Internet Draft                                        Diana Rawlins
    Expiration:  May 2002                                      WorldCom
    File: draft-ietf-rap-feedback-frwk-01.txt             Amol Kulkarni

                 Framework of COPS-PR Policy Usage Feedback
                       Last Updated November 20, 2001

Status of this Memo
     This document is an Internet-Draft and is in full conformance with
     all provisions of Section 10 of RFC2026.

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Conventions used in this document
     The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
     in this document are to be interpreted as described in [RFC-2119].

     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
     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

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

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 context’s namespace directly represent
     unique objects of the PEP’s 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

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
        901 International Parkway
        Richardson, Texas 75081
        Phone: 972-729-1044

        Amol Kulkarni
        2111 NE 25th Ave
        Hillsboro, Oregon 97124
        Phone: 503-712-1168

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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