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 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 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. Moran, et al. Expires July 26, 2004 [Page 1] Internet-Draft Presence Filtering Requirements January 2004 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 Moran, et al. Expires July 26, 2004 [Page 2] Internet-Draft Presence Filtering Requirements January 2004 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 Moran, et al. Expires July 26, 2004 [Page 3] Internet-Draft Presence Filtering Requirements January 2004 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 Moran, et al. Expires July 26, 2004 [Page 4] Internet-Draft Presence Filtering Requirements January 2004 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 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 element of a certain presentity when there is a local server policy constraining the delivery of the 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. Moran, et al. Expires July 26, 2004 [Page 5] 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. Moran, et al. Expires July 26, 2004 [Page 6] 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 Moran, et al. Expires July 26, 2004 [Page 7] Internet-Draft Presence Filtering Requirements January 2004 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 Moran, et al. Expires July 26, 2004 [Page 8] Internet-Draft Presence Filtering Requirements January 2004 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 Moran, et al. Expires July 26, 2004 [Page 9] Internet-Draft Presence Filtering Requirements January 2004 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. Moran, et al. Expires July 26, 2004 [Page 10] Internet-Draft Presence Filtering Requirements January 2004 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 Moran, et al. Expires July 26, 2004 [Page 11] Internet-Draft Presence Filtering Requirements January 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. 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