SIMPLE WG T. Moran Internet-Draft Expires: July 26, 2004 H. Khartabil
Internet-DraftE. Leppanen Expires: February 12, 2004Nokia T. Moran August 14, 2003January 26, 2004 Requirements for Presence Specific Event Notification Filtering draft-ietf-simple-pres-filter-reqs-02draft-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 February 12,July 26, 2004. Copyright Notice Copyright (C) The Internet Society (2003).(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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Event Filtering Model . . . . . . . . . . . . . . . . . . . 3 3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 3 3.4 4. Requirements for Specification of Filters . . . . . . . . . 4 3.14.1 Package Identification . . . . . . . . . . . . . . . . . . . 4 3.24.2 Target URI . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.34.3 Notification Triggering . . . . . . . . . . . . . . . . . . 4 3.45 4.4 Notification Content . . . . . . . . . . . . . . . . . . . . 5 4.5. Requirements for Uploading Filter CriteriaFilters (Operational Rules) . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4.16 5.1 Subscription . . . . . . . . . . . . . . . . . . . . . . . . 5 4.1.16 5.1.1 Maintaining a Filter . . . . . . . . . . . . . . . . . . . . 5 4.1.26 5.1.2 Changing a Filter . . . . . . . . . . . . . . . . . . . . . 6 4.25.2 Server Support For Filters . . . . . . . . . . . . . . . . . 6 5.6. Interaction with Other Features . . . . . . . . . . . . . . 6 5.17 6.1 Resource Lists . . . . . . . . . . . . . . . . . . . . . . . 6 5.27 6.2 Partial Notifications . . . . . . . . . . . . . . . . . . . 7 5.36.3 Authorization . . . . . . . . . . . . . . . . . . . . . . . 7 6.7. Security Considerations . . . . . . . . . . . . . . . . . . 7 7.8. Example Applications for Notification Filtering . . . . . . 8 8.9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 9.9 10. Changes from previous versions . . . . . . . . . . . . . . . 9 10.1 Main changes from version 02 . . . . . . . . . . . . . . . . 9 10.2 Main changes from version 01 . . . . . . . . . . . . . . . . 8 10.9 10.3 Main changes from version 00 . . . . . . . . . . . . . . . . 910 References . . . . . . . . . . . . . . . . . . . . . . . . . 910 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 1011 Intellectual Property and Copyright Statements . . . . . . . 1112 1. Introduction SIP event notification is described in . 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  (user presence) and  (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 . The document describing the Presence event package  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 34 and Section 45 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 78 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'Event Filtering Model There are two parts to be interpreted as described in RFC 2119 the event filtering model. From a Presence service view point, presence information is collected by a Presence Agent and indicate requirement levels for compliant implementations. 3. Requirements for Specification of Filtersis published by one or more Presence User Agents. The following requirements relate to the creationfirst part of filter criteria. 3.1 Package Identification REQ xx: It MUST be possible forthe creator ofmodel enables the filterwatcher to specifylimit the package the filter applies to. 3.2 Target URI REQ xx: It MUST be possible forpresence information delivered to it. Allowing the watcher to indicate,select the information of interest to it results in the filter,ability to limit the targetcontents 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 whoseor 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 certainfilter is applied to.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  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 xx:A1: It MUST be possible for the watcher to indicate, increator of the filter criteria,to specify the package the target presentity list whose presence information a certainfilter is appliedapplies to. 4.2 Target URI REQ xx:A2: It MUST be possible for the watcher to indicate, in the filter criteria,filter, the target presentity sub-listwhose presence information a certain filter is applied to. REQ xx:A3: It MUST be possible for the watcher to indicate, in the filter criteria,filter, the target domain that contains presentities whose presence informationa certain filter is applied to. 3.3For 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 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 <status> 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 <status> element value of CLOSED.watcher. REQ xx:B1: The triggering conditions MUST be based on the presence information. For example, the change of value of the <status> element. REQ xx: ItB2:It MUST be possible to specify logical expressions based on the valuedefine a set of elements defined in the packageconditions for the purpose of triggering. This covers expressions (tests) related to the changevalues of an element's value, and reaching acertain value of an element.elements in a presence document that determine when to send notifications. REQ xx:B3: It MUST be possible to construct one filter that combinecombines multiple triggering conditions. 3.44.4 Notification Content This chapter presents requirements for specifying the filter for choosing content to be sent in the notifications. REQ xx: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 xx:C2: It MUST be possible for the watcher to specify the presence information elements (XML elements and/or attributes) in  to be delivered in the notification. REQ xx: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 . REQ xx:C4: 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:C5: It MUST be possible to construct one filter that combine multiple elements and attributes to be included the notifications. 4.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 Filter CriteriaFilters (Operational Rules) REQ xx:D1: It MUST be possible for the watcher to upload filter criteriafilters to the server (notifier) and know the status - accepted or rejected. 4.1rejected, if the server policy allows. 5.1 Subscription REQ xx:D2: It MUST be possible to place a filter in the body of the SUBSCRIBE request. REQ xx: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. 18.104.22.168.1 Maintaining a Filter REQ xx: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 xx: The watcherD5: modifying a filter across subscription refreshes SHOULD be bandwidth efficient. REQ D6: It MUST NOT be required for a watcher to re-setexplicitly remove a filter when refreshing a subscription, onceif the filtersubscription was terminated or has been set. REQ xx: Maintaining aexpired. I.e. The filter across subscription refreshes SHOULD be bandwidth efficient. 4.1.2is automatically removed with the subscription. 5.1.2 Changing a Filter REQ xx:E1: It MUST be possible to change the filter during a subscription. REQ xx:E2: It MUST be possible for the watcher to remove a set filter, reverting back to a server defined default. 4.25.2 Server Support For Filters REQ xx:F1: It MUST be possible for a server not supporting filtering to inform the watcher of the failure. REQ xx:F2: It MUST be possible for a server not understanding a filtering to inform the watcher of the failure. REQ xx: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 xx:F4: It MUST be possible for athe server to terminate a subscription based onif a filter becoming invalidis no longer acceptable, e.g., due to sever localpolicy change. (How do I word this in a requirement text?) 5.change or server load. 6. Interaction with Other Features 5.16.1 Resource Lists REQ xx:G1: It MUST be possible to support filtering for subscriptions to resourceevent lists . REQ xx: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 for a watcherto specify a filter criteriafor a resourcean event list and/or any nested suband a filters for resources within that list ofin the resource list.same subscription request. REQ xx:G5: Some event lists may contain an other event list as a resource. I.e. nested lists. It MUST be possible for athe watcher to specify different filter for any individual member of a resource listindicate, in the filter, a resourcenested event list subscription.that a certain filter is applied to. REQ xx:G6: It MUST be possible for a watcher to specify different filter criteriafor individual members ofresources within any ofnested sub lists of a resource list in a resourcelist subscription. Anyof an event list, if the nested sub lists may be located in a different domain from the parentsubscription is for an event list. REQ xx:G7: It MUST be possible for each watcher to define his/her own filter criteriafilters within resourcean event list subscription if there are several simultaneous watchers using the same list. 5.26.2 Partial Notifications REQ xx:H1: It MUST be possible to use filtering along with the partial notification  within the same subscription. 5.3 Authorization REQ xx:6.3 Authorization SHOULD occur irrespective of the filtering. 6.7. Security Considerations Security requirements specified for  also applies to thepresence filtering. Additional security considerations related to the presence filteringare described as follows. REQ xx:I1: It SHOULD be possible for the server to hide the fact that a filter was not acceptable. REQ xx:I2: The presence of filter criteriafilters 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 thatMUST be possible to authenticate messages containing filter criteria are authenticatedcarrying filters and authorized.authorise the watcher to upload filters. REQ xx:I3: Modification to the Filter Criteriafilters 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 criteriafilters SHOULD be integrity protected between those nodes that are authorised to modify it (e.g., the resource list servers). REQ xx:I4: Processing of requests and looking up filter criteriafilters 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 criteriafilters allowed in a request should be limited. REQ xx:I5: Requests containing filter criteriafilters 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:I6: The resource list servers SHOULD convey only those parts of filter informationNOT forward filters targeted to the same destination as thea different domain than a fanned out individual subscriptions, if the filter information is conveyed further withinsubscription request. REQ I7: Authorization SHOULD occur irrespective of the subscription. 7.filtering. 8. Example Applications for Notification Filtering 1.o A watcher wishes to get to know presentity's availability and willingness for messaging (e.g. IM and MMS). 2.o A watcher is interested in getting information about the communication means and contact addresses the presentity is currently available for communication. 3.o A watcher requires a notification if the state of a buddy has changed to 'open'. 4.o 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.o A Basic location tracking service requires notification when the presentity's cell id changes. The notification should include the cell id. 6.o A watcher is interested in being notified when a presentity gains a new communication capability such as a new networked multi-player game. 8.9. Acknowledgements The authors would like to thank Andrew Allen, Sreenivas Addagatla, Mikko Lonnfors, Juha Kalliokulju, Aki Niemi, Jose Costa-Requena andCosta-Requena, Markus IsomakiIsomaki, Paul Kyzivat, Aki Niemi and Chris Boulton for their valuable input. 9.10. 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 10.10.3 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  Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.  Sugano, H., "CPIM Presence Information Data Format", draft-ietf-impp-cpim-pidf-08.txt, May 2003.  Schulzrinne, H., "RPIDS"RPID -- Rich Presence Information Data Format for Presence Based on the Session Initiation Protocol (SIP)", draft-schulzrinne-simple-rpids-01.txt, FebruaryFormat", draft-ietf-simple-rpid-00.txt, July 2003.  Kiss, K., "Requirements for Presence Service based on 3GPP specifications and wireless environment characteristics", draft-kiss-simple-presence-wireless-reqs-02, February 2003.  Rosenberg, J., "Session Initiation Protocol (SIP) Extensions for Presence", draft-ietf-simple-presence-10.txt, January 2003.  Roach, A., "Session Initiation Protocol (SIP)-Specific Event Notification", RFC 3265, June 2002.  Rosenberg, J., "A Watcher Information Event Template-Package for the Session Initiation Protocol (SIP)", draft-ietf-simple-winfo-package-05.txt, January 2003.  Rosenberg, J.,Roach, A., "A Session Initiation Protocol (SIP) Event Notification Extension for Resource Lists", draft-ietf-simple-event-list-03.txt, MayJune 2003.  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: firstname.lastname@example.org Hisham Khartabil Nokia P.O BOX 321 Helsinki Finland Phone: +358 7180 76161 EMail: email@example.com Eva Leppanen Nokia P.O BOX 785 Tampere Finland Phone: +358 7180 77066 EMail: firstname.lastname@example.org Tim Moran 2800 Britt Drive Argyle, Texas 76226 USA Phone: +1 972 849 8821 EMail: email@example.comIntellectual 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. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. 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