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. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assignees.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
Niemi Expires July 23, 2003 [Page 7]
Internet-Draft Event Throttle Requirements January 2003
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
Niemi Expires July 23, 2003 [Page 8]