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Versions: 00 01 02 03 04 05 06 07 08 rfc3460                            
 Policy Framework Working Group                                 B. Moore
 INTERNET-DRAFT                                               L. Rafalow
 Category: Standards Track                                           IBM
                                                              Y. Ramberg
                                                                 Y. Snir
                                                            J. Strassner
                                                           A. Westerinen
                                                           Cisco Systems
                                                               R. Chadha
                                                  Telcordia Technologies
                                                              M. Brunner
                                                                     NEC
                                                                R. Cohen
                                                               Ntear LLC
                                                          February, 2001
 
                   Policy Core Information Model Extensions
 
                      <draft-ietf-policy-pcim-ext-00.txt>
                      Friday, February 23, 2001, 11:07 AM
 
 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-Drafts.
 
   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 progress."
 
   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt
 
   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html
 
 Copyright Notice
 
   Copyright (C) The Internet Society (2001).  All Rights Reserved.
 
 Abstract
 
   This document proposes a number of changes to the Policy Core Information
   Model (PCIM, RFC 3060).  These changes include both extensions of PCIM
   into areas that it did not previously cover, and changes to the existing
   PCIM classes and associations.  Both sets of changes are done in a way
   that, to the extent possible, preserves interoperability with
   implementations of the original PCIM model.
 
 
 
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   Table of Contents
 
   1. Introduction......................................................4
   2. Overview of the Changes...........................................4
      2.1. How to Change an Information Model...........................4
      2.2. List of Changes to the Model.................................5
      2.2.1. Changes to PolicyRepository................................5
      2.2.2. Additional Associations and Additional Reusable Elements...5
      2.2.3. Priorities and Decision Strategies.........................5
      2.2.4. Policy Roles...............................................6
      2.2.5. CompoundPolicyConditions and CompoundPolicyActions.........6
      2.2.6. Variables and Values.......................................7
      2.2.7. Packet Filtering...........................................7
   3. The Updated Class and Association Class Hierarchies...............7
   4. Areas of Extension to PCIM.......................................11
      4.1. Scope of Policies:  Domain Policies and Device Policies.....11
      4.2. Reusable Policy Elements....................................12
      4.3. Policy Sets.................................................13
      4.4. Nested Policy Rules.........................................13
      4.4.1. Usage Rules for Nested Rules..............................13
      4.4.2. Motivation................................................14
      4.4.3. Usage Example.............................................15
      4.5. Priorities and Decision Strategies..........................16
      4.5.1. Structuring Decision Strategies...........................17
      4.5.2. Deterministic Decisions...................................18
      4.5.3. Multiple PolicySet Trees For a Resource...................19
      4.6. Policy Roles................................................19
      4.6.1. Comparison of Roles in PCIM with Roles in snmpconf........19
      4.6.2. Addition of PolicyRoleCollection to PCIMe.................20
      4.6.3. Roles for PolicyGroups....................................21
      4.7. Compound Policy Conditions and Compound Policy Actions......22
      4.7.1. Compound Policy Conditions................................23
      4.7.2. Compound Policy Actions...................................23
      4.8. Variables and Values........................................25
      4.8.1. Simple Policy Conditions..................................25
      4.8.2. Using Simple Policy Conditions............................26
      4.8.3. The Simple Condition Operator.............................27
      4.8.4. SimplePolicyActions.......................................28
      4.8.5. Policy Variables..........................................30
      4.8.6. Explicitly Bound Policy Variables.........................30
      4.8.7. Implicitly Bound Policy Variables.........................31
      4.8.8. Structure and Usage of Pre-Defined Variables..............32
      4.8.9. Rationale for Modeling Implicit Variables as Classes......33
      4.8.10. Policy Values............................................34
      4.9. Packet Filtering............................................34
   5. Class Definitions................................................36
      5.1. The Abstract Class "PolicySet"..............................36
      5.2. Updates to PCIM's Class "PolicyGroup".......................37
      5.3. Updates to PCIM's Class "PolicyRule"........................37
      5.4. The Class "SimplePolicyCondition"...........................38
      5.5. The Class "CompoundPolicyCondition".........................38
      5.6. The Class "CompoundFilterCondition".........................39
 
 
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      5.7. The Class "SimplePolicyAction"..............................39
      5.8. The Class "CompoundPolicyAction"............................40
      5.9. The Abstract Class "PolicyVariable".........................41
      5.10. The Class "PolicyExplicitVariable".........................41
      5.10.1. The Single-Valued Property "ModelClass"..................42
      5.10.2. The Single-Valued Property ModelProperty.................42
      5.11. The Abstract Class "PolicyImplicitVariable"................42
      5.11.1. The Multi-Valued Property "ValueTypes"...................42
      5.12. Subclasses of "PolicyImplicitVariable" Specified in PCIMe..43
      5.12.1. The Class "PolicySourceIPVariable".......................43
      5.12.2. The Class "PolicyDestinationIPVariable"..................43
      5.12.3. The Class "PolicySourcePortVariable".....................43
      5.12.4. The Class "PolicyDestinationPortVariable"................44
      5.12.5. The Class "PolicyIPProtocolVariable".....................44
      5.12.6. The Class "PolicyIPVersionVariable"......................44
      5.12.7. The Class "PolicyIPToSVariable"..........................44
      5.12.8. The Class "PolicyDSCPVariable"...........................45
      5.12.9. The Class "PolicySourceMACVariable"......................45
      5.12.10. The Class "PolicyDestinationMACVariable"................45
      5.12.11. The Class "PolicyVLANVariable"..........................45
      5.12.12. The Class "PolicyCoSVariable"...........................46
      5.12.13. The Class "PolicyEthertypeVariable".....................46
      5.12.14. The Class "PolicySourceSAPVariable".....................46
      5.12.15. The Class "PolicyDestinationSAPVariable"................46
      5.12.16. The Class "PolicySNAPVariable"..........................47
      5.12.17. The Class "PolicyFlowDirectionVariable".................47
      5.13. The Abstract Class "PolicyValue"...........................47
      5.14. Subclasses of "PolicyValue" Specified in PCIMe.............48
      5.14.1. The Class "PolicyIPv4AddrValue"..........................48
      5.14.2. The Class "PolicyIPv6AddrValue...........................49
      5.14.3. The Class "PolicyMACAddrValue"...........................50
      5.14.4. The Class "PolicyStringValue"............................50
      5.14.5. The Class "PolicyBitStringValue".........................51
      5.14.6. The Class "PolicyIntegerValue"...........................51
      5.14.7. The Class "PolicyBooleanValue"...........................52
      5.15. The Class "PolicyRoleCollection"...........................53
      5.15.1. The Single-Valued Property "PolicyRole"..................53
      5.16. The Class "ReusablePolicyContainer"........................53
      5.17. Deprecation of PCIM's Class "PolicyRepository".............53
   6. Association and Aggregation Definitions..........................54
      6.1. The Abstract Aggregation "PolicySetComponent"...............54
      6.2. Update to PCIM's Aggregation "PolicyGroupInPolicyGroup".....54
      6.3. Update to PCIM's Aggregation "PolicyRuleInPolicyGroup"......55
      6.4. The Aggregation "PolicyGroupInPolicyRule"...................55
      6.5. The Aggregation "PolicyRuleInPolicyRule"....................56
      6.6. The Abstract Aggregation "CompoundedPolicyCondition"........56
      6.7. Update to PCIM's Aggregation "PolicyConditionInPolicyRule"..57
      6.8. The Aggregation "PolicyConditionInPolicyCondition"..........57
      6.9. The Abstract Aggregation "CompoundedPolicyAction"...........57
      6.10. Update to PCIM's Aggregation "PolicyActionInPolicyRule"....57
      6.11. The Aggregation "PolicyActionInPolicyAction"...............58
      6.12. The Aggregation "PolicyVariableInSimplePolicyCondition"....58
 
 
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      6.13. The Aggregation "PolicyValueInSimplePolicyCondition".......59
      6.14. The Aggregation "PolicyVariableInSimplePolicyAction".......59
      6.15. The Aggregation "PolicyValueInSimplePolicyAction"..........60
      6.16. The Association "ReusablePolicy"...........................61
      6.17. Deprecate PCIM's "PolicyConditionInPolicyRepository".......61
      6.18. Deprecate PCIM's "PolicyActionInPolicyRepository"..........61
      6.19. The Association PolicyValueConstraintInVariable............61
      6.20. The Aggregation "PolicyContainerInPolicyContainer".........62
      6.21. Deprecate PCIM's "PolicyRepositoryInPolicyRepository"......62
      6.22. The Aggregation "ElementInPolicyRoleCollection"............63
      6.22.1. The Weak Association "PolicyRoleCollectionInSystem"......63
   7. Intellectual Property............................................64
   8. Acknowledgements.................................................64
   9. Security Considerations..........................................64
   10. References......................................................64
   11. Authors' Addresses..............................................65
   12. Full Copyright Statement........................................67
   13. Appendix A: Open Issues.........................................67
 
 
 1. Introduction
 
   This document (PCIM Extensions, abbreviated here to PCIMe) proposes a
   number of changes to the Policy Core Information Model (PCIM, RFC 3060
   [3]).  These changes include both extensions of PCIM into areas that it
   did not previously cover, and changes to the existing PCIM classes and
   associations.  Both sets of changes are done in a way that, to the extent
   possible, preserves interoperability with implementations of the original
   PCIM model.
 
   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, reference [1].
 
 
 2. Overview of the Changes
 
 2.1. How to Change an Information Model
 
   The Policy Core Information Model is closely aligned with the DMTF's CIM
   Core Policy model.  Since there is no separately documented set of rules
   for specifying IETF information models such as PCIM, it is reasonable to
   look to the CIM specifications for guidance on how to modify and extend
   the model.  Among the CIM rules for changing an information model are the
   following.  Note that everything said here about "classes" applies to
   association classes (including aggregations) as well as to non-
   association classes.
 
     o   Properties may be added to existing classes.
     o   Classes, and individual properties, may be marked as DEPRECATED.
         If there is a replacement feature for the deprecated class or
         property, it is identified explicitly.  Otherwise the notation "No
 
 
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         value" is used.  In this document, the notation "DEPRECATED FOR
         <feature-name>" is used to indicate that a feature has been
         deprecated, and to identify its replacement feature.
     o   Classes may be inserted into the inheritance hierarchy above
         existing classes, and properties from the existing classes may
         then be "pulled up" into the new classes.  The net effect is that
         the existing classes have exactly the same properties they had
         before, but the properties are inherited rather than defined
         explicitly in the classes.
     o   New subclasses may be defined below existing classes.
 
 
 2.2. List of Changes to the Model
 
   The following subsections provide a very brief overview of the changes to
   PCIM being proposed in PCIMe.
 
 2.2.1. Changes to PolicyRepository
 
   Because of the potential for confusion with the Policy Framework
   component Policy Repository (from the four-box picture: Policy Management
   Tool, Policy Repository, PDP, PEP), "PolicyRepository" is a bad name for
   the PCIM class representing a container of reusable policy elements.
   Thus the class PolicyRepository is being replaced with the class
   ReusablePolicyContainer.  To accomplish this change, it is necessary to
   deprecate the PCIM class PolicyRepository and its three associations, and
   replace them with a new class ReusablePolicyContainer and new
   associations.
 
   As a separate change, the associations for ReusablePolicyContainer are
   being broadened, to allow a ReusablePolicyContainer to contain any
   reusable policy elements.  In PCIM, the only associations defined for a
   PolicyRepository were for it to contain reusable policy conditions and
   policy actions.
 
 2.2.2. Additional Associations and Additional Reusable Elements
 
   The PolicyRuleInPolicyRule and PolicyGroupInPolicyRule aggregations are
   being imported from QPIM.  These associations make it possible to define
   larger "chunks" of reusable policy to place in a ReusablePolicyContainer.
   These aggregations also introduce new semantics representing the
   contextual implications of having one PolicyRule executing within the
   scope of another PolicyRule.
 
 2.2.3. Priorities and Decision Strategies
 
   Drawing from both QPIM and ICIM, the Priority property is being
   deprecated in PolicyRule, and placed instead on the aggregations
   PolicyRuleInPolicyGroup, PolicyGroupInPolicyGroup,
   PolicyGroupInPolicyRule, and PolicyRuleInPolicyRule.  (This is
   accomplished by placing the Priority property on the abstract aggregation
   PolicySetComponent, from which these four aggregations are derived.)  The
 
 
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   QPIM rules for resolving relative priorities across nested PolicyGroups
   and PolicyRules are being incorporated into PCIMe as well.  With the
   removal of the Priority property from PolicyRule, a new modeling
   dependency is introduced: in order to prioritize a PolicyRule relative to
   other PolicyRules, the rules must be placed in either a common
   PolicyGroup or a common PolicyRule.
 
   In the absence of any clear, general criterion for detecting policy
   conflicts, the PCIM restriction stating that priorities are relevant only
   in the case of conflicts is being removed.  In its place, a
   PolicyDecisionStrategy property is being added to the PolicyGroup and
   PolicyRule classes, to allow the policy administrator to select one of
   two behaviors with respect to rule evaluation: either perform the actions
   for all PolicyRules whose conditions evaluate to TRUE, or perform the
   actions only for the highest-priority PolicyRule whose conditions
   evaluate to TRUE.  (Once again this is accomplished by placing the
   PolicyDecisionStrategy property in an abstract class PolicySet, from
   which PolicyGroup and PolicyRule are derived.)  The QPIM rules for
   applying decision strategies to a nested set of PolicyGroups and
   PolicyRules are also being imported.
 
 2.2.4. Policy Roles
 
   The concept of policy roles is added to PolicyGroups (being present
   already in the PolicyRule class).  This is accomplished via a new
   superclass for both PolicyRules and PolicyGroups - PolicySets.  For
   nested PolicyRules and PolicyGroups, any roles associated with the outer
   rule or group are automatically "inherited" by the nested one.
   Additional roles may be added at the level of the nested rule or group.
 
   It was also observed that there was no mechanism in PCIM for assigning
   roles to resources.  For example, while it was possible to associate a
   PolicyRule with the role "FrameRelay&&WAN", there was no way to indicate
   which interfaces matched this criterion.  A new PolicyRoleCollection
   class is defined in PCIMe, representing the collection of resources
   associated with a particular role.  The linkage between a PolicyRule or
   PolicyGroup and a set of resources is then represented by an instance of
   PolicyRoleCollection.  Equivalent values should be defined in entries in
   the PolicyRoles property, inherited by PolicyRules and PolicyGroups from
   PolicySet, and in the PolicyRole property in PolicyRoleCollection.
 
 
 2.2.5. CompoundPolicyConditions and CompoundPolicyActions
 
   The concept of a CompoundPolicyCondition is also being imported into
   PCIMe from QPIM, and broadened to include a parallel
   CompoundPolicyAction.  In both cases the idea is to create reusable
   "chunks" of policy that can exist as named elements in a
   ReusablePolicyContainer.  The "Compound" classes and their associations
   incorporate the condition and action semantics that PCIM defined at the
   PolicyRule level: DNF/CNF for conditions, and ordering for actions.
 
 
 
 
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   Compound conditions and actions are defined to work with any component
   conditions and actions.  In other words, while the components may be
   instances, respectively, of SimplePolicyCondition and SimplePolicyAction
   (discussed immediately below), they need not be.
 
 2.2.6. Variables and Values
 
   The SimplePolicyCondition / PolicyVariable / PolicyValue structure is
   being imported into PCIMe from QPIM.  A list of PCIMe-level variables is
   defined, as well as a list of PCIMe-level values.  Other variables and
   values may, if necessary, be defined in submodels of PCIMe.
 
   A corresponding SimplePolicyAction / PolicyVariable / PolicyValue
   structure is also defined.  While the semantics of a
   SimplePolicyCondition are "variable matches value", a SimplePolicyAction
   has the semantics "set variable to value".
 
 2.2.7. Packet Filtering
 
   For packet filtering done in the context of a PolicyCondition, a set of
   PolicyVariables and PolicyValues are defined, corresponding to the fields
   in an IP packet header plus the most common Layer 2 frame header fields.
   It is expected that policy conditions that filter on these header fields
   will be expressed in terms of CompoundPolicyConditions built up from
   SimplePolicyConditions that use these variables and values.  An
   additional PolicyVariable, PacketDirection, is also defined, to indicate
   whether a packet being filtered is traveling inbound or outbound on an
   interface.
 
   For packet filtering in other contexts (specifically, for the packet
   classifier filters modeled in QDDIM), these variables and values need not
   be used.  Filter classes derived from the CIM FilterEntryBase class
   hierarchy may still be used in these contexts.
 
 
 3. The Updated Class and Association Class Hierarchies
 
   The following figure shows the class inheritance hierarchy for PCIMe.
   Changes from the PCIM hierarchy are noted parenthetically.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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   ManagedElement (abstract)
      |
      +--Policy (abstract)
      |  |
      |  +---PolicySet (abstract -- new - 4.3)
      |  |   |
      |  |   +---PolicyGroup (moved - 4.3)
      |  |   |
      |  |   +---PolicyRule (moved - 4.3)
      |  |
      |  +---PolicyCondition (abstract)
      |  |   |
      |  |   +---PolicyTimePeriodCondition
      |  |   |
      |  |   +---VendorPolicyCondition
      |  |   |
      |  |   +---SimplePolicyCondition (new - 4.8.1)
      |  |   |
      |  |   +---CompoundPolicyCondition (new - 4.7.1)
      |  |       |
      |  |       +---CompoundFilterCondition (new - 4.9)
      |  |
      |  +---PolicyAction (abstract)
      |  |   |
      |  |   +---VendorPolicyAction
      |  |   |
      |  |   +---SimplePolicyAction (new - 4.8.4)
      |  |   |
      |  |   +---CompoundPolicyAction (new - 4.7.2)
      |  |
      |  +---PolicyVariable (abstract -- new - 4.8.5)
      |  |   |
      |  |   +---PolicyExplicitVariable (new - 4.8.6)
      |  |   |
      |  |   +---PolicyImplicitVariable (abstract -- new - 4.8.7)
      |  |       |
      |  |       +---(subtree of more specific classes -- new - 5.12)
      |  |
      |  +---PolicyValue (abstract -- new - 4.8.10)
      |      |
      |      +---(subtree of more specific classes -- new - 5.14)
      |
      +--Collection (abstract -- newly referenced)
         |
         +--PolicyRoleCollection (new - 4.6.2)
   (continued on following page)
 
 
 
 
 
 
 
 
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   (continued from previous page)
   ManagedElement(abstract)
      |
      +--ManagedSystemElement (abstract)
         |
         +--LogicalElement (abstract)
            |
            +--System (abstract)
               |
               +--AdminDomain (abstract)
                  |
                  +---ReusablePolicyContainer (new - 4.2)
                  |
                  +---PolicyRepository (deprecated - 4.2)
 
 
   Figure 1.    Class Inheritance Hierarchy for PCIMe
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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   The following figure shows the association class hierarchy for PCIMe.  As
   before, changes from PCIM are noted parenthetically.
 
   [unrooted]
      |
      +---PolicyComponent (abstract)
      |   |
      |   +---PolicySetComponent (abstract -- new - 4.3)
      |   |    |
      |   |    +---PolicyGroupInPolicyGroup (moved - 4.3)
      |   |    |
      |   |    +---PolicyRuleInPolicyGroup (moved - 4.3)
      |   |    |
      |   |    +---PolicyGroupInPolicyRule (new - 4.3)
      |   |    |
      |   |    +---PolicyRuleInPolicyRule (new - 4.3)
      |   |
      |   +---CompoundedPolicyCondition (abstract -- new - 4.7.1)
      |   |    |
      |   |    +---PolicyConditionInPolicyRule  (moved - 4.7.1)
      |   |    |
      |   |    +---PolicyConditionInPolicyCondition (new - 4.7.1)
      |   |
      |   +---PolicyRuleValidityPeriod
      |   |
      |   +---CompoundedPolicyAction (abstract -- new - 4.7.2)
      |   |    |
      |   |    +---PolicyActionInPolicyRule  (moved - 4.7.2)
      |   |    |
      |   |    +---PolicyActionInPolicyAction (new - 4.7.2)
      |   |
      |   +---PolicyVariableInSimplePolicyCondition (new - 4.8.2)
      |   |
      |   +---PolicyValueInSimplePolicyCondition (new - 4.8.2)
      |   |
      |   +---PolicyVariableInSimplePolicyAction (new - 4.8.4)
      |   |
      |   +---PolicyValueInSimplePolicyAction (new - 4.8.4)
 
   (continued on following page)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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   (continued from previous page)
   [unrooted]
      |
      +---Dependency (abstract)
      |   |
      |   +---PolicyInSystem (abstract)
      |   |   |
      |   |   +---PolicyGroupInSystem
      |   |   |
      |   |   +---PolicyRuleInSystem
      |   |   |
      |   |   +---ReusablePolicy (new - 4.2)
      |   |   |
      |   |   +---PolicyConditionInPolicyRepository (deprecated - 4.2)
      |   |   |
      |   |   +---PolicyActionInPolicyRepository (deprecated - 4.2)
      |   |
      |   +---PolicyValueConstraintInVariable (new - 4.8)
      |   |
      |   +---PolicyRoleCollectionInSystem (new - 4.6.2)
      |
      +---Component (abstract)
      |   |
      |   +---SystemComponent
      |       |
      |       +---PolicyContainerInPolicyContainer (new - 4.2)
      |       |
      |       +---PolicyRepositoryInPolicyRepository (deprecated - 4.2)
      |
      +---MemberOfCollection (newly referenced)
          |
          +--- ElementInPolicyRoleCollection (new - 4.6.2)
 
 
   Figure 2.    Association Class Inheritance Hierarchy for PCIMe
 
   In addition to these changes that show up at the class and association
   class level, there are other changes from PCIM involving individual class
   properties.  In some cases new properties are introduced into existing
   classes, and in other cases existing properties are deprecated (without
   deprecating the classes that contain them).
 
 
 4. Areas of Extension to PCIM
 
   The following subsections describe each of the areas for which PCIM
   extensions are being defined.
 
 4.1. Scope of Policies:  Domain Policies and Device Policies
 
   Policies vary in level of abstraction, from the business-level expression
   of service level agreements (SLAs) to the specification of a set of rules
 
 
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   that apply to devices in a network.  Those latter policies can,
   themselves, be classified into at least two groups: those policies
   consumed by a Policy Decision Point (PDP) that specify the rules for an
   administrative and functional domain, and those policies consumed by a
   Policy Enforcement Point (PEP) that specify the device-specific rules for
   a functional domain.  The higher-level rules consumed by a PDP may have
   late binding variables unspecified, or specified by a classification,
   whereas the device-level rules are likely to have fewer unresolved
   bindings.
 
   There is a relationship between these levels of policy specification that
   is out of scope for this standards effort, but that is necessary in the
   development and deployment of a usable policy-based configuration system.
   An SLA-level policy transformation to the domain-level policy may be
   thought of as analogous to a visual builder that takes human input and
   develops a programmatic rule specification.  The relationship between the
   domain-level policy and the device-level policy may be thought of as
   analogous to that of a compiler and linkage editor that translates the
   rules into specific instructions that can be executed on a specific type
   of platform.
 
 
   The policy core information model may be used to specify rules at any and
   all of these levels of abstraction.  However, at different levels of
   abstraction, different mechanisms may be more or less appropriate.
 
 4.2. Reusable Policy Elements
 
   In PCIM, a distinction was drawn between reusable PolicyConditions and
   PolicyActions and rule-specific ones.  The PolicyRepository class was
   also defined, to serve as a container for these reusable elements.  The
   name "PolicyRepository" has proven to be an unfortunate choice for the
   class that serves as a container for reusable policy elements.  This term
   is already used in documents like the Policy Framework, to denote the
   location from which the PEP retrieves all policy specifications, and into
   which the Policy Management Tool places all policy specifications.
   Consequently, the PolicyRepository class is being deprecated, in favor of
   a new class ReusablePolicyContainer.
 
   When a class is deprecated, any associations that refer to it must also
   be deprecated.  So replacements are needed for the two associations
   PolicyConditionInPolicyRepository and PolicyActionInPolicyRepository, as
   well as for the aggregation PolicyRepositoryInPolicyRepository.  In
   addition to renaming the PolicyRepository class to
   ReusablePolicyContainer, however, PCIMe is also broadening the types of
   policy elements that can be reusable.  Consequently, rather than
   providing one-for-one replacements for the two associations, a single
   higher-level association ReusablePolicy is defined.  This new association
   allows any policy element (that is, an instance of any subclass of the
   abstract class Policy) to be placed in a ReusablePolicyContainer.
 
   Summarizing, the following changes in Sections 5 and 6 are the result of
   this item:
 
 
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     o The class ReusablePolicyContainer is defined.
     o PCIM's PolicyRepository class is deprecated.
     o The association ReusablePolicy is defined.
     o PCIM's PolicyConditionInPolicyRepository association is deprecated.
     o PCIM's PolicyActionInPolicyRepository association is deprecated.
     o The aggregation PolicyContainerInPolicyContainer is defined.
     o PCIM's PolicyRepositoryInPolicyRepository aggregation is deprecated.
 
 4.3. Policy Sets
 
   A "policy" can be thought of as a coherent set of rules to administer,
   manage, and control access to network resources (PolTerm, reference
   [12]).  The structuring of these coherent sets of rules into subsets is
   enhanced in this document.  In section 4.4, we discuss the new options
   for the nesting of policy rules.
 
   A new abstract class, PolicySet, is introduced to provide an abstraction
   for a set of rules.  It is derived from Policy, and it is inserted into
   the inheritance hierarchy above both PolicyGroup and PolicyRule.  This
   reflects the additional structure flexibility and semantic capability of
   both subclasses.
 
   Two properties are defined in PolicySet: PolicyDecisionStrategy and
   PolicyRoles.  PolicyDecisionStrategy is added to PolicySet to define the
   evaluation relationship between the rules in the policy set.  See section
   4.5 for more information.  PolicyRoles is added to PolicySet to name the
   retrieval sets.  See section 4.6 for more information.
 
   Along with the definition of the PolicySet class, a new abstract
   aggregation class is defined that will also be discussed in the following
   sections.  PolicySetComponent is defined as a subclass of
   PolicyComponent; it provides the containment relationship for a
   PolicySet.  PolicyGroupInPolicyGroup and PolicyRuleInPolicyGroup are
   modified to subclass from PolicySetComponent.  PolicyGroupInPolicyRule
   and PolicyRuleInPolicyRule, discussed in the next section, are also
   defined as subclasses of PolicySetComponent.
 
 4.4. Nested Policy Rules
 
   As previously discussed, policy is described by a set of policy rules
   that may be grouped into subsets.   In this section we introduce the
   notion of nested rules, or the ability to define rules within rules.
   Nested rules are also called sub-rules, and we use both terms in this
   document interchangeably.  Two new aggregations are defined for this
   purpose: PolicyRuleInPolicyRule and PolicyGroupInPolicyRule.
 
 4.4.1. Usage Rules for Nested Rules
 
   The relationship between rules and sub-rules is defined as follows:
 
     o   The parent rule's condition clause is a pre-condition for
         evaluation of all nested rules. If the parent rule's condition
 
 
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         clause evaluates to FALSE, all sub-rules SHALL be skipped and
         their condition clauses SHALL NOT be evaluated.
     o   If the parent rule's condition evaluates to TRUE, the set of sub-
         rules SHALL BE executed according to the decision strategy and
         priorities as discussed in Section 4.5.
     o   If the parent rule's condition evaluates to TRUE, the parent
         rule's set of actions is executed BEFORE the evaluation and
         execution of the sub-rules.  The parent rule's actions are not to
         be confused with default actions.  A default action is one that is
         to be executed only if none of the more specific sub-rules are
         executed.  If a default action needs to be specified, it needs to
         be defined as an action that is part of a catchall sub-rule
         associated with the parent rule.  The association linking the
         default action(s) in this special sub-rule should have the lowest
         priority relative to all other sub-rule associations:
 
                if precondition then parent rule's action
                      if condA then actA
                      if condB then ActB
                      if True then default action
 
         Default actions have meaning when FirstMatching decision
         strategies are in effect (see section 4.5).
 
    o    Policy rules have an implicit context in which they are executed.
         For example, the context of a policy rule could be all packets
         running on an interface or set of interfaces on which the rule is
         applied.  Similarly, a parent rule provides a context to all of
         its sub-rules.  The context of the sub-rules is the restriction of
         the context of the parent rule to the set of cases that match the
         parent rule's condition clause.
 
 4.4.2. Motivation
 
   The motivation for introducing nested rules includes enhancing the
   definition of Policy, defining and reusing context hierarchies,
   optimizing how a rule is evaluated, and providing finer-grained control
   over condition evaluation.
 
   Rule nesting enhances Policy readability, expressiveness and reusability.
   The ability to nest policy rules and form sub-rules is important for
   manageability and scalability, as it enables complex policy rules to be
   constructed from multiple simpler policy rules.  These enhancements ease
   the policy management tools' task, allowing policy rules to be expressed
   in a way closer to how humans think.
 
   Sub-rules enable the policy designer to define a hierarchy of rules.
   This hierarchy has the property that sub-rules can be scoped by their
   parent rules.  This scoping, or context of evaluation and execution, is a
   powerful tool in enabling the policy designer to obtain the fine-grained
   control needed to appropriately manage resources for certain
   applications.  The example in the following section demonstrates that
 
 
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   expressing relative bandwidth allocation rules can be done very naturally
   using a hierarchical rule structure.
 
   Rule nesting can be used to optimize the way policy rules are evaluated
   and executed. Once the parent rule's condition clause is evaluated to
   FALSE, all sub-rules are skipped, optimizing the number of lookups
   required. Note that this is not the prime reason for rule nesting, but
   rather a side benefit. Optimization of rule execution can be done in the
   PDP or in the PEP by dedicated code.  This is similar to the relation
   between a high level programming language like C and machine code.  An
   optimizer can create a more efficient machine code than any optimization
   done by the programmer within the source code.  Nevertheless, if the PEP
   or PDP does not do optimization, the administrator writing the policy can
   optimize the policy rules for execution using rule nesting.
 
   In a model where condition evaluation may have side effects, nesting
   rules allow control of condition evaluation, as sub-rule conditions SHALL
   NOT be evaluated if the condition of the parent rule evaluates to FALSE.
 
   Nested rules are not designed for policy repository retrieval
   optimization.  It is assumed that all rules and groups that are assigned
   to a role are retrieved by the PDP or PEP from the policy repository and
   enforced.  Optimizing the number of rules retrieved should be done by
   clever selection of roles.
 
 4.4.3. Usage Example
 
   This section provides a usage example that aims to clarify the motivation
   for the definition of rule nesting and the use of the relative context.
   Consider the following example, where a set of rules is used to specify
   the minimal bandwidth allocations on an interface.  The policy reads:
 
         On any interface on which these rules apply, allocate at
         least 30% of the interface bandwidth to UDP flows, and at
         least 40% of the interface bandwidth to TCP flows.
 
   This single rule is translated to a set of two rules:
 
     If (IP protocol is UDP) THEN Set MinBW to 30%  (1)
     If (IP protocol is TCP) THEN Set MinBW to 40%  (2)
 
   Now, let's add some sub-rules to further differentiate how bandwidth
   should be allocated to specific UDP and TCP applications (indentation
   indicates rule nesting):
 
     If (IP protocol is UDP) THEN Set MinBW to 30%     (1)
           If (protocol is TFTP) THEN Set MinBW to 10%   (1a)
           If (protocol is NFS) THEN Set MinBW to 40%    (1b)
     If (IP protocol is TCP) THEN Set MinBW to 40%     (2)
           If (protocol is HTTP) THEN Set MinBW to 20%   (2a)
           If (protocol is FTP) THEN Set MinBW to 30%    (2b)
 
 
 
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   This means that for UDP flows, TFTP should be allocated 10% of the
   bandwidth while NFS should be allocated 40%.  For TCP flows, HTTP should
   be allocated 20% of the bandwidth while FTP should be allocated 30%.
 
   The context of each of the two high-level rules (those marked (1) and (2)
   above) is all flows running on an interface.  The two sub-rules of the
   UDP rule, marked (1a) and (1b) above specify a more granular context:
   within UDP flows, TFTP should be allocated 10% of the bandwidth while NFS
   should be allocated 40%.  The context of these sub-rules is therefore UDP
   flows only. Similar functionality applies for the hierarchy of rules
   treating TCP flows.
 
   A context hierarchy enhances reusability.  The rules that divide
   bandwidth between TFTP and NFS can be re-used and associated to rules
   that allocate different percentages of the bandwidth for different
   interfaces (or even for the same interface, but under different
   conditions) for UDP.
 
 4.5. Priorities and Decision Strategies
 
   A "decision strategy" is used to specify the evaluation method for the
   policies in a PolicySet.  Two decision strategies are defined:
   "FirstMatching" and "AllMatching."  The FirstMatching strategy is used to
   cause the evaluation of the rules in a set such that the actions of only
   the first rule that matches are enforced on a given examination of the
   PolicySet.  The AllMatching strategy is used to cause the evaluation of
   all rules in a set; for all of the rules that match, the actions are
   enforced.  (Strawman:  Implementations MUST support the FirstMatching
   decision strategy; implementations MAY support the AllMatching decision
   strategy.)
 
   As previously discussed, the PolicySet subclasses are PolicyGroup and
   PolicyRule, and either subclass may contain PolicySets of either
   subclass.  Loops, including the degenerate case of a PolicySet that
   contains itself, are not allowed when PolicySets contain other
   PolicySets.  The containment relationship is specified using the
   PolicySetComponent subclasses: PolicyGroupInPolicyGroup,
   PolicyRuleInPolicyGroup, PolicyGroupInPolicyRule and
   PolicyRuleInPolicyRule.
 
   The order of evaluation within a PolicySet is established by the Priority
   property of the PolicySetComponent aggregation.  Instances of the
   subclasses of PolicySetComponent specify the relative priority of the
   contained policy groups and rules within the containing group or rule.
   The use of PCIM's PolicyRule.Priority property is deprecated in favor of
   this new property.  The separation of the priority property from the rule
   has two advantages.  First, it generalizes the concept of priority, so it
   can be used for both groups and rules; and, second, it places the
   priority on the relationship between the parent policy set and the
   subordinate policy group or rule.  The assignment of a priority value,
   then, becomes much easier in that the value is used only in relationship
   to other priorities in the same set.
 
 
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   Together, the PolicySet.PolicyDecisionStrategy and
   PolicySetComponent.Priority determine the processing for the rules
   contained in a PolicySet.  As before, the larger priority value
   represents the higher priority.  Unlike the earlier definition,
   PolicySetComponent.Priority MUST have a unique value when compared with
   others defined for the aggregating PolicySet.  Thus, the evaluation of
   rules within a set is deterministically specified.
 
   For a FirstMatching decision strategy, the order of evaluation, then, is
   high to low priority.  The first rule (i.e., the one with the highest
   priority) in the set that evaluates to True, is the only rule whose
   actions are enforced for a particular evaluation pass through the
   PolicySet.
 
   For an AllMatching decision strategy, the order of evaluation is also
   from high priority to low priority; however, all of the matching rules
   are executed.  Although higher priority rules are evaluated first, lower
   priority rules may get the "last word."  So, for example, if two rules
   both evaluate to True, and the higher priority rule sets the DSCP to 3
   and the lower priority rule sets the DSCP to 4, the lower priority rule
   will be evaluated later and, therefore, will "win," in this example,
   setting the DSCP to 4.  Thus, conflicts between rules are resolved by
   this evaluation order.
 
 4.5.1. Structuring Decision Strategies
 
   When policy sets are nested, as shown in Figure 3, the decision
   strategies may be nested arbitrarily.  In this example, the evaluation
   order for the nested rules is 1A, 1B1, 1X2, 1B3, 1C, 1C1, 1X2 and 1C3.
   (Note that PolicyRule 1X2 is included in both PolicyGroup 1B and
   PolicyRule 1C, but with different priorities.)  Of course, the evaluation
   order is also dependent on which rules, if any, match.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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   PolicyGroup 1: FirstMatching
     |
     +-- Pri=6 -- PolicyRule 1A
     |
     +-- Pri=5 -- PolicyGroup 1B: AllMatching
     |              |
     |              +-- Pri=5 -- PolicyGroup 1B1: AllMatching
     |              |              |
     |              |              +---- etc.
     |              |
     |              +-- Pri=4 -- PolicyRule 1X2
     |              |
     |              +-- Pri=3 -- PolicyRule 1B3: FirstMatching
     |                             |
     |                             +---- etc.
     |
     +-- Pri=4 -- PolicyRule 1C: FirstMatching
                    |
                    +-- Pri=4 -- PolicyRule 1C1
                    |
                    +-- Pri=3 -- PolicyRule 1X2
                    |
                    +-- Pri=2 -- PolicyRule 1C3
 
 
   Figure 3.    Nested PolicySets with Different Decision Strategies
 
     o   Because PolicyGroup 1 has a FirstMatching decision strategy, if
         the conditions of PolicyRule 1A match, its actions are enforced
         and the evaluation stops.
 
     o   If it does not match, PolicyGroup 1B is evaluated using an
         AllMatching strategy.  Since PolicyGroup 1B1 also has an
         AllMatching strategy all of the rules and groups of rules
         contained in PolicyGroup 1B1 are evaluated and enforced as
         appropriate. PolicyRule 1X2 and PolicyRule 1B3 are also evaluated
         and enforced as appropriate.  If any of the sub-rules in the
         subtrees of PolicyGroup 1B evaluate to True, then PolicyRule 1C is
         not evaluated because the FirstMatching strategy of PolicyGroup 1
         has been satisfied.
 
     o   If neither PolicyRule 1A nor PolicyGroup 1B yield a match, then
         PolicyRule 1C is evaluated.  Since it is first matching, rules
         1C1, 1X2, and 1C3 are evaluated until the first match, if any.
 
 4.5.2. Deterministic Decisions
 
   As mentioned above, we propose that Priority values are to be unique
   within a containing PolicySet.  Although there are certainly cases where
   rules need not have a unique priority value (i.e., where evaluation and
   execution order is not important), it is believed that the flexibility
 
 
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   gained by this capability is not sufficiently beneficial to justify the
   possible variations in implementation behavior and the resulting
   confusion that might occur.
 
   Therefore, all PolicySetComponent.Priority values MUST be unique among
   the values in the aggregating PolicySet.  Each PolicySet, then, has a
   deterministic behavior based upon the decision strategy and uniquely
   defined order of evaluation.
 
 4.5.3. Multiple PolicySet Trees For a Resource
 
   As shown in the example in Figure 3, PolicySet trees are defined by the
   PolicySet subclass instances and the PolicySetComponent subclass
   aggregation instances between them.  Each PolicySet tree has a defined
   set of decision strategies and evaluation orders.  However, a given
   resource may have multiple, disjoint PolicySet trees; we need a join
   algorithm that describes the decision strategy and evaluation order among
   the top-level (called "unrooted") PolicySet instances.  (Note that an
   unrooted PolicySet instance may only be unrooted in a given context.)
 
   <<Solution under discussion - see Open Issue 9>>
 
 4.6. Policy Roles
 
   A policy role is defined in [12] as "an administratively specified
   characteristic of a managed element (for example, an interface).  It is a
   selector for policy rules and PRovisioning Classes (PRCs), to determine
   the applicability of the rule/PRC to a particular managed element."
 
   In PCIMe, PolicyRoles is defined as a property of PolicySet, which is
   inherited by both PolicyRules and PolicyGroups.  In this draft, we also
   add PolicyRole as the identifying name of a collection of resources
   (PolicyRoleCollection), where each element in the collection has the
   specified role characteristic.
 
 
 4.6.1. Comparison of Roles in PCIM with Roles in snmpconf
 
   In the Configuration Management with SNMP (snmpconf) working group's
   Policy Based Management MIB [13], policy rules are of the form
 
 
     if <policyFilter> then <policyAction>
 
   where <policyFilter> is a set of conditions that are used to determine
   whether or not the policy applies to an object instance. The policy
   filter can perform comparison operations on SNMP variables already
   defined in MIBS (e.g., "ifType == ethernet").
 
   The policy management MIB defined in [13] defines a Role table that
   enables one to associate Roles with elements, where roles have the same
   semantics as in PCIM. Then, since the policyFilter in a policy allows one
   to define conditions based on the comparison of the values of SNMP
 
 
 
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   variables, one can filter elements based on their roles as defined in the
   Role group.
 
   This approach differs from that adopted in PCIM in the following ways.
   First, in PCIM, a set of role(s) is associated with a policy rule as the
   values of the PolicyRoles property of a policy rule. The semantics of
   role(s) are then expected to be implemented by the PDP (i.e. policies are
   applied to the elements with the appropriate roles). In [draft-ietf-
   snmpconf-pm-04], however, no special processing is required for realizing
   the semantics of roles; roles are treated just as any other SNMP
   variables and comparisons of role values can be included in the policy
   filter of a policy rule.
 
   Secondly, in PCIM, there is no formally defined way of associating a role
   with an object instance, whereas in [13] this is done via the use of the
   Role tables (pmRoleESTable and pmRoleSETable). The Role tables associate
   Role values with elements.
 
 
 4.6.2. Addition of PolicyRoleCollection to PCIMe
 
   In order to remedy the latter shortcoming in PCIM (i.e. the lack of a way
   of associating a role with an object instance), we define a new class
   PolicyRoleCollection that subclasses from the CIM Collection class.
   Resources that share a common role belong to a PolicyRoleCollection
   instance.  Membership in this collection is indicated using the
   aggregation ElementInPolicyRoleCollection.  The resource's role is
   specified in the PolicyRole property of the PolicyRoleCollection class.
 
   A PolicyRoleCollection always exists in the context of a system.  As was
   done in PCIM for PolicyRules and PolicyGroups, this is captured by an
   association, PolicyRoleCollectionInSystem.  Remember that in PCIM, a
   System is a base class for describing network devices and administrative
   domains.
 
   When associating a PolicyRoleCollection with a System, this should be
   done consistently with the system that scopes the policy rules/groups
   that are applied to the resources in that collection.  A
   PolicyRoleCollection is associated with the same system as the applicable
   PolicyRules and/or PolicyGroups, or to a System higher in the tree formed
   by the SystemComponent association.  When a PEP belongs to multiple
   Systems (i.e., AdminDomains), and scoping by a single domain is
   impractical, two alternatives exist.  One is to arbitrarily limit domain
   membership to one System/AdminDomain.  The other option is to define a
   more global AdminDomain that simply includes the others, and/or that
   spans the business or enterprise.
 
   As an example, suppose that there are 20 traffic trunks in a network, and
   that an administrator would like to assign three of them to provide
   "gold" service.  Also, the administrator has defined several policy rules
   which specify how the "gold" service is delivered.  For these rules, the
   PolicyRoles property (inherited from PolicySet) is set to "Gold Service".
 
 
 
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   In order to associate three traffic trunks with "gold" service, an
   instance of the PolicyRoleCollection class is created and its PolicyRole
   property is also set to "Gold Service".  Following this, the
   administrator associates three traffic trunks with the new instance of
   PolicyRoleCollection via the ElementInPolicyRoleCollection aggregation.
   This enables a PDP to determine that the "Gold Service" policy rules
   apply to the three aggregated traffic trunks.
 
 
   Note that roles are used to optimize policy retrieval.  It is not
   mandatory to implement roles or, if they have been implemented, to group
   elements in a PolicyRoleCollection.  However, if roles are used, then
   either the collection approach should be implemented, or elements should
   be capable of reporting their "pre-programmed" roles (as is done in
   COPS).
 
 4.6.3. Roles for PolicyGroups
 
   In PCIM, role(s) are only associated with policy rules.  However, it may
   be desirable to associate role(s) with groups of policy rules.  For
   example, a network administrator may want to define a group of rules that
   apply only to Ethernet interfaces.  A policy group can be defined with a
   role-combination="Ethernet", and all the relevant policy rules can be
   placed in this policy group.  (Note that in PCIMe, role(s) are made
   available to PolicyGroups as well as to PolicyRules by moving PCIM's
   PolicyRoles property up from PolicyRule to the new abstract class
   PolicySet.  The property is then inherited by both PolicyGroup and
   PolicyRule.)  Then every policy rule in this policy group implicitly
   inherits this role-combination from the containing policy group.  A
   similar implicit inheritance applies to nested policy groups.
 
   Note that there is no explicit copying of role(s) from container to
   contained entity.  Obviously, this implicit inheritance of role(s) leads
   to the possibility of defining inconsistent role(s) (as explained in the
   example below); the handling of such inconsistencies is beyond the scope
   of PCIMe.
 
   As an example, suppose that there is a PolicyGroup PG1 that contains
   three PolicyRules, PR1, PR2, and PR3.  Assume that PG1 has the roles
   "Ethernet" and "Fast".  Also, assume that the contained policy rules have
   the role(s) shown below:
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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   +------------------------------+
   | PolicyGroup PG1              |
   | PolicyRoles = Ethernet, Fast |
   +------------------------------+
              |
              |        +------------------------+
              |        | PolicyRule PR1         |
              |--------| PolicyRoles = Ethernet |
              |        +------------------------+
              |
              |        +--------------------------+
              |        | PolicyRule PR2           |
              |--------| PolicyRoles = <undefined>|
              |        +--------------------------+
              |
              |        +------------------------+
              |        | PolicyRule PR3         |
              |--------| PolicyRoles = Slow     |
                       +------------------------+
 
   Figure 4.    Inheritance of Roles
 
   In this example, the PolicyRoles property value for PR1 is consistent
   with the value in PG1, and in fact, did not need to be redefined.  The
   value of PolicyRoles for PR2 is undefined.  Its roles are implicitly
   inherited from PG1. Lastly, the value of PolicyRoles for PR3 is "Slow".
   This appears to be in conflict with the role, "Fast," defined in PG1.
   However, whether these roles are actually in conflict is not clear.  In
   one scenario, the policy administrator may have wanted only "Fast"-
   "Ethernet" rules in the policy group.  In another scenario, the
   administrator may be indicating that PR3 applies to all "Ethernet"
   interfaces regardless of whether they are "Fast" or "Slow."  Only in the
   former scenario (only "Fast"-"Ethernet" rules in the policy group) is
   there a role conflict.
 
 
   Note that it is possible to override implicitly inherited roles via
   appropriate conditions on a PolicyRule.  For example, suppose that PR3
   above had defined the following conditions:
 
     (interface is not "Fast") and (interface is "Slow")
 
   This results in unambiguous semantics for PR3.
 
 
 4.7. Compound Policy Conditions and Compound Policy Actions
 
   Compound policy conditions and compound policy actions are introduced to
   provide additional reusable "chunks" of policy.
 
 
 
 
 
 
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 4.7.1. Compound Policy Conditions
 
   A CompoundPolicyCondition is a PolicyCondition representing a Boolean
   combination of simpler conditions.  The conditions being combined may be
   SimplePolicyConditions (discussed below in section 4.7), but the utility
   of reusable combinations of policy conditions is not necessarily limited
   to the case where the component conditions are simple ones.
 
   The PCIM extensions to introduce compound policy conditions are
   relatively straightforward.  Since the purpose of the extension is to
   apply the DNF / CNF logic from PCIM's PolicyConditionInPolicyRule
   aggregation to a compound condition that aggregates simpler conditions,
   the following changes are required:
 
      o Create a new aggregation PolicyConditionInPolicyCondition, with the
        same GroupNumber and ConditionNegated properties as
        PolicyConditionInPolicyRule.  The cleanest way to do this is to
        move the properties up to a new abstract aggregation superclass
        CompoundedPolicyCondition, from which the existing aggregation
        PolicyConditionInPolicyRule and a new aggregation
        PolicyConditionInPolicyCondition are derived.  For now there is no
        need to re-document the properties themselves, since they are
        already documented in PCIM as part of the definition of the
        PolicyConditionInPolicyRule aggregation.
      o It is also necessary to define a concrete subclass
        CompoundPolicyCondition of PolicyCondition, to introduce the
        ConditionListType property.  This property has the same function,
        and works in exactly the same way, as the corresponding property
        currently defined in PCIM for the PolicyRule class.
 
   The class and property definitions for representing compound policy
   conditions are below, in Section 5.
 
 
 4.7.2. Compound Policy Actions
 
   A compound action is a convenient construct to represent a sequence of
   actions to be applied as a single atomic action within a policy rule.  In
   many cases, actions are related to each other and should be looked upon
   as sub-actions of one "logical" action.  An example of such a logical
   action is "shape & mark" (i.e., shape a certain stream to a set of
   predefined bandwidth characteristics and then mark these packets with a
   certain DSCP value).  This logical action is actually composed of two
   different QoS actions, which should be performed in a well-defined order
   and as a complete set.
 
   The CompoundPolicyAction construct allows one to create a logical
   relationship between a number of actions, and to define the activation
   logic associated with this logical action.
 
   The CompoundPolicyAction construct allows the reusability of these
   complex actions, by storing them in a ReusablePolicyContainer and reusing
 
 
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   them in different policy rules.  Note that a compound action may also be
   aggregated by another compound action.
 
   As was the case with CompoundPolicyCondition, the PCIM extensions to
   introduce compound policy actions are relatively straightforward.  This
   time the goal is to apply the property ActionOrder from PCIM's
   PolicyActionInPolicyRule aggregation to a compound action that aggregates
   simpler actions.  The following changes are required:
 
      o Create a new aggregation PolicyActionInPolicyAction, with the same
        ActionOrder property as PolicyActionInPolicyRule.  The cleanest way
        to do this is to move the property up to a new abstract aggregation
        superclass CompoundedPolicyAction, from which the existing
        aggregation PolicyActionInPolicyRule and a new aggregation
        PolicyActionInPolicyAction are derived.  For now there is no need
        to re-document the ActionOrder property itself, since it is already
        documented in PCIM as part of the definition of the
        PolicyActionInPolicyRule aggregation.
      o It is also necessary to define a concrete subclass
        CompoundPolicyAction of PolicyAction, to introduce the
        SequencedActions property.  This property has the same function,
        and works in exactly the same way, as the corresponding property
        currently defined in PCIM for the PolicyRule class.
      o Finally, a new property ExecutionStrategy is needed for both the
        PCIM class PolicyRule and the new class CompoundPolicyAction.  This
        property allows the policy administrator to specify how the PEP
        should behave in the case where there are multiple actions
        aggregated by a PolicyRule or by a CompoundPolicyAction.
 
   The class and property definitions for representing compound policy
   actions are below, in Section 5.
 
   Compound actions allow the definition of logically complex policy rules
   and action behavior.  The following example illustrates two advantages of
   using compound actions.
 
   A QoS policy domain may include a rule that defines the following
   behavior:
 
     If (CONDITION) Then Do:
       "Shape traffic to <X> and Set DSCP to EF (high priority traffic);
        if canÆt shape than Set DSCP to BE (best effort)."
 
   This rule can be realized by defining two CompoundPolicyAction instances,
   A and B.  Two sub-actions are grouped into CompoundPolicyAction A:
 
        Shape traffic to <X>
        Mark to EF (DSCP).
 
   The ExecutionStrategy property of CompoundPolicyAction A would be defined
   as "Mandatory Do all".  This means that if shaping or marking cannot both
   be done, then nothing should be done.
 
 
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   A second action, CompoundPolicyAction B, would hold the Mark to BE sub-
   action.
 
   CompoundPolicyAction A and CompoundPolicyAction B would be aggregated
   into the policy rule using the PolicyActionInPolicyRule aggregation.  The
   CompoundPolicyAction A will be ordered for execution before the
   CompoundPolicyAction B.  The PolicyRule's ExecutionStrategy property
   would be set to "Do until success".  In this way, CompoundPolicyAction A
   will be enforced on all PEPs that support shaping, while
   CompoundPolicyAction B will be enforced otherwise.
 
 4.8. Variables and Values
 
   The following subsections introduce several related concepts, including
   PolicyVariables and PolicyValues (and their numerous subclasses),
   SimplePolicyConditions, and SimplePolicyActions.
 
 4.8.1. Simple Policy Conditions
 
   The SimplePolicyCondition class models elementary Boolean conditional
   expressions of the form: "If (<variable> MATCH <value>)".  The "If"
   clause and the "MATCH" are implied in the formal notation.  The
   relationship is always 'MATCH' and is interpreted based on the variable
   and the value.  Section 4.8.3 explains the semantics of the operator and
   how to extend them.  Arbitrarily complex Boolean expressions can be
   formed by chaining together any number of simple conditions using
   relational operators.  Individual simple conditions can be negated as
   well.  Arbitrarily complex Boolean expressions are modeled by the class
   CompoundPolicyCondition (described in section 4.7.1).
 
   For example, the expression "If SourcePort == 80" can be modeled by a
   simple condition.  In this example, 'SourcePort' is a variable, '==' is
   the relational operator denoting the equality relationship (which is
   generalized by PCIMe to a "match" relationship), and '80' is an integer
   value.  The complete interpretation of a simple condition depends on the
   binding of the variable.  Section 4.8.5 describes variables and their
   binding rules.
 
   The SimplePolicyCondition class refines the basic structure of the
   PolicyCondition class defined in PCIM by using the pair <variable> and
   <value> to form the condition.  Note that the operator between the
   variable and the value is always implied in PCIMe: it is not a part of
   the formal notation.
 
   The variable specifies the attribute of an object that should be matched
   when evaluating the condition.  For example, for a QoS derivation, this
   object could represent the flow that is being conditioned.  A set of
   predefined variables that cover network attributes that are commonly used
   for filtering is introduced here in PCIMe to encourage interoperability.
   This list covers layer 3 IP attributes such as IP network addresses,
   protocols and ports, as well as a set of layer 2 attributes (e.g., MAC
   addresses).
 
 
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   The PCIMe defines a single operator, "match", as explained in section
   4.8.3.
 
   The bound variable is matched against a value to produce the Boolean
   result.  For example, in the condition "If the source IP address of the
   flow belongs to the 10.1.x.x subnet", a source IP address variable is
   matched against a 10.1.x.x subnet value.  The operator specifies the type
   of relation between the variable and the value evaluated in the
   condition.
 
 4.8.2. Using Simple Policy Conditions
 
   Simple conditions can be used in policy rules directly, or as building
   blocks for creating compound policy conditions.
 
   Simple condition composition MUST enforce the following data-type
   conformance rule: The ValueTypes property of the variable must be
   compatible with the type of the value class used.  The simplest (and
   friendliest, from a user point-of-view) is to equate the type of the
   value class with the name of the class.  By ensuring that the ValueTypes
   property of the variable matches the name of the value class used, we
   know that the variable and value instance values are compatible with each
   other.
 
   Composing a simple condition requires that an instance of the class
   SimplePolicyCondition be created, and that instances of the variable and
   value classes that it uses also exist.  Note that the variable and/or
   value instances may already exist as reusable objects in an appropriate
   ReusablePolicyContainer.
 
   Two aggregations are used in order to create the pair <variable>,
   <value>.  The aggregation PolicyVariableInSimplePolicyCondition relates a
   SimplePolicyCondition to a single variable instance.  Similarly, the
   aggregation PolicyValueInSimplePolicyCondition relates a
   SimplePolicyCondition to a single value instance.  Both aggregations are
   defined in this document.
 
   Figure 5 depicts a SimplePolicyCondition with its associated variable and
   value.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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                              +-----------------------+
                              | SimplePolicyCondition |
                              +-----------------------+
                                    *         @
                                    *         @
              +------------------+  *         @  +---------------+
              | (PolicyVariable) |***         @@@| (PolicyValue) |
              +------------------+               +---------------+
                 #            #
                 #    ooo     #
                 #            #
   +---------------+        +---------------+
   | (PolicyValue) |  ooo   | (PolicyValue) |
   +---------------+        +---------------+
 
   Aggregation Legend:
     ****  PolicyVariableInSimplePolicyCondition
     @@@@  PolicyValueInSimplePolicyCondition
     ####  PolicyValueConstraintInVariable
 
   Figure 5.    SimplePolicyCondition
 
   Note:  The class names in parenthesis denote subclasses.  The named
   classes in the figure are abstract and cannot, therefore, be
   instantiated.
 
 4.8.3. The Simple Condition Operator
 
   A simple condition models an elementary Boolean expression conditional
   clause of the form "If variable MATCHes value".  However, the formal
   notation of the SimplePolicyCondition, together with its associations,
   models only a pair, {variable, value}. The "If" term and the "MATCH"
   operator are not directly modeled -- they are implied.
 
   The implied MATCH operator carries an overloaded semantics.  For example,
   in the simple condition "If DestinationPort MATCH '80'" the
   interpretation of the MATCH operator is equality (the 'equal' operator).
   Clearly, a different interpretation is needed in the following cases:
 
     o   "If DestinationPort MATCH {'80', '8080'}"  -- operator is 'IS SET
         MEMBER'
 
     o   "If DestinationPort MATCH {'1 to 255'}" -- operator is 'IN INTEGER
         RANGE'
 
     o   "If SourceIPAddress MATCH 'MyCompany.com'" -- operator is 'IP
         ADDRESS AS RESOLVED BY DNS'
 
   The examples above illustrate the implicit, context dependant nature of
   the interpretation of the MATCH operator. The interpretation depends on
   the actual variable and value instances in the simple condition.  PCIMe
   does not contain text to explicitly detail the possible interpretations
 
 
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   of MATCH operations. The interpretation is always derived from the value
   instance associated with the simple condition.  Text accompanying the
   value class definition SHOULD be used as a guideline for interpreting the
   semantics of the MATCH relationship.
 
 
   The PolicyValueConstraintInVariable association specifies additional
   constraints on the possible values that can be matched with a variable
   within a simple condition.  Using this association a source or
   destination port can be constrained to be matched against integer values
   in the range 0-65535.  A source or destination IP address can be
   constrained to be matched against a specified list of IPv4 address
   values, etc.  In order to check whether a value X can be used with a
   variable A constrained by value Y, the following conformance test should
   be made.  If all events for which the SimplePolicyCondition (A match X)
   evaluates to TRUE also evaluate to TRUE for the SimplePolicyCondition (A
   match Y), than X conforms to the constraint Y.  If multiple values Y1,
   Y2, ..., Yn constrain a variable, then the conformance test involves
   checking against the condition (A match Y1) OR (A match Y2) OR ... OR (A
   match Yn).
 
 4.8.4. SimplePolicyActions
 
   The SimplePolicyAction class models the elementary set operation. "SET
   <variable> TO <value>".  The set operator MUST overwrite an old value of
   the variable.
 
   For example, the action  "set DSCP to EF" can be modeled by a simple
   action.  In this example, 'DSCP' is an implicit variable referring to the
   IP packet header DSCP field.  'EF' is an integer or bit string value (6
   bits).  The complete interpretation of a simple action depends on the
   binding of the variable.  Section [4.8.4] describes variables and their
   binding rules for conditions.
 
   The SimplePolicyAction class refines the basic structure of the
   PolicyAction class defined in PCIM, by specifying the contents of the
   action using the <variable> <value> pair to form the action.  The
   variable specifies the attribute of an object that has passed the
   condition by evaluating to true.  This means the binding of the variable
   is delayed until the condition evaluates to true for one or more objects.
   The value of the object's attribute is set to <value>.
 
   SimplePolicyActions can be used in policy rules directly, or as building
   blocks for creating CompoundPolicyActions.
 
   SimplePolicyAction execution MUST enforce the following data type
   conformance and translation rule: The ValueTypes property of the variable
   must be compatible with the type of the value class used.  The following
   table shows the compatibility and transformation rules.  'ND' means the
   transformation is not defined.
 
 
 
 
 
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   +------------------------------------------------------------------+
   |variable  |             value type                                |
   |type      |                                                       |
   +------------------------------------------------------------------+
   |          |String |Integer|BitString| IPv4Addr | IPv6Addr |MACAddr|
   +------------------------------------------------------------------+
   | String   |   X   |to text|  [0|1]  | A.B.C.D  | dotted   | X:X.. |
   +------------------------------------------------------------------+
   | Integer  |"atoi" |   X   |BinaryVal| 32bit int|    ND    |   ND  |
   +------------------------------------------------------------------+
   | BitString|convert|convert|    X    |     ND   |    ND    |   ND  |
   +------------------------------------------------------------------+
   | IPv4Addr |convert|convert|   ND    |     X    |    ND    |   ND
   +------------------------------------------------------------------+
   | IPv6Addr |convert|   ND  |   ND    | v4 format|     X    |   ND  |
   +------------------------------------------------------------------+
   | MACAddr  |   ND  |   ND  |   ND    |    ND    |    ND    |    X  |
   +------------------------------------------------------------------+
 
   Composing a simple action requires that an instance of the class
   SimplePolicyAction be created, and that instances of the variable and
   value classes that it uses also exist.  Note that the variable and/or
   value instances may already exist as reusable objects in an appropriate
   ReusablePolicyContainer.
 
   Two aggregations are used in order to create the pair <variable> <value>.
   The aggregation PolicyVariableInSimplePolicyAction relates a
   SimplePolicyAction to a single variable instance.  Similarly, the
   aggregation PolicyValueInSimplePolicyAction relates a SimplePolicyAction
   to a single value instance.  Both aggregations are defined in this
   document.
 
   Figure 6 depicts a SimplePolicyAction with its associated variable and
   value.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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                                 +-----------------------+
                                 | SimplePolicyAction    |
                                 |                       |
                                 +-----------------------+
                                       *         @
                                       *         @
                 +------------------+  *         @  +---------------+
                 | (PolicyVariable) |***         @@@| (PolicyValue) |
                 +------------------+               +---------------+
                    #            #
                    #    ooo     #
                    #            #
      +---------------+        +---------------+
      | (PolicyValue) |  ooo   | (PolicyValue) |
      +---------------+        +---------------+
 
      Aggregation Legend:
        ****  PolicyVariableInSimplePolicyAction
        @@@@  PolicyValueInSimplePolicyAction
        ####  PolicyValueConstraintInVariable
 
   Figure 6.    SimplePolicyAction
 
 4.8.5. Policy Variables
 
   A variable generically represents information that changes (or "varies"),
   and that is set or evaluated by software.  In policy, conditions and
   actions can abstract information as "policy variables" to be evaluated in
   logical expressions, or set by actions.
 
   PCIMe defines two types of PolicyVariables, a PolicyImplicitVariable and
   a PolicyExplicitVariable.  The semantic difference between these classes
   is based on modeling context.  Explicit variables are bound to exact
   model constructs, while implicit variables are defined and evaluated
   outside of a model, in a more subjective context.  For example, one can
   imagine a PolicyCondition testing for a CIM ManagedSystemElement's Status
   property set to "Error."  The Status property is an explicitly defined
   PolicyVariable (i.e., it is defined in the context of the CIM Schema and
   evaluated in the context of a specific instance).  On the other hand,
   network packets are not explicitly modeled or instantiated, since there
   is no perceived value (at this time) in managing at the packet level.
   Therefore, a PolicyCondition can make no explicit reference to a model
   construct that represents a network packet's source address.  In this
   case, an implicit PolicyVariable is defined to allow evaluation of a
   packet's source address.
 
 
 4.8.6. Explicitly Bound Policy Variables
 
   Explicitly bound policy variables indicate the class and property names
   of the model construct to be evaluated or set.  The CIM Schema defines
   and constrains "appropriate" values for the variable (i.e., model
 
 
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   property) using data types and other information such as class/property
   qualifiers.
 
 
   A PolicyExplicitVariable is "explicit" because its model semantics are
   exactly defined.  It is NOT explicit due to an exact binding to a
   particular object.  If PolicyExplicitVariable is only tied to instances
   (either via association or by a object identification property in the
   class itself), then we are forcing element-specific rules.  On the other
   hand, if we only specify the object's model context (class and property
   name), but leave the binding to the policy framework (for example, using
   policy roles), then greater flexibility results for either general or
   element-specific rules.
 
   For example, an element-specific rule is obtained by a condition
   (variable/operator/value triplet) that defines, for example, CIM
   LogicalDevice DeviceID="12345".  Alternately, if a PolicyRule's
   PolicyRoles is "edge device" and your condition (variable/operator/value
   triplet) is Status="Error", then a general rule results for all edge
   devices in error.
 
   Refer to Section 5.10 for the formal definition of the class
   PolicyExplicitVariable.
 
 
 4.8.7. Implicitly Bound Policy Variables
 
   Implicitly bound policy variables define the data type and semantics of a
   variable.  This determines how the variable is bound to a value in a
   condition clause.  Further instructions are provided for specifying data
   type and/or value constraints for implicitly bound variables.
 
   Implicitly bound variables can be interpreted by different sub-models to
   mean different things, depending on the particular context in which they
   are used.  For example, an implicitly bound variable named "SourceIP" may
   be interpreted by a QoS policy information model to denote the source
   address field in the IP header of a packet if a device is configured to
   select certain packets for particular treatment.  The same variable may
   be bound to the sender address delivered by a RSVP PATH message for a
   decision by a policy server.  It is incumbent upon the particular domain-
   specific information model to provide full and unambiguous interpretation
   details (binding rules, type and value constraints) for the implicitly
   bound variables it uses.
 
   PCIMe introduces an abstract class, PolicyImplicitVariable, to model
   implicitly bound variables.  This class is derived from the abstract
   class PolicyVariable also defined in PCIMe.  Each of the implicitly bound
   variables introduced by PCIMe (and those that are introduced by domain-
   specific sub-models) MUST be derived from the PolicyImplicitVariable
   class.  The rationale for using this mechanism for modeling is explained
   below in Section 4.8.9.
 
   A domain-specific policy information model that extends PCIMe may define
   additional implicitly bound variables either by deriving them directly
 
 
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   from the class PolicyImplicitVariable, or by further refining an existing
   variable class such as SourcePort.  When refining a class such as
   SourcePort, existing binding rules, type or value constraints may be
   narrowed.
 
 4.8.8. Structure and Usage of Pre-Defined Variables
 
   A class derived from PolicyImplicitVariable to model a particular
   implicitly bound variable SHOULD be constructed so that its name depicts
   the meaning of the variable.  For example, a class defined to model the
   source port of a TCP/UDP flow SHOULD be named 'SourcePort'.
 
   PCIMe defines one association and one general-purpose mechanism that
   together characterize each of the implicitly bound variables that it
   introduces:
 
     1.  The PolicyValueConstraintInVariable association defines the set of
         value classes that could be matched to this variable.
 
     2.  The list of constraints on the values that the PolicyVariable can
         hold (i.e., values that the variable must match) are defined by
         the appropriate properties of an associated PolicyValue class.
 
   In the example presented above, a PolicyImplicitVariable represents the
   SourcePort of incoming traffic.  The ValueTypes property of an instance
   of this class will hold the class name PolicyIntegerValue.  This by
   itself constrains the data type of the SourcePort instance to be an
   integer.  However, we can further constrain the particular values that
   the SourcePort variable can hold by entering valid ranges in the
   IntegerList property of the PolicyIntegerValue instance (0 - 65535 in
   this document).
 
   The combination of the VariableName and the
   PolicyValueConstraintInVariable association provide a consistent and
   extensible set of metadata that define the semantics of variables that
   are used to form policy conditions.  Since the
   PolicyValueConstraintInVariable association points to another class, any
   of the properties in the PolicyValue class can be used to constrain
   values that the PolicyImplicitVariable can hold. For example:
 
     o   The ValueTypes property can be used to ensure that only proper
         classes are used in the expression.  For example, the SourcePort
         variable will not be allowed to ever be of type
         PolicyIPv4AddrValue, since source ports have different semantics
         than IP addresses and may not be matched.  However, integer value
         types are allowed as the property ValueTypes holds the string
         "PolicyIntegerValue", which is the class name for integer values.
 
     o   The PolicyValueConstraintInVariable association also ensures that
         variable-specific semantics are enforced (e.g., the SourcePort
         variable may include a constraint association to a value object
         defining a specific integer range that should be matched).
 
 
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 4.8.9. Rationale for Modeling Implicit Variables as Classes
 
 An implicitly bound variable can be modeled in one of several ways,
 including a single class with an enumerator for each individual implicitly
 bound variable and an abstract class extended for each individual variable.
 The reasons for using a class inheritance mechanism for specifying
 individual implicitly bound variables are these:
 
 
     1.  It is easy to extend.  A domain-specific information model can
         easily extend the PolicyImplicitVariable class or its subclasses
         to define domain-specific and context-specific variables.  For
         example, a domain-specific QoS policy information model may
         introduce an implicitly bound variable class to model applications
         by deriving a qosApplicationVariable class from the
         PolicyImplicitVariable abstract class.
 
     2.  Introduction of a single structural class for implicitly bound
         variables would have to include an enumerator property that
         contains all possible individual implicitly bound variables.  This
         means that a domain-specific information model wishing to
         introduce an implicitly bound variable must extend the enumerator
         itself.  This results in multiple definitions of the same class,
         differing in the values available in the enumerator class.  One
         definition, in this document, would include the common implicitly
         bound variables' names, while a second definition, in the domain-
         specific information model document, may include additional values
         ('qosApplicationVariable' in the example above).  It wouldnÆt even
         be obvious to the application developer that multiple class
         definitions existed.  It would be harder still for the application
         developer to actually find the correct class to use.
 
     3.  In addition, an enumerator-based definition would require each
         additional value to be registered with IANA to ascertain adherence
         to standards. This would make the process cumbersome.
 
     4.  A possible argument against the inheritance mechanism would cite
         the fact that this approach results in an explosion of class
         definitions compared to an enumerator class, which only introduces
         a single class.  While, by itself, this is not a strike against
         the approach, it may be argued that data models implemented, which
         are mapped to this information model, may be more difficult to
         optimize for applications.  This argument is rejected on the
         grounds that application optimization is of lesser value for an
         information model than clarity and ease of extension.  In
         addition, it is hard to claim that the inheritance model places an
         absolute burden on the optimization.  For example, a data model
         may still use enumeration to denote instances of pre-defined
         variables and claim PCIMe compliance, as long as the data moel can
         be mapped correctly to the definitions specified in this document.
         Furthermore, the very nature of implicitly bound variables is to
         be interpreted in context.  This means that unless an additional
         variable is required by a sub-model (in which case both approaches
 
 
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         result in some overhead), there's an upper limit on the class
         explosion.  After all, once properly documented, no need exists
         for a sub-model to add a class definition.  The implementation
         needs only to cite and use the PCIMe variable, but impose the
         documented context-dependent semantics.
 
 4.8.10. Policy Values
 
   The abstract class PolicyValue is used for modeling values and constants
   used in policy conditions.  Different value types are derived from this
   class, to represent the various attributes required.  Extensions of the
   abstract class PolicyValue, defined in this document, provide a list of
   values for representing basic network attributes.  Values can be used to
   represent constants as named values.  Named values can be kept in a
   reusable policy container to be reused by multiple conditions.  Examples
   of constants include well-known ports, well-known protocols, server
   addresses, and other similar concepts.
 
   The PolicyValue subclasses define three basic types of values: scalars,
   ranges and sets.  For example, a well-known port number could be defined
   using the PolicyIntegerValue class, defining a single value (80 for
   HTTP), a range (80-88), or a set (80, 82, 8080) of ports, respectively.
   For details, please see the class definition for each value type in
   Section 5.12 of this document.
 
   PCIMe defines the following subclasses of the abstract class PolicyValue:
 
   Classes for general use:
 
     - PolicyStringValue,
     - PolicyIntegerValue,
     - PolicyBitStringValue
     - PolicyBooleanValue.
 
   Classes for layer 3 Network values:
 
     - PolicyIPv4AddrValue,
     - PolicyIPv6AddrValue.
 
   Classes for layer 2 Network values:
 
     - PolicyMACAddrValue.
 
   For details, please see the class definition section of each class in
   Section 5.14 of this document.
 
 4.9. Packet Filtering
 
   In addition to filling in the holes in the overall Policy infrastructure,
   PCIMe proposes a single mechanism for expressing packet filters in policy
   conditions.  This is being done in response to concerns that even though
   the initial "wave" of submodels derived from PCIM were all filtering on
 
 
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   IP packets, each was doing it in a slightly different way.  PCIMe
   proposes a common way to express IP packet filters.  The following figure
   illustrates how packet-filtering conditions are expressed in PCIMe.
 
                    +---------------------------------+
                    | CompoundFilterCondition         |
                    |   - IsMirrored   boolean        |
                    |   - ConditionListType (DNF|CNF) |
                    +---------------------------------+
                     +               +               +
                     +               +               +
                     +               +               +
                 SimplePC        SimplePC        SimplePC
                 *      @        *      @        *      @
                 *      @        *      @        *      @
                 *      @        *      @        *      @
     FlowDirection    "In"     SrcIP  <addr1>  DstIP  <addr2>
 
   Aggregation Legend:
     ++++  PolicyConditionInPolicyCondition
     ****  PolicyVariableInSimplePolicyCondition
     @@@@  PolicyValueInSimplePolicyCondition
 
   Figure 7.    Packet Filtering in Policy Conditions
 
   In Figure 7, each SimplePolicyCondition represents a single field to be
   filtered on: Source IP address, Destination IP address, Source port, etc.
   An additional SimplePolicyCondition indicates the direction that a packet
   is traveling on an interface: inbound or outbound.  Because of the
   FlowDirection condition, care must be taken in aggregating a set of
   SimplePolicyConditions into a CompoundFilterCondition.  Otherwise, the
   resulting CompoundPolicyCondition may match all inbound packets, or all
   outbound packets, when this is probably not what was intended.
 
   Individual SimplePolicyConditions may be negated when they are aggregated
   by a CompoundFilterCondition.
 
   CompoundFilterCondition is a subclass of CompoundPolicyCondition.  It
   introduces one additional property, the Boolean property IsMirrored.  The
   purpose of this property is to allow a single CompoundFilterCondition to
   match packets traveling in both directions on a higher-level connection
   such as a TCP session.  When this property is TRUE, additional packets
   match a filter, beyond those that would ordinarily match it.  An example
   will illustrate how this property works.
 
   Suppose we have a CompoundFilterCondition that aggregates the following
   three filters, which are ANDed together:
 
     o   FlowDirection = "In"
     o   Source IP = 9.1.1.1
     o   Source Port = 80
 
 
 
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   Regardless of whether IsMirrored is TRUE or FALSE, inbound packets will
   match this CompoundFilterCondition if their Source IP address = 9.1.1.1
   and their Source port = 80.  If IsMirrored is TRUE, however, an outbound
   packet will also match the CompoundFilterCondition if its Destination IP
   address = 9.1.1.1 and its Destination port = 80.
 
   IsMirrored "flips" the following Source/Destination packet header fields:
 
     o   FlowDirection "In" / FlowDirection "Out"
     o   Source IP address / Destination IP address
     o   Source port / Destination port
     o   Source MAC address / Destination MAC address
     o   Source [layer-2] SAP / Destination [layer-2] SAP.
 
 
 5. Class Definitions
 
   The following definitions supplement those in PCIM itself.  PCIM
   definitions that are not DEPRECATED here are still current parts of the
   overall Policy Core Information Model.
 
 5.1. The Abstract Class "PolicySet"
 
   PolicySet is an abstract class that may group policies into a structured
   set of policies.
 
     NAME             PolicySet
     DESCRIPTION      An abstract class that represents a set of policies
                      that form a coherent set.  The set of contained
                      policies has a common decision strategy and a common
                      set of policy roles.  Subclasses include PolicyGroup
                      and PolicyRule.
     DERIVED FROM     Policy
     ABSTRACT         TRUE
     PROPERTIES       PolicyDecisionStrategy
                      PolicyRoles
 
   The PolicyDecisionStrategy property specifies the evaluation method for
   policy groups and rules contained within the policy set.
 
     NAME             PolicyDecisionStrategy
     DESCRIPTION      The evaluation method used for policies contained in
                      the PolicySet.  FirstMatching enforces the actions of
                      the first rule that evaluates to TRUE; AllMatching
                      enforces the actions of all rules that evaluate to
                      TRUE.
     SYNTAX           uint16
     VALUES           1 [FirstMatching], 2 [AllMatching]
     DEFAULT VALUE    1 [FirstMatching]
 
   The definition of PolicyRoles is unchanged from PCIM.  It is, however,
   moved from the class Policy up to the superclass PolicySet.
 
 
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 5.2. Updates to PCIM's Class "PolicyGroup"
 
   The PolicyGroup class is modified to be derived from PolicySet.
 
     NAME             PolicyGroup
     DESCRIPTION      A container for a set of related PolicyRules and
                      PolicyGroups.
     DERIVED FROM     PolicySet
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.3. Updates to PCIM's Class "PolicyRule"
 
   The PolicyRule class is modified to be derived from PolicySet, and to
   deprecate the use of Priority in the rule.  PolicyRoles is now inherited
   from the parent class PolicySet.  Finally, a new property
   ExecutionStrategy is introduced, paralleling the property of the same
   name in the class CompoundPolicyAction.
 
     NAME             PolicyRule
     DESCRIPTION      The central class for representing the "If Condition
                      then Action" semantics associated with a policy rule.
     DERIVED FROM     PolicySet
     ABSTRACT         FALSE
     PROPERTIES       Enabled
                      ConditionListType
                      RuleUsage
                      Priority DEPRECATED FOR PolicySetComponent.Priority
                      Mandatory
                      SequencedActions
                      ExecutionStrategy
 
   The property ExecutionStrategy defines the execution strategy to be used
   upon the sequenced actions aggregated by this PolicyRule. (An equivalent
   ExecutionStrategy property is also defined for the CompoundPolicyAction
   class, to provide the same indication for the sequenced actions
   aggregated by a CompoundPolicyAction.)  This draft defines four execution
   strategies:
 
     Mandatory Do all û execute ALL actions that are part of the modeled
                        set.  If one or more of the actions cannot be
                        executed, none of the actions should be executed.
     Do until success û execute actions according to predefined order, until
                        successful execution of a single action.
     Do All -           execute ALL actions which are part of the modeled
                        set, according to their predefined order. Continue
                        doing this, even if one or more of the actions
                        fails.
     Do until Failure - execute actions according to predefined order, until
                        the first failure in execution of a single sub-
                        action.
 
 
 
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   The property definition is as follows:
 
     NAME             ExecutionStrategy
     DESCRIPTION      An enumeration indicating how to interpret the action
                      ordering for the actions aggregated by this
                      PolicyRule.
     SYNTAX           uint16 (ENUM, {1=Mandatory Do All, 2=Do Until Success,
                      3=Do All, 4=Do Until Failure} )
     DEFAULT VALUE    Do All (3)
 
 5.4. The Class "SimplePolicyCondition"
 
   A simple policy condition is composed of an ordered triplet:
 
     <Variable>  MATCH  <Value>
 
   No formal modeling of the MATCH operator is provided.  The 'match'
   relationship is implied.  Such simple conditions are evaluated by
   answering the question:
 
     Does <variable> match <value>?
 
   The 'match' relationship is to be interpreted by analyzing the variable
   and value instances associated with the simple condition.
 
   Simple conditions are building blocks for more complex Boolean
   Conditions, modeled by the CompoundPolicyCondition class.
 
   The SimplePolicyCondition class is derived from the PolicyCondition class
   defined in PCIM.
 
   A variable and a value must be associated with a simple condition to make
   it a meaningful condition, using, respectively, the aggregations
   PolicyVariableInSimplePolicyCondition and
   PolicyValueInSimplePolicyCondition.
 
   The class definition is as follows:
 
     NAME             SimplePolicyCondition
     DERIVED FROM     PolicyCondition
     ABSTRACT         False
     PROPERTIES       (none)
 
 5.5. The Class "CompoundPolicyCondition"
 
   This class represents a compound policy condition, formed by aggregation
   of simpler policy conditions.
 
     NAME             CompoundPolicyCondition
     DESCRIPTION      A subclass of PolicyCondition that introduces the
                      ConditionListType property, used for assigning DNF /
                      CNF semantics to subordinate policy conditions.
     DERIVED FROM     PolicyCondition
 
 
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     ABSTRACT         FALSE
     PROPERTIES       ConditionListType
 
   The ConditionListType property is used to specify whether the list of
   policy conditions associated with this compound policy condition is in
   disjunctive normal form (DNF) or conjunctive normal form (CNF).  If this
   property is not present, the list type defaults to DNF.  The property
   definition is as follows:
 
     NAME             ConditionListType
     DESCRIPTION      Indicates whether the list of policy conditions
                      associated with this policy rule is in disjunctive
                      normal form (DNF) or conjunctive normal form (CNF).
     SYNTAX           uint16
     VALUES           DNF(1), CNF(2)
     DEFAULT VALUE    DNF(1)
 
 
 5.6. The Class "CompoundFilterCondition"
 
   This subclass of CompoundPolicyCondition introduces one additional
   property, the boolean IsMirrored.  This property turns on or off the
   "flipping" of corresponding source and destination fields in a filter
   specification.
 
     NAME             CompoundFilterCondition
     DESCRIPTION      A subclass of CompoundPolicyCondition that introduces
                      the IsMirrored property.
     DERIVED FROM     CompoundPolicyCondition
     ABSTRACT         FALSE
     PROPERTIES       IsMirrored
 
   The IsMirrored property indicates whether packets that "mirror" a
   compound filter condition should be treated as matching the filter.  The
   property definition is as follows:
 
     NAME             IsMirrored
     DESCRIPTION      Indicates whether packets that mirror the specified
                      filter are to be treated as matching the filter.
     SYNTAX           boolean
     DEFAULT VALUE    FALSE
 
 5.7. The Class "SimplePolicyAction"
 
   The SimplePolicyAction class models the elementary set operation. "SET
   <variable> TO <value>".  The set operator MUST overwrite an old value of
   the variable.
 
   Two aggregations are used in order to create the pair <variable> <value>.
   The aggregation PolicyVariableInSimplePolicyAction relates a
   SimplePolicyAction to a single variable instance.  Similarly, the
   aggregation PolicyValueInSimplePolicyAction relates a SimplePolicyAction
 
 
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   to a single value instance.  Both aggregations are defined in this
   document.
 
 
     NAME             SimplePolicyAction
     DESCRIPTION      A subclass of PolicyAction that introduces the notion
                      of "SET variable TO value".
     DERIVED FROM     PolicyAction
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.8. The Class "CompoundPolicyAction"
 
   The CompoundPolicyAction class is used to represent an expression
   consisting of an ordered sequence of action terms.  Each action term is
   represented as a subclass of the PolicyAction class, defined in [PCIM].
   Compound actions are constructed by associating dependent action terms
   together using the PolicyActionInPolicyAction aggregation.
 
   The class definition is as follows:
 
     NAME             CompoundPolicyAction
     DESCRIPTION      A class for representing sequenced action terms.  Each
                      action term is defined to be a subclass of the
                      PolicyAction class.
     DERIVED FROM     PolicyAction
     ABSTRACT         FALSE
     PROPERTIES       SequencedActions
                      ExecutionStrategy
 
   This is a concrete class, and is therefore directly instantiable.
 
   The Property SequencedActions is identical to the SequencedActions
   property defined in PCIM for the class PolicyRule.
 
   The property ExecutionStrategy defines the execution strategy to be used
   upon the sequenced actions associated with this compound action. (An
   equivalent ExecutionStrategy property is also defined for the PolicyRule
   class, to provide the same indication for the sequenced actions
   associated with a PolicyRule.)  This draft defines four execution
   strategies:
 
     Mandatory Do all û execute ALL actions that are part of the modeled
                        set.  If one or more of the sub-actions cannot be
                        executed, none of the actions should be executed.
     Do until success û execute actions according to predefined order, until
                        successful execution of a single sub-action.
     Do All -           execute ALL actions which are part of the modeled
                        set, according to their predefined order. Continue
                        doing this, even if one or more of the sub-actions
                        fails.
 
 
 
 
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     Do until Failure - execute actions according to predefined order, until
                        the first failure in execution of a single sub-
                        action.
 
   The property definition is as follows:
 
     NAME             ExecutionStrategy
     DESCRIPTION      An enumeration indicating how to interpret the action
                      ordering for the actions aggregated by this
                      CompoundPolicyAction.
     SYNTAX           uint16 (ENUM, {1=Mandatory Do All, 2=Do Until Success,
                      3=Do All, 4=Do Until Failure} )
     DEFAULT VALUE    Do All (3)
 
 5.9. The Abstract Class "PolicyVariable"
 
   Variables are used for building individual conditions.  The variable
   specifies the property of a flow or an event that should be matched when
   evaluating the condition.  However, not every combination of a variable
   and a value creates a meaningful condition. For example, a source IP
   address variable can not be matched against a value that specifies a port
   number.  A given variable selects the set of matchable value types.
 
   A variable can have constraints that limit the set of values within a
   particular value type that can be matched against it in a condition.  For
   example, a source-port variable limits the set of values to represent
   integers to the range of 0-65535.  Integers outside this range cannot be
   matched to the source-port variable, even though they are of the correct
   data type.  Constraints for a given variable are indicated through the
   PolicyValueConstraintInVariable association.
 
   The PolicyVariable is an abstract class.  Implicit and explicit context
   variable classes are defined as sub classes of the PolicyVariable class.
   A set of implicit variables is defined in this document as well.
 
 
   The class definition is as follows:
 
     NAME             PolicyVariable
     DERIVED FROM     Policy
     ABSTRACT         TRUE
     PROPERTIES       (none)
 
 5.10. The Class "PolicyExplicitVariable"
 
   Explicitly defined policy variables are evaluated within the context of
   the CIM Schema and its modeling constructs.  The PolicyExplicitVariable
   class indicates the exact model property to be evaluated or manipulated.
 
   The class definition is as follows:
 
     NAME             PolicyExplicitVariable
     DERIVED FROM     PolicyVariable
 
 
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     ABSTRACT         False
     PROPERTIES       ModelClass, ModelProperty
 
 5.10.1. The Single-Valued Property "ModelClass"
 
   This property is a string specifying the class name whose property is
   evaluated or set as a PolicyVariable.  The property is defined as
   follows:
 
     NAME             ModelClass
     SYNTAX           String
 
 5.10.2. The Single-Valued Property ModelProperty
 
   This property is a string specifying the property name, within the
   ModelClass, which is evaluated or set as a PolicyVariable.  The property
   is defined as follows:
 
     NAME             ModelProperty
     SYNTAX           String
 
 5.11. The Abstract Class "PolicyImplicitVariable"
 
   Implicitly defined policy variables are evaluated outside of the context
   of the CIM Schema and its modeling constructs.  Subclasses specify the
   data type and semantics of the PolicyVariables.
 
   Interpretation and evaluation of a PolicyImplicitVariable can vary,
   depending on the particular context in which it is used.  For example, a
   "SourceIP" address may denote the source address field of an IP packet
   header, or the sender address delivered by an RSVP PATH message.
 
   The class definition is as follows:
 
     NAME             PolicyImplicitVariable
     DERIVED FROM     PolicyVariable
     ABSTRACT         True
     PROPERTIES       ValueTypes[ ]
 
 5.11.1. The Multi-Valued Property "ValueTypes"
 
   This property is a set of strings specifying an unordered list of
   possible value/data types that can be used in simple conditions and
   actions, with this variable.  The value types are specified by their
   class names (subclasses of PolicyValue such as PolicyStringValue).  The
   list of class names enables an application to search on a specific name,
   as well as to ensure that the data type of the variable is of the correct
   type.
 
   The list of default ValueTypes for each subclass of
   PolicyImplicitVariable is specified within that variable's definition.
 
 
 
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   The property is defined as follows:
 
     NAME             ValueTypes
     SYNTAX           String
 
 5.12. Subclasses of "PolicyImplicitVariable" Specified in PCIMe
 
   The following subclasses of PolicyImplicitVariable are defined in PCIMe.
 
 5.12.1. The Class "PolicySourceIPVariable"
 
     NAME             PolicySourceIPVariable
     DESCRIPTION      The source IP address.
 
                      ALLOWED VALUE TYPES:
                        - PolicyIPv4AddrValue
                        - PolicyIPv6AddrValue
 
     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.12.2. The Class "PolicyDestinationIPVariable"
 
     NAME             PolicyDestinationIPVariable
     DESCRIPTION      The destination IP address.
 
                      ALLOWED VALUE TYPES:
                        - PolicyIPv4AddrValue
                        - PolicyIPv6AddrValue
 
     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.12.3. The Class "PolicySourcePortVariable"
 
     NAME             PolicySourcePortVariable
     DESCRIPTION      Ports are defined as the abstraction that transport
                      protocols use to distinguish among multiple
                      destinations within a given host computer.  For TCP
                      and UDP flows, the PolicySourcePortVariable is
                      logically bound to the source port field.
 
                      ALLOWED VALUE TYPES:
                        - PolicyIntegerValue
                        - PolicyBitStringValue
 
     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 
 
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 5.12.4. The Class "PolicyDestinationPortVariable"
 
     NAME             PolicyDestinationPortVariable
     DESCRIPTION      Ports are defined as the abstraction that transport
                      protocols use to distinguish among multiple
                      destinations within a given host computer.  For TCP
                      and UDP flows, the PolicyDestinationPortVariable is
                      logically bound to the destination port field.
 
                      ALLOWED VALUE TYPES:
                        - PolicyIntegerValue
                        - PolicyBitStringValue
 
     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.12.5. The Class "PolicyIPProtocolVariable"
 
     NAME             PolicyIPProtocolVariable
     DESCRIPTION      The IP protocol number.
 
                      ALLOWED VALUE TYPES:
                        - PolicyIntegerValue
                        - PolicyBitStringValue
 
     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.12.6. The Class "PolicyIPVersionVariable"
 
     NAME             PolicyIPVersionVariable
     DESCRIPTION      The IP version number.  The well-known values are 4
                      and 6.
 
                      ALLOWED VALUE TYPES:
                        - PolicyIntegerValue
                        - PolicyBitStringValue
 
     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.12.7. The Class "PolicyIPToSVariable"
 
     NAME             PolicyIPToSVariable
     DESCRIPTION      The IP TOS octet.
 
                      ALLOWED VALUE TYPES:
                        - PolicyIntegerValue
                        - PolicyBitStringValue
 
 
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     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.12.8. The Class "PolicyDSCPVariable"
 
     NAME             PolicyDSCPVariable
     DESCRIPTION      The 6 bit Differentiated Service Code Point.
 
                      ALLOWED VALUE TYPES:
                        - PolicyIntegerValue
                        - PolicyBitStringValue
 
     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.12.9. The Class "PolicySourceMACVariable"
 
     NAME             PolicySourceMACVariable
     DESCRIPTION      The source MAC address.
 
                      ALLOWED VALUE TYPES:
                        - PolicyMACAddrValue
 
     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.12.10. The Class "PolicyDestinationMACVariable"
 
     NAME             PolicyDestinationMACVariable
     DESCRIPTION      The destination MAC address.
 
                      ALLOWED VALUE TYPES:
                        - PolicyMACAddrValue
 
     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.12.11. The Class "PolicyVLANVariable"
 
     NAME             PolicyVLANVariable
     DESCRIPTION      The virtual Bridged Local Area Network Identifier, a
                      12-bit field as defined in the IEEE 802.1q standard.
 
                      ALLOWED VALUE TYPES:
                        - PolicyIntegerValue
                        - PolicyBitStringValue
 
 
 
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     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.12.12. The Class "PolicyCoSVariable"
 
     NAME             PolicyCoSVariable
     DESCRIPTION      Class of Service, a 3-bit field, used in the layer 2
                      header to select the forwarding treatment.  Bound to
                      the IEEE 802.1q user-priority field.
 
                      ALLOWED VALUE TYPES:
                        - PolicyIntegerValue
                        - PolicyBitStringValue
 
     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.12.13. The Class "PolicyEthertypeVariable"
 
     NAME             PolicyEthertypeVariable
     DESCRIPTION      The Ethertype protocol number of Ethernet frames.
 
                      ALLOWED VALUE TYPES:
                        - PolicyIntegerValue
                        - PolicyBitStringValue
 
     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.12.14. The Class "PolicySourceSAPVariable"
 
     NAME             PolicySourceSAPVariable
     DESCRIPTION      The Source SAP number.
 
                      ALLOWED VALUE TYPES:
                        - PolicyIntegerValue
                        - PolicyBitStringValue
 
     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.12.15. The Class "PolicyDestinationSAPVariable"
 
     NAME             PolicyDestinationSAPVariable
     DESCRIPTION      The Destination SAP number.
 
                      ALLOWED VALUE TYPES:
                        - PolicyIntegerValue
 
 
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                        - PolicyBitStringValue
 
     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.12.16. The Class "PolicySNAPVariable"
 
     NAME             PolicySNAPVariable
     DESCRIPTION      The protocol number over a SNAP SAP encapsulation.
 
                      ALLOWED VALUE TYPES:
                        - PolicyIntegerValue
                        - PolicyBitStringValue
 
     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.12.17. The Class "PolicyFlowDirectionVariable"
 
     NAME             PolicyFlowDirectionVariable
     DESCRIPTION      The direction of a flow relative to a network element.
                      Direction may be "IN" and/or "OUT".
 
                      ALLOWED VALUE TYPES:
                        - PolicyStringValue
 
     DERIVED FROM     PolicyImplicitVariable
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
   To match on both inbound and outbound flows, the associated
   PolicyStringValue object has two entries in its StringList property: "IN"
   and "OUT".
 
 5.13. The Abstract Class "PolicyValue"
 
   This is an abstract class that serves as the base class for all
   subclasses that are used to define value objects in the PCIMe.  It is
   used for defining values and constants used in policy conditions.  The
   class definition is as follows:
 
     NAME             PolicyValue
     DERIVED FROM     Policy
     ABSTRACT         True
     PROPERTIES       (none)
 
 
 
 
 
 
 
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 5.14. Subclasses of "PolicyValue" Specified in PCIMe
 
   The following subsections contain the PolicyValue subclasses defined in
   PCIMe.  Additional subclasses may be defined in models derived from
   PCIMe.
 
 5.14.1. The Class "PolicyIPv4AddrValue"
 
   This class is used to provide a list of IPv4Addresses, hostnames and
   address range values to be matched against in a policy condition.  The
   class definition is as follows:
 
     NAME             PolicyIPv4AddrValue
     DERIVED FROM     PolicyValue
     ABSTRACT         False
     PROPERTIES       IPv4AddrList[ ]
 
   The IPv4AddrList property provides an unordered list of strings, each
   specifying a single IPv4 address, a hostname, or a range of IPv4
   addresses, according to the ABNF definition [8] of an IPv4 address, as
   specified below:
 
       IPv4address = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT
       IPv4prefix  = IPv4address "/" 1*2DIGIT
       IPv4range = IPv4address"-"IPv4address
       IPv4maskedaddress = IPv4address","IPv4address
       Hostname (as defined in [9])
 
 
   In the above definition, each string entry is either:
 
     1.  A single Ipv4address in dot notation, as defined above.  Example:
         121.1.1.2
 
     2.  An IPv4prefix address range, as defined above, specified by an
         address and a prefix length, separated by "/".  Example:
         2.3.128.0/15
 
     3.  An IPv4range address range defined above, specified by a starting
         address in dot notation and an ending address in dot notation,
         separated by "-".  The range includes all addresses between the
         range's starting and ending addresses, including these two
         addresses.  Example: 1.1.22.1-1.1.22.5
 
     4.  An IPv4maskedaddress address range, as defined above, specified by
         an address and mask.  The address and mask are represented in dot
         notation, separated by a comma ",".  The masked address appears
         before the comma, and the mask appears after the comma.  Example:
         2.3.128.0,255.255.248.0.
 
     5.  A single Hostname.  The Hostname format follows the guidelines and
         restrictions specified in [9].  Example: www.bigcompany.com.
 
 
 
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   The property definition is as follows:
 
     NAME             IPv4AddrList
     SYNTAX           String
     FORMAT           IPv4address | IPv4prefix | IPv4range |
                      IPv4maskedaddress | hostname
 
 5.14.2. The Class "PolicyIPv6AddrValue
 
   This class is used to define a list of IPv6 addresses, hostnames, and
   address range values. The class definition is as follows:
 
     NAME             PolicyIPv6AddrValue
     DERIVED FROM     PolicyValue
     ABSTRACT         False
     PROPERTIES       IPv6AddrList[ ]
 
   The property IPv6AddrList provides an unordered list of strings, each
   specifying an IPv6 address, a hostname, or a range of IPv6 addresses.
   IPv6 address format definition uses the standard address format defined
   in [10].  The ABNF definition [8] as specified in [10] is:
 
       IPv6address = hexpart [ ":" IPv4address ]
       IPv4address = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT
       IPv6prefix  = hexpart "/" 1*2DIGIT
       hexpart = hexseq | hexseq "::" [ hexseq ] | "::" [ hexseq ]
       hexseq  = hex4 *( ":" hex4)
       hex4    = 1*4HEXDIG
       IPv6range = IPv6address"-"IPv6address
       IPv6maskedaddress = IPv6address","IPv6address
       Hostname (as defines in [NAMES])
 
 
   Each string entry is either:
 
     1.  A single IPv6address as defined above.
 
     2.  A single Hostname.  Hostname format follows guidelines and
         restrictions specified in [9].
 
     3.  An IPv6range address range, specified by a starting address in dot
         notation and an ending address in dot notation, separated by "-".
         The range includes all addresses between the range's starting and
         ending addresses, including these two addresses.
 
     4.  An IPv4maskedaddress address range defined above specified by an
         address and mask. The address and mask are represented in dot
         notation separated by a comma ",".
 
     5.  A single IPv6prefix as defined above.
 
 
 
 
 
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 5.14.3. The Class "PolicyMACAddrValue"
 
   This class is used to define a list of MAC addresses and MAC address
   range values.  The class definition is as follows:
 
     NAME             PolicyMACAddrValue
     DERIVED FROM     PolicyValue
     ABSTRACT         False
     PROPERTIES       MACAddrList[ ]
 
 
   The property MACAddrList provides an unordered list of strings, each
   specifying a MAC address or a range of MAC addresses.  The 802 MAC
   address canonical format is used. The ABNF definition [8] is:
 
       MACaddress  = 1*4HEXDIG ":" 1*4HEXDIG ":" 1*4HEXDIG
       MACmaskedaddress = MACaddress","MACaddress
 
 
   Each string entry is either:
 
     1.  A single MAC address. Example: 0000:00A5:0000
 
     2.  A MACmaskedaddress address range defined specified by an address
         and mask.  The mask specifies the relevant bits in the address.
         Example: 0000:00A5:0000,FFFF:FFFF:0000 defines a range of MAC
         addresses in which the first four octets are equal to 0000:00A5.
 
   The property definition is as follows:
 
     NAME             MACAddrList
     SYNTAX           String
     FORMAT           MACaddress | MACmaskedaddress
 
 5.14.4. The Class "PolicyStringValue"
 
   This class is used to represent a single string value, or a set of string
   values.  Each value can have wildcards. The class definition is as
   follows:
 
     NAME             PolicyStringValue
     DERIVED FROM     PolicyValue
     ABSTRACT         False
     PROPERTIES       StringList[ ]
 
   The property StringList provides an unordered list of strings, each
   representing a single string with wildcards.  The asterisk character "*"
   is used as a wildcard, and represents an arbitrary substring replacement.
   For example, the value "abc*def" matches the string "abcxyzdef", and the
   value "abc*def*" matches the string "abcxxxdefyyyzzz".  The syntax
   definition is identical to the substring assertion syntax defined in
   [11].  If the asterisk character is required as part of the string value
   itself, it MUST be quoted as described in section 4.3 of [11].
 
 
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   The property definition is as follows:
 
     NAME                 StringList
     SYNTAX               String
 
 5.14.5. The Class "PolicyBitStringValue"
 
   This class is used to represent a single bit string value, or a set of
   bit string values.  The class definition is as follows:
 
     NAME             PolicyBitStringValue
     DERIVED FROM     PolicyValue
     ABSTRACT         False
     PROPERTIES       BitStringList[ ]
 
   The property BitStringList provides an unordered list of strings, each
   representing a single bit string or a set of bit strings.  The number of
   bits specified SHOULD equal the number of bits of the expected variable.
   For example, for a one-octet variable, 8 bits should be specified.  If
   the variable does not have a fixed length, the bit string should be
   matched against the variable's most significant bit string.  The formal
   definition of a bit string is:
 
       binary-digit = "0" / "1"
       bitString = 1*binary-digit
       maskedBitString = bitString","bitString
 
 
   Each string entry is either:
 
     1.  A single bit string. Example: 00111010
 
     2.  A range of bit strings specified using a bit string and a bit
         mask.  The bit string and mask fields have the same number of bits
         specified.  The mask bit string specifies the significant bits in
         the bit string value.  For example, 110110, 100110 and 110111
         would match the maskedBitString 100110,101110 but 100100 would
         not.
 
   The property definition is as follows:
 
     NAME             BitStringList
     SYNTAX           String
     FORMAT           bitString | maskedBitString
 
 5.14.6. The Class "PolicyIntegerValue"
 
   This class provides a list of integer and integer range values.  Integers
   of arbitrary sizes can be represented.  The class definition is as
   follows:
 
     NAME             PolicyIntegerValue
     DERIVED FROM     PolicyValue
 
 
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     ABSTRACT         False
     PROPERTIES       IntegerList[ ]
 
   The property IntegerList provides an unordered list of integers and
   integer range values, represented as strings.  The format of this
   property takes one of the following forms:
 
     1.  An integer value.
 
     2.  A range of integers. The range is specified by a starting integer
         and an ending integer, separated by '-'.  The starting integer
         MUST be less than or equal to the ending integer.  The range
         includes all integers between the starting and ending integers,
         including these two integers.  Care must be taken in reading
         integer ranges involving negative integers, since the unary minus
         and the range indicator are the same character '-'.
 
   To represent a range of integers that is not bounded, the reserved words
   -INFINITY and/or INFINITY can be used in place of the starting and ending
   integers.
 
   The ABNF definition [8] is:
 
     integer = [-]1*DIGIT | "INFINITY" | "-INFINITY"
     integerrange = integer"-"integer
 
   Using ranges, the operators greater-than, greater-than-or-equal-to, less-
   than, and less-than-or-equal-to can be expressed.  For example, "X is-
   greater-than 5" (where X is an integer) can be translated to "X matches
   6-INFINITY".  This enables the match condition semantics of the operator
   for the SimplePolicyCondition class to be kept simple (i.e., just the
   value "match").
 
 
   The property definition is as follows:
 
     NAME             IntegerList
     SYNTAX           String
     FORMAT           integer | integerrange
 
 5.14.7. The Class "PolicyBooleanValue"
 
   This class is used to represent a Boolean (TRUE/FALSE) value.  The class
   definition is as follows:
 
     NAME             PolicyBooleanValue
     DERIVED FROM     PolicyValue
     ABSTRACT         False
     PROPERTIES       BooleanValue
 
   The property definition is as follows:
 
     NAME             BooleanValue
 
 
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     SYNTAX           boolean
 
 5.15. The Class "PolicyRoleCollection"
 
   This class represents a collection of managed elements that share a
   common role. The PolicyRoleCollection always exists in the context of a
   system, specified using the PolicyRoleCollectionInSystem association.
   The value of the PolicyRole property in this class specifies the role,
   and can be matched with the value(s) in the PolicyRoles array in
   PolicyRules and PolicyGroups.  ManagedElements that share the role
   defined in this collection are aggregated into the collection via the
   association ElementInPolicyRoleCollection.
 
     NAME             PolicyRoleCollection
     DESCRIPTION      A subclass of the CIM Collection class used to group
                      together managed elements that share a role.
     DERIVED FROM     Collection
     ABSTRACT         FALSE
     PROPERTIES       PolicyRole
 
 5.15.1. The Single-Valued Property "PolicyRole"
 
   This property represents the role associated with a PolicyRoleCollection.
   The property definition is as follows:
 
 
     NAME             PolicyRole
     DESCRIPTION      A string representing the role associated with a
                      PolicyRoleCollection.
     SYNTAX           string
 
 5.16. The Class "ReusablePolicyContainer"
 
   The new class ReusablePolicyContainer is defined as follows:
 
     NAME             ReusablePolicyContainer
     DESCRIPTION      A class representing an administratively defined
                      container for reusable policy-related information.
                      This class does not introduce any additional
                      properties beyond those in its superclass AdminDomain.
                      It does, however, participate in a number of unique
                      associations.
     DERIVED FROM     AdminDomain
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 5.17. Deprecation of PCIM's Class "PolicyRepository"
 
   The class definition of PolicyRepository (from PCIM) is updated as
   follows, with an indication that the class has been deprecated.  Note
   that when an element of the model is deprecated, its replacement element
   is identified explicitly.
 
 
 
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     NAME             PolicyRepository
     DEPRECATED FOR   ReusablePolicyContainer
     DESCRIPTION      A class representing an administratively defined
                      container for reusable policy-related information.
                      This class does not introduce any additional
                      properties beyond those in its superclass AdminDomain.
                      It does, however, participate in a number of unique
                      associations.
     DERIVED FROM     AdminDomain
     ABSTRACT         FALSE
     PROPERTIES       (none)
 
 
 6. Association and Aggregation Definitions
 
   The following definitions supplement those in PCIM itself.  PCIM
   definitions that are not DEPRECATED here are still current parts of the
   overall Policy Core Information Model.
 
 6.1. The Abstract Aggregation "PolicySetComponent"
 
   PolicySetComponent is a new abstract aggregation class that collects
   instances of PolicySet subclasses (PolicyGroups and PolicyRules) into
   coherent sets of policies.
 
     NAME             PolicySetComponent
     DESCRIPTION      An abstract class representing the components of a
                      policy set that have the same decision strategy, and
                      are prioritized within the set.
     DERIVED FROM     PolicyComponent
     ABSTRACT         TRUE
     PROPERTIES       GroupComponent[ref PolicySet[0..n]]
                      PartComponent[ref PolicySet[0..n]]
                      Priority
 
   The definition of the Priority property is unchanged from its previous
   definition in [PCIM].
 
     NAME             Priority
     DESCRIPTION      A non-negative integer for prioritizing this PolicySet
                      component relative to other components of the same
                      PolicySet.  A larger value indicates a higher
                      priority.
     SYNTAX           uint16
     DEFAULT VALUE    0
 
 
 6.2. Update to PCIM's Aggregation "PolicyGroupInPolicyGroup"
 
 The PolicyGroupInPolicyGroup aggregation class is modified to be derived
 from PolicySetComponent.
 
 
 
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     NAME             PolicyGroupInPolicyGroup
     DESCRIPTION      A class representing the aggregation of PolicyGroups
                      by a higher-level PolicyGroup.
     DERIVED FROM     PolicySetComponent
     ABSTRACT         FALSE
     PROPERTIES       GroupComponent[ref PolicyGroup[0..n]]
                      PartComponent[ref PolicyGroup[0..n]]
 
 6.3. Update to PCIM's Aggregation "PolicyRuleInPolicyGroup"
 
   The PolicyRuleInPolicyGroup aggregation class is modified to be derived
   from PolicySetComponent.
 
     NAME             PolicyRuleInPolicyGroup
     DESCRIPTION      A class representing the aggregation of PolicyRules by
                      a PolicyGroup.
     DERIVED FROM     PolicySetComponent
     ABSTRACT         FALSE
     PROPERTIES       GroupComponent[ref PolicyGroup[0..n]]
                      PartComponent[ref PolicyRule[0..n]]
 
 6.4. The Aggregation "PolicyGroupInPolicyRule"
 
   A policy rule may aggregate one or more policy groups, via the
   PolicyGroupInPolicyRule aggregation.  Grouping of policy groups and their
   subclasses into a policy rule is for administrative convenience,
   scalability and manageability, as it enables more complex policies to be
   constructed from multiple simpler policies.
 
   Policy rules do not have to contain policy groups.  In addition, a policy
   group may also be used by itself, without belonging to a policy rule, and
   policy rules may be individually aggregated by other policy rules by the
   PolicyRuleInPolicyRule aggregation.  Note that it is assumed that this
   aggregation is used to form directed acyclic graphs and NOT ring
   structures.
 
   The class definition for this aggregation is as follows:
 
     NAME             PolicyGroupInPolicyRule
     DERIVED FROM     PolicySetComponent
     ABSTRACT         False
     PROPERTIES       GroupComponent[ref PolicyRule[0..n]]
                      PartComponent[ref PolicyGroup[0..n]]
 
   The reference property "GroupComponent" is inherited from
   PolicySetComponent, and overridden to become an object reference to a
   PolicyRule that contains one or more PolicyGroups.  Note that for any
   single instance of the aggregation class PolicyGroupInPolicyRule, this
   property (like all reference properties) is single-valued.  The [0..n]
   cardinality indicates that there may be 0, 1 or more than one PolicyRules
   that contain any given PolicyGroup.
 
 
 
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   The reference property "PartComponent" is inherited from
   PolicySetComponent, and overridden to become an object reference to a
   PolicyGroup contained by one or more PolicyRules.  Note that for any
   single instance of the aggregation class PolicyGroupInPolicyRule, this
   property (like all reference properties) is single-valued.  The [0..n]
   cardinality indicates that a given PolicyRule may contain 0, 1, or more
   than one PolicyGroup.
 
 6.5. The Aggregation "PolicyRuleInPolicyRule"
 
   A policy rule may aggregate one or more policy rules, via the
   PolicyRuleInPolicyRule aggregation.  The ability to nest policy rules and
   form sub-rules is important for manageability and scalability, as it
   enables complex policy rules to be constructed from multiple simpler
   policy rules.
 
   A policy rule does not have to contain sub-rules.  A policy rule may
   contain a group of sub-rules using the PolicyGroupInPolicyRule
   aggregation.  Note that it is assumed that this aggregation is used to
   form directed a-cyclic graphs and NOT ring structures.
 
   The class definition for this aggregation is as follows:
 
     NAME             PolicyRuleInPolicyRule
     DERIVED FROM     PolicySetComponent
     ABSTRACT         False
     PROPERTIES       GroupComponent[ref PolicyRule[0..n]]
                      PartComponent[ref PolicyRule[0..n]]
 
   The reference property "GroupComponent" is inherited from
   PolicySetComponent, and overridden to become an object reference to a
   PolicyRule that contains one or more PolicyRules.  Each contained
   PolicyRule can be conceptualized as a sub-rule of the containing
   PolicyRule.  This nesting can be done to any desired level.  However, the
   deeper the nesting, the more complex the results of the decisions taken
   by the nested rules.
 
   Note that for any single instance of the aggregation class
   PolicyRuleInPolicyRule, this property is single-valued.  The [0..n]
   cardinality indicates that there may be 0, 1  or more than one
   PolicyRules that contain any given PolicyRule.
 
   The reference property "PartComponent" is inherited from
   PolicySetComponent, and overridden to become an object reference to a
   PolicyRule contained by a PolicyRule.  Note that for any single instance
   of the aggregation class PolicyRuleInPolicyRule, this property is single-
   valued.  The [0..n] cardinality indicates that a given PolicyRule may
   contain 0, 1, or more than one other PolicyRules.
 
 6.6. The Abstract Aggregation "CompoundedPolicyCondition"
 
     NAME             CompoundedPolicyCondition
 
 
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     DESCRIPTION      A class representing the aggregation of
                      PolicyConditions by an aggregating instance.
     DERIVED FROM     PolicyComponent
     ABSTRACT         TRUE
     PROPERTIES       PartComponent[ref PolicyCondition[0..n]]
                      GroupNumber
                      ConditionNegated
 
 
 6.7. Update to PCIM's Aggregation "PolicyConditionInPolicyRule"
 
   The PCIM aggregation "PolicyConditionInPolicyRule" is updated, to make it
   a subclass of the new abstract aggregation CompoundedPolicyCondition.
   The properties GroupNumber and ConditionNegated are now inherited, rather
   than specified explicitly as they were in PCIM.
 
     NAME             PolicyConditionInPolicyRule
     DESCRIPTION      A class representing the aggregation of
                      PolicyConditions by a PolicyRule.
     DERIVED FROM     CompoundedPolicyCondition
     ABSTRACT         FALSE
     PROPERTIES       GroupComponent[ref PolicyRule[0..n]]
 
 
 6.8. The Aggregation "PolicyConditionInPolicyCondition"
 
   A second subclass of CompoundedPolicyCondition is defined, representing
   the compounding of policy conditions into a higher-level policy
   condition.
 
     NAME             PolicyConditionInPolicyCondition
     DESCRIPTION      A class representing the aggregation of
                      PolicyConditions by another PolicyCondition.
     DERIVED FROM     CompoundedPolicyCondition
     ABSTRACT         FALSE
     PROPERTIES       GroupComponent[ref PolicyCondition[0..n]]
 
 6.9. The Abstract Aggregation "CompoundedPolicyAction"
 
     NAME             CompoundedPolicyAction
     DESCRIPTION      A class representing the aggregation of PolicyActions
                      by an aggregating instance.
     DERIVED FROM     PolicyComponent
     ABSTRACT         TRUE
     PROPERTIES       PartComponent[ref PolicyAction[0..n]]
                      ActionOrder
 
 6.10. Update to PCIM's Aggregation "PolicyActionInPolicyRule"
 
   The PCIM aggregation "PolicyActionInPolicyRule" is updated, to make it a
   subclass of the new abstract aggregation CompoundedPolicyAction.  The
 
 
 
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   property ActionOrder is now inherited, rather than specified explicitly
   as it was in PCIM.
 
     NAME             PolicyActionInPolicyRule
     DESCRIPTION      A class representing the aggregation of PolicyActions
                      by a PolicyRule.
     DERIVED FROM     CompoundedPolicyAction
     ABSTRACT         FALSE
     PROPERTIES       GroupComponent[ref PolicyRule[0..n]]
 
 6.11. The Aggregation "PolicyActionInPolicyAction"
 
   A second subclass of CompoundedPolicyAction is defined, representing the
   compounding of policy actions into a higher-level policy action.
 
     NAME             PolicyActionInPolicyAction
     DESCRIPTION      A class representing the aggregation of PolicyActions
                      by another PolicyAction.
     DERIVED FROM     CompoundedPolicyAction
     ABSTRACT         FALSE
     PROPERTIES       GroupComponent[ref PolicyAction[0..n]]
 
 6.12. The Aggregation "PolicyVariableInSimplePolicyCondition"
 
   A simple policy condition is represented as an ordered triplet {variable,
   operator, value}.  This aggregation provides the linkage between a
   SimplePolicyCondition instance and a single PolicyVariable.  The
   aggregation PolicyValueInSimplePolicyCondition links the
   SimplePolicyCondition to a single PolicyValue.  The Operator property of
   SimplePolicyCondition represents the third element of the triplet, the
   operator.
 
   The class definition for this aggregation is as follows:
 
 
     NAME             PolicyVariableInSimplePolicyCondition
     DERIVED FROM     PolicyComponent
     ABSTRACT         False
     PROPERTIES       GroupComponent[ref SimplePolicyCondition[0..n]]
                      PartComponent[ref PolicyVariable[1..1] ]
 
   The reference property "GroupComponent" is inherited from
   PolicyComponent, and overridden to become an object reference to a
   SimplePolicyCondition that contains exactly one PolicyVariable.  Note
   that for any single instance of the aggregation class
   PolicyVariableInSimplePolicyCondition, this property is single-valued.
   The [0..n] cardinality indicates that there may be 0, 1, or more
   SimplePolicyCondition objects that contain any given policy variable
   object.
 
   The reference property "PartComponent" is inherited from PolicyComponent,
   and overridden to become an object reference to a PolicyVariable that is
 
 
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   defined within the scope of a SimplePolicyCondition.  Note that for any
   single instance of the association class
   PolicyVariableInSimplePolicyCondition, this property (like all reference
   properties) is single-valued.  The [1..1] cardinality indicates that a
   SimplePolicyCondition must have exactly one policy variable defined
   within its scope in order to be meaningful.
 
 6.13. The Aggregation "PolicyValueInSimplePolicyCondition"
 
   A simple policy condition is represented as an ordered triplet {variable,
   operator, value}.  This aggregation provides the linkage between a
   SimplePolicyCondition instance and a single PolicyValue.  The aggregation
   PolicyVariableInSimplePolicyCondition links the SimplePolicyCondition to
   a single PolicyVariable.  The Operator property of SimplePolicyCondition
   represents the third element of the triplet, the operator.
 
   The class definition for this aggregation is as follows:
 
     NAME             PolicyValueInSimplePolicyCondition
     DERIVED FROM     PolicyComponent
     ABSTRACT         False
     PROPERTIES       GroupComponent[ref SimplePolicyCondition[0..n]]
                      PartComponent[ref PolicyValue[1..1] ]
 
   The reference property "GroupComponent" is inherited from
   PolicyComponent, and overridden to become an object reference to a
   SimplePolicyCondition that contains exactly one PolicyValue.  Note that
   for any single instance of the aggregation class
   PolicyValueInSimplePolicyCondition, this property is single-valued.  The
   [0..n] cardinality indicates that there may be 0, 1, or more
   SimplePolicyCondition objects that contain any given policy value object.
 
   The reference property "PartComponent" is inherited from PolicyComponent,
   and overridden to become an object reference to a PolicyValue that is
   defined within the scope of a SimplePolicyCondition.  Note that for any
   single instance of the association class
   PolicyValueInSimplePolicyCondition, this property (like all reference
   properties) is single-valued.  The [1..1] cardinality indicates that a
   SimplePolicyCondition must have exactly one policy value defined within
   its scope in order to be meaningful.
 
 6.14. The Aggregation "PolicyVariableInSimplePolicyAction"
 
   A simple policy action is represented as a pair {variable, value}. This
   aggregation provides the linkage between a SimplePolicyAction instance
   and a single PolicyVariable.  The aggregation
   PolicyValueInSimplePolicyAction links the SimplePolicyAction to a single
   PolicyValue.
 
   The class definition for this aggregation is as follows:
 
 
 
 
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     NAME             PolicyVariableInSimplePolicyAction
     DERIVED FROM     PolicyComponent
     ABSTRACT         False
     PROPERTIES       GroupComponent[ref SimplePolicyAction[0..n]]
                      PartComponent[ref PolicyVariable[1..1] ]
 
   The reference property "GroupComponent" is inherited from
   PolicyComponent, and overridden to become an object reference to a
   SimplePolicyAction that contains exactly one PolicyVariable.  Note that
   for any single instance of the aggregation class
   PolicyVariableInSimplePolicyAction, this property is single-valued.  The
   [0..n] cardinality indicates that there may be 0, 1, or more
   SimplePolicyAction objects that contain any given policy variable object.
 
   The reference property "PartComponent" is inherited from PolicyComponent,
   and overridden to become an object reference to a PolicyVariable that is
   defined within the scope of a SimplePolicyAction.  Note that for any
   single instance of the association class
   PolicyVariableInSimplePolicyAction, this property (like all reference
   properties) is single-valued.  The [1..1] cardinality indicates that a
   SimplePolicyAction must have exactly one policy variable defined within
   its scope in order to be meaningful.
 
 6.15. The Aggregation "PolicyValueInSimplePolicyAction"
 
   A simple policy action is represented as a pair {variable, value}.  This
   aggregation provides the linkage between a SimplePolicyAction instance
   and a single PolicyValue.  The aggregation
   PolicyVariableInSimplePolicyAction links the SimplePolicyAction to a
   single PolicyVariable.
 
   The class definition for this aggregation is as follows:
 
 
     NAME             PolicyValueInSimplePolicyAction
     DERIVED FROM     PolicyComponent
     ABSTRACT         False
     PROPERTIES       GroupComponent[ref SimplePolicyAction[0..n]]
                      PartComponent[ref PolicyValue[1..1] ]
 
   The reference property "GroupComponent" is inherited from
   PolicyComponent, and overridden to become an object reference to a
   SimplePolicyAction that contains exactly one PolicyValue.  Note that for
   any single instance of the aggregation class
   PolicyValueInSimplePolicyAction, this property is single-valued.  The
   [0..n] cardinality indicates that there may be 0, 1, or more
   SimplePolicyAction objects that contain any given policy value object.
 
   The reference property "PartComponent" is inherited from PolicyComponent,
   and overridden to become an object reference to a PolicyValue that is
   defined within the scope of a SimplePolicyAction.  Note that for any
   single instance of the association class PolicyValueInSimplePolicyAction,
 
 
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   this property (like all reference properties) is single-valued.  The
   [1..1] cardinality indicates that a SimplePolicyAction must have exactly
   one policy value defined within its scope in order to be meaningful.
 
 6.16. The Association "ReusablePolicy"
 
   The association ReusablePolicy makes it possible to include any subclass
   of the abstract class "Policy" in a ReusablePolicyContainer.
 
     NAME             ReusablePolicy
     DESCRIPTION      A class representing the inclusion of a reusable
                      policy element in a ReusablePolicyContainer.  Reusable
                      elements may be PolicyGroups, PolicyRules,
                      PolicyConditions, PolicyActions, PolicyVariables,
                      PolicyValues, or instances of any other subclasses of
                      the abstract class Policy.
     DERIVED FROM     PolicyInSystem
     ABSTRACT         FALSE
     PROPERTIES       Antecedent[ref ReusablePolicyContainer[0..1]]
 
 
 6.17. Deprecate PCIM's "PolicyConditionInPolicyRepository"
 
     NAME             PolicyConditionInPolicyRepository
     DEPRECATED FOR   ReusablePolicy
     DESCRIPTION      A class representing the inclusion of a reusable
                      PolicyCondition in a PolicyRepository.
     DERIVED FROM     PolicyInSystem
     ABSTRACT         FALSE
     PROPERTIES       Antecedent[ref PolicyRepository[0..1]]
                      Dependent[ref PolicyCondition[0..n]]
 
 6.18. Deprecate PCIM's "PolicyActionInPolicyRepository"
 
     NAME             PolicyActionInPolicyRepository
     DEPRECATED FOR   ReusablePolicy
     DESCRIPTION      A class representing the inclusion of a reusable
                      PolicyAction in a PolicyRepository.
     DERIVED FROM     PolicyInSystem
     ABSTRACT         FALSE
     PROPERTIES       Antecedent[ref PolicyRepository[0..1]]
                      Dependent[ref PolicyAction[0..n]]
 
 6.19. The Association PolicyValueConstraintInVariable
 
   This association links a PolicyValue object to a PolicyVariable object,
   modeling specific value constraints.  Using this association, a variable
   (instance) may be constrained to be bound-to/assigned only a set of
   allowed values.  For example, modeling an enumerated source port
   variable, one creates an instance of the PolicySourcePortVariable class
   and associates it with the set of values (integers) representing the
 
 
 
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   allowed enumeration, using appropriate number of instances of the
   PolicyValueConstraintInVariable association.
 
   Note that a single variable instance may be constrained by any number of
   values and a single value may be used to constrain any number of
   variables.  These relationships are manifested by the n-to-m cardinality
   of the association.
 
 
   The class definition for the association is as follows:
 
     NAME             PolicyValueConstraintInVariable
     DESCRIPTION      A class representing the association of a constraints
                      object to a variable object.
     DERIVED FROM     Dependency
     ABSTRACT         FALSE
     PROPERTIES       Antecedent [ref PolicyVariable[0..n]]
                      Dependent [ref PolicyValue [0..n]]
 
   The reference property Antecedent is inherited from Dependency.  Its type
   and cardinality are overridden to provide the semantics of a variable
   optionally having value constraints.  The [0..n] cardinality indicates
   that any number of variables may be constrained by a given value.
 
   The reference property "Dependent" is inherited from Dependency, and
   overridden to become an object reference to a PolicyValue that is used to
   constrain the values that a particular PolicyVariable can have.  The
   [0..n] cardinality indicates that a given policy variable may have 0, 1
   or more than one PolicyValues defined to model the constraints on the
   values that the policy variable can take.
 
 
 6.20. The Aggregation "PolicyContainerInPolicyContainer"
 
   The aggregation PolicyContainerInPolicyContainer provides for nesting of
   one ReusablePolicyContainer inside another one.
 
     NAME             PolicyContainerInPolicyContainer
     DESCRIPTION      A class representing the aggregation of
                      ReusablePolicyContainers by a higher-level
                      ReusablePolicyContainer.
     DERIVED FROM     SystemComponent
     ABSTRACT         FALSE
     PROPERTIES       GroupComponent[ref ReusablePolicyContainer [0..n]]
                      PartComponent[ref ReusablePolicyContainer [0..n]]
 
 6.21. Deprecate PCIM's "PolicyRepositoryInPolicyRepository"
 
     NAME             PolicyRepositoryInPolicyRepository
     DEPRECATED FOR   PolicyContainerInPolicyContainer
     DESCRIPTION      A class representing the aggregation of
                      PolicyRepositories by a higher-level PolicyRepository.
     DERIVED FROM     SystemComponent
     ABSTRACT         FALSE
 
 
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     PROPERTIES       GroupComponent[ref PolicyRepository[0..n]]
                      PartComponent[ref PolicyRepository[0..n]]
 
 6.22. The Aggregation "ElementInPolicyRoleCollection"
 
   The following aggregation is used to associate ManagedElements with a
   PolicyRoleCollection object that represents a role played by these
   ManagedElements.
 
 
     NAME             ElementInPolicyRoleCollection
     DESCRIPTION      A class representing the inclusion of a ManagedElement
                      in a collection, specified as having a given role.
                      All the managed elements in the collection share the
                      same role.
     DERIVED FROM     MemberOfCollection
     ABSTRACT         FALSE
     PROPERTIES       Collection[ref PolicyRoleCollection [0..n]]
                      Member[ref ManagedElement [0..n]]
 
 6.22.1. The Weak Association "PolicyRoleCollectionInSystem"
 
   A PolicyRoleCollection is defined within the scope of a System.  This
   association links a PolicyRoleCollection to the System in whose scope it
   is defined.
 
   When associating a PolicyRoleCollection with a System, this should be
   done consistently with the system that scopes the policy rules/groups
   that are applied to the resources in that collection.  A
   PolicyRoleCollection is associated with the same system as the applicable
   PolicyRules and/or PolicyGroups, or to a System higher in the tree formed
   by the SystemComponent association.
 
   The class definition for the association is as follows:
 
 
     NAME             PolicyRoleCollectionInSystem
     DESCRIPTION      A class representing the fact that a
                      PolicyRoleCollection is defined within the scope of a
                      System.
     DERIVED FROM     Dependency
     ABSTRACT         FALSE
     PROPERTIES       Antecedent[ref System[1..1]]
                      Dependent[ref PolicyRoleCollection[weak]]
 
   The reference property Antecedent is inherited from Dependency, and
   overridden to restrict its cardinality to [1..1].  It serves as an object
   reference to a System that provides a scope for one or more
   PolicyRoleCollections.  Since this is a weak association, the cardinality
   for this object reference is always 1, that is, a PolicyRoleCollection is
   always defined within the scope of exactly one System.
 
   The reference property Dependent is inherited from Dependency, and
   overridden to become an object reference to a PolicyRoleCollection
 
 
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   defined within the scope of a System.  Note that for any single instance
   of the association class PolicyRoleCollectionInSystem, this property
   (like all Reference properties) is single-valued.  The [0..n] cardinality
   indicates that a given System may have 0, 1, or more than one
   PolicyRoleCollections defined within its scope.
 
 
 7. Intellectual Property
 
   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to pertain to
   the implementation or use of the technology described in this document or
   the extent to which any license under such rights might or might not be
   available; neither does it represent that it has made any effort to
   identify any such rights.  Information on the IETF's procedures with
   respect to rights in standards-track and standards-related documentation
   can be found in BCP-11.
 
   Copies of claims of rights made available for publication and any
   assurances of licenses to be made available, or the result of an attempt
   made to obtain a general license or permission for the use of such
   proprietary rights by implementers or users of this specification can be
   obtained from the IETF Secretariat.
 
   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary rights
   which may cover technology that may be required to practice this
   standard.  Please address the information to the IETF Executive Director.
 
 
 8. Acknowledgements
 
   The starting point for this document was PCIM itself [3], and the first
   three submodels derived from it [5], [6], [7].  The authors of these
   documents created the extensions to PCIM, and asked the questions about
   PCIM, that are reflected in PCIMe.
 
 
 9. Security Considerations
 
   The Policy Core Information Model (PCIM) [3] describes the general
   security considerations related to the general core policy model.  The
   extensions defined in this document do not introduce any additional
   considerations related to security.
 
 
 
 10. References
 
 [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.
 
 [2]  Hovey, R., and S. Bradner, "The Organizations Involved in the IETF
      Standards Process", BCP 11, RFC 2028, October 1996.
 
 
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 [3]  Strassner, J., and E. Ellesson, B. Moore, A. Westerinen, "Policy Core
      Information Model -- Version 1 Specification", RFC 3060, February
      2001.
 
 [4]  Distributed Management Task Force, Inc., "DMTF Technologies: CIM
      Standards û CIM Schema: Version 2.5", available via links on the
      following DMTF web page: http://www.dmtf.org/spec/cim_schema_v25.html.
 
 [5]  Snir, Y., and Y. Ramberg, J. Strassner, R. Cohen, "Policy Framework
      QoS Information Model", work in progress, draft-ietf-policy-qos-info-
      model-02.txt, November 2000.
 
 [6]  Jason, J., and L. Rafalow, E. Vyncke, "IPsec Configuration Policy
      Model", work in progress, draft-ietf-ipsp-config-policy-model-02.txt,
      March 2001.
 
 [7]  Chadha, R., and M. Brunner, M. Yoshida, J. Quittek, G. Mykoniatis, A.
      Poylisher, R. Vaidyanathan, A. Kind, F. Reichmeyer, "Policy Framework
      MPLS Information Model for QoS and TE", work in progress, draft-
      chadha-policy-mpls-te-01.txt, December 2000.
 
 [8]  Crocker, D., and P. Overell, "Augmented BNF for Syntax Specifications:
      ABNF", RFC 2234, November 1997.
 
 [9]  P. Mockapetris, "DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION",
      RFC1035, November 1987.
 
 [10] R. Hinden, S. Deering, "IP Version 6 Addressing Architecture",
      RFC2373, July 1998.
 
 [11] M. Wahl, A. Coulbeck, "Lightweight Directory Access Protocol (v3):
      Attribute Syntax Definitions", RFC 2252.
 
 [12] A. Westerinen, et al., "Policy Terminology", <draft-ietf-policy-
      terminology-01.txt>, November 2000.
 
 [13] S. Waldbusser, and J. Saperia, T. Hongal, "Policy Based Management
      MIB", <draft-ietf-snmpconf-pm-04.txt>, November 2000.
 
 
 11. Authors' Addresses
 
   Bob Moore
       IBM Corporation, BRQA/502
       4205 S. Miami Blvd.
       Research Triangle Park, NC 27709
       Phone:   +1 919-254-4436
       Fax:     +1 919-254-6243
       E-mail:  remoore@us.ibm.com
 
   Lee Rafalow
       IBM Corporation, BRQA/502
 
 
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       4205 S. Miami Blvd.
       Research Triangle Park, NC 27709
       Phone:   +1 919-254-4455
       Fax:     +1 919-254-6243
       E-mail:  rafalow@us.ibm.com
 
   Yoram Ramberg
       Cisco Systems
       4 Maskit Street
       Herzliya Pituach, Israel  46766
       Phone:  +972-9-970-0081
       Fax:    +972-9-970-0219
       E-mail:  yramberg@cisco.com
 
   Yoram Snir
       Cisco Systems
       4 Maskit Street
       Herzliya Pituach, Israel  46766
       Phone:  +972-9-970-0085
       Fax:    +972-9-970-0366
       E-mail:  ysnir@cisco.com
 
   John Strassner
       Cisco Systems
       Building 20
       725 Alder Drive
       Milpitas, CA  95035
       Phone:  +1-408-527-1069
       Fax:    +1-408-527-2477
       E-mail:  johns@cisco.com
 
   Andrea Westerinen
       Cisco Systems
       Building 20
       725 Alder Drive
       Milpitas, CA  95035
       Phone:  +1-408-853-8294
       Fax:    +1-408-527-6351
       E-mail:  andreaw@cisco.com
 
   Ritu Chadha
       Telcordia Technologies
       MCC 1J-218R
       445 South Street
       Morristown NJ 07960.
       Phone:  +1-973-829-4869
       Fax:    +1-973-829-5889
       E-mail: chadha@research.telcordia.com
 
   Marcus Brunner
       NEC Europe Ltd.
       C&C Research Laboratories
 
 
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       Adenauerplatz 6
       D-69115 Heidelberg, Germany
       Phone: +49 (0)6221 9051129
       Fax:   +49 (0)6221 9051155
       E-mail: brunner@ccrle.nec.de
 
   Ron Cohen
       Ntear LLC
       Phone:
       Fax:
       E-mail:  ronc@ntear.com
 
 
 12. Full Copyright Statement
 
   Copyright (C) The Internet Society (2001).  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 English.
 
   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 "AS
   IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK
   FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
   LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT
   INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR
   FITNESS FOR A PARTICULAR PURPOSE.
 
 
 13. Appendix A: Open Issues
 
   The PCIMe authors do not all agree with everything included in the -00
   draft of the document.  Input is solicited from the working group as a
   whole on the following open issues:
 
     1.  Unrestricted use of DNF/CNF for CompoundPolicyConditions.
         Alternative:  for the conditions aggregated by a
         CompoundPolicyCondition, allow only ANDing, with negation of
         individual conditions.  Note that this is sufficient to build
 
 
 
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         multi-field packet filters from single-field
         SimplePolicyConditions.
 
     2.  For a PolicyVariable in a SimplePolicyCondition, restrict the set
         of possible values both via associated PolicyValue objects (tied
         in with the PolicyValueConstraintInVariable association) and via
         the ValueTypes property in the PolicyVariable class.  Alternative:
         restrict values only via associated PolicyValue objects.
 
     3.  Transactional semantics, including rollback, for the
         ExecutionStrategy property in PolicyRule and in
         CompoundPolicyAction.  Alternative: have only 'Do until success'
         and 'Do all'.
 
     4.  Stating that CompoundFilterConditions are the preferred way to do
         packet filtering in a PolicyCondition.  Alternative:  make
         CompoundFilterConditions and FilterEntries available to submodels,
         with no stated (or implied) preference.
 
     5.  Prohibiting equal values for Priority within a PolicySet.
         Alternative: allow equal values, with resulting indeterminacy in
         PEP behavior.
 
     6.  Modeling a SimplePolicyAction with just a related PolicyVariable
         and PolicyValue -- the "set" or "apply" operation is implicit.
         Alternative: include an Operation property in SimplePolicyAction,
         similar to the Operation property in SimplePolicyCondition.
 
     7.  Representation of PolicyValues: should values like IPv4 addresses
         be represented only as strings (as in LDAP), or natively (e.g., an
         IPv4 address would be a four-octet field) with mappings to other
         representations such as strings?
 
     8.  The nesting of rules and groups within rules introduces
         significant change and complexity in the model.  This nesting
         introduces program state (procedural language) into the model
         (heretofore a declarative model) as well as implicit hierarchical
         contexts on which the rules operate.  These require a much more
         sophisticated rule-evaluation engine than in the past.
 
         Alternative: Maintain the declarative model, by prohibiting
         program state in rule evaluation (i.e., no rules within rules).
 
      9. Need to specify a join algorithm for disjoint rule sets.
 
      10.  Clarify PolicyImplicitVariables.
 
      11.  Clarify PolicyExplicitVariables.
 
 
 
 
 
 
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