Internet Draft Diana Rawlins
Expiration: May 2002 WorldCom
File: draft-ietf-rap-feedback-frwk-01.txt Amol Kulkarni
Intel
Framework of COPS-PR Policy Usage Feedback
Last Updated November 20, 2001
Status of this Memo
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Conventions used in this document
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 [RFC-2119].
Abstract
Common Open Policy Services Protocol [COPS], RFC 2748, defined the
capability of reporting information to the PDP. The types of
report information are success, failure and accounting of an
installed state. This document focuses on the accounting report
type and the necessary framework for the monitoring and reporting
of usage feedback for an installed state.
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Table of Contents
1 Introduction...................................................3
2 Overview.......................................................3
3 Requirements for Normal Operations.............................3
4 Periodic Nature of Policy Usage Feedback.......................4
4.1 Reporting Intervals..........................................4
5 Suspension, Resumption and Halting of Usage Monitoring and
Reporting........................................................5
6 Solicited Feedback.............................................5
7 Usage reports on shared objects................................5
8 Context........................................................6
9 Delete Request States..........................................6
10 Failover......................................................6
11 Security Considerations.......................................6
12 Authors' Addresses............................................6
13 References....................................................7
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1 Introduction
Policy usage reported by the PEP makes a richer set of information
available to the PDP for decision-making. This report accounting
information can impact future decisions made by the PDP and the
resulting policy installed by the PDP at the PEP. For example, a
PDP making policy for a SIP signaled multimedia session may need
to base the decision in part on usage information related to
previously installed QoS policy decisions. Furthermore, the PDP
may coordinate this usage information with other external systems
to determine the future policy such as the case with the PDP
coordinating multimedia session QoS and clearinghouse
authorizations [SIP-AAA-QOS.]
The scope of this document is to describe the framework for policy
usage monitored and reported by the PEP and collected at the PDP.
The charging, rating and billing models as well as other
accounting or statistics gathering events detectable by the PDP
are beyond the scope of this framework.
2 Overview
There are two aspects to defining policies for usage feedback. One
aspect is defining what to monitor and the second is defining what
to report. The selection criteria policy specifies the conditions
for the monitoring and recording of the associated usage policy.
It is a PRID that defines an entity such as an IP filter or
dropper. The usage criteria policy class defines what metrics are
recorded and reported by the PEP to the PDP in the Report message.
For example, a usage policy may be defined to provide counts of
packets received. The selection criteria policy may identify the
filter on which to base the packet counts. A third policy may be
used to associated, or link, the selection and usage policies. The
linkage criteria associate what needs to be monitored to what
needs to be reported. The valid combinations of selection PRCs for
a usage PRC must be identified and well understood between the PDP
and the PEP.
3 Requirements for Normal Operations
Per [COPS], the PDP specifies the minimum feedback interval in the
Accounting Timer object that is included in the Client Accept
message during connection establishment. This specifies the
maximum frequency with which the PEP issues unsolicited accounting
type reports. The purpose of this interval is to pace the number
of report messages sent to the PDP. It is not the goal of the
interval defined by the ACCT Timer value to provide precision
synchronization or timing.
The selection and usage criteria for feedback reporting are
defined by the PDP. Feedback policies, which define the necessary
selection and usage criteria, are included by the PDP in a
Decision message to the PEP. The usage is then periodically
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reported by the PEP at intervals no more frequently than specified
in the Accounting Timer object, except as noted in the following
sections. (There are exceptions where reports containing feedback
are provided prior the interval in several cases described in
sections 6 and 7.) The PDP may also solicit usage feedback which
is to be reported back immediately by the PEP. Usage information
may be cleared upon reporting. This is specified in the usage
policy criteria.
The PEP monitors and tracks the usage information. The PDP is the
collection point for the policy usage information reported by the
PEP clients within the administrative domain. The PDP may also
collect other accounting event information that is outside the
scope of this document.
4 Periodic Nature of Policy Usage Feedback
Generally the accounting policy is periodic in nature and the
reporting is unsolicited. The unsolicited reports are supplied per
the interval defined by the PDP. The periodic unsolicited reports
are dictated by timer intervals and use a deterministic amount of
network resources.
The PDP informs the PEP of the minimal feedback interval during
client connection establishment with the Accounting Timer object.
The PDP may specify feedback intervals in the specific usage
policies as well. The unsolicited monitoring and reporting by the
PEP may be suspended and resumed at the direction of the PDP.
4.1 Reporting Intervals
The generation of usage feedback by the PEP to the PDP is done
under different conditions that include feedback on demand,
periodic feedback or feedback when a defined threshold is reached.
The periodic feedback for a usage policy can be further defined in
terms of providing feedback if there is a change or providing
feedback periodically regardless of a change in value.
The periodic interval is defined in terms of the Accounting
Object, ACCT Timer value. A single interval is equal to the number
of seconds specified by the ACCT Timer value. The PDP may define a
specific number of intervals, which are to pass before the PEP
provides the usage feedback for a specific policy in a report.
When the ACCT Timer value is equal to zero there is no unsolicited
usage feedback provided by the PEP. However, the PEP still
monitors and tracks the usage per the PDP policy and reports it
when the PDP solicits the feedback.
Reporting may be based on a defined threshold value in the usage
PRC that is reached.
The PDP may solicit usage feedback in the middle of an interval.
The PEP shall provide the requested usage information and clear
the usage information if the usage policy requires that the
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attribute be cleared after reporting. The PEP should continue to
maintain the same interval schedule as defined by the PDP in the
Accounting Timer object and established at client connection
acceptance.
5 Suspension, Resumption and Halting of Usage Monitoring and Reporting
The PDP may direct the PEP to suspend usage feedback report
messages and then at a later time instruct the PEP to resume the
reporting of feedback. The PDP may also instruct the PEP to
suspend the monitoring and tracking of usage which also results in
the suppression of the feedback reports until the PDP later tells
the PEP to resume the monitoring (and reporting). When the PDP
suspends monitoring or suspends reporting, it also specifies
whether the PEP is to provide an unsolicited feedback report of
the current monitored usage of the affected usage policy. The PDP
may suspend and resume monitoring and reporting for specific usage
policies or for all usage policies.
Halting of usage monitoring and feedback is done by issuing a
Decision Remove of the feedback usage policies. The PEP is to stop
any monitoring and reporting associated with the policy
immediately.
6 Solicited Feedback
There may be instances when it is useful for the PDP to control
the feedback per an on-demand basis rather than a periodic basis.
The PDP may solicit the PEP for usage feedback with a Decision.
The PDP may solicit usage feedback at any time during the
accounting interval defined by the ACCT Timer. The PEP responds
immediately and reports the appropriate usage policies and should
continue to follow the usage feedback interval schedule
established during connection acceptance.
7 Usage reports on shared objects
While some objects in a contexts namespace directly represent
unique objects of the PEPs configuration, other COPS objects can
be shared between multiple actual assignments in the PEP.
Whenever the PEP creates multiple actual configuration instances
from the same COPS objects, these assignments can potentially
collect their own statistics independently. Since the individual
assignments do not have a direct representation as COPS objects,
additional information must be provided to uniquely identify the
assignment that generates the usage information.
The feedback framework allows this information to be distributed
between a Selection Criteria PRC and the corresponding Usage PRC,
however both PRCs together always must contain sufficient
information for the finest granularity of usage collection
supported by the PEP.
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If all the additional information is not part of the Selection
Criteria PRC, all matching assignments are selected to collect
usage information. The necessary data to differentiate these
assignments is part of the Usage PRC.
Implementations based on the feedback framework should always
provide a Selection Criteria PRC that contains a complete set of
information to select a unique assignment, while underspecified
Selection Criteria PRCs (together with extended Usage PRCs) are
optional.
8 Context
The monitoring and recording of usage policies is subject to
context switches in a manner similar to that of the enforcement
policy. Usage policy is monitored, recorded and reported while the
associated policy information context is active. When the context
is deactivated a report containing the usage policies for that
context is provided to the PDP. The PEP does not perform any
monitoring, tracking or reporting of policy usage for a given
context while the context is inactive.
9 Delete Request States
The PEP MUST send any outstanding usage data monitored during the
feedback interval to the PDP via an unsolicited report immediately
prior to issuing a Delete Request State. This is also the case
when the PDP initiates the Delete Request State.
10 Failover
In the event the connection is lost between the PEP and PDP, the
PEP continues to track usage information as long as it continues
to enforce installed (cached) policy. When the locally installed
policy at the PEP expires, the usage policy data also expires and
is no longer monitored.
Upon successful reconnection where the PEP is still caching
policy, the PDP indicates deterministically to the PEP that the
PEP may resume usage feedback reporting. The PEP reports all
cached usage and resumes periodic reporting making any needed
adjustment to the interval schedule as specified in the
reconnection acceptance ACCT Timer.
11 Security Considerations
The feedback information is sensitive and requires that authorized
messaging occur between the PEP and the PDP. This protection can
be accomplished with IPSEC between the PEP and the PDP or using
the security mechanisms described in the base COPS protocol.
12 Authors' Addresses
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Diana Rawlins
WorldCom
901 International Parkway
Richardson, Texas 75081
Phone: 972-729-1044
Email: Diana.Rawlins@wcom.com
Amol Kulkarni
JF3-206
2111 NE 25th Ave
Hillsboro, Oregon 97124
Phone: 503-712-1168
Email: amol.kulkarni@intel.com
13 References
[COPS] Boyle, J., Cohen, R., Durham, D., Herzog, S., Rajan, R.,
and A. Sastry, "The COPS (Common Open Policy Service) Protocol"
RFC 2748, January 2000.
[SIP-AAA-QOS] Gross, G., Sinnreich, H. Rawlins D., Havinis, T. "QoS
and AAA Usage with SIP Based IP Communications" draft-gross-sipaq-
00.txt, November 2000.
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