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Versions: 00 01 02 03                                                   
SIMPLE WG                                                       T. Moran
Internet-Draft
Expires: July 26, 2004                                      H. Khartabil
                                                             E. Leppanen
                                                                   Nokia
                                                        January 26, 2004


    Requirements for Presence Specific Event Notification Filtering
                 draft-ietf-simple-pres-filter-reqs-03

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
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   The list of current Internet-Drafts can be accessed at http://
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   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on July 26, 2004.

Copyright Notice

   Copyright (C) The Internet Society (2004). All Rights Reserved.

Abstract

   This document defines a set of structured requirements whereby a
   presence information subscriber may select specific information to be
   received in the presence information notification sent by the
   notifier. The purpose is to limit the content and frequency of
   notifications so that only essential information on a need basis is
   delivered by the server.







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Table of Contents

   1.    Introduction . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.    Event Filtering Model  . . . . . . . . . . . . . . . . . . .  3
   3.    Conventions  . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.    Requirements for Specification of Filters  . . . . . . . . .  4
   4.1   Package Identification . . . . . . . . . . . . . . . . . . .  4
   4.2   Target URI . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.3   Notification Triggering  . . . . . . . . . . . . . . . . . .  5
   4.4   Notification Content . . . . . . . . . . . . . . . . . . . .  5
   5.    Requirements for Uploading Filters (Operational Rules) . . .  6
   5.1   Subscription . . . . . . . . . . . . . . . . . . . . . . . .  6
   5.1.1 Maintaining a Filter . . . . . . . . . . . . . . . . . . . .  6
   5.1.2 Changing a Filter  . . . . . . . . . . . . . . . . . . . . .  6
   5.2   Server Support For Filters . . . . . . . . . . . . . . . . .  6
   6.    Interaction with Other Features  . . . . . . . . . . . . . .  7
   6.1   Resource Lists . . . . . . . . . . . . . . . . . . . . . . .  7
   6.2   Partial Notifications  . . . . . . . . . . . . . . . . . . .  7
   6.3   Authorization  . . . . . . . . . . . . . . . . . . . . . . .  7
   7.    Security Considerations  . . . . . . . . . . . . . . . . . .  7
   8.    Example Applications for Notification Filtering  . . . . . .  8
   9.    Acknowledgements . . . . . . . . . . . . . . . . . . . . . .  9
   10.   Changes from previous versions . . . . . . . . . . . . . . .  9
   10.1  Main changes from version 02 . . . . . . . . . . . . . . . .  9
   10.2  Main changes from version 01 . . . . . . . . . . . . . . . .  9
   10.3  Main changes from version 00 . . . . . . . . . . . . . . . . 10
         References . . . . . . . . . . . . . . . . . . . . . . . . . 10
         Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 11
         Intellectual Property and Copyright Statements . . . . . . . 12






















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1. Introduction

   SIP event notification is described in [6]. It defines a general
   framework for subscriptions and notifications for SIP event packages.
   Concrete applications of the general event framework to a specific
   group of events are described in [5] (user presence) and [7] (watcher
   information).

   The presence information refers to a set of presence attributes
   describing the availability and willingness of the user (presentity)
   for communication. The user makes his presence information available
   for other users (watchers).

   As the inherent usage of event packages grows, the client needs some
   mechanisms for controlling the event notifications at the source.
   Evidence of this need is found in [4].

   The document describing the Presence event package [5] mentions the
   possibility for filtering. Accordingly, the SUBSCRIBE request may
   contain a body for filtering the presence information subscription.
   However, the definition of filtering was considered out of scope and
   was left as future work.

   These mechanisms are expected to be particularly valuable to users of
   wireless devices. The characteristics of these devices typically
   include low bandwidth, low data processing capabilities, small
   display and limited battery power. Such devices can benefit from the
   ability to filter the amount of information generated at the source
   of the event notifications.

   However, it is expected that the control mechanisms for event
   notifications add value for all users irrespectively of their device
   or network access characteristics.

   Section 4 and Section 5 of this draft propose a set of requirements
   whereby a client may specify which notifications it is interested in.
   That is, a means to specify filtering rules to be executed by the
   server. Section 8 provides a few example applications of notification
   filtering.

2. Event Filtering Model

   There are two parts to the event filtering model. From a Presence
   service view point, presence information is collected by a Presence
   Agent and is published by one or more Presence User Agents. The first
   part of the model enables the watcher to limit the presence
   information delivered to it. Allowing the watcher to select the
   information of interest to it results in the ability to limit the



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   contents of a presence information document, therefore reducing the
   size of a notification message.


                                                   +--+
                                                --|  |PUA
                            PA               ---  +--+
    Watcher              +---------+     ----
    +-----+              |         |  ---
    |     |              |         |--            +--+
    |     |--------------|         |--------------|  |PUA
    |     |              |         |--            +--+
    +-----+              |         |  ---
                         +---------+     ----
                                             ---  +--+
                                                --|  |PUA
                                                  +--+


   The second part of the model defines the triggering. In a filter-less
   subscription, it might be a Presence Agent's default policy to
   deliver a notification message every time there is a change to the
   presence information of a presentity or whenever a PUA publishes new
   and updated presence information from its own point of view. This
   model enables the watcher to select the events or changes in presents
   information that trigger notifications to be sent. Other changes that
   are not defined as triggers in a filter do not result in a
   notification message being delivered to the watcher.

3. Conventions

   In this document, the key words 'MUST', 'MUST NOT', 'REQUIRED',
   'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY',
   and 'OPTIONAL' are to be interpreted as described in RFC 2119 [1]
   and indicate requirement levels for compliant implementations.

4. Requirements for Specification of Filters

   The following requirements relate to the creation of filters.

4.1 Package Identification

   REQ A1: It MUST be possible for the creator of the filter to specify
   the package the filter applies to.

4.2 Target URI

   REQ A2: It MUST be possible for the watcher to indicate, in the



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   filter, the target presentity whose presence information a certain
   filter is applied to.

   REQ A3: It MUST be possible for the watcher to indicate, in the
   filter, the target domain that a certain filter is applied to. For
   example an event list might have many resources from different
   domains, a watcher needs to be able to set a filter for one of those
   domains.

4.3 Notification Triggering

   This chapter presents requirements for specifying the triggering
   conditions that result in notifications to be sent to the watcher.

   REQ B1: The triggering conditions MUST be based on the presence
   information. For example, the change of value of the <status>
   element.

   REQ B2:It MUST be possible to define a set of conditions for the
   values of certain elements in a presence document that determine when
   to send notifications.

   REQ B3: It MUST be possible to construct one filter that combines
   multiple triggering conditions.

4.4 Notification Content

   This chapter presents requirements for specifying the filter for
   choosing content to be sent in the notifications.

   REQ C1: It MUST NOT be possible to break any server side policy
   constraints when applying the content filter. For example, it must
   not be possible for a watcher to request a notification to contain
   the <contact> element of a certain presentity when there is a local
   server policy constraining the delivery of the <contact> element.

   REQ C2: It MUST be possible for the watcher to specify the presence
   information elements (XML elements and/or attributes) in [2] to be
   delivered in the notification.

   REQ C3: It MUST be possible for the watcher to specify presence
   information in any extension to PIDF to be delivered in the
   notifications, based on  XML elements and/or attributes. See for
   example [3].

   REQ C4: It MUST be possible for the watcher to specify presence
   information in any extension to be delivered in the notifications,
   based on  namespaces.



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   REQ C5: It MUST be possible to construct one filter that combine
   multiple elements and attributes to be included the notifications.

   REQ C6: It MUST be possible for the watcher to specify presence
   information in PIDF or any any extension to it  to be excluded from
   the notifications, based on  elements and/or attributes.

5. Requirements for Uploading Filters (Operational Rules)

   REQ D1: It MUST be possible for the watcher to upload filters to the
   server (notifier) and know the status - accepted or rejected, if the
   server policy allows.

5.1 Subscription

   REQ D2: It MUST be possible to place a filter in the body of the
   SUBSCRIBE request.

   REQ D3: It MAY be possible to deliver a filter to a server using
   other means. For example, it may be possible for the filter to be
   (permanently) stored in the server.

5.1.1 Maintaining a Filter

   REQ D4: The watcher MUST NOT be required to re-set a filter at any
   time during the subscription, once the filter has been set. This
   includes subscription refreshes

   REQ D5: modifying a filter across subscription refreshes SHOULD be
   bandwidth efficient.

   REQ D6: It MUST NOT be required for a watcher to explicitly remove a
   filter if the subscription was terminated or has expired. I.e. The
   filter is automatically removed with the subscription.

5.1.2 Changing a Filter

   REQ E1: It MUST be possible to change the filter during a
   subscription.

   REQ E2: It MUST be possible for the watcher to remove a set filter,
   reverting back to a server defined default.

5.2 Server Support For Filters

   REQ F1: It MUST be possible for a server not supporting filtering  to
   inform the watcher of the failure.

   REQ F2:  It MUST be possible for a server not understanding a
   filtering  to inform the watcher of the failure.



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   REQ F3: It MUST be possible for a server not accepting a filter to
   inform the watcher of the reasons for not accepting the filter.

   REQ F4: It MUST be possible for the server to terminate a
   subscription if a filter is no longer acceptable, e.g., due to policy
   change or server load.

6. Interaction with Other Features

6.1 Resource Lists

   REQ G1: It MUST be possible to support filtering for subscriptions to
   event lists [8].

   REQ G2: It MUST be possible for the watcher to indicate, in the
   filter, the target event list that a certain filter is applied to by
   the Resource List Server.

   REQ G3: It MUST be possible for a watcher to specify individual
   filters for any resource in an event list if the subscription is for
   an event list.

   REQ G4: It MUST be possible to specify a filter for an event list and
   a filters for resources within that list in the same subscription
   request.

   REQ G5: Some event lists may contain an other event list as a
   resource. I.e. nested lists. It MUST be possible for the watcher to
   indicate, in the filter, a nested event list that a certain filter is
   applied to.

   REQ G6: It MUST be possible for a watcher to specify different filter
   for resources within any nested list of an event list, if the
   subscription is for an event list.

   REQ G7: It MUST be possible for each watcher to define his/her own
   filters within an event list subscription if there are several
   simultaneous watchers using the same list.

6.2 Partial Notifications

   REQ H1: It MUST be possible to use filtering along with the partial
   notification [9] within the same subscription.

6.3 Authorization


7. Security Considerations

   Security requirements specified for [5] also applies to presence



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   filtering. Additional security considerations are described as
   follows.

   REQ I1: It SHOULD be possible for the server to hide the fact that a
   filter was not acceptable.

   REQ I2: The presence of filters in the body in a SIP message has a
   significant effect on the way in which the request is handled at a
   server. As a result, it MUST be possible to authenticate messages
   carrying filters and authorise the watcher to upload filters.

   REQ I3: Modification to filters by an intermediary could also result
   in the watcher either not receiving notifications of presence
   information they are interested in or receiving a very large presence
   document. Therefore the filters SHOULD be integrity protected between
   those nodes that are authorised to modify it (e.g., the resource list
   servers).

   REQ I4: Processing of requests and looking up filters requires some
   amount of computation. This enables a DoS attack whereby a user can
   send requests with substantial numbers messages with large contents,
   in the hopes of overloading the server. To prevent this the number of
   filters allowed in a request should be limited.

   REQ I5: Requests containing filters can reveal sensitive information
   about a UA's capabilities. If this information is sensitive, it
   SHOULD be encrypted using methods that allow it to be read by those
   nodes that need to do so (e.g., the resource list servers).

   REQ I6: The resource list servers SHOULD NOT forward filters targeted
   to a different domain than a fanned out subscription request.

   REQ I7: Authorization SHOULD occur irrespective of the filtering.

8. Example Applications for Notification Filtering

   o  A watcher wishes to get to know presentity's availability and
      willingness for messaging (e.g. IM and MMS).

   o  A watcher is interested in getting information about the
      communication means and contact addresses the presentity is
      currently available for communication.

   o  A watcher requires a notification if the state of a buddy has
      changed to 'open'.

   o  A watcher only wants to be notified when the presentity's location
      is Dallas or Fort Worth. The notification should include the



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      vehicle license, driver name, and city.

   o  A Basic location tracking service requires notification when the
      presentity's cell id changes. The notification should include the
      cell id.

   o  A watcher is interested in being notified when a presentity gains
      a new communication capability such as a new networked
      multi-player game.


9. Acknowledgements

   The authors would like to thank Andrew Allen, Sreenivas Addagatla,
   Mikko Lonnfors, Juha Kalliokulju, Aki Niemi, Jose Costa-Requena,
   Markus Isomaki, Paul Kyzivat, Aki Niemi and Chris Boulton for their
   valuable input.

10. Changes from previous versions

10.1 Main changes from version 02

   o  Added filtering model section.

   o  Rephrased some requirements for clarity.

   o  Rearranged requirements into more appropriate sections.


10.2 Main changes from version 01

   o  "Overview of Operation" section removed .

   o  "Common Syntax" section removed.

   o  "Discovery of Items" section removed as agreed in IETF 57

   o  Added requirement about filtering using namespaces.

   o  Added requirement about filtering using domain name.

   o  Clarified and split larger requirements into smaller more concrete
      requirements.

   o  Updated the Authors of this ID






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10.3 Main changes from version 00

   o  Overview of functionality chapter added.

   o  More specific requirements for supporting filtering with the
      resource lists, and nested lists.

   o  Interaction with other features chapter added.

   o  More specific requirements to support getting information about
      the structure of presence document, and changes in it.

   o  Several filter specific additions to security considerations.

   o  Several editorial changes, e.g., reference and terminology
      updates.

References

   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [2]  Sugano, H., "CPIM Presence Information Data Format",
        draft-ietf-impp-cpim-pidf-08.txt, May 2003.

   [3]  Schulzrinne, H., "RPID -- Rich Presence Information Data
        Format",  draft-ietf-simple-rpid-00.txt, July 2003.

   [4]  Kiss, K., "Requirements for Presence Service based on 3GPP
        specifications and wireless environment characteristics",
        draft-kiss-simple-presence-wireless-reqs-02, February 2003.

   [5]  Rosenberg, J., "Session Initiation Protocol (SIP) Extensions for
        Presence",  draft-ietf-simple-presence-10.txt, January 2003.

   [6]  Roach, A., "Session Initiation Protocol (SIP)-Specific Event
        Notification", RFC 3265, June 2002.

   [7]  Rosenberg, J., "A Watcher Information Event Template-Package for
        the Session Initiation Protocol (SIP)",
        draft-ietf-simple-winfo-package-05.txt, January 2003.

   [8]  Roach, A., "A Session Initiation Protocol (SIP) Event
        Notification Extension for Resource Lists",
        draft-ietf-simple-event-list-03.txt, June 2003.

   [9]  Lonnfors, M., "Partial Notification of Presence Information",
        draft-lonnfors-simple-partial-notify-01.txt, May 2003.



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Authors' Addresses

   Tim Moran
   2800 Britt Drive
   Argyle, Texas 76226
   USA

   Phone: +1 972 849 8821
   EMail: tl_moran@att.net


   Hisham Khartabil
   Nokia
   P.O BOX 321
   Helsinki
   Finland

   Phone: +358 7180 76161
   EMail: hisham.khartabil@nokia.com


   Eva Leppanen
   Nokia
   P.O BOX 785
   Tampere
   Finland

   Phone: +358 7180 77066
   EMail: eva-maria.leppanen@nokia.com






















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Intellectual Property Statement

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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Acknowledgment

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   Internet Society.











































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