Internet Draft                                        Diana Rawlins
    Expiration:  September 2002                                WorldCom
    File: draft-ietf-rap-feedback-frwk-02.txt             Amol Kulkarni
                                                       Martin Bokaemper
                                                     Unisphere Networks
                                                           Kwok Ho Chan
                                                        Nortel Networks

                 Framework of COPS-PR Policy Usage Feedback
                         Last Updated March 1, 2002

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

     Internet-Drafts are working documents of the Internet Engineering
     Task Force (IETF), its areas, and its working groups. Note that
     other groups may also distribute working documents as Internet-

     Internet-Drafts are draft documents valid for a maximum of six
     months and may be updated, replaced, or obsoleted by other
     documents at any time.  It is inappropriate to use Internet-Drafts
     as reference material or to cite them other than as "work in

     The list of current Internet-Drafts can be accessed at

     The list of Internet-Draft Shadow Directories can be accessed at

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 COPS Report Type of
     Accounting and the necessary framework for the monitoring and
     reporting of usage feedback for an installed state.

Rawlins et al.          Expires September 2002                [Page 1]

Internet Draft              COPS-FEED-FRWK                  March 2002

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............................................7
     13 References....................................................7

Rawlins et al.          Expires September 2002                [Page 2]

Internet Draft              COPS-FEED-FRWK                  March 2002

1 Introduction
     Policy usage reported by the PEP makes a richer set of information
     available to the PDP for decision-making. This feedback on policy
     usage 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 three main aspects to define policies for usage
     - which objects are monitored
     - the metrics to be monitored and reported for these objects
     - when the reports are delivered

     In the framework a selection criteria policy specifies one or more
     objects that should be monitored û for example a dropper or the
     instances of an IP Filter for all its interfaces.

     A usage feedback class is used to specify which metrics are to be
     collected for a set of objects - instances of the specified class
     carry the usage information when it is reported.
     The valid combinations of monitored object classes and usage
     feedback classes are reported by the PEP as capabilities.

     Finally selection criteria policy and usage feedback class are
     bound together in a linkage policy, which also contains the
     information when reports are generated. Reports are usually sent
     periodically but more restrictions can be placed on the generation
     of reports, like thresholds or a change in the data.

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 report messages. The purpose of this interval is to pace the
     number of report messages sent to the PDP. It is not the goal of

Rawlins et al.          Expires September 2002                [Page 3]

Internet Draft              COPS-FEED-FRWK                  March 2002

     the interval defined by the ACCT Timer value to provide precision
     synchronization or timing.

     The selection and the associated usage criteria and intervals for
     feedback reporting are defined by the PDP. Feedback policies,
     which define the necessary selection and linkages to usage
     feedback criteria, are included by the PDP in a Decision message
     to the PEP. The usage feedback is then periodically reported by
     the PEP at intervals defined in the linkage policies at a rate no
     more frequently than specified in the Accounting Timer object.
     Note that there are exceptions where reports containing feedback
     are provided prior the Accounting Timer 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 feedback information. The
     PDP is the collection point for the policy usage feedback
     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 policy usage feedback 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
     feedback 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

Rawlins et al.          Expires September 2002                [Page 4]

Internet Draft              COPS-FEED-FRWK                  March 2002

     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
     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 of the usage feedback policies.

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 contextÆs namespace directly represent
     unique objects of the PEPÆs 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.

Rawlins et al.          Expires September 2002                [Page 5]

Internet Draft              COPS-FEED-FRWK                  March 2002

     The feedback framework allows this information to be distributed
     between a selection criteria PRC and the corresponding usage
     feedback PRC, however both PRCs together always must contain
     sufficient information for the finest granularity of usage
     collection supported by the PEP.

     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 feedback 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 feedback
     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 message containing the usage feedback
     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 feedback data monitored
     during the feedback interval to the PDP via an unsolicited report
     message 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 feedback information as long as it
     continues to enforce installed (cached) policy. When the locally
     installed policy at the PEP expires, the usage feedback 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

Rawlins et al.          Expires September 2002                [Page 6]

Internet Draft              COPS-FEED-FRWK                  March 2002

     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, TLS [COPS
     TLS] or using the security mechanisms described in the base COPS

12 Authors' Addresses

        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

        Kwok Ho Chan
        Nortel Networks, Inc.
        600 Technology Park Drive
        Billerica, MA 01821 USA
        Phone: 978-288-8175

        Martin Bokaemper
        Unisphere Networks
        700 Silver Seven Road
        Kanata, ON, K2V 1C3, Canada
        Phone: 613-591-2735

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.

     [COPS-TLS], Walker, J., Kulkarni, A.,öCOPS Over TLSö, draft-ietf-
     rap-cops-tls-02.txt, October 2001.

Rawlins et al.          Expires September 2002                [Page 7]