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Network Working Group D. Rawlins Request for Comments: 3483 WorldCom Category: Informational A. Kulkarni

                                                          M. Bokaemper
                                                      Juniper Networks
                                                               K. Chan
                                                       Nortel Networks
                                                            March 2003
Framework for Policy Usage Feedback for Common Open Policy Service
                with Policy Provisioning (COPS-PR)

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2003).  All Rights Reserved.


 Common Open Policy Services (COPS) Protocol (RFC 2748), defines the
 capability of reporting information to the Policy Decision Point
 (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.

Conventions used in this document

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 document are to be interpreted as described in [RFC2119].

Rawlins, et al. Informational [Page 1] RFC 3483 COPS Feedback Framework March 2003

Table of Contents

 Glossary........................................................... 2
 1  Introduction.................................................... 2
 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........................................... 7
 10 Failover........................................................ 7
 11 Security Considerations......................................... 7
 12 References...................................................... 8
    12.1 Normative References....................................... 8
    12.2 Informative References..................................... 8
 13 Authors' Addresses.............................................. 9
 14 Full Copyright Statement........................................10


 COPS - Common Open Policy Service.  See [RFC2748].
 COPS-PR - COPS Usage for Policy Provisioning.  See [RFC3084].
 PDP - Policy Decision Point.  See [RFC2753].
 PEP - Policy Enforcement Point.  See [RFC2753].
 PIB - Policy Information Base.  The database of policy information.
 PRC - Provisioning Class.  A type of policy data.
 PRI - Provisioning Instance.  An instance of a PRC.
 QoS - Quality of Service.

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].

Rawlins, et al. Informational [Page 2] RFC 3483 COPS Feedback Framework March 2003

 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 feedback:
  1. which objects are monitored
  2. the metrics to be monitored and reported for these objects
  3. when the reports are delivered
 In the framework, a selection criteria policy specifies one or more
 objects that should be monitored (e.g., 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 of
 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 [RFC2748], 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 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

Rawlins, et al. Informational [Page 3] RFC 3483 COPS Feedback Framework March 2003

 there are exceptions where reports containing feedback are provided
 prior to the Accounting Timer interval (see section 6).  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 monitors and
 tracks the usage per the PDP policy and reports it when the PDP
 solicits the feedback.

Rawlins, et al. Informational [Page 4] RFC 3483 COPS Feedback Framework March 2003

 Reporting may be based on reaching a defined threshold value in the
 usage PRC.
 The PDP may solicit usage feedback in the middle of an interval by
 sending a COPS decision message.  The exact contents of the message
 are out of the scope of this framework document and need to be
 defined in a document that actually implements usage feedback using
 this framework.
 The PEP, upon receiving a solicit decision from the PDP, 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 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 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

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.

Rawlins, et al. Informational [Page 5] RFC 3483 COPS Feedback Framework March 2003

 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.  As an example, if the PEP needs to
 create multiple usage objects for an IP address, it may use the port
 number to uniquely identify each object, i.e., the (IP address, port
 number) combination is now the unique identifier of the object.
 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

8 Context

 COPS-PR [RFC3084] allows multiple, independent, disjoint instances of
 policies to be configured on the PEP.  Each instance is known as a
 context, and only one context can be active at any given moment.  The
 PDP directs the PEP to switch between contexts using a single
 decision message.
 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.

Rawlins, et al. Informational [Page 6] RFC 3483 COPS Feedback Framework March 2003

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

11 Security Considerations

 This document provides a framework for policy usage feedback, using
 COPS-PR as the transport mechanism.  As feedback information is
 sensitive, it MUST be transported in a secured manner.  COPS
 [RFC2748] and COPS-PR [RFC3084] provide for such secured transport,
 with mandatory and suggested security mechanisms.
 The usage feedback information themselves MUST be secured, with their
 security requirement specified in their respective documents.

Rawlins, et al. Informational [Page 7] RFC 3483 COPS Feedback Framework March 2003

12 References

12.1 Normative References

 [RFC2119]     Bradner, S., "Key words to use in the RFCs", BCP 14,
               RFC 2119, March 1997.
 [RFC2748]     Boyle, J., Cohen, R., Durham, D., Herzog, S., Rajan, R.
               and A. Sastry, "The COPS (Common Open Policy Service)
               Protocol", RFC 2748, January 2000.
 [RFC2753]     Yavatkar, R., Pendarakis, D. and R. Guerin, "A
               Framework for Policy-based Admission Control", RFC
               2753, January 2000.
 [RFC3084]     Chan, K., Durham, D., Gai, S., Herzog, S., McCloghrie,
               K., Reichmeyer, F., Seligson, J., Smith, A. and R.
               Yavatkar, "COPS Usage for Policy Provisioning (COPS-
               PR)", RFC 3084, March 2001.

12.2 Informative References

 [SIP-AAA-QOS] Gross, G., Sinnreich, H. Rawlins D. and T. Havinis,
               "QoS and AAA Usage with SIP Based IP Communications",
               Work in Progress.

Rawlins, et al. Informational [Page 8] RFC 3483 COPS Feedback Framework March 2003

13 Authors' Addresses

 Diana Rawlins
 901 International Parkway
 Richardson, Texas 75081
 Phone: 972-729-4071
 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
 Juniper Networks
 700 Silver Seven Road
 Kanata, ON, K2V 1C3, Canada
 Phone: 613-591-2735

Rawlins, et al. Informational [Page 9] RFC 3483 COPS Feedback Framework March 2003

14 Full Copyright Statement

 Copyright (C) The Internet Society (2003).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an


 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Rawlins, et al. Informational [Page 10]

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