SIMPLE WG H. Khartabil Internet-Draft E. Leppanen Expires: February 12, 2004 Nokia T. Moran August 14, 2003 Requirements for Presence Specific Event Notification Filtering 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. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on 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 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. Khartabil, et al. Expires February 12, 2004 [Page 1] Internet-Draft Presence Filtering Requirements August 2003 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Requirements for Specification of Filters . . . . . . . . . 4 3.1 Package Identification . . . . . . . . . . . . . . . . . . . 4 3.2 Target URI . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.3 Notification Triggering . . . . . . . . . . . . . . . . . . 4 3.4 Notification Content . . . . . . . . . . . . . . . . . . . . 5 4. Requirements for Uploading Filter Criteria (Operational Rules) . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4.1 Subscription . . . . . . . . . . . . . . . . . . . . . . . . 5 4.1.1 Maintaining a Filter . . . . . . . . . . . . . . . . . . . . 5 4.1.2 Changing a Filter . . . . . . . . . . . . . . . . . . . . . 6 4.2 Server Support For Filters . . . . . . . . . . . . . . . . . 6 5. Interaction with Other Features . . . . . . . . . . . . . . 6 5.1 Resource Lists . . . . . . . . . . . . . . . . . . . . . . . 6 5.2 Partial Notifications . . . . . . . . . . . . . . . . . . . 7 5.3 Authorization . . . . . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . 7 7. Example Applications for Notification Filtering . . . . . . 8 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . 11 Khartabil, et al. Expires February 12, 2004 [Page 2] Internet-Draft Presence Filtering Requirements August 2003 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 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 3 and Section 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 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. Khartabil, et al. Expires February 12, 2004 [Page 3] Internet-Draft Presence Filtering Requirements August 2003 3. Requirements for Specification of Filters The following requirements relate to the creation of filter criteria. 3.1 Package Identification REQ xx: It MUST be possible for the creator of the filter to specify the package the filter applies to. 3.2 Target URI REQ xx: It MUST be possible for the watcher to indicate, in the filter, the target presentity whose presence information a certain filter is applied to. REQ xx: It MUST be possible for the watcher to indicate, in the filter criteria, the target presentity list whose presence information a certain filter is applied to. REQ xx: It MUST be possible for the watcher to indicate, in the filter criteria, the target presentity sub-list whose presence information a certain filter is applied to. REQ xx: It MUST be possible for the watcher to indicate, in the filter criteria, the target domain that contains presentities whose presence information a certain filter is applied to. 3.3 Notification Triggering This chapter presents requirements for specifying the triggering conditions that result in notifications to be sent to the client. REQ xx: It MUST NOT be possible to break any server side policy constraints when applying the triggering conditions. For example, it must not be possible for a watcher to request a notification when the element value of a certain presentity has changed from OPEN to CLOSED when there is a local server policy constraining the delivery of any tuple with a element value of CLOSED. REQ xx: The triggering conditions MUST be based on the presence information. For example, the change of value of the 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 triggering. This covers expressions (tests) related to the change of an element's value, and reaching a certain value of an element. Khartabil, et al. Expires February 12, 2004 [Page 4] Internet-Draft Presence Filtering Requirements August 2003 REQ xx: It MUST be possible to construct one filter that combine multiple 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 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 element of a certain presentity when there is a local server policy constraining the delivery of the element. REQ xx: 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 xx: 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 xx: It MUST be possible for the watcher to specify presence information in any extension to be delivered in the 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. 4.1 Subscription REQ xx: It MUST be possible to place a filter in the body of the SUBSCRIBE request. REQ xx: 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. 4.1.1 Maintaining a Filter REQ xx: The watcher MUST NOT be required to re-set a filter at any Khartabil, et al. Expires February 12, 2004 [Page 5] Internet-Draft Presence Filtering Requirements August 2003 time during the subscription, once the filter has been set. REQ xx: The watcher SHOULD NOT be required to re-set a filter when refreshing a subscription, once the filter has been set. REQ xx: Maintaining a filter across subscription refreshes SHOULD be bandwidth efficient. 4.1.2 Changing a Filter REQ xx: It MUST be possible to change the filter during a subscription. REQ xx: It MUST be possible for the watcher to remove a set filter, reverting back to a server defined default. 4.2 Server Support For Filters REQ xx: It MUST be possible for a server not supporting filtering to inform the watcher of the failure. REQ xx: It MUST be possible for a server not understanding a filtering to inform the watcher of the failure. REQ xx: It MUST be possible for a server not accepting a filter to inform the watcher of the reasons for not accepting the filter. REQ xx: It MUST be possible for a server to terminate a subscription based on a filter becoming invalid due to sever local policy change. (How do I word this in a requirement text?) 5. Interaction with Other Features 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 Khartabil, et al. Expires February 12, 2004 [Page 6] Internet-Draft Presence Filtering Requirements August 2003 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. 5.2 Partial Notifications REQ xx: It MUST be possible to use filtering along with the partial notification [9] within the same subscription. 5.3 Authorization REQ xx: Authorization SHOULD occur irrespective of the filtering. 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. REQ xx: It SHOULD be possible for the server to hide 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 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). Khartabil, et al. Expires February 12, 2004 [Page 7] REQ xx: The resource list servers SHOULD convey only those parts of filter information targeted to the same destination as the fanned out individual subscriptions, if the filter information is conveyed further within the subscription. 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 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 interested in being notified when a presentity gains a new communication capability such as a new networked multi-player game. 8. Acknowledgements The authors would like to thank 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. Khartabil, et al. Expires February 12, 2004 [Page 8] Internet-Draft Presence Filtering Requirements August 2003 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", Khartabil, et al. Expires February 12, 2004 [Page 9] Internet-Draft Presence Filtering Requirements August 2003 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 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 Tim Moran 2800 Britt Drive Argyle, Texas 76226 USA Phone: +1 972 849 8821 EMail: tl_moran@att.net Khartabil, et al. 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