T. MoranH. Khartabil Internet-Draft Expires: December 17, 2003 S. AddagatlaE. 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-01draft-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 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 infomationinformation 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 4.23.1 Package Identification . . . . . . . . . . . . . . . . . . . 4 4.33.2 Target URI . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.43.3 Notification Triggering . . . . . . . . . . . . . . . . . . 4 4.53.4 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 5.34.2 Server does notSupport Filter Criteria .For Filters . . . . . . . . . 6 5.4 Server can no Longer Support Filter Criteria. . . . . . . . 7 6.6 5. Interaction with Other Features . . . . . . . . . . . . . . 7 6.16 5.1 Resource Lists . . . . . . . . . . . . . . . . . . . . . . . 7 6.26 5.2 Partial Notifications . . . . . . . . . . . . . . . . . . . 7 6.35.3 Authorization . . . . . . . . . . . . . . . . . . . . . . . 7 7.6. Security Considerations . . . . . . . . . . . . . . . . . . 7 8.7. Example Applications for Notification Filtering . . . . . . 8 9.8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 98 9. Main changes from version 01 . . . . . . . . . . . . . . . . 8 10. Main changes from version 00 . . . . . . . . . . . . . . . . 9 References . . . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 10 Intellectual Property and Copyright Statements . . . . . . . 1211 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 Internet Draftdocument describing the Presence event package  mentions the possibility for afiltering. Accordingly, the SUBSCRIBE request may contain a body for filtering the presence information subscription. However, the definition of thefiltering has been leftwas considered out of thescope 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 43 and Section 54 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 87 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  and indicate requirement levels for compliant implementations. 3. Overview of functionality Filter Criteria set by a watcher may be set based on some predetermined knowledgeRequirements for Specification of Filters The following requirements relate to the structurecreation of the presence information, or the filtering mechanism may itselffilter criteria. 3.1 Package Identification REQ xx: It MUST be used to first discoverpossible for the structurecreator of the presence information thus enabling the setting newfilter criteriato 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 betweenspecify the notifier andpackage the watcher. The filtering shouldfilter applies to. 3.2 Target URI REQ xx: It MUST be considered as a post processing operation onpossible for the presence document after it has been modified duewatcher to indicate, in the rules offilter, the authorization. Astarget 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 containingcertain filter criteria may eitheris applied to. REQ xx: It MUST be accepted or rejected by the notifier based on the presence of filter criteria. 4. Requirementspossible for Specification of Filters The following requirements relatethe watcher to indicate, in the creation offilter criteria. 4.1 Common Syntax A common set of constructs MUST be defined forcriteria, the creation of rules. There MUST be a common set of operations that followtarget presentity list whose presence information a common syntax. The usercertain filter is applied to. REQ xx: It MUST be possible to define different rulesfor different purposes using a common filtering mechanism. 4.2 Package Identification A means is REQUIRED wherebythe user may specifywatcher to indicate, in the packagefilter criteria, the rules applytarget presentity sub-list whose presence information a certain filter is applied to. 4.3 Target URIREQ xx: It MUST be possible for the watcher to indicate, in the filter criteria to indicatecriteria, the target presentity, resource list or sub list of the resource list to whichdomain that contains presentities whose presence information a certain filter criteriais applied if this is different from the Request-URI in the subscription. 4.4to. 3.3 Notification Triggering This chapter presents requirements for specifying the desiredtriggering conditions for whenthat result in notifications areto 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 ofbreak 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 inapplying the notifications. It MUSTtriggering conditions. For example, it must not be possible for thea watcher to specify the presence information elements  (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 . E.g. the following two cases must be possible: o It MUST be possible forrequest a notification when the watcher<status> element value of a certain presentity has changed from OPEN to defineCLOSED when there is a criteria which allowslocal server policy constraining the completedelivery of any tuple and all information withinwith a tuple to be transmitted. o It<status> element value of CLOSED. REQ xx: The triggering conditions MUST be possible forbased 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 whattriggering. This covers expressions (tests) related to send inthe notification. The existencechange of an element SHOULD be considered aselement's value, and reaching a criterion.certain value of an element. REQ xx: It MUST be possible to construct expressionsone filter that combine multiple tests. 4.6 Discovery of Itemstriggering 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 forto 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 itemscontain the <contact> element of a certain presentity when there is a local server policy constraining the presence information thatdelivery 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 newspecify the presence information items.elements (XML elements and/or attributes) in  to be delivered in the notification. REQ xx: It MUST be possible for the watcher using the filter criteriato determine whatspecify presence information is available before subscribingin any extension to PIDF to be delivered in the notifications, based on XML elements and/or attributes. See for example . REQ xx: It MUST be possible for the watcher to specify presence information within 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 Placing4.1 Subscription REQ xx: It MUST be possible to place a filter criteriain the body of the subscription MUSTSUBSCRIBE request. REQ xx: It MAY be supported. Other means of delivering thepossible to deliver a filter criteriato thea server MAY be supported. E.g.using other means. For example, it shouldmay be possible for the rulesfilter to be (permanently) stored in the server, as inserver. 4.1.1 Maintaining a resource list case. 5.1.1 Retention ofFilter CriteriaREQ xx: The serverwatcher MUST retain theNOT be required to re-set a filter criteria throughat any time during the lifetime ofsubscription, once the subscription dialog until there is a modificationfilter has been set. REQ xx: The watcher SHOULD NOT be required to re-set a filter when refreshing a subscription, once the filter settings. 5.1.2has been set. REQ xx: Maintaining a filter across subscription refreshes SHOULD be bandwidth efficient. 4.1.2 Changing a Filter CriteriaREQ xx: It MUST be possible to change the filter settingsduring a subscription. REQ xx: It MUST be possible for the watcher to reset the filter settingsremove a set filter, reverting back to the service (server)a server defined default. Changing filter criteria SHOULD be bandwidth efficient. 5.24.2 Server does notSupport For Filters If theREQ xx: It MUST be possible for a server doesnot support filters (the content type) then itsupporting filtering to inform the watcher of the failure. REQ xx: It MUST be possible to indicate so infor a response. 5.3 Server doesserver not Support Filter Criteriaunderstanding a filtering to inform the watcher of the failure. REQ xx: It MUST be possible for thea server to explicitly indicate that it doesnot support or understand the filter criteria. This indication MAY includeaccepting a reason aboutfilter to inform the refusalwatcher of the subscription. 5.4 Server can no Longer Support Filter Criteria The serverreasons for not accepting the filter. REQ xx: It MUST be ablepossible for a server to terminate thea subscription if the any of the active filters are no longer applicablebased on a filter becoming invalid due to asever local policy change. (How do I word this in the server. 6.a requirement text?) 5. Interaction with Other Features 6.15.1 Resource Lists REQ xx: It MUST be possible to support filtering for subscriptions to resource lists . 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. 6.25.2 Partial Notifications REQ xx: It MUST be possible to use filtering along with the partial notification  within the same subscription. 6.35.3 Authorization REQ xx: Authorization SHOULD occur irrespective of the filtering. 7.6. Security Considerations Security requirements specified for  also applies to the presence filtering. Additional security considerations related to the presence filtering are described as follows. The filter criteria should notREQ 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 setpossible for him and thus discover whatthe presentity wantsserver 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 shouldSHOULD 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 shouldSHOULD convey only those parts of filter information targettedtargeted 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 Subscriberwatcher 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 intrestedinterested 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  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 -- Rich Presence Information Data Format for Presence Based on the Session Initiation Protocol (SIP)", draft-schulzrinne-simple-rpids-01.txt, February 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., "A Session Initiation Protocol (SIP) Event Notification Extension for Resource Lists", draft-ietf-simple-event-list-03.txt, May 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 Sreenivas AddagatlaHisham Khartabil Nokia 6000 Connection Drive Irving, Texas 75039 USAP.O BOX 321 Helsinki Finland Phone: +1 972 374 1917+358 7180 76161 EMail: email@example.com@nokia.com Eva Leppanen Nokia P.O BOX 785 Tampere Finland Phone: +358 7180 77066 EMail: firstname.lastname@example.org Andrew Allen 1937 McRae Lane Mundelein, Illinois 60060Tim Moran 2800 Britt Drive Argyle, Texas 76226 USA Phone: +1 972 849 8821 EMail: AndrewAllen007@email@example.com 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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