SIMPLE WG                                                       T. Moran                                                   H. Khartabil
Internet-Draft
Expires: December 17, 2003                                  S. Addagatla                                               E. Leppanen
Expires: February 12, 2004                                         Nokia
                                                                A. Allen
                                                           June 18,
                                                                T. Moran
                                                         August 14, 2003

    Requirements for Presence Specific Event Notification Filtering
                 draft-ietf-simple-pres-filter-reqs-01
                 draft-ietf-simple-pres-filter-reqs-02

Status of this Memo

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

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   This Internet-Draft will expire on December 17, 2003. February 12, 2004.

Copyright Notice

   Copyright (C) The Internet Society (2003). 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 infomation 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.

Table of Contents

   1.    Introduction . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.    Conventions  . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.    Overview of functionality  . . . . . . . . . . . . . . . . .  4
   4.    Requirements for Specification of Filters  . . . . . . . . .  4
   4.1   Common Syntax  . . . . . . . . . . . . . . . . . . . . . . .  4
   4.2
   3.1   Package Identification . . . . . . . . . . . . . . . . . . .  4
   4.3
   3.2   Target URI . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.4
   3.3   Notification Triggering  . . . . . . . . . . . . . . . . . .  4
   4.5
   3.4   Notification Content Limiting  . . . . . . . . . . . . . . .  5
   4.6   Discovery of Items . . . . . . . . . . . . . . . . . . . . .  5
   5.
   4.    Requirements for Uploading Filter Criteria (Operational
         Rules) . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   5.1   SUBSCRIBE Method . . . . .  5
   4.1   Subscription . . . . . . . . . . . . . . . . .  6
   5.1.1 Retention of Filter Criteria . . . . . . .  5
   4.1.1 Maintaining a Filter . . . . . . . . .  6
   5.1.2 Changing Filter Criteria . . . . . . . . . . .  5
   4.1.2 Changing a Filter  . . . . . . .  6
   5.2   Server does not Support Filters . . . . . . . . . . . . . .  6
   5.3
   4.2   Server does not Support Filter Criteria  . For Filters . . . . . . . . .  6
   5.4   Server can no Longer Support Filter Criteria . . . . . . . .  7
   6.  6
   5.    Interaction with Other Features  . . . . . . . . . . . . . .  7
   6.1  6
   5.1   Resource Lists . . . . . . . . . . . . . . . . . . . . . . .  7
   6.2  6
   5.2   Partial Notifications  . . . . . . . . . . . . . . . . . . .  7
   6.3
   5.3   Authorization  . . . . . . . . . . . . . . . . . . . . . . .  7
   7.
   6.    Security Considerations  . . . . . . . . . . . . . . . . . .  7
   8.
   7.    Example Applications for Notification Filtering  . . . . . .  8
   9.
   8.    Acknowledgements . . . . . . . . . . . . . . . . . . . . . .  9  8
   9.    Main changes from version 01 . . . . . . . . . . . . . . . .  8
   10.   Main changes from version 00 . . . . . . . . . . . . . . . .  9
         References . . . . . . . . . . . . . . . . . . . . . . . . .  9
         Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 10
         Intellectual Property and Copyright Statements . . . . . . . 12 11

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 Internet Draft document describing the Presence event package [5] mentions the
   possibility for a filtering. Accordingly, the SUBSCRIBE request may
   contain a body for filtering the presence information subscription.
   However, the definition of the filtering has been left was considered out of the scope of the Internet Draft. As an example, the body of
   the SUBSCRIBE request may include a restriction on the set of data
   returned in NOTIFY requests. 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 notification. 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 3 and Section 5 4 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 7 provides a few example applications of notification
   filtering.

2. 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.

3. Overview of functionality

   Filter Criteria set by a watcher may be set based on some
   predetermined knowledge Requirements for Specification of Filters

   The following requirements relate to the structure creation of the presence information,
   or the filtering mechanism may itself filter criteria.

3.1 Package Identification

   REQ xx: It MUST be used to first discover possible for the
   structure creator of the presence information thus enabling the setting new filter criteria to deliver the values of interest.

   The filtering may be performed either by the presence server of the
   presentity (the notifier) or by some intermediate server between specify
   the
   notifier and package the watcher. The filtering should filter applies to.

3.2 Target URI

   REQ xx: It MUST be considered as a
   post processing operation on possible for the presence document after it has been
   modified due watcher to indicate, in the rules of
   filter, the authorization. As target presentity whose presence information a result the
   authorization policy always overides any of the data or notifications
   requested by any of the filter criteria.

   Subscriptions containing certain
   filter criteria may either is applied to.

   REQ xx: It MUST be accepted or
   rejected by the notifier based on the presence of filter criteria.

4. Requirements possible for Specification of Filters

   The following requirements relate the watcher to indicate, in the creation of
   filter criteria.

4.1 Common Syntax

   A common set of constructs MUST be defined for criteria, the creation of rules.
   There MUST be a common set of operations that follow target presentity list whose presence
   information a common syntax.
   The user certain filter is applied to.

   REQ xx: It MUST be possible to define different rules for different
   purposes using a common filtering mechanism.

4.2 Package Identification

   A means is REQUIRED whereby the user may specify watcher to indicate, in the package
   filter criteria, the
   rules apply target presentity sub-list whose presence
   information a certain filter is applied to.

4.3 Target URI

   REQ xx: It MUST be possible for the watcher to indicate, in the
   filter criteria to
   indicate criteria, the target presentity, resource list or sub list of the
   resource list to which domain that contains presentities whose
   presence information a certain filter criteria is applied if this
   is different from the Request-URI in the subscription.

4.4 to.

3.3 Notification Triggering

   This chapter presents requirements for specifying the desired triggering
   conditions for when that result in notifications are to be sent to the client.

   The scope of the 'when' part is to allow a possibility for the user
   to specify such rules for the notification triggering where the
   criteria is based on the presence information, e.g., the value of the
   status element.

   The notification triggering criteria would override the default
   trigger conditions of the server/service as defined in the package
   when they are within the server's local policy constraints.

   REQ xx: It MUST NOT be possible to specify logical expressions based on the value
   of elements defined in the package for the purpose of break any server side policy
   constraints when to send
   notifications. This covers expressions (tests) related to the change
   of an element's value, and reaching a certain value of an element.

   It MUST be possible to construct expressions that combine multiple
   tests.

4.5 Notification Content Limiting

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

   It MUST triggering conditions. For example, it
   must not be possible for the a watcher to specify the presence
   information elements [2] (XML elements and/or attributes) to be
   delivered in the notification. The specified elements MUST be
   possible to cover also extensions to PIDF formated presence
   information, see for example [3].

   E.g. the following two cases must be possible:

   o  It MUST be possible for request a notification when the watcher
   <status> element value of a certain presentity has changed from OPEN
   to define CLOSED when there is a criteria which
      allows local server policy constraining the complete
   delivery of any tuple and all information within with a tuple to be
      transmitted.

   o  It <status> element value of CLOSED.

   REQ xx: The triggering conditions MUST be possible for based on the watcher to define a criteria which
      result notifies to contain values only for defined attributes. presence
   information. For example, the change of value of the <status>
   element.

   REQ xx: It MUST be possible to specify logical expressions based on
   the value of elements defined in the package for the purpose of determining
   what
   triggering. This covers expressions (tests) related to send in the notification. The existence change of
   an element SHOULD
   be considered as element's value, and reaching a criterion. certain value of an element.

   REQ xx: It MUST be possible to construct expressions one filter that combine
   multiple
   tests.

4.6 Discovery of Items triggering conditions.

3.4 Notification Content

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

   REQ xx: It MUST NOT be possible for 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 learn new items contain
   the <contact> element of a certain presentity when there is a local
   server policy constraining the presence information that delivery of the notifier may make available to <contact> element.

   REQ xx: It MUST be possible for the
   watcher. E.g., watcher to discover additions of new tuples and/or other new specify the presence
   information items. elements (XML elements and/or attributes) in [2] to be
   delivered in the notification.

   REQ xx: It MUST be possible for the watcher using the filter criteria to
   determine what specify presence
   information is available before subscribing in any extension to PIDF to be delivered in the
   notifications, based on  XML elements and/or attributes. See for
   example [3].

   REQ xx: It MUST be possible for the watcher to specify presence
   information with in any extension to be delivered in the actual values.

5. notifications,
   based on  namespaces.

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

4. Requirements for Uploading Filter Criteria (Operational Rules)

   REQ xx: It MUST be possible for the watcher to upload filter criteria
   to the server (notifier) and know the status - accepted or rejected.

5.1 SUBSCRIBE Method

   Placing

4.1 Subscription

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

   REQ xx: It MAY be
   supported. Other means of delivering the possible to deliver a filter criteria to the a server MAY be supported. E.g. using
   other means. For example, it should may be possible for the rules filter to be
   (permanently) stored in the server, as in server.

4.1.1 Maintaining a resource list case.

5.1.1 Retention of Filter Criteria

   REQ xx: The server watcher MUST retain the NOT be required to re-set a filter criteria through at any
   time during the lifetime of subscription, once the subscription dialog until there is a modification filter has been set.

   REQ xx: The watcher SHOULD NOT be required to re-set a filter when
   refreshing a subscription, once the filter
   settings.

5.1.2 has been set.

   REQ xx: Maintaining a filter across subscription refreshes SHOULD be
   bandwidth efficient.

4.1.2 Changing a Filter Criteria

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

   REQ xx: It MUST be possible for the watcher to reset the filter settings remove a set filter,
   reverting back to
   the service (server) a server defined default.

   Changing filter criteria SHOULD be bandwidth efficient.

5.2

4.2 Server does not Support For Filters

   If the

   REQ xx: It MUST be possible for a server does not support filters (the content type) then it supporting filtering  to
   inform the watcher of the failure.

   REQ xx:  It MUST be possible to indicate so in for a response.

5.3 Server does server not Support Filter Criteria understanding a
   filtering  to inform the watcher of the failure.

   REQ xx: It MUST be possible for the a server to explicitly indicate that it
   does not support or understand the filter criteria. This indication
   MAY include accepting a reason about filter to
   inform the refusal watcher of the subscription.

5.4 Server can no Longer Support Filter Criteria

   The server reasons for not accepting the filter.

   REQ xx: It MUST be able possible for a server to terminate the a subscription if the any of
   the active filters are no longer applicable
   based on a filter becoming invalid due to a sever local policy change.
   (How do I word this in the
   server.

6. a requirement text?)

5. Interaction with Other Features

6.1

5.1 Resource Lists

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

   REQ xx: It MUST be possible for a watcher to specify filter criteria
   for a resource list and/or any nested sub list of the resource list.

   REQ xx: It MUST be possible for a watcher to specify different filter
   for any individual member of a resource list in a resource list
   subscription.

   REQ xx: It MUST be possible for a watcher to specify different filter
   criteria for individual members of any of nested sub lists of a
   resource list in a resource list subscription. Any of the nested sub
   lists may be located in a different domain from the parent list.

   REQ xx: It MUST be possible for each watcher to define own filter
   criteria within resource list subscription if there are several
   simultaneous watchers using the same list.

6.2

5.2 Partial Notifications

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

6.3

5.3 Authorization

   REQ xx: Authorization SHOULD occur irrespective of the filtering.

7.

6. Security Considerations

   Security requirements specified for [5] also applies to the presence
   filtering. Additional security considerations related to the presence
   filtering are described as follows.

   The filter criteria should not

   REQ xx: It SHOULD be rejected based on the authorization
   policy since this would enable the watcher by experimentation with
   the use of filter criteria to determine the authorization policy the
   presentity has set possible for him and thus discover what the presentity
   wants server to hide from him. the fact that a
   filter was not acceptable.

   REQ xx: The presence of filter criteria 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 is especially important that messages
   containing filter criteria are authenticated and authorized.

   REQ xx: Modification to the Filter Criteria 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 filter criteria should SHOULD be integrity
   protected between those nodes that are authorised to modify it (e.g.,
   the resource list servers).

   REQ xx: Processing of requests and looking up filter criteria
   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 filter criteria allowed in a request
   should be limited.

   REQ xx: Requests containing filter criteria 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 xx: The resource list servers should SHOULD convey only those parts of
   filter information targetted targeted to the same destination as the fanned out
   individual subscriptions, if the filter information is conveyed
   further within the subscription.

8.

7. Example Applications for Notification Filtering

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

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

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

   4.  A Subscriber watcher only wants to be notified when the presentity's
       location is Dallas or Fort Worth. The notification should include
       the vehicle license, driver name, and city.

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

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

9.

8. Acknowledgements

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

9. 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

10. 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., "RPIDS -- Rich Presence Information Data Format
        for Presence Based on the Session Initiation Protocol (SIP)",
        draft-schulzrinne-simple-rpids-01.txt, February 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]  Rosenberg, J., "A Session Initiation Protocol (SIP) Event
        Notification Extension for Resource Lists",
        draft-ietf-simple-event-list-03.txt, May 2003.

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

Authors' Addresses

   Tim Moran
   2800 Britt Drive
   Argyle, Texas 76226
   USA

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

   Sreenivas Addagatla

   Hisham Khartabil
   Nokia
   6000 Connection Drive
   Irving, Texas 75039
   USA
   P.O BOX 321
   Helsinki
   Finland

   Phone: +1 972 374 1917 +358 7180 76161
   EMail: sreenivas.addagatla@nokia.com hisham.khartabil@nokia.com

   Eva Leppanen
   Nokia
   P.O BOX 785
   Tampere
   Finland

   Phone: +358 7180 77066
   EMail: eva-maria.leppanen@nokia.com
   Andrew Allen
   1937 McRae Lane
   Mundelein, Illinois 60060

   Tim Moran
   2800 Britt Drive
   Argyle, Texas 76226
   USA

   Phone: +1 972 849 8821
   EMail: AndrewAllen007@aol.com tl_moran@att.net

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