draft-ietf-sipcore-event-rate-control-05.txt   draft-ietf-sipcore-event-rate-control-06.txt 
Network Working Group A. Niemi Network Working Group A. Niemi
Internet-Draft K. Kiss Internet-Draft K. Kiss
Updates: 3265 (if approved) Nokia Updates: 3265 (if approved) Nokia
Intended status: Standards Track S. Loreto Intended status: Standards Track S. Loreto
Expires: April 21, 2011 Ericsson Expires: September 2, 2011 Ericsson
October 18, 2010 March 1, 2011
Session Initiation Protocol (SIP) Event Notification Extension for Session Initiation Protocol (SIP) Event Notification Extension for
Notification Rate Control Notification Rate Control
draft-ietf-sipcore-event-rate-control-05 draft-ietf-sipcore-event-rate-control-06
Abstract Abstract
This document specifies mechanisms for adjusting the rate of Session This document specifies mechanisms for adjusting the rate of Session
Initiation Protocol (SIP) event notifications. These mechanisms can Initiation Protocol (SIP) event notifications. These mechanisms can
be applied in subscriptions to all SIP event packages. be applied in subscriptions to all SIP event packages. This document
updates RFC 3265.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 21, 2011. This Internet-Draft will expire on September 2, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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skipping to change at page 3, line 13 skipping to change at page 3, line 13
than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Definitions and Document Conventions . . . . . . . . . . . . . 5 2. Definitions and Document Conventions . . . . . . . . . . . . . 5
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Use Case for Limiting the Maximum Rate of Notifications . 5 3.1. Use Case for Limiting the Maximum Rate of Notifications . 5
3.2. Use Case for Setting a Minimum Rate for Notifications . . 6 3.2. Use Case for Setting a Minimum Rate for Notifications . . 6
3.3. Use Case for Specifying an Adaptive Minimum Rate of 3.3. Use Case for Specifying an Adaptive Minimum Rate of
Notifications . . . . . . . . . . . . . . . . . . . . . . 7 Notifications . . . . . . . . . . . . . . . . . . . . . . 6
3.4. Requirements . . . . . . . . . . . . . . . . . . . . . . . 7 3.4. Requirements . . . . . . . . . . . . . . . . . . . . . . . 7
4. Basic Operations . . . . . . . . . . . . . . . . . . . . . . . 8 4. Basic Operations . . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Subscriber Behavior . . . . . . . . . . . . . . . . . . . 8 4.1. Subscriber Behavior . . . . . . . . . . . . . . . . . . . 8
4.2. Notifier Behavior . . . . . . . . . . . . . . . . . . . . 9 4.2. Notifier Behavior . . . . . . . . . . . . . . . . . . . . 9
5. Operation of the Maximum Rate Mechanism . . . . . . . . . . . 9 5. Operation of the Maximum Rate Mechanism . . . . . . . . . . . 9
5.1. Subscriber Behavior . . . . . . . . . . . . . . . . . . . 9 5.1. Subscriber Behavior . . . . . . . . . . . . . . . . . . . 9
5.2. Notifier Behavior . . . . . . . . . . . . . . . . . . . . 10 5.2. Notifier Behavior . . . . . . . . . . . . . . . . . . . . 10
5.3. Selecting the Maximum Rate . . . . . . . . . . . . . . . . 11 5.3. Selecting the Maximum Rate . . . . . . . . . . . . . . . . 11
5.4. The Maximum Rate Mechanism for Resource List Server . . . 11 5.4. The Maximum Rate Mechanism for Resource List Server . . . 11
5.5. Buffer Policy Description . . . . . . . . . . . . . . . . 13 5.5. Buffer Policy Description . . . . . . . . . . . . . . . . 13
5.5.1. Partial State Notifications . . . . . . . . . . . . . 13 5.5.1. Partial State Notifications . . . . . . . . . . . . . 13
5.5.2. Full State Notifications . . . . . . . . . . . . . . . 13 5.5.2. Full State Notifications . . . . . . . . . . . . . . . 13
5.6. Estimated Bandwidth Savings . . . . . . . . . . . . . . . 14 5.6. Estimated Bandwidth Savings . . . . . . . . . . . . . . . 14
6. Operation of the Minimum Rate Mechanism . . . . . . . . . . . 14 6. Operation of the Minimum Rate Mechanism . . . . . . . . . . . 14
6.1. Subscriber Behavior . . . . . . . . . . . . . . . . . . . 14 6.1. Subscriber Behavior . . . . . . . . . . . . . . . . . . . 14
6.2. Notifier Behavior . . . . . . . . . . . . . . . . . . . . 15 6.2. Notifier Behavior . . . . . . . . . . . . . . . . . . . . 15
6.3. Selecting the Minimum Rate . . . . . . . . . . . . . . . . 16
7. Operation of the Adaptive Minimum Rate Mechanism . . . . . . . 16 7. Operation of the Adaptive Minimum Rate Mechanism . . . . . . . 16
7.1. Subscriber Behavior . . . . . . . . . . . . . . . . . . . 16 7.1. Subscriber Behavior . . . . . . . . . . . . . . . . . . . 16
7.2. Notifier Behavior . . . . . . . . . . . . . . . . . . . . 16 7.2. Notifier Behavior . . . . . . . . . . . . . . . . . . . . 17
7.3. Calculating the Timeout . . . . . . . . . . . . . . . . . 17 7.3. Selecting the Adaptive Minimum Rate . . . . . . . . . . . 18
7.4. Calculating the Timeout . . . . . . . . . . . . . . . . . 18
8. Usage of the Maximum Rate, Minimum Rate and Adaptive 8. Usage of the Maximum Rate, Minimum Rate and Adaptive
Minimum Rate Mechanisms in a combination . . . . . . . . . . . 18 Minimum Rate Mechanisms in a combination . . . . . . . . . . . 19
9. Protocol Element Definitions . . . . . . . . . . . . . . . . . 19 9. Protocol Element Definitions . . . . . . . . . . . . . . . . . 21
9.1. "min-interval", "max-interval" and "average-interval" 9.1. "max-rate", "min-rate" and "adaptive-min-rate" Header
Header Field Parameters . . . . . . . . . . . . . . . . . 19 Field Parameters . . . . . . . . . . . . . . . . . . . . . 21
9.2. Grammar . . . . . . . . . . . . . . . . . . . . . . . . . 20 9.2. Grammar . . . . . . . . . . . . . . . . . . . . . . . . . 21
9.3. Event Header Field Usage in Responses to the NOTIFY 9.3. Event Header Field Usage in Responses to the NOTIFY
request . . . . . . . . . . . . . . . . . . . . . . . . . 20 request . . . . . . . . . . . . . . . . . . . . . . . . . 21
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
11. Security Considerations . . . . . . . . . . . . . . . . . . . 21 11. Security Considerations . . . . . . . . . . . . . . . . . . . 22
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
13.1. Normative References . . . . . . . . . . . . . . . . . . . 22 13.1. Normative References . . . . . . . . . . . . . . . . . . . 23
13.2. Informative References . . . . . . . . . . . . . . . . . . 23 13.2. Informative References . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction 1. Introduction
The SIP events framework [RFC3265] defines a generic framework for The SIP events framework [RFC3265] defines a generic framework for
subscriptions to and notifications of events related to SIP systems. subscriptions to and notifications of events related to SIP systems.
This framework defines the methods SUBSCRIBE and NOTIFY, and This framework defines the methods SUBSCRIBE and NOTIFY, and
introduces the concept of an event package, which is a concrete introduces the concept of an event package, which is a concrete
application of the SIP events framework to a particular class of application of the SIP events framework to a particular class of
events. events.
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The resource list extension [RFC4662] to the SIP events framework The resource list extension [RFC4662] to the SIP events framework
also deals with rate limiting of event notifications. The extension also deals with rate limiting of event notifications. The extension
allows a subscriber to subscribe to a heterogeneous list of resources allows a subscriber to subscribe to a heterogeneous list of resources
with a single SUBSCRIBE request, rather than having to install a with a single SUBSCRIBE request, rather than having to install a
subscription for each resource separately. The event list subscription for each resource separately. The event list
subscription also allows rate limiting, or throttling of subscription also allows rate limiting, or throttling of
notifications, by means of the Resource List Server (RLS) buffering notifications, by means of the Resource List Server (RLS) buffering
notifications of resource state changes, and sending them in batches. notifications of resource state changes, and sending them in batches.
However, the event list mechanism provides no means for the However, the event list mechanism provides no means for the
subscriber to set the interval for the throttling; it is strictly an subscriber to set the interval for the throttling.
implementation decision whether batching of notifications is
supported, and by what means. Some event packages are also interested in specifying an absolute or
an adaptive minimum rate at which notifications need to be generated
by a notifier. This helps the subscriber to effectively use
different trigger criterias within a subscription to eliminate
unnecessary notifications but at the same time make sure that the
current event state is periodically received.
This document defines an extension to the SIP events framework This document defines an extension to the SIP events framework
defining the following three Event header field parameters that allow defining the following three Event header field parameters that allow
a subscriber to set a maximum, a minimum and an adaptive minimum rate a subscriber to set a maximum, a minimum and an adaptive minimum rate
of event notifications generated by the notifier: of notifications generated by the notifier:
min-interval: specifies a minimum notification time period (maximum
rate) between two notifications, in seconds.
max-interval: specifies a maximum notification time period (minimum max-rate: specifies a maximum rate of notifications (a minimum time
rate) between two notifications, in seconds. period between two notifications).
average-interval: specifies an average maximum notification time min-rate: specifies a minimum rate notifications (a maximum time
period (adaptive minimum rate) between two notifications, in period between two notifications).
seconds.
The requirements and model are further discussed in Section 3. All average-rate: specifies an adaptive minimum rate of notifications
these mechanisms are simply timer values that indicate the minimum, (an adaptive maximum time period between two notifications).
maximum and average maximum time period allowed between two
notifications. As a result of these mechanisms, a compliant notifier
will adjust the rate at which it generates notifications.
These mechanisms are applicable to any event subscription, both These mechanisms are applicable to any event subscription, both
single event subscription and event list subscription. single event subscription and event list subscription. A notifier
compliant to this specification will adjust the rate at which it
generates notifications.
2. Definitions and Document Conventions 2. Definitions and Document Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119] and document are to be interpreted as described in RFC 2119 [RFC2119] and
indicate requirement levels for compliant implementations. indicate requirement levels for compliant implementations.
Indented passages such as this one are used in this document to Indented passages such as this one are used in this document to
provide additional information and clarifying text. They do not provide additional information and clarifying text. They do not
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3. Overview 3. Overview
3.1. Use Case for Limiting the Maximum Rate of Notifications 3.1. Use Case for Limiting the Maximum Rate of Notifications
A presence client in a mobile device contains a list of 100 buddies A presence client in a mobile device contains a list of 100 buddies
or presentities. In order to decrease the processing and network or presentities. In order to decrease the processing and network
load of watching 100 presentities, the presence client has employed a load of watching 100 presentities, the presence client has employed a
Resource List Server (RLS) with the list of buddies, and therefore Resource List Server (RLS) with the list of buddies, and therefore
only needs a single subscription to the RLS in order to receive only needs a single subscription to the RLS in order to receive
notification of the presence state of the resource list. notifications of the presence state of the resource list.
In order to control the buffer policy of the RLS, the presence client In order to control the buffer policy of the RLS, the presence client
sets a maximum rate ("min-interval" parameter), i.e. a minimum time sets a maximum rate of notifications. The RLS will buffer
interval between two notifications. The RLS will buffer notifications that are generated faster than they are allowed to be
notifications that do not comply with the maximum rate and batch all sent due to the maximum rate and batch all of the buffered state
of the buffered state changes together in a single notification only changes together in a single notification. The maximum rate applies
when allowed by the maximum rate. The maximum rate applies to the to the overall resource list, which means that there is a hard cap
overall resource list, which means that there is a hard cap imposed imposed by the maximum rate to the number of notifications per second
by the maximum rate to the number of notifications the presence the presence client can expect to receive.
client can expect to receive. For example, with a "min-interval" of
20 seconds, the presence application can expect to receive a
notification no more frequently than every 20 seconds.
The presence client can also modify the "min-interval" parameter The presence client can also modify the maximum rate of notifications
during the lifetime of the subscription. For example, if the User during the lifetime of the subscription. For example, if the mobile
Interface (UI) of the application shows inactivity for a period of device detects inactivity from the user for a period of time, the
time, it can simply pause the notifications by setting the "min- presence client can simply pause notifications by choosing a "max-
interval" parameter to the subscription expiration time, while still rate" parameter that allows only a single notification for the
keeping the subscription alive. When the user becomes active again, remainder of the subscription lifetime. When the user becomes active
the presence client can resume the stream of notifications by re- again, the presence client can resume the stream of notifications by
subscribing with a "min-interval" parameter set to the earlier used re-subscribing with a "max-rate" parameter set to the earlier used
value. Application of the mechanism defined by RFC 5839 [RFC5839] value. Application of the mechanism defined by RFC 5839 [RFC5839]
can also eliminate the transmission of a (full-state) notification can also eliminate the transmission of a (full-state) notification
carrying the latest resource state to the presence client after a carrying the latest resource state to the presence client after a
subscription refresh. subscription refresh.
3.2. Use Case for Setting a Minimum Rate for Notifications 3.2. Use Case for Setting a Minimum Rate for Notifications
A location application is monitoring the movement of a target. In A location application is monitoring the movement of a target. In
order to decrease the processing and network load, the location order to decrease the processing and network load, the location
application has made a subscription with a set of location filters application has made a subscription to a Location Server with a set
[I-D.ietf-geopriv-loc-filters] that specify trigger criteria, e.g. to of location filters [I-D.ietf-geopriv-loc-filters] that specify
send an update only when the target has moved at least n meters. trigger criteria, e.g. to send an update only when the target has
However, the application is also interested in receiving the current moved at least n meters. However, the application is also interested
state periodically even if the state of the target has not changed in receiving the current state periodically even if the state of the
enough to satisfy any of the trigger criteria, e.g. has not moved at target has not changed enough to satisfy any of the trigger criteria,
least n meters within the period. e.g., has not moved at least n meters within the period.
In order to control the actual state, the location application sets a The location application sets a minimum rate of notifications and
minimum rate ("max-interval" parameter), i.e. a maximum time interval include it in the subscription sent to the Location Server. The "min-
between two notifications. rate" parameter indicates the minimum number of notifications per
second the notifier needs to generate.
The location application can also modify the "max-interval" parameter The location application can also modify the minimum rate of
during the lifetime of the subscription. When the subscription to notifications during the lifetime of the subscription. For example,
the movement of a target is made, the notifier may not have the when the subscription to the movement of a target is made, the
location information available. Thus, the first notification might notifier may not have the location information available. Thus, the
be empty, or certain values might be absent. An important use case first notification might be empty, or certain values might be absent.
is placing constraints on when complete state should be provided An important use case is placing constraints on when complete state
after creating the subscription. The "max-interval" parameter should be provided after creating the subscription. Once state is
indicates to the notifier the maximum amount of time that should be acquired and the second notification is sent, the subscriber updates
allowed to elapse between NOTIFY requests containing complete state or changes the "min-rate" parameter to a more sensible value. This
information. Once state is acquired and the second notification is update can be performed in the response to the notification that
sent, the subscriber updates or changes the "max-interval" parameter contains the complete state information.
to a more sensible value. This update can be performed in the 200 OK
response to the NOTIFY request that contains the complete state
information.
3.3. Use Case for Specifying an Adaptive Minimum Rate of Notifications 3.3. Use Case for Specifying an Adaptive Minimum Rate of Notifications
The minimum rate mechanism introduces a static and instantaneous rate The minimum rate mechanism introduces a static and instantaneous rate
control without the functionality to increase or decrease the control without the functionality to increase or decrease the
notification frequency adaptively. However, there are some notification rate adaptively. However, there are some applications
applications that would work better with an adaptive minimum rate that would work better with an adaptive minimum rate control.
control. This section illustrates the tracking scenario.
A tracking application is monitoring the movement of a target. In A location application is monitoring the movement of a target. In
order to decrease the processing in the application, the tracking order to decrease the processing in the application, the location
application wants to make a subscription that dynamically decreases application wants to make a subscription that dynamically decreases
the minimum rate of notifications if the target has sent out several the minimum rate of notifications if the target has sent out several
notifications recently. However, if there have have been only few notifications recently. However, if there have have been only few
recent notifications by the target, the tracking application wants recent notifications by the target, the location application wants
the minimum rate of notifications to increase. the minimum rate of notifications to increase.
The application sets an adaptive minimum rate ("average-interval" The location application sets an adaptive minimum rate of
parameter), i.e. an average maximum time interval between two notifications and include it in the subscription sent to the Location
notifications. The "average-interval" parameter value is used by the Server. The "adaptive-min-rate" parameter value is used by the
notifier to dynamically calculate the actual maximum time ("timeout" notifier to dynamically calculate the actual maximum time between two
parameter) between two notifications. In order to dynamically notifications. In order to dynamically calculate the maximum time,
calculate the maximum time, the notifier takes into consideration the the notifier takes into consideration the rate at which notifications
frequency at which notifications have been sent recently. In the have been sent recently. In the adaptive minimum rate mechanism the
adaptive minimum rate mechanism the notifier can increase or decrease notifier can increase or decrease the notification rate compared to
the notification frequency compared to minimum rate mechanism based the minimum rate mechanism based on the recent number of
on the recent number of notifications sent out in the last period. notifications sent out in the last period.
The tracking application can also modify the "average-interval" The location application can also modify the "adaptive-min-rate"
parameter during the lifetime of the subscription. parameter during the lifetime of the subscription.
3.4. Requirements 3.4. Requirements
REQ1: The subscriber must be able to set a maximum rate ("min- REQ1: The subscriber must be able to set a maximum rate of
interval" parameter) of notifications in a specific notifications in a specific subscription.
subscription.
REQ2: The subscriber must be able to set a minimum rate ("max- REQ2: The subscriber must be able to set a minimum rate of
interval" parameter) of notifications in a specific notifications in a specific subscription.
subscription.
REQ3: The subscriber must be able to set an adaptive minimum rate REQ3: The subscriber must be able to set an adaptive minimum rate
("average-interval" parameter), which adjusts the minimum of notifications in a specific subscription, which adjusts
rate of notifications based on a moving average. the minimum rate of notifications based on a moving average.
REQ4: It must be possible to apply the maximum rate, the minimum REQ4: It must be possible to apply the maximum rate, the minimum
rate and the adaptive minimum rate mechanisms all together, rate and the adaptive minimum rate mechanisms all together,
or in any combination, in a specific subscription. or in any combination, in a specific subscription.
REQ5: It must be possible to use any of the different rate control REQ5: It must be possible to use any of the different rate control
mechanisms in subscriptions to any events. mechanisms in subscriptions to any events.
REQ6: It must be possible to use any of the different rate control REQ6: It must be possible to use any of the different rate control
mechanisms together with any other event filtering mechanisms together with any other event filtering
mechanisms. mechanisms.
REQ7: The notifier must be allowed to use a policy in which the REQ7: The notifier must be allowed to use a policy in which the
"min-interval", "max-interval" and "average-interval" maximum rate, minimum rate and adaptive minimum rate
paremeters are adjusted from the value given by the parameters are adjusted from the value given by the
subscriber. subscriber.
For example, due to congestion reasons, local policy at For example, due to congestion reasons, local policy at
the notifier could temporarily dictate a policy that in the notifier could temporarily dictate a policy that in
effect increases the subscriber-configured minimum time effect further decreases the maximum rate of
period between two notifications. In another example, the notifications. In another example, the notifier can
notifier can decrease the proposed minimum time by the increase the subscriber proposed maximum rate so that at
subscriber to match it with the remaining expiry time left least one notification is generated during the remainder
for the subscription. of the subscription lifetime.
REQ8: The different rate control mechanisms must address corner REQ8: The different rate control mechanisms must address corner
cases for setting the time periods between two notifications. cases for setting the notification rates appropriately. At a
At a minimum, the mechanisms must address the situation when minimum, the mechanisms must address the situation when the
the time between two notifications would exceed the time between two notifications would exceed the subscription
subscription duration and should provide mechanisms for duration and should provide procedures for avoiding this
avoiding this situation. situation.
REQ9: The different rate control mechanisms must be possible to be REQ9: The different rate control mechanisms must be possible to be
invoked, modified, or removed in the course of an active invoked, modified, or removed in the course of an active
subscription. subscription.
REQ10: The different rate control mechanisms must allow for the REQ10: The different rate control mechanisms must allow for the
application of authentication and integrity protection application of authentication and integrity protection
mechanisms to subscriptions invoking that mechanism. mechanisms to subscriptions invoking that mechanism.
4. Basic Operations 4. Basic Operations
4.1. Subscriber Behavior 4.1. Subscriber Behavior
In general, the way in which a subscriber generates SUBSCRIBE In general, the way in which a subscriber generates SUBSCRIBE
requests and processes NOTIFY requests is according to RFC 3265 requests and processes NOTIFY requests is according to RFC 3265
[RFC3265]. [RFC3265].
A subscriber that wants to have a maximum, minimum or adaptive A subscriber that wants to have a maximum, minimum or adaptive
minimum rate of event notifications in a specific event subscription minimum rate of event notifications in a specific event subscription
does so by including a "min-interval", "max-interval" or "average- does so by including a "max-rate", "min-rate" or "adaptive-min-rate"
interval" Event header field parameter(s) as part of the SUBSCRIBE Event header field parameter(s) as part of the SUBSCRIBE request.
request.
A subscriber that wants to update a previously agreed event rate A subscriber that wants to update a previously agreed event rate
control parameter does so by including the updated "min-interval", control parameter does so by including the updated "max-rate", "min-
"max-interval" or "average-interval" Event header field parameter(s) rate" or "adaptive-min-rate" Event header field parameter(s) as part
as part of a subsequent SUBSCRIBE request or a 2xx response to the of a subsequent SUBSCRIBE request or a 2xx response to the NOTIFY
NOTIFY request. If the subscriber did not include at least one of request. If the subscriber did not include at least one of the "max-
the "min-interval, "max-interval", or "average-interval" header field rate", "min-rate" or "adaptive-min-rate" header field parameters in
parameters in the most recent SUBSCRIBE request in a given dialog, it the most recent SUBSCRIBE request in a given dialog, the subscriber
MUST NOT include an Event header field with any of those parameters MUST NOT include an Event header field with any of those parameters
in a 2xx response to a NOTIFY request in that dialog. in a 2xx response to a NOTIFY request in that dialog.
4.2. Notifier Behavior 4.2. Notifier Behavior
In general, the way in which a notifier processes SUBSCRIBE requests In general, the way in which a notifier processes SUBSCRIBE requests
and generates NOTIFY requests is according to RFC 3265 [RFC3265]. and generates NOTIFY requests is according to RFC 3265 [RFC3265].
A notifier that supports the different rate control mechanisms will A notifier that supports the different rate control mechanisms MUST
comply with the value given in "min-interval", "max-interval" and adjust its rate of notification according to the rate control values
"average-interval" parameters and adjust its rate of notification agreed with the subscriber. If the notifier needs to lower the
accordingly. However, if the notifier needs to lower the
subscription expiration value or if a local policy or other subscription expiration value or if a local policy or other
implementation-determined constraint at the notifier can not satisfy implementation-determined constraint at the notifier can not satisfy
the rate control request, then the notifier can adjust (i.e. increase the rate control request, then the notifier can adjust (i.e. increase
or decrease) appropriately the subscriber requested rate control. or decrease) appropriately the subscriber requested rate control
values. The notifier MUST reflect back the possibly adjusted rate
control values in a "max-rate", "min-rate" or "adaptive-min-rate"
Subscription-State header field parameter of the subsequent NOTIFY
requests.
5. Operation of the Maximum Rate Mechanism 5. Operation of the Maximum Rate Mechanism
5.1. Subscriber Behavior 5.1. Subscriber Behavior
A subscriber that wishes to apply a maximum rate to notifications in A subscriber that wishes to apply a maximum rate to notifications in
a subscription MUST construct a SUBSCRIBE request that includes a a subscription MUST construct a SUBSCRIBE request that includes the
minimum time interval between two consecutive notifications included "max-rate" Event header field parameter specifying the requested
in the "min-interval" Event header field parameter. The value of maximum number of notifications per second. The value of this
this parameter is an integral number of seconds in decimal. parameter is the reciprocal value of the "min-interval" parameter,
the minimum time interval between two consecutive notifications. The
value of the "min-interval" parameter is a positive decimal integer
measured in seconds. For example, when the subscriber wants to
receive notifications no more frequently than once in every seven
seconds, then it sets the value of the "max-rate" parameter to 1/7.
Note that the witnessed time between two consecutive received Note that the witnessed time between two consecutive received
notifications may not conform to the "min-interval" value for a notifications may not conform to the "max-rate" value for a number
number of reasons. For example, network jitter and of reasons. For example, network jitter and retransmissions may
retransmissions may result in the subscriber receiving the result in the subscriber receiving the notifications more frequent
notifications with smaller intervals than the "min-interval" value than the "max-rate" value recommends.
recommends.
A subscriber that wishes to update the previously agreed maximum rate A subscriber that wishes to update the previously agreed maximum rate
of notifications MUST include the updated "min-interval" Event header of notifications MUST include the updated "max-rate" Event header
field parameter in a subsequent SUBSCRIBE request or a 2xx response field parameter in a subsequent SUBSCRIBE request or a 2xx response
to the NOTIFY request. to the NOTIFY request.
A subscriber that wishes to remove the maximum rate control from A subscriber that wishes to remove the maximum rate control from
notifications MUST indicate so by not including a "min-interval" notifications MUST indicate so by not including a "max-rate" Event
Event header field parameter in a subsequent SUBSCRIBE request or a header field parameter in a subsequent SUBSCRIBE request or a 2xx
2xx response to the NOTIFY request. response to the NOTIFY request.
There are two main consequences for the subscriber when applying the There are two main consequences for the subscriber when applying the
maximum rate mechanism: state transitions may be lost, and event maximum rate mechanism: state transitions may be lost and event
notifications may be delayed. If either of these side effects notifications may be delayed. If either of these side effects
constitute a problem to the application that utilizes the event constitute a problem to the application that utilizes the event
notifications, developers are instructed not to use the mechanism. notifications, developers are instructed not to use the mechanism.
5.2. Notifier Behavior 5.2. Notifier Behavior
A notifier that supports the maximum rate mechanism MUST extract the A notifier that supports the maximum rate mechanism MUST extract the
value of the "min-interval" Event header parameter from a SUBSCRIBE value of the "max-rate" Event header parameter from a SUBSCRIBE
request or a 2xx response to the NOTIFY request and use it as the request or a 2xx response to the NOTIFY request and use it as the
suggested minimum time allowed between two notifications. This value suggested maximum number of notifications per second. This value can
can be adjusted by the notifier, as defined in Section 5.3. be adjusted by the notifier, as defined in Section 5.3.
A compliant notifier MUST reflect back the possibly adjusted minimum A compliant notifier MUST reflect back the possibly adjusted maximum
time interval in a "min-interval" Subscription-State header field rate of notifications in a "max-rate" Subscription-State header field
parameter of the subsequent NOTIFY requests. The indicated "min- parameter of the subsequent NOTIFY requests. The indicated "max-
interval" value is adopted by the notifier, and the notification rate rate" value is adopted by the notifier, and the notification rate is
is adjusted accordingly. adjusted accordingly.
A notifier that does not understand this extension will not reflect A notifier that does not understand this extension will not reflect
the "min-interval" Subscription-State header field parameter in the the "max-rate" Subscription-State header field parameter in the
NOTIFY requests; the absence of this parameter indicates to the NOTIFY requests; the absence of this parameter indicates to the
subscriber that no rate control is supported by the notifier. subscriber that no rate control is supported by the notifier.
A compliant notifier MUST NOT generate notifications more frequently A compliant notifier MUST NOT generate notifications more frequently
than the maximum rate allows for, except when generating the than the maximum rate allows for, except when generating the
notification either upon receipt of a SUBSCRIBE request (the first notification either upon receipt of a SUBSCRIBE request (the first
notification), when the subscription state is changing from "pending" notification), when the subscription state is changing from "pending"
to "active" state or upon termination of the subscription (the last to "active" state or upon termination of the subscription (the last
notification). Such notifications reset the timer for the next notification). Such notifications reset the timer for the next
notification. notification.
When a local policy dictates a maximum rate for notifications, a When a local policy dictates a maximum rate for notifications, a
notifier will not generate notifications more frequently than the notifier will not generate notifications more frequently than the
local policy maximum rate, even if the subscriber is not asking for local policy maximum rate, even if the subscriber is not asking for
maximum rate control. The notifier MAY inform the subscriber about maximum rate control. The notifier MAY inform the subscriber about
such local policy maximum rate using the "min-interval" Subscription- such local policy maximum rate using the "max-rate" Subscription-
State header field parameter included in the subsequent NOTIFY State header field parameter included in subsequent NOTIFY requests.
requests.
Retransmissions of NOTIFY requests are not affected by the maximum Retransmissions of NOTIFY requests are not affected by the maximum
rate mechanism, i.e., the maximum rate mechanism only applies to the rate mechanism, i.e., the maximum rate mechanism only applies to the
generation of new transactions. In other words, the maximum rate generation of new transactions. In other words, the maximum rate
mechanism does not in any way break or modify the normal mechanism does not in any way break or modify the normal
retransmission mechanism specified in RFC 3261 [RFC3261]. retransmission mechanism specified in RFC 3261 [RFC3261].
5.3. Selecting the Maximum Rate 5.3. Selecting the Maximum Rate
Special care needs to be taken when selecting the "min-interval" Special care needs to be taken when selecting the maximum rate. For
value. For example, the maximum rate could potentially set a minimum example, the maximum rate could potentially set a minimum time value
time value between notifications that exceeds the subscription between notifications that exceeds the subscription expiration value.
expiration value. Such a configuration would effectively quench the Such a configuration would effectively quench the notifier, resulting
notifier, resulting in exactly two notifications to be generated. If in exactly two notifications to be generated. If the subscriber
the subscriber requests a "min-interval" value greater than the requests a maximum rate that would result in no notification before
subscription expiration, the notifier MUST lower the "min-interval" the subscription expiration, the notifier MUST increase the maximum
value and set it to the expiration time left. According to RFC 3265 rate and set it to the reciprocal value of the subscription
[RFC3265] the notifier may also shorten the subscription expiry expiration time left. According to RFC 3265 [RFC3265] the notifier
anytime during an active subscription. If the subscription expiry is may also shorten the subscription expiry anytime during an active
shortened during an active subscription, the notifier MUST also lower subscription. If the subscription expiry is shortened during an
the "min-interval" value and set it to the reduced expiration time. active subscription, the notifier MUST also increase the "max-rate"
value and set it to reciprocal value of the reduced subscription
expiration time.
In some cases it makes sense to pause the notification stream on an In some cases it makes sense to pause the notification stream on an
existing subscription dialog on a temporary basis without terminating existing subscription dialog on a temporary basis without terminating
the subscription, e.g. due to inactivity on the application user the subscription, e.g. due to inactivity on the application user
interface. Whenever a subscriber discovers the need to perform the interface. Whenever a subscriber discovers the need to perform the
notification pause operation, it SHOULD set the "min-interval" value notification pause operation, it SHOULD set the maximum rate to the
to the remaining subscription expiration value. This results in reciprocal value of the remaining subscription expiration value.
receiving no further notifications until the subscription expires or This results in receiving no further notifications until the
the subscriber sends a SUBSCRIBE request resuming notifications. subscription expires or the subscriber sends a SUBSCRIBE request
resuming notifications.
The notifier MAY decide to increase or decrease the proposed maximum The notifier MAY decide to increase or decrease the proposed "max-
rate value by the subscriber based on its local policy, static rate" value by the subscriber based on its local policy, static
configuration or other implementation-determined constraints. The configuration or other implementation-determined constraints. In
notifier MUST include the adjusted "min-interval" value in the addition, different event packages MAY define additional constraints
Subscription-State header field's "min-interval" parameter in each of for the allowed maximum rate ranges. Such constraints are out of the
the NOTIFY requests. In addition, different event packages MAY scope of this specification.
define additional constraints to the allowed "min-interval"
intervals. Such constraints are out of the scope of this
specification.
5.4. The Maximum Rate Mechanism for Resource List Server 5.4. The Maximum Rate Mechanism for Resource List Server
When applied to a list subscription [RFC4662], the maximum rate When applied to a list subscription [RFC4662], the maximum rate
mechanism has some additional considerations. Specifically, the mechanism has some additional considerations. Specifically, the
maximum rate applies to the aggregate notification stream resulting maximum rate applies to the aggregate notification stream resulting
from the list subscription, rather than explicitly controlling the from the list subscription, rather than explicitly controlling the
notification of each of the implied constituent events. Moreover, notification of each of the implied constituent events. Moreover,
the RLS can use the maximum rate mechanism on its own to control the the RLS can use the maximum rate mechanism on its own to control the
rate of the back-end subscriptions to avoid overflowing its buffer. rate of the back-end subscriptions to avoid overflowing its buffer.
skipping to change at page 12, line 28 skipping to change at page 12, line 26
`-.. | _.--' `-.. | _.--'
``-._ | _.--' ``-._ | _.--'
+'--'--'-+ +'--'--'-+
|Resource| |Resource|
| List | | List |
| Server | | Server |
+---.----+ +---.----+
| |
| |
)--+---( )--+---(
| | .------------. | | .--------.
|Buffer|<======'min-interval| |Buffer|<======'max-rate|
| | `------------' | | `--------'
)--.---( )--.---(
| |
| |
.---+---. .---+---.
| Event | | Event |
|Watcher| |Watcher|
`-------' `-------'
Figure 1: Model for the Resource List Server (RLS) Supporting Figure 1: Model for the Resource List Server (RLS) Supporting
Throttling Throttling
skipping to change at page 14, line 15 skipping to change at page 14, line 13
simply replaces that notification with the new notification, simply replaces that notification with the new notification,
discarding the older state. discarding the older state.
5.6. Estimated Bandwidth Savings 5.6. Estimated Bandwidth Savings
It is difficult to estimate the total bandwidth savings accrued by It is difficult to estimate the total bandwidth savings accrued by
using the maximum rate mechanism over a subscription, since such using the maximum rate mechanism over a subscription, since such
estimates will vary depending on the usage scenarios. However, it is estimates will vary depending on the usage scenarios. However, it is
easy to see that given a subscription where several full state easy to see that given a subscription where several full state
notifications would have normally been sent in any given interval set notifications would have normally been sent in any given interval set
by the "min-interval" parameter, only a single notification is sent by the "max-rate" parameter, only a single notification is sent
during the same interval when using the maximum rate mechanism during the same interval when using the maximum rate mechanism
yielding bandwidth savings of several times the notification size. yielding bandwidth savings of several times the notification size.
With partial-state notifications, drawing estimates is further With partial-state notifications, drawing estimates is further
complicated by the fact that the states of consecutive updates may or complicated by the fact that the states of consecutive updates may or
may not overlap. However, even in the worst case scenario, where may not overlap. However, even in the worst case scenario, where
each partial update is to a different part of the full state, a rate each partial update is to a different part of the full state, a rate
controlled notification merging all of these n partial states controlled notification merging all of these n partial states
together should at a maximum be the size of a full-state update. In together should at a maximum be the size of a full-state update. In
this case, the bandwidth savings are approximately n times the size this case, the bandwidth savings are approximately n times the size
skipping to change at page 14, line 40 skipping to change at page 14, line 38
[RFC3320] and TLS compression [RFC3943]. However, such compression [RFC3320] and TLS compression [RFC3943]. However, such compression
schemes are complementary rather than competing mechanisms to the schemes are complementary rather than competing mechanisms to the
maximum rate mechanism. After all, they can both be applied maximum rate mechanism. After all, they can both be applied
simultaneously. simultaneously.
6. Operation of the Minimum Rate Mechanism 6. Operation of the Minimum Rate Mechanism
6.1. Subscriber Behavior 6.1. Subscriber Behavior
A subscriber that wishes to apply a minimum rate to notifications in A subscriber that wishes to apply a minimum rate to notifications in
a subscription MUST construct a SUBSCRIBE request that includes a a subscription MUST construct a SUBSCRIBE request that includes the
maximum time interval between two consecutive notifications included "min-rate" Event header field parameter specifying the requested
in the "max-interval" Event header field parameter. The value of minimum number of notifications per second. The value of this
this parameter is an integral number of seconds in decimal. parameter is the reciprocal value of the "max-interval" parameter,
the maximum time interval between two consecutive notifications. The
value of the "max-interval" parameter is a positive decimal integer
measured in seconds. For example, when the subscriber wants to
receive notifications at least once in every seven seconds, then it
sets the value of the "min-rate" parameter to 1/7.
A subscriber that wishes to update the previously agreed minimum rate A subscriber that wishes to update the previously agreed minimum rate
of notifications MUST include the updated "max-interval" Event header of notifications MUST include the updated "min-rate" Event header
field parameter in a subsequent SUBSCRIBE request or a 2xx response field parameter in a subsequent SUBSCRIBE request or a 2xx response
to the NOTIFY request. to the NOTIFY request.
A subscriber that wishes to remove the minimum rate control from A subscriber that wishes to remove the minimum rate control from
notifications MUST indicate so by not including a "max-interval" notifications MUST indicate so by not including a "min-rate" Event
Event header field parameter in a subsequent SUBSCRIBE request or a header field parameter in a subsequent SUBSCRIBE request or a 2xx
2xx response to the NOTIFY request. response to the NOTIFY request.
The main consequence for the subscriber when applying the minimum The main consequence for the subscriber when applying the minimum
rate mechanism is that it can receive a notification even if nothing rate mechanism is that it can receive a notification even if nothing
has changed in the current state of the notifier. However, RFC 5839 has changed in the current state of the notifier. However, RFC 5839
[RFC5839] defines a mechanism that allows sending only an etag [RFC5839] defines a mechanism that allows suppressing a NOTIFY
instead of the full resource state in a notification if the state has request or a NOTIFY request body if the state has not changed.
not changed.
6.2. Notifier Behavior 6.2. Notifier Behavior
A notifier that supports the minimum rate mechanism MUST extract the A notifier that supports the minimum rate mechanism MUST extract the
value of the "max-interval" Event header field parameter from a value of the "min-rate" Event header field parameter from a SUBSCRIBE
SUBSCRIBE request or a 2xx response to the NOTIFY request and use it request or a 2xx response to the NOTIFY request and use it as the
as the suggested maximum time allowed between two notifications. suggested minimum number of notifications per second. This value can
be adjusted by the notifier, as defined in Section 6.3.
The notifier MAY decide to increase or decrease the proposed minimum A compliant notifier MUST reflect back the possibly adjusted minimum
rate value based on its local policy, static configuration or other rate of notifications in a "min-rate" Subscription-State header field
implementation-determined constraints. A compliant notifier MUST parameter of the subsequent NOTIFY requests. The indicated "min-
reflect back the possibly adjusted maximum time interval in a "max- rate" value is adopted by the notifier, and the notification rate is
interval" Subscription-State header field parameter of the subsequent adjusted accordingly.
NOTIFY requests. The indicated "max-interval" value is adopted by
the notifier, and the notification rate is adjusted accordingly.
A notifier that does not understand this extension, will not reflect A notifier that does not understand this extension, will not reflect
the "max-interval" Subscription-State header field parameter in the the "min-rate" Subscription-State header field parameter in the
NOTIFY requests; the absence of this parameter indicates to the NOTIFY requests; the absence of this parameter indicates to the
subscriber that no rate control is supported by the notifier. subscriber that no rate control is supported by the notifier.
A compliant notifier MUST generate notifications when state changes A compliant notifier MUST generate notifications when state changes
occur or when the time since the most recent notification exceeds the occur or when the time since the most recent notification exceeds the
value in the "max-interval" parameter. Depending on the event "max-interval" value, the reciprocal value of the "min-rate"
package and subscriber preferences indicated in the SUBSCRIBE parameter. Depending on the event package and subscriber preferences
request, the NOTIFY request sent as a result of a max-interval indicated in the SUBSCRIBE request, the NOTIFY request sent as a
expiration MUST contain either the current full state or the partial result of a minimum rate mechanism MUST contain either the current
state showing the difference between the current state and the last full state or the partial state showing the difference between the
successfully communicated state. current state and the last successfully communicated state. If the
subscriber and the notifier support the procedures in RFC 5839
[RFC5839] the complete NOTIFY request or the NOTIFY request body can
be suppressed if the state has not changed from the previous
notification.
Retransmissions of NOTIFY requests are not affected by the minimum Retransmissions of NOTIFY requests are not affected by the minimum
rate mechanism, i.e., the minimum rate mechanism only applies to the rate mechanism, i.e., the minimum rate mechanism only applies to the
generation of new transactions. In other words, the minimum rate generation of new transactions. In other words, the minimum rate
mechanism does not in any way break or modify the normal mechanism does not in any way break or modify the normal
retransmission mechanism. retransmission mechanism.
6.3. Selecting the Minimum Rate
The minimum rate mechanism can be used to generate a lot of
notifications, creating additional processing load for the notifier.
Some of the notifications may also be unnecessary possibly repeating
already known state information to the subscriber. It is difficult
to provide generic guidelines for the acceptable minimum rate value
ranges, however the subscriber SHOULD request for the lowest possible
minimum rate. Different event packages MAY define additional
constraints for the allowed minimum rate values. Such constraints
are out of the scope of this specification.
The notifier MAY decide to increase or decrease the proposed "min-
rate" value by the subscriber based on its local policy, static
configuration or other implementation-determined constraints.
7. Operation of the Adaptive Minimum Rate Mechanism 7. Operation of the Adaptive Minimum Rate Mechanism
7.1. Subscriber Behavior 7.1. Subscriber Behavior
A subscriber that wishes to apply an adaptive minimum rate to A subscriber that wishes to apply an adaptive minimum rate to
notifications in a subscription MUST construct a SUBSCRIBE request notifications in a subscription MUST construct a SUBSCRIBE request
that includes an average maximum time interval between two that includes the "adaptive-min-rate" Event header field parameter
consecutive notifications included in a "average-interval" Event specifying an adaptive minimum number of notifications per second.
header field parameter. The value of this parameter is an integral The value of this parameter is the reciprocal value of the "adaptive-
number of seconds in decimal. max-interval" parameter, the adaptive maximum time interval between
two consecutive notifications. The value of the "adaptive-max-
interval" parameter is a positive decimal integer measured in
seconds. For example, when the subscriber wants to receive
notifications once in every seven seconds on an average, then it sets
the value of the "adaptive-min-rate" parameter to 1/7.
A subscriber that wishes to update the previously agreed adaptive A subscriber that wishes to update the previously agreed adaptive
minimum rate of notifications MUST include the updated "average- minimum rate of notifications MUST include the updated "adaptive-min-
interval" Event header field parameter in a subsequent SUBSCRIBE rate" Event header field parameter in a subsequent SUBSCRIBE request
request or a 2xx response to the NOTIFY request. or a 2xx response to the NOTIFY request.
A subscriber that wishes to remove the adaptive minimum rate control A subscriber that wishes to remove the adaptive minimum rate control
from notifications MUST indicate so by not including a "average- from notifications MUST indicate so by not including a "adaptive-min-
interval" Event header field parameter in a subsequent SUBSCRIBE rate" Event header field parameter in a subsequent SUBSCRIBE request
request or a 2xx response to the NOTIFY request. or a 2xx response to the NOTIFY request.
The main consequence for the subscriber when applying the adative The main consequence for the subscriber when applying the adaptive
minimum rate mechanism is that it can receive a notification even if minimum rate mechanism is that it can receive a notification even if
nothing has changed in the current state of the notifier. However, nothing has changed in the current state of the notifier. However,
RFC 5839 [RFC5839] defines a mechanism that allows sending only an RFC 5839 [RFC5839] defines a mechanism that allows suppressing a
etag instead of the full resource state in a notification if the NOTIFY request or a NOTIFY request body if the state has not changed.
state has not changed.
7.2. Notifier Behavior 7.2. Notifier Behavior
A notifier that supports the adaptive minimum rate mechanism MUST A notifier that supports the adaptive minimum rate mechanism MUST
extract the value of the "average-interval" Event header parameter extract the value of the "adaptive-min-rate" Event header parameter
from a SUBSCRIBE request or a 2xx response to the NOTIFY request and from a SUBSCRIBE request or a 2xx response to the NOTIFY request and
use it to calculate the actual maximum time between two notifications use it to calculate the actual maximum time between two notifications
as defined in Section 7.3. as defined in Section 7.4.
The notifier MAY decide to increase or decrease the proposed The "adaptive-min-rate" value can be adjusted by the notifier, as
"average-interval" based on its local policy, static configuration or defined in Section 7.3.
other implementation-determined constraints. A compliant notifier
MUST reflect back the possibly adjusted time interval in an "average- A compliant notifier MUST reflect back the possibly adjusted adaptive
interval" Subscription-State header field parameter of the subsequent minimum rate of notifications in an "adaptive-min-rate" Subscription-
NOTIFY requests. The indicated "average-interval" value is adopted State header field parameter of the subsequent NOTIFY requests. The
by the notifier, and the notification rate is adjusted accordingly. indicated "adaptive-min-rate" value is adopted by the notifier, and
the notification rate is adjusted accordingly.
A notifier that does not understand this extension will not reflect A notifier that does not understand this extension will not reflect
the "average-interval" Subscription-State header parameter in the the "adaptive-min-rate" Subscription-State header parameter in the
NOTIFY requests; the absence of this parameter indicates to the NOTIFY requests; the absence of this parameter indicates to the
subscriber that no rate control is supported by the notifier. subscriber that no rate control is supported by the notifier.
A compliant notifier SHOULD generate notifications when state changes A compliant notifier MUST generate notifications when state changes
occur or when the time since the most recent notification exceeds the occur or when the time since the most recent notification exceeds the
value calculated using the formula defined in Section 7.3. value calculated using the formula defined in Section 7.4. Depending
on the event package and subscriber preferences indicated in the
SUBSCRIBE request, the NOTIFY request sent as a result of a minimum
rate mechanism MUST contain either the current full state or the
partial state showing the difference between the current state and
the last successfully communicated state. If the subscriber and the
notifier support the procedures in RFC 5839 [RFC5839] the complete
NOTIFY request or the NOTIFY request body can be suppressed if the
state has not changed from the previous notification.
The adaptive minimum rate mechanism is implemented as follows: The adaptive minimum rate mechanism is implemented as follows:
1) When a subscription is first created, the notifier creates a 1) When a subscription is first created, the notifier creates a
record that keeps track of the number of notifications that have record ("count" parameter) that keeps track of the number of
been sent in the "period". This record is initialized to contain notifications that have been sent in the "period". The "count"
a history of having sent one message every "average-interval" parameter is initialized to contain a history of having sent a
seconds for the "period". "period * adaptive-min-rate" number of notifications for the
"period".
2) The "timeout" value is calculated according to the equation given 2) The "timeout" value is calculated according to the equation given
in Section 7.3. in Section 7.4.
3) If the timeout period passes without a NOTIFY request being sent 3) If the timeout period passes without a NOTIFY request being sent
in the subscription, then the current resource state is sent in the subscription, then the current resource state is sent
(subject to any filtering associated with the subscription). (subject to any filtering associated with the subscription).
4) Whenever a NOTIFY request is sent (regardless of whether due to a 4) Whenever a NOTIFY request is sent (regardless of whether due to a
timeout or a state change), the notifier updates the notification "timeout" event or a state change), the notifier updates the
history record, recalculates the value of "timeout," and returns notification history record stored in the "count" parameter,
to step 3. recalculates the value of "timeout," and returns to step 3.
Retransmissions of NOTIFY requests are not affected by the timeout, Retransmissions of NOTIFY requests are not affected by the timeout,
i.e., the timeout only applies to the generation of new transactions. i.e., the timeout only applies to the generation of new transactions.
In other words, the timeout does not in any way break or modify the In other words, the timeout does not in any way break or modify the
normal retransmission mechanism specified in RFC 3261 [RFC3261]. normal retransmission mechanism specified in RFC 3261 [RFC3261].
7.3. Calculating the Timeout 7.3. Selecting the Adaptive Minimum Rate
The adaptive minimum rate mechanism can be used to generate a lot of
notifications, creating additional processing load for the notifier.
Some of the notifications may also be unnecessary possibly repeating
already known state information to the subscriber. It is difficult
to provide generic guidelines for the acceptable adaptive minimum
rate value ranges, however the subscriber SHOULD request for the
lowest possible adaptive minimum rate value. Different event
packages MAY define additional constraints for the allowed adaptive
minimum rate values. Such constraints are out of the scope of this
specification.
The notifier MAY decide to increase or decrease the proposed
"adaptive-min-rate" value based on its local policy, static
configuration or other implementation-determined constraints.
7.4. Calculating the Timeout
The formula used to vary the absolute pacing in a way that will meet The formula used to vary the absolute pacing in a way that will meet
the adaptive minimum rate requested over the period is given in the adaptive minimum rate requested over the period is given in
equation (1): equation (1):
timeout = (average-interval ^ 2) * count / period (1) timeout = count /(adaptive-min-rate ^ 2) * period (1)
The output of the formula, "timeout", is the time to the next The output of the formula, "timeout", is the time to the next
notification, expressed in seconds. The formula has three inputs: notification, expressed in seconds. The formula has three inputs:
average-interval: The value of the "average-interval" parameter adaptive-min-rate: The value of the "adaptive-min-rate" parameter
conveyed in the Subscription-State header field, in seconds. conveyed in the Subscription-State header field.
period: The rolling average period, in seconds. The value of the period: The rolling average period, in seconds. The granularity of
"period" parameter is chosen by the notifier, however the notifier the values for the "period" parameter is set by local policy at
MUST choose a value greater than the value of the "average- the notifier, however the notifier MUST choose a value greater
interval" parameter. The granularity of the values for the than the value of the "adaptive-max-interval" parameter, the
"period" parameter is set by local policy at the notifier. It is reciprocal value of the "adaptive-min-rate" parameter. It is also
an implementation decision whether the notifier uses the same RECOMMENDED that the notifier chooses a "period" parameter several
value of the "period" parameter for all subscriptions or times larger than "adaptive-max-interval" parameter in order to
individual values for each subscription. maximize the effectiveness of the equation (1). It is an
implementation decision whether the notifier uses the same value
of the "period" parameter for all subscriptions or individual
values for each subscription.
count: The number of notifications that have been sent during the count: The number of notifications that have been sent during the
last "period" of seconds not including any retransmissions of last "period" of seconds not including any retransmissions of
requests. requests.
In case both the maximum rate and the adaptive minimum rate In case both the maximum rate and the adaptive minimum rate
mechanisms are used in the same subscription the formula used to mechanisms are used in the same subscription the formula used to
dynamically calculate the timeout is given in equation (2): dynamically calculate the timeout is given in equation (2):
timeout = MAX[min-interval, (average-interval ^ 2) * count / period] (2) timeout = MAX[1/max-rate, count /(adaptive-min-rate ^ 2) * period] (2)
min-interval: The value of the "min-interval" parameter conveyed in max-rate: The value of the "max-rate" parameter conveyed in the
the Subscription-State header field, in seconds. Subscription-State header field.
The formula in (2) makes sure that for all the possible values of the The formula in (2) makes sure that for all the possible values of the
"min-interval" and "average-interval" parameters, with "average- "max-rate" and "adaptive-min-rate" parameters, with "adaptive-min-
interval" > "min-interval", the timeout never results in a lower rate" < "max-rate", the timeout never results in a lower value than
value than the value of the "min-interval" parameter. "min-interval", the reciprocal value of the "max-rate" parameter.
In some situation it may be beneficial for the notifier to achieve an In some situation it may be beneficial for the notifier to achieve an
adaptive minimum rate in a different way than the algorithm detailed adaptive minimum rate in a different way than the algorithm detailed
in this document allows. However, the notifier MUST comply with any in this document allows. However, the notifier MUST comply with any
"min-interval" or "max-interval" parameters that have been "max-rate" or "min-rate" parameters that have been negotiated.
negotiated.
8. Usage of the Maximum Rate, Minimum Rate and Adaptive Minimum Rate 8. Usage of the Maximum Rate, Minimum Rate and Adaptive Minimum Rate
Mechanisms in a combination Mechanisms in a combination
Applications can subscribe to an event package using all the rate Applications can subscribe to an event package using all the rate
control mechanisms individually, or in combination; in fact there is control mechanisms individually, or in combination; in fact there is
no technical incompatibility among them. However there are some no technical incompatibility among them. However there are some
combinations of the different rate control mechanisms that make combinations of the different rate control mechanisms that make
little sense to be used together. This section lists all the little sense to be used together. This section lists all the
combinations that are possible to insert in a subscription; the combinations that are possible to insert in a subscription; the
utility to use each combination in a subscription is also analyzed. utility to use each combination in a subscription is also analyzed.
maximum rate and minimum rate: This combination allows to reduce the maximum rate and minimum rate: This combination allows to reduce the
notification frequency rate, but at the same time assures the notification rate, but at the same time assures the reception of a
reception of a notification every time the most recent notification every time the most recent notification exceeds a
notification exceeds a specified interval. specified interval.
A subscriber SHOULD choose a "max-interval" value higher than the A subscriber SHOULD choose a "min-rate" value lower than the "max-
"min-interval" value, otherwise the notifier MUST adjust the rate" value, otherwise the notifier MUST adjust the subscriber
subscriber provided "max-interval" value to a value equal to or provided "min-rate" value to a value equal to or lower than the
higher than the "min-interval" value. "max-rate" value.
maximum rate and adaptive minimum rate: It works in a similar way as maximum rate and adaptive minimum rate: It works in a similar way as
the combination above, but with the difference that the interval the combination above, but with the difference that the interval
at which notifications are assured changes dynamically. at which notifications are assured changes dynamically.
A subscriber SHOULD choose a "average-interval" value higher than A subscriber SHOULD choose a "adaptive-min-rate" value lower than
the "min-interval" value, otherwise the notifier MUST adjust the the "max-rate" value, otherwise the notifier MUST adjust the
subscriber provided "average-interval" value to a value equal to subscriber provided "adaptive-min-rate" value to a value equal to
or higher than the "min-interval" value. or lower than the "max-rate" value.
minimum rate and adaptive minimum rate: When using the adaptive minimum rate and adaptive minimum rate: When using the adaptive
minimum rate mechanism, frequent state changes in a short period minimum rate mechanism, frequent state changes in a short period
can result in no notifications for a longer period following the can result in no notifications for a longer period following the
short period. The addition of the minimum rate mechanism ensures short period. The addition of the minimum rate mechanism ensures
the subscriber always receives notifications after a specified the subscriber always receives notifications after a specified
interval. interval.
A subscriber SHOULD choose a "max-interval" value higher than the A subscriber SHOULD choose a "min-rate" value lower than the
"average-interval" value, otherwise the notifier MUST NOT consider "adaptive-min-rate" value, otherwise the notifier MUST NOT
the "max-interval" value. consider the "min-rate" value.
maximum rate, minimum rate and adaptive minimum rate: This maximum rate, minimum rate and adaptive minimum rate: This
combination makes little sense to be used although not forbidden. combination makes little sense to be used although not forbidden.
A subscriber SHOULD choose a "max-interval" and "average-interval" A subscriber SHOULD choose a "min-rate" and "adaptive-min-rate"
values higher than the "min-interval" value, otherwise the values lower than the "max-rate" value, otherwise the notifier
notifier MUST adjust the subscriber provided "max-interval" and MUST adjust the subscriber provided "min-rate" and "adaptive-min-
"average-interval" values to a value equal to or higher than the rate" values to a value equal to or lower than the "max-rate"
"min-interval" value. value.
A subscriber SHOULD choose a "max-interval" value higher than the A subscriber SHOULD choose a "min-rate" value lower than the
"average-interval" value, otherwise the notifier MUST NOT consider "adaptive-min-rate" value, otherwise the notifier MUST NOT
the "max-interval" value. consider the "min-rate" value.
9. Protocol Element Definitions 9. Protocol Element Definitions
This section describes the protocol extensions required for the This section describes the protocol extensions required for the
different rate control mechanisms. different rate control mechanisms.
9.1. "min-interval", "max-interval" and "average-interval" Header Field 9.1. "max-rate", "min-rate" and "adaptive-min-rate" Header Field
Parameters Parameters
The "min-interval", "max-interval" and "average-interval" parameters The "max-rate", "min-rate" and "adaptive-min-rate" parameters are
are added to the rule definitions of the Event header field and the added to the rule definitions of the Event header field and the
Subscription-State header field in RFC 3265 [RFC3265] grammar. Usage Subscription-State header field in RFC 3265 [RFC3265] grammar. Usage
of this parameter is described in Section 5, Section 6 and Section 7. of this parameter is described in Section 5, Section 6 and Section 7.
9.2. Grammar 9.2. Grammar
This section describes the Augmented BNF [RFC5234] definitions for This section describes the Augmented BNF [RFC5234] definitions for
the new header field parameters. Note that we derive here from the the new header field parameters. Note that we derive here from the
ruleset present in RFC 3265 [RFC3265], adding additional alternatives ruleset present in RFC 3265 [RFC3265], adding additional alternatives
to the alternative sets of "event-param" and "subexp-params" defined to the alternative sets of "event-param" and "subexp-params" defined
therein. therein. The "delta-seconds" element is defined in RFC 3261
[RFC3261].
event-param =/ min-interval-param
subexp-params =/ min-interval-param
min-interval-param = "min-interval" EQUAL delta-seconds
event-param =/ max-interval-param
subexp-params =/ max-interval-param
max-interval-param = "max-interval" EQUAL delta-seconds
event-param =/ average-interval-param event-param =/ max-rate-param / min-rate-param / amin-rate-param
subexp-params =/ average-interval-param subexp-params =/ max-rate-param / min-rate-param / amin-rate-param
average-interval-param = "average-interval" EQUAL delta-seconds max-rate-param = "max-rate" EQUAL ("1" SLASH delta-seconds)
min-rate-param = "min-rate" EQUAL ("1" SLASH delta-seconds)
amin-rate-param = "adaptive-min-rate" EQUAL ("1" SLASH delta-seconds)
9.3. Event Header Field Usage in Responses to the NOTIFY request 9.3. Event Header Field Usage in Responses to the NOTIFY request
This table expands the table described in Section 7.2 of RFC 3265 This table expands the table described in Section 7.2 of RFC 3265
[RFC3265] allowing the Event header field to appear in a 2xx response [RFC3265] allowing the Event header field to appear in a 2xx response
to a NOTIFY request. The use of the Event header field in responses to a NOTIFY request. The use of the Event header field in responses
other than 2xx to NOTIFY requests is undefined and out of scope of other than 2xx to NOTIFY requests is undefined and out of scope of
this specification. this specification.
Header field where proxy ACK BYE CAN INV OPT REG PRA SUB NOT Header field where proxy ACK BYE CAN INV OPT REG PRA SUB NOT
----------------------------------------------------------------- -----------------------------------------------------------------
Event 2xx - - - - - - - - o Event 2xx - - - - - - - - o
A subscriber that wishes to update the value for maximum, minimum or A subscriber that wishes to update the previously agreed value for
adaptive minimum rate of notifications can do so by including all maximum, minimum or adaptive minimum rate of notifications MUST
desired values for the "min-interval", "max-interval" and "average- include all desired values for the "max-rate", "min-rate" and
interval" parameters in an Event header field of the 2xx response to "adaptive-min-rate" parameters in an Event header field of the 2xx
a NOTIFY request. Any of the other header field parameters currently response to a NOTIFY request. Any of the other header field
defined for the Event header field by other specifications do not parameters currently defined for the Event header field by other
have a meaning if the Event header field is included in the 2xx specifications do not have a meaning if the Event header field is
response to the NOTIFY request. These header field parameters MUST included in the 2xx response to the NOTIFY request. These header
be ignored by the notifier, if present. field parameters MUST be ignored by the notifier, if present.
The event type listed in the Event header field of the 2xx response The event type listed in the Event header field of the 2xx response
to the NOTIFY request MUST match the event type of the Event header to the NOTIFY request MUST match the event type of the Event header
field in the corresponding NOTIFY request. field in the corresponding NOTIFY request.
10. IANA Considerations 10. IANA Considerations
This specification registers three new SIP header field parameters, This specification registers three new SIP header field parameters,
defined by the following information which is to be added to the defined by the following information which is to be added to the
Header Field Parameters and Parameter Values sub-registry under Header Field Parameters and Parameter Values sub-registry under
http://www.iana.org/assignments/sip-parameters. http://www.iana.org/assignments/sip-parameters.
Predefined Predefined
Header Field Parameter Name Values Reference Header Field Parameter Name Values Reference
-------------------- --------------- ---------- --------- -------------------- --------------- ---------- ---------
Event min-interval No [RFCxxxx] Event max-rate No [RFCxxxx]
Subscription-State min-interval No [RFCxxxx] Subscription-State max-rate No [RFCxxxx]
Event max-interval No [RFCxxxx] Event min-rate No [RFCxxxx]
Subscription-State max-interval No [RFCxxxx] Subscription-State min-rate No [RFCxxxx]
Event average-interval No [RFCxxxx] Event adaptive-min-rate No [RFCxxxx]
Subscription-State average-interval No [RFCxxxx] Subscription-State adaptive-min-rate No [RFCxxxx]
(Note to the RFC Editor: please replace "xxxx" with the RFC number of (Note to the RFC Editor: please replace "xxxx" with the RFC number of
this specification, when assigned.) this specification, when assigned.)
This specification also updates the reference defining the Event This specification also updates the reference defining the Event
header field in the Header Fields sub-registry under header field in the Header Fields sub-registry under
http://www.iana.org/assignments/sip-parameters. http://www.iana.org/assignments/sip-parameters.
Header Name compact Reference Header Name compact Reference
----------- ------- --------- ----------- ------- ------------------
Event o [RFC3265][RFCxxxx] Event o [RFC3265][RFCxxxx]
(Note to the RFC Editor: please replace "xxxx" with the RFC number of (Note to the RFC Editor: please replace "xxxx" with the RFC number of
this specification, when assigned.) this specification, when assigned.)
11. Security Considerations 11. Security Considerations
Naturally, the security considerations listed in RFC 3265 [RFC3265], Naturally, the security considerations listed in RFC 3265 [RFC3265],
which the rate control mechanisms described in this document extends, which the rate control mechanisms described in this document extends,
apply in entirety. In particular, authentication and message apply in entirety. In particular, authentication and message
skipping to change at page 24, line 4 skipping to change at page 25, line 15
Authors' Addresses Authors' Addresses
Aki Niemi Aki Niemi
Nokia Nokia
P.O. Box 407 P.O. Box 407
NOKIA GROUP, FIN 00045 NOKIA GROUP, FIN 00045
Finland Finland
Phone: +358 50 389 1644 Phone: +358 50 389 1644
Email: aki.niemi@nokia.com Email: aki.niemi@nokia.com
Krisztian Kiss Krisztian Kiss
Nokia Nokia
323 Fairchild Dr 200 South Mathilda Ave
Mountain View, CA 94043 Sunnyvale, CA 94086
US US
Phone: +1 650 391 5969 Phone: +1 650 391 5969
Email: krisztian.kiss@nokia.com Email: krisztian.kiss@nokia.com
Salvatore Loreto Salvatore Loreto
Ericsson Ericsson
Hirsalantie 11 Hirsalantie 11
Jorvas 02420 Jorvas 02420
Finland Finland
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