Network Working Group A. Niemi Internet-Draft Nokia Expires: July 23, 2003 January 22, 2003 Requirements for Limiting the Rate of Event Notifications draft-niemi-sipping-event-throttle-reqs-00 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 23, 2003. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract All event packages are required to specify a maximum rate at which event notifications are generated by a single notifier. Such a limit is provided in order to reduce network congestion. In addition to the fixed limits introduced by specific event packages, further mechanisms for limiting the rate of event notification are also allowed to be defined by event package specifications but none have been specified so far. This memo discusses the requirements for a throttle mechanism that allows a subscriber to further limit the rate of event notification. Niemi Expires July 23, 2003 [Page 1] Internet-Draft Event Throttle Requirements January 2003 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Example Use Case . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 Normative References . . . . . . . . . . . . . . . . . . . . . . 5 Informative References . . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . . 7 Niemi Expires July 23, 2003 [Page 2] Internet-Draft Event Throttle Requirements January 2003 1. Introduction The SIP events framework described in RFC 3265 [2] mandates that each event package specification defines an absolute maximum on the rate at which notifications are allowed to be generated by a single notifier. Such a limit is provided in order to reduce network congestion. All of the existing event package specifications include a maximum notification rate recommendation, ranging from once in every five seconds [3], [4], [5] to once per second [6]. Per the SIP events framework, each event package specification is also allowed to define additional throttling mechanisms which allow the subscriber to further limit the rate of event notification. So far none of the event package specifications have defined such throttling mechanisms. This memo discusses the requirements for a generic throttling mechanism, which allows the subscriber to limit the rate of event notifications. It is intended that the throttle mechanism is not event package specific, but commonly available to be used with all event subscriptions. 2. Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119 [1]. 3. Example Use Case There are many applications that potentially would make use of a throttle mechanism. This chapter only illustrates one possible use case, in which a mobile device uses the event throttling mechanism to limit the amount of traffic it may receive. A mobile application is watching the state of 100 presentities each generating notifications at a maximum rate of once per five seconds. Assuming that the arrival times of notifications are evenly distributed, this will result in a maximum notification frequency of: f = 100 * (1 / 5s) = 100 / 5 Hz = 20 Hz experienced by the mobile. The same watcher subscribing using a throttle mechanism to limit the maximum rate at which notifications are to be generated to once per 20 seconds can expect a maximum notification frequency of: Niemi Expires July 23, 2003 [Page 3] Internet-Draft Event Throttle Requirements January 2003 f = 100 * (1 / 20s) = 100 / 20 Hz = 5 Hz thus resulting in 75% reduction in the maximum rate of incoming presence notifications. Note that the actual rate of notification is the sum of many factors, and this example only makes a very broad assumption on the absolute maximum rate at which the notifications might be generated. 4. Requirements REQ1: The subscriber MUST be able to limit using a throttle mechanism the maximum rate at which the notifier is allowed to generate notifications in a subscription. REQ2: The subscriber MUST be able to indicate that it requires the use of a throttle mechanism in the subscription. REQ3: The subscriber SHOULD be allowed to indicate support for the throttle mechanism without requiring it. REQ4: The notifier MUST be able to indicate that it does not support the use of a throttle mechanism in the subscription. REQ5: If the throttle mechanism isn't required by the subscriber, the notifier SHOULD be able to ignore it. REQ6: It MUST be possible to use the throttle mechanism in subscriptions to all events. REQ7: It MUST be possible to use the throttle mechanism together with any event filtering mechanism. REQ8: The notifier MUST be allowed to use a maximum rate lower than the one given by the subscriber. REQ9: Authentication and integrity protection SHOULD be applied to subscriptions that apply the throttle mechanism. Note that Section 5 contains further discussion on the security implications of the throttle mechanism. 5. Security Considerations Naturally all of the security considerations for event subscriptions Niemi Expires July 23, 2003 [Page 4] Internet-Draft Event Throttle Requirements January 2003 and notifications also apply to subscriptions and notifications that use the throttle mechanism. In addition, using the event throttle mechanism introduces some new security issues to consider: The throttle mechanism might allow a subscriber to set a very low maximum notification rate - one that possibly exceeds the subscription expiration. Such a limit inserted by a malicious third party would result in very few if any notifications to be generated, which could be perceived as theft of service to the subscriber. Similarly, the throttle mechanism might allow the subscriber to set a very high maximum rate of notification that possibly is higher than the default recommended rate of notification. Such a high rate inserted by a malicious third party could result in denial of service of the notifier due to performance issues. Using the throttle mechanism potentially allows a subscriber to increase the number of active subscriptions due to the decrease in the maximum rate of notifications generated by a single notifier. If a malicious third party is able to remove the throttle from the subscriptions, the subscriber might be flooded with notifications. All of the above problems can be avoided by ensuring that the integrity and authenticity of subscriptions is protected by applying relevant security measures. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Informative References [2] Roach, A., "Session Initiation Protocol (SIP)-Specific Event Notification", RFC 3265, June 2002. [3] Rosenberg, J., "A Presence Event Package for the Session Initiation Protocol (SIP)", draft-ietf-simple-presence-09 (work in progress), December 2002. [4] Rosenberg, J., "A Session Initiation Protocol (SIP) Event Package for Registrations", draft-ietf-sipping-reg-event-00 (work in progress), October 2002. [5] Rosenberg, J., "A Watcher Information Event Template-Package for the Session Initiation Protocol (SIP)", draft-ietf-simple-winfo-package-04 (work in progress), December Niemi Expires July 23, 2003 [Page 5] Internet-Draft Event Throttle Requirements January 2003 2002. [6] Mahy, R., "A Message Summary and Message Waiting Indication Event Package for the Session Initiation Protocol (SIP)", draft-ietf-sipping-mwi-01 (work in progress), November 2002. Author's Address Aki Niemi Nokia P.O. Box 321 NOKIA GROUP, FIN 00045 Finland Phone: +358 50 389 1644 EMail: aki.niemi@nokia.com Niemi Expires July 23, 2003 [Page 6] Internet-Draft Event Throttle Requirements January 2003 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. 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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