im@example.com" or "mailto:fred@flintstone.com");
 o  the "availableUntil" attribute specifies the latest date and time
    that the entity is capable of receiving messages;
 o  the "tupleInfo" attribute specifies arbitrary information about
    the entity (using a URI); and,
 o  each "capability" element contains a specification as to the kinds
    of content the entity is capable of receiving.
 Each "capability" element contains arbitrary character data formatted
 according to the standard indicated in the element's "baseline"
 attribute.

Rose, et al. Experimental [Page 10] RFC 3343 The Application Exchange (APEX) Presence April 2003

4. The Presence Service

 Section 5 contains the APEX service registration for the presence
 service:
 o  Within an administrative domain, the service is addressed using
    the well-known endpoint of "apex=presence".
 o  Section 6 defines the syntax of the operations exchanged with the
    service.
 o  A consumer of the service initiates communications by sending data
    containing the subscribe, watch, or publish operation.
 o  In addition to replying to these operations, the service may also
    initiate communications by sending data containing the terminate,
    publish, or notify operations.
 An implementation of the service must maintain information about both
 presence entries and in-progress operations in persistent storage.
 Consult Section 6.1.1 of [1] for a discussion on the properties of
 long-lived transaction-identifiers.

Rose, et al. Experimental [Page 11] RFC 3343 The Application Exchange (APEX) Presence April 2003

4.1 Use of XML and MIME

 Section 4.1 of [1] describes how arbitrary MIME content is exchanged
 as a BEEP [2] payload.  For example, to transmit:
     <data content='...'>
          <originator identity='apex=presence@example.com' />
         <recipient identity='fred@example.com' />
     </data>
 where "..." refers to: <reply code='250' transID='1' />
 then the corresponding BEEP message might look like this:
     C: MSG 1 1 . 42 1234
     C: Content-Type: multipart/related; boundary="boundary";
     C:               start="<1@example.com>";
     C:               type="application/beep+xml"
     C:
     C: --boundary
     C: Content-Type: application/beep+xml
     C: Content-ID: <1@example.com>
     C:
     C: <data content='cid:2@example.com'>
     C:     <originator identity='fred@example.com' />
     C:     <recipient identity='apex=presence@example.com' />
     C: </data>
     C: --boundary
     C: Content-Type: application/beep+xml
     C: Content-ID: <2@example.com>
     C:
     C: <reply code='250' transID='1' />
     C: --boundary--
     C: END
 or this:
     C: MSG 1 1 . 42 1234
     C: Content-Type: application/beep+xml
     C:
     C: <data content='#Content'>
     C:     <originator identity='fred@example.com' />
     C:     <recipient identity='apex=presence@example.com' />
     C:     <data-content Name='Content'>
     C:         <reply code='250' transID='1' />
     C:     </data-content>
     C: </data>
     C: END

Rose, et al. Experimental [Page 12] RFC 3343 The Application Exchange (APEX) Presence April 2003

4.2 The Subscribe Operation

 When an application wants to (periodically) receive the presence
 information associated with an endpoint, it sends a "subscribe"
 element to the service.
 The "subscribe" element has a "publisher" attribute, a "duration"
 attribute, a "transID" attribute, and no content:
 o  the "publisher" attribute specifies the endpoint associated with
    the presence entry;
 o  the "transID" attribute specifies the transaction-identifier
    associated with this operation; and,
 o  the "duration" attribute specifies the maximum number of seconds
    for which the originator is interested in receiving updated
    presence information.
 When the service receives a "subscribe" element, we refer to the
 "publisher" attribute of that element as the "subject", and the
 service performs these steps:
 1. If the subject is outside of this administrative domain, a "reply"
    element having code 553 is sent to the originator.
 2. If the subject does not refer to a valid endpoint, a "reply"
    element having code 550 is sent to the originator.
 3. If the subject's access entry does not contain a
    "presence:subscribe" token for the originator, a "reply" element
    having code 537 is sent to the originator.
 4. If the originator already has an in-progress subscribe operation
    for the subject, then the previous subscribe operation is silently
    terminated, and processing continues.
 5. If the "transID" attribute refers to an in-progress subscribe or
    watch operation for the originator, a "reply" element having code
    555 is sent to the originator.
 6.  Otherwise:
    1. A "publish" element, corresponding to the subject's presence
       entry, is immediately sent to the originator.

Rose, et al. Experimental [Page 13] RFC 3343 The Application Exchange (APEX) Presence April 2003

    2. For each endpoint currently watching subscribers to the
       subject's presence information, a "notify" element is
       immediately as sent (c.f., Step 6.3 of Section 4.6).
    3. For up to the amount of time indicated by the "duration"
       attribute of the "subscribe" element, if the subject's presence
       entry changes, an updated "presence" element is sent to the
       originator using the publish operation (Section 4.4).  Finally,
       when the amount of time indicated by the "duration" attribute
       expires, a terminate operation (Section 4.5) is sent to the
       originator.
    Note that if the duration is zero-valued, then the subscribe
    operation is making a one-time poll of the presence information.
    Accordingly, Step 6.3 above does not occur.
 Regardless of whether a "publish" or "reply" element is sent to the
 originator, the "transID" attribute is identical to the value found
 in the "subscribe" element sent by the originator.

4.3 The Watch Operation

 When an application wants to (periodically) receive notices about
 endpoints that are subscribed to receive presence entry, it sends a
 "watch" element to the service.
 The "watch" element has a "publisher" attribute, a "duration"
 attribute, a "transID" attribute, and no content:
 o  the "publisher" attribute specifies the endpoint associated with
    the presence entry;
 o  the "transID" attribute specifies the transaction-identifier
    associated with this operation; and,
 o  the "duration" attribute specifies the maximum number of seconds
    for which the originator is interested in watching subscribers.
 When the service receives a "watch" element, we refer to the
 "publisher" attribute of that element as the "subject", and the
 service performs these steps:
 1. If the subject is outside of this administrative domain, a "reply"
    element having code 553 is sent to the originator.
 2. If the subject does not refer to a valid endpoint, a "reply"
    element having code 550 is sent to the originator.

Rose, et al. Experimental [Page 14] RFC 3343 The Application Exchange (APEX) Presence April 2003

 3. If the subject's access entry does not contain a "presence:watch"
    token for the originator, a "reply" element having code 537 is
    sent to the originator.
 4. If the originator already has an in-progress watch operation for
    the subject, then the previous watch operation is silently
    terminated, and processing continues.
 5. If the "transID" attribute refers to an in-progress subscribe or
    watch operation for the originator, a "reply" element having code
    555 is sent to the originator.
 6. Otherwise:
    1. A "reply" element having code 250 is sent to the originator.
    2. For each endpoint currently subscribing to the subject's
       presence information, a "notify" element is immediately sent to
       the originator (c.f., Section 4.6).
    3. For up to the amount of time indicated by the "duration"
       attribute of the "watch" element, whenever a subscribe
       operation succeeds or a subscription is terminated, a "notify"
       element is sent to the originator.  Finally, when the amount of
       time indicated by the "duration" attribute expires, a terminate
       operation (Section 4.5) is sent to the originator.
    Note that if the duration is zero-valued, then the watch operation
    is making a one-time poll of the presence information.
    Accordingly, Step 6.3 above does not occur.
 Regardless of whether a "notify" or "reply" element is sent to the
 originator, the "transID" attribute is identical to the value found
 in the "presence" element sent by the originator.

4.4 The Publish Operation

 When an application wants to modify the presence entry associated
 with an endpoint, it sends a "publish" element to the service.  In
 addition, the service sends a "publish" element to endpoints that
 have subscribed to see presence information (c.f., Section 4.2).
 The "publish" element has a "publisher" attribute, a "transID"
 attribute, a "timeStamp" attribute, and contains a "presence"
 element:
 o  the "publisher" attribute specifies the endpoint to be associated
    with the presence entry;

Rose, et al. Experimental [Page 15] RFC 3343 The Application Exchange (APEX) Presence April 2003

 o  the "transID" attribute specifies the transaction-identifier
    associated with this operation;
 o  the "timeStamp" attribute specifies the application's notion of
    the current date and time; and,
 o  the "presence" element contains the desired presence entry for the
    endpoint.
 When the service sends a "publish" element, the "transID" attribute
 specifies the transaction-identifier associated with the subscribe
 operation that caused this "publish" element to be sent, and the
 "timeStamp" attribute specifies the service's notion of the current
 date and time.  No reply is sent by the receiving endpoint.
 When the service receives a "publish" element, we refer to the
 "publisher" attribute of that element as the "subject", and the
 service performs these steps:
 1. If the "publisher" attribute of the "publish" element doesn't
    match the "publisher" attribute of the "presence" element
    contained in the "publish" element, a "reply" element having code
    503 is sent to the originator.
 2. If the subject is outside of this administrative domain, a "reply"
    element having code 553 is sent to the originator.
 3. If the subject does not refer to a valid endpoint, a "reply"
    element having code 550 is sent to the originator.
 4. If the subject's access entry does not contain a
    "presence:publish" token for the originator, a "reply" element
    having code 537 is sent to the originator.
 5. If the "lastUpdate" attribute of the "publish" element is not
    semantically identical to the "lastUpdate" attribute of the
    subject's presence entry, a "reply" element having code 555 is
    sent to the originator.  (This allows a simple mechanism for
    atomic updates.)
 6. Otherwise:
    1. The subject's presence entry is updated from the "publish"
       element.
    2. The "lastUpdate" attribute of the presence entry is set to the
       service's notion of the current date and time.

Rose, et al. Experimental [Page 16] RFC 3343 The Application Exchange (APEX) Presence April 2003

    3. A "reply" element having code 250 is sent to the originator.
 When sending the "reply" element, the "transID" attribute is
 identical to the value found in the "publish" element sent by the
 originator.

4.5 The Terminate Operation

 When an application no longer wishes to subscribe to presence
 information or to watch endpoints that are subscribed to receive
 presence information, it sends a "terminate" element to the service;
 similarly, when the service no longer considers an application to be
 subscribing or watching, a "terminate" element is sent to the
 application.
 The "terminate" element contains only a "transID" attribute that
 specifies the transaction-identifier associated an in-progress
 subscribe or watch operation.  Section 9.1 of [1] defines the syntax
 for the "terminate" element.
 When the service receives a "terminate" element, it performs these
 steps:
 1. If the transaction-identifier does not refer to a previous
    subscribe or watch operation for the originator, an "error"
    element having code 550 is returned.
 2. Otherwise, the previous subscribe or watch operation for the
    originator is terminated, and a "reply" element having code 250 is
    sent to the originator.
 Note that following a terminate operation, the originator may receive
 further presence or watcher updates.  Although the service will send
 no further updates after processing a terminate operation and sending
 the reply operation, earlier updates may be in transit.

4.6 The Notify Operation

 The service sends a "notify" element to endpoints that are watching
 other endpoints subscribed to presence information (c.f., Section
 4.3).
 The "notify" element has a "subscriber" attribute, a "transID"
 attribute, a "duration" attribute, an "action" attribute, and no
 content:
 o  the "subscriber" attribute specifies the endpoint that is
    subscribed to presence information; and,

Rose, et al. Experimental [Page 17] RFC 3343 The Application Exchange (APEX) Presence April 2003

 o  the "transID" attribute specifies the transaction-identifier
    associated with the watch operation that caused this "notify"
    element to be sent;
 o  the "action" attribute specifies whether a subscription or its
    termination has occurred; and,
 o  if a subscription is being reported, the "duration" attribute
    specifies the requested duration of the subscription.
 No reply is sent by the receiving endpoint.

4.7 The Reply Operation

 While processing operations, the service may respond with a "reply"
 element.  Consult Sections 10.2 and 6.1.2 of [1], respectively, for
 the definition and an exposition of the syntax of the reply element.

5. Registration: The Presence Service

 Well-Known Endpoint: apex=presence
 Syntax of Messages Exchanged: c.f., Section 6
 Sequence of Messages Exchanged: c.f., Section 4
 Access Control Tokens: presence:subscribe, presence:watch,
    presence:publish
 Contact Information: c.f., the "Authors' Addresses" section of this
    memo

6. The Presence Service DTD

 <!--
   DTD for the APEX presence service, as of 2001-05-08
   Refer to this DTD as:
     <!ENTITY % APEXPRESENCE PUBLIC "-//IETF//DTD APEX PRESENCE//EN"
                "">
     %APEXPRESENCE;
   -->
 <!ENTITY % APEXCORE PUBLIC "-//IETF//DTD APEX CORE//EN" "">
 %APEXCORE;

Rose, et al. Experimental [Page 18] RFC 3343 The Application Exchange (APEX) Presence April 2003

 <!--
   Synopsis of the APEX presence service
     service WKE: apex=presence
     message exchanges:
         consumer initiates    service replies
         ==================    ================
         subscribe             publish or reply
         terminate             reply
         watch                 reply
         publish               reply
         service initiates     consumer replies
         =================     ================
         terminate             (nothing)
         publish               (nothing)
         notify                (nothing)
     access control:
         token                 target
         ==================    ======
         presence:subscribe    for "publisher" of "subscribe" element
         presence:watch        for "publisher" of "watch" element
         presence:publish      for "publisher" of "publish" element
   -->
 <!ELEMENT subscribe   EMPTY>
 <!ATTLIST subscribe
           publisher   %ENDPOINT;        #REQUIRED
           transID     %UNIQID;          #REQUIRED
           duration    %SECONDS;         #REQUIRED>
 <!ELEMENT watch       EMPTY>
 <!ATTLIST watch
           publisher   %ENDPOINT;        #REQUIRED
           transID     %UNIQID;          #REQUIRED
           duration    %SECONDS;         #REQUIRED>
 <!-- publisher attributes must match in publish and presence -->
 <!ELEMENT publish     (presence)>
 <!ATTLIST publish
           publisher   %ENDPOINT;        #REQUIRED
           transID     %UNIQID;          #REQUIRED
           timeStamp   %TIMESTAMP;       #REQUIRED>

Rose, et al. Experimental [Page 19] RFC 3343 The Application Exchange (APEX) Presence April 2003

 <!ELEMENT notify      EMPTY>
 <!ATTLIST notify
           subscriber  %ENDPOINT;        #REQUIRED
           transID     %UNIQID;          #REQUIRED
           duration    %SECONDS;         "0"
           action     (subscribe|terminate)
                                         "subscribe">
 <!--
   presence entries
   -->
 <!ELEMENT presence    (tuple+)>
 <!ATTLIST presence
           publisher   %ENDPOINT;        #REQUIRED
           lastUpdate  %TIMESTAMP;       #REQUIRED
           publisherInfo
                       %URI;             "">
 <!ELEMENT tuple       (capability*)>
 <!ATTLIST tuple
           destination %URI;             #REQUIRED
           availableUntil
                       %TIMESTAMP;       #REQUIRED
           tupleInfo   %URI;             "">
 <!-- e.g., baseline='urn:ietf:rfc:rfc2533' -->
 <!ELEMENT capability (#PCDATA)>
 <!ATTLIST capability
           baseline    %URI              #REQUIRED>

Rose, et al. Experimental [Page 20] RFC 3343 The Application Exchange (APEX) Presence April 2003

7. Security Considerations

 Consult [1]'s Section 11 for a discussion of security issues.
 In addition, timestamps issued by the the presence service may
 disclose location information.  If this information is considered
 sensitive, the special timezone value "-00:00" may be used (after
 converting the local time accordingly).

References

 [1]   Rose, M., Klyne, G. and D. Crocker, "The Application Exchange
       Core", RFC 3340, July 2002.
 [2]   Rose, M., "The Blocks Extensible Exchange Protocol Core", RFC
       3080, March 2001.
 [3]   Rose, M., Klyne, G. and D. Crocker, "The Application Exchange
       (APEX) Access Service", RFC 3341, July 2002.

Rose, et al. Experimental [Page 21] RFC 3343 The Application Exchange (APEX) Presence April 2003

Acknowledgements

 The authors gratefully acknowledge the contributions of: Neil Cook,
 Eric Dixon, Darren New, Scott Pead, and Bob Wyman.

Authors' Addresses

 Marshall T. Rose
 Dover Beach Consulting, Inc.
 POB 255268
 Sacramento, CA  95865-5268
 US
 Phone: +1 916 483 8878
 EMail: mrose@dbc.mtview.ca.us
 Graham Klyne
 Nine by Nine
 EMail: gk@ninebynine.org
 David H. Crocker
 Brandenburg InternetWorking
 675 Spruce Drive
 Sunnyvale, CA  94086
 US
 Phone: +1 408 246 8253
 EMail: dcrocker@brandenburg.com
 URI:   http://www.brandenburg.com/

Rose, et al. Experimental [Page 22] RFC 3343 The Application Exchange (APEX) Presence April 2003

Full Copyright Statement

 Copyright (C) The Internet Society (2003).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Rose, et al. Experimental [Page 23]

/data/webs/external/dokuwiki/data/pages/rfc/rfc3343.txt · Last modified: 2003/04/29 18:47 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki