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Network Working Group B. Moore, Ed.
Request for Comments: 3460 IBM
Updates: 3060 January 2003
Category: Standards Track
Policy Core Information Model (PCIM) Extensions
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document specifies a number of changes to the Policy Core
Information Model (PCIM, RFC 3060). Two types of changes are
included. First, several completely new elements are introduced, for
example, classes for header filtering, that extend PCIM into areas
that it did not previously cover. Second, there are cases where
elements of PCIM (for example, policy rule priorities) are
deprecated, and replacement elements are defined (in this case,
priorities tied to associations that refer to policy rules). Both
types of changes are done in such a way that, to the extent possible,
interoperability with implementations of the original PCIM model is
preserved. This document updates RFC 3060.
Table of Contents
1. Introduction....................................................5
2. Changes since RFC 3060..........................................5
3. Overview of the Changes.........................................6
3.1. How to Change an Information Model.........................6
3.2. List of Changes to the Model...............................6
3.2.1. Changes to PolicyRepository.........................6
3.2.2. Additional Associations and Additional Reusable
Elements............................................7
3.2.3. Priorities and Decision Strategies..................7
3.2.4. Policy Roles........................................8
3.2.5. CompoundPolicyConditions and
CompoundPolicyActions...............................8
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RFC 3460 PCIM Extensions January 2003
3.2.6. Variables and Values................................9
3.2.7. Domain-Level Packet Filtering.......................9
3.2.8. Device-Level Packet Filtering.......................9
4. The Updated Class and Association Class Hierarchies............10
5. Areas of Extension to PCIM.....................................13
5.1. Policy Scope..............................................13
5.1.1. Levels of Abstraction: Domain- and Device-Level
Policies...........................................13
5.1.2. Administrative and Functional Scopes...............14
5.2. Reusable Policy Elements..................................15
5.3. Policy Sets...............................................16
5.4. Nested Policy Rules.......................................16
5.4.1. Usage Rules for Nested Rules.......................17
5.4.2. Motivation.........................................17
5.5. Priorities and Decision Strategies........................18
5.5.1. Structuring Decision Strategies....................19
5.5.2. Side Effects.......................................21
5.5.3. Multiple PolicySet Trees For a Resource............21
5.5.4. Deterministic Decisions............................22
5.6. Policy Roles..............................................23
5.6.1. Comparison of Roles in PCIM with Roles in
snmpconf...........................................23
5.6.2. Addition of PolicyRoleCollection to PCIMe..........24
5.6.3. Roles for PolicyGroups.............................25
5.7. Compound Policy Conditions and Compound Policy Actions....27
5.7.1. Compound Policy Conditions.........................27
5.7.2. Compound Policy Actions............................27
5.8. Variables and Values......................................28
5.8.1. Simple Policy Conditions...........................29
5.8.2. Using Simple Policy Conditions.....................29
5.8.3. The Simple Condition Operator......................31
5.8.4. SimplePolicyActions................................33
5.8.5. Policy Variables...................................35
5.8.6. Explicitly Bound Policy Variables..................36
5.8.7. Implicitly Bound Policy Variables..................37
5.8.8. Structure and Usage of Pre-Defined Variables.......38
5.8.9. Rationale for Modeling Implicit Variables
as Classes.........................................39
5.8.10. Policy Values.....................................40
5.9. Packet Filtering..........................................41
5.9.1. Domain-Level Packet Filters........................41
5.9.2. Device-Level Packet Filters........................42
5.10. Conformance to PCIM and PCIMe............................43
6. Class Definitions..............................................44
6.1. The Abstract Class "PolicySet"............................44
6.2. Update PCIM's Class "PolicyGroup".........................45
6.3. Update PCIM's Class "PolicyRule"..........................45
6.4. The Class "SimplePolicyCondition".........................46
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6.5. The Class "CompoundPolicyCondition".......................47
6.6. The Class "CompoundFilterCondition".......................47
6.7. The Class "SimplePolicyAction"............................48
6.8. The Class "CompoundPolicyAction"..........................48
6.9. The Abstract Class "PolicyVariable".......................50
6.10. The Class "PolicyExplicitVariable".......................50
6.10.1. The Single-Valued Property "ModelClass"...........51
6.10.2. The Single-Valued Property ModelProperty..........51
6.11. The Abstract Class "PolicyImplicitVariable"..............51
6.11.1. The Multi-Valued Property "ValueTypes"............52
6.12. Subclasses of "PolicyImplicitVariable" Specified
in PCIMe.................................................52
6.12.1. The Class "PolicySourceIPv4Variable"..............52
6.12.2. The Class "PolicySourceIPv6Variable"..............52
6.12.3. The Class "PolicyDestinationIPv4Variable".........53
6.12.4. The Class "PolicyDestinationIPv6Variable".........53
6.12.5. The Class "PolicySourcePortVariable"..............54
6.12.6. The Class "PolicyDestinationPortVariable".........54
6.12.7. The Class "PolicyIPProtocolVariable"..............54
6.12.8. The Class "PolicyIPVersionVariable"...............55
6.12.9. The Class "PolicyIPToSVariable"...................55
6.12.10. The Class "PolicyDSCPVariable"...................55
6.12.11. The Class "PolicyFlowIdVariable".................56
6.12.12. The Class "PolicySourceMACVariable"..............56
6.12.13. The Class "PolicyDestinationMACVariable".........56
6.12.14. The Class "PolicyVLANVariable"...................56
6.12.15. The Class "PolicyCoSVariable"....................57
6.12.16. The Class "PolicyEthertypeVariable"..............57
6.12.17. The Class "PolicySourceSAPVariable"..............57
6.12.18. The Class "PolicyDestinationSAPVariable".........58
6.12.19. The Class "PolicySNAPOUIVariable"................58
6.12.20. The Class "PolicySNAPTypeVariable"...............59
6.12.21. The Class "PolicyFlowDirectionVariable"..........59
6.13. The Abstract Class "PolicyValue".........................59
6.14. Subclasses of "PolicyValue" Specified in PCIMe...........60
6.14.1. The Class "PolicyIPv4AddrValue"...................60
6.14.2. The Class "PolicyIPv6AddrValue....................61
6.14.3. The Class "PolicyMACAddrValue"....................62
6.14.4. The Class "PolicyStringValue".....................63
6.14.5. The Class "PolicyBitStringValue"..................63
6.14.6. The Class "PolicyIntegerValue"....................64
6.14.7. The Class "PolicyBooleanValue"....................65
6.15. The Class "PolicyRoleCollection".........................65
6.15.1. The Single-Valued Property "PolicyRole"...........66
6.16. The Class "ReusablePolicyContainer".................66
6.17. Deprecate PCIM's Class "PolicyRepository"................66
6.18. The Abstract Class "FilterEntryBase".....................67
6.19. The Class "IpHeadersFilter"..............................67
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6.19.1. The Property HdrIpVersion.........................68
6.19.2. The Property HdrSrcAddress........................68
6.19.3. The Property HdrSrcAddressEndOfRange..............68
6.19.4. The Property HdrSrcMask...........................69
6.19.5. The Property HdrDestAddress.......................69
6.19.6. The Property HdrDestAddressEndOfRange.............69
6.19.7. The Property HdrDestMask..........................70
6.19.8. The Property HdrProtocolID........................70
6.19.9. The Property HdrSrcPortStart......................70
6.19.10. The Property HdrSrcPortEnd.......................70
6.19.11. The Property HdrDestPortStart....................71
6.19.12. The Property HdrDestPortEnd......................71
6.19.13. The Property HdrDSCP.............................72
6.19.14. The Property HdrFlowLabel.................... ...72
6.20. The Class "8021Filter"...................................72
6.20.1. The Property 8021HdrSrcMACAddr....................73
6.20.2. The Property 8021HdrSrcMACMask....................73
6.20.3. The Property 8021HdrDestMACAddr...................73
6.20.4. The Property 8021HdrDestMACMask...................73
6.20.5. The Property 8021HdrProtocolID....................74
6.20.6. The Property 8021HdrPriorityValue.................74
6.20.7. The Property 8021HdrVLANID........................74
6.21. The Class FilterList.....................................74
6.21.1. The Property Direction............................75
7. Association and Aggregation Definitions........................75
7.1. The Aggregation "PolicySetComponent"......................75
7.2. Deprecate PCIM's Aggregation "PolicyGroupInPolicyGroup"...76
7.3. Deprecate PCIM's Aggregation "PolicyRuleInPolicyGroup"....76
7.4. The Abstract Association "PolicySetInSystem"..............77
7.5. Update PCIM's Weak Association "PolicyGroupInSystem"......77
7.6. Update PCIM's Weak Association "PolicyRuleInSystem".......78
7.7. The Abstract Aggregation "PolicyConditionStructure".......79
7.8. Update PCIM's Aggregation "PolicyConditionInPolicyRule"...79
7.9. The Aggregation "PolicyConditionInPolicyCondition"........79
7.10. The Abstract Aggregation "PolicyActionStructure".........80
7.11. Update PCIM's Aggregation "PolicyActionInPolicyRule".....80
7.12. The Aggregation "PolicyActionInPolicyAction".............80
7.13. The Aggregation "PolicyVariableInSimplePolicyCondition"..80
7.14. The Aggregation "PolicyValueInSimplePolicyCondition".....81
7.15. The Aggregation "PolicyVariableInSimplePolicyAction".....82
7.16. The Aggregation "PolicyValueInSimplePolicyAction"........83
7.17. The Association "ReusablePolicy".........................83
7.18. Deprecate PCIM's "PolicyConditionInPolicyRepository".....84
7.19. Deprecate PCIM's "PolicyActionInPolicyRepository"........84
7.20. The Association ExpectedPolicyValuesForVariable..........84
7.21. The Aggregation "ContainedDomain"........................85
7.22. Deprecate PCIM's "PolicyRepositoryInPolicyRepository"....86
7.23. The Aggregation "EntriesInFilterList"....................86
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7.23.1. The Reference GroupComponent......................86
7.23.2. The Reference PartComponent.......................87
7.23.3. The Property EntrySequence........................87
7.24. The Aggregation "ElementInPolicyRoleCollection"..........87
7.25. The Weak Association "PolicyRoleCollectionInSystem"......87
8. Intellectual Property..........................................88
9. Acknowledgements..............................................89
10. Contributors..................................................89
11. Security Considerations.......................................91
12. Normative References..........................................91
13. Informative References........................................91
Author's Address..................................................92
Full Copyright Statement..........................................93
1. Introduction
This document specifies a number of changes to the Policy Core
Information Model (PCIM), RFC 3060 [1]. Two types of changes are
included. First, several completely new elements are introduced, for
example, classes for header filtering, that extend PCIM into areas
that it did not previously cover. Second, there are cases where
elements of PCIM (for example, policy rule priorities) are
deprecated, and replacement elements are defined (in this case,
priorities tied to associations that refer to policy rules). Both
types of changes are done in such a way that, to the extent possible,
interoperability with implementations of the original PCIM model is
preserved.
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 BCP 14, RFC 2119 [8].
2. Changes since RFC 3060
Section 3.2 contains a short discussion of the changes that this
document makes to the RFC 3060 information model. Here is a very
brief list of the changes:
1. Deprecate and replace PolicyRepository and its associations.
2. Clarify and expand the ways that PolicyRules and PolicyGroups are
aggregated.
3. Change how prioritization for PolicyRules is represented, and
introduce administrator-specified decision strategies for rule
evaluation.
4. Expand the role of PolicyRoles, and introduce a means of
associating a PolicyRole with a resource.
5. Introduce compound policy conditions and compound policy actions
into the model.
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6. Introduce variables and values into the model.
7. Introduce variable and value subclasses for packet-header
filtering.
8. Introduce classes for device-level packet-header filtering.
3. Overview of the Changes
3.1. 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
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.
3.2. List of Changes to the Model
The following subsections provide a very brief overview of the
changes to PCIM defined in PCIMe. In several cases, the origin of
the change is noted, as QPIM [11], ICPM [12], or QDDIM [15].
3.2.1. 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
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RFC 3460 PCIM Extensions January 2003
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.
3.2.2. Additional Associations and Additional Reusable Elements
The PolicyRuleInPolicyRule and PolicyGroupInPolicyRule aggregations
have, in effect, been imported from QPIM. ("In effect" because these
two aggregations, as well as PCIM's two aggregations
PolicyGroupInPolicyGroup and PolicyRuleInPolicyGroup, are all being
combined into a single aggregation PolicySetComponent.) These
aggregations 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.
3.2.3. Priorities and Decision Strategies
Drawing from both QPIM and ICPM, the Priority property has been
deprecated in PolicyRule, and placed instead on the aggregation
PolicySetComponent. The QPIM rules for resolving relative priorities
across nested PolicyGroups and PolicyRules have been 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/PolicyGroup relative to other
PolicyRules/PolicyGroups, the elements being prioritized must all
reside in one of three places: in a common PolicyGroup, in a common
PolicyRule, or in a common System.
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 has been added to the PolicyGroup and
PolicyRule classes. This property allows 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. (This is accomplished by placing
the PolicyDecisionStrategy property in an abstract class PolicySet,
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from which PolicyGroup and PolicyRule are derived.) The QPIM rules
for applying decision strategies to a nested set of PolicyGroups and
PolicyRules have also been imported.
3.2.4. 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 - PolicySet. 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 a nested rule or group.
It was also observed that there is no mechanism in PCIM for assigning
roles to resources. For example, while it is possible in PCIM to
associate a PolicyRule with the role "FrameRelay&&WAN", there is no
way to indicate which interfaces match this criterion. A new
PolicyRoleCollection class has been 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 the PolicyRoles property of PolicyRules
and PolicyGroups, and in the PolicyRole property in
PolicyRoleCollection.
3.2.5. CompoundPolicyConditions and CompoundPolicyActions
The concept of a CompoundPolicyCondition has also been 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.
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.
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3.2.6. Variables and Values
The SimplePolicyCondition / PolicyVariable / PolicyValue structure
has been 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. For example, QPIM defines a set of implicit variables
corresponding to fields in RSVP flows.
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".
3.2.7. Domain-Level Packet Filtering
For packet filtering specified at the domain level, 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 domain-level 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.
3.2.8. Device-Level Packet Filtering
For packet filtering expressed at the device level, including the
packet classifier filters modeled in QDDIM, the variables and values
discussed in Section 3.2.7 need not be used. Filter classes derived
from the CIM FilterEntryBase class hierarchy are available for use in
these contexts. These latter classes have two important differences
from the domain-level classes:
o They support specification of filters for all of the fields in a
particular protocol header in a single object instance. With the
domain-level classes, separate instances are needed for each
header field.
o They provide native representations for the filter values, as
opposed to the string representation used by the domain-level
classes.
Device-level filter classes for the IP-related headers (IP, UDP, and
TCP) and the 802 MAC headers are defined, respectively, in Sections
6.19 and 6.20.
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4. 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.
ManagedElement (abstract)
|
+--Policy (abstract)
| |
| +---PolicySet (abstract -- new - 5.3)
| | |
| | +---PolicyGroup (moved - 5.3)
| | |
| | +---PolicyRule (moved - 5.3)
| |
| +---PolicyCondition (abstract)
| | |
| | +---PolicyTimePeriodCondition
| | |
| | +---VendorPolicyCondition
| | |
| | +---SimplePolicyCondition (new - 5.8.1)
| | |
| | +---CompoundPolicyCondition (new - 5.7.1)
| | |
| | +---CompoundFilterCondition (new - 5.9)
| |
| +---PolicyAction (abstract)
| | |
| | +---VendorPolicyAction
| | |
| | +---SimplePolicyAction (new - 5.8.4)
| | |
| | +---CompoundPolicyAction (new - 5.7.2)
| |
| +---PolicyVariable (abstract -- new - 5.8.5)
| | |
| | +---PolicyExplicitVariable (new - 5.8.6)
| | |
| | +---PolicyImplicitVariable (abstract -- new - 5.8.7)
| | |
| | +---(subtree of more specific classes -- new - 6.12)
| |
| +---PolicyValue (abstract -- new - 5.8.10)
| |
| +---(subtree of more specific classes -- new - 6.14)
|
+--Collection (abstract -- newly referenced)
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RFC 3460 PCIM Extensions January 2003
| |
| +--PolicyRoleCollection (new - 5.6.2)
ManagedElement(abstract)
|
+--ManagedSystemElement (abstract)
|
+--LogicalElement (abstract)
|
+--System (abstract)
| |
| +--AdminDomain (abstract)
| |
| +---ReusablePolicyContainer (new - 5.2)
| |
| +---PolicyRepository (deprecated - 5.2)
|
+--FilterEntryBase (abstract -- new - 6.18)
| |
| +--IpHeadersFilter (new - 6.19)
| |
| +--8021Filter (new - 6.20)
|
+--FilterList (new - 6.21)
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 (new - 5.3)
| |
| +---PolicyGroupInPolicyGroup (deprecated - 5.3)
| |
| +---PolicyRuleInPolicyGroup (deprecated - 5.3)
| |
| +---PolicyConditionStructure (abstract -- new - 5.7.1)
| | |
| | +---PolicyConditionInPolicyRule (moved - 5.7.1)
| | |
| | +---PolicyConditionInPolicyCondition (new - 5.7.1)
| |
| +---PolicyRuleValidityPeriod
| |
| +---PolicyActionStructure (abstract -- new - 5.7.2)
| | |
| | +---PolicyActionInPolicyRule (moved - 5.7.2)
| | |
| | +---PolicyActionInPolicyAction (new - 5.7.2)
| |
| +---PolicyVariableInSimplePolicyCondition (new - 5.8.2)
| |
| +---PolicyValueInSimplePolicyCondition (new - 5.8.2)
| |
| +---PolicyVariableInSimplePolicyAction (new - 5.8.4)
| |
| +---PolicyValueInSimplePolicyAction (new - 5.8.4)
[unrooted]
|
+---Dependency (abstract)
| |
| +---PolicyInSystem (abstract)
| | |
| | +---PolicySetInSystem (abstract, new - 5.3)
| | | |
| | | +---PolicyGroupInSystem
| | | |
| | | +---PolicyRuleInSystem
| | |
| | +---ReusablePolicy (new - 5.2)
| | |
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| | +---PolicyConditionInPolicyRepository (deprecated - 5.2)
| | |
| | +---PolicyActionInPolicyRepository (deprecated - 5.2)
| |
| +---ExpectedPolicyValuesForVariable (new - 5.8)
| |
| +---PolicyRoleCollectionInSystem (new - 5.6.2)
|
+---Component (abstract)
| |
| +---SystemComponent
| | |
| | +---ContainedDomain (new - 5.2)
| | |
| | +---PolicyRepositoryInPolicyRepository (deprecated - 5.2)
| |
| +---EntriesInFilterList (new - 7.23)
|
+---MemberOfCollection (newly referenced)
|
+--- ElementInPolicyRoleCollection (new - 5.6.2)
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).
5. Areas of Extension to PCIM
The following subsections describe each of the areas for which PCIM
extensions are being defined.
5.1. Policy Scope
Policy scopes may be thought of in two dimensions: 1) the level of
abstraction of the policy specification and 2) the applicability of
policies to a set of managed resources.
5.1.1. Levels of Abstraction: Domain- and Device-Level 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 that apply to devices in a network. Those latter
policies can, themselves, be classified into at least two groups:
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RFC 3460 PCIM Extensions January 2003
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, called domain-level policies, 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.
PCIM and PCIMe 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.
5.1.2. Administrative and Functional Scopes
Administrative scopes for policy are represented in PCIM and in these
extensions to PCIM as System subclass instances. Typically, a
domain-level policy would be scoped by an AdminDomain instance (or by
a hierarchy of AdminDomain instances) whereas a device-level policy
might be scoped by a System instance that represents the PEP (e.g.,
an instance of ComputerSystem, see CIM [2]). In addition to
collecting policies into an administrative domain, these System
classes may also aggregate the resources to which the policies apply.
Functional scopes (sometimes referred to as functional domains) are
generally defined by the submodels derived from PCIM and PCIMe, and
correspond to the service or services to which the policies apply.
So, for example, Quality of Service may be thought of as a functional
scope, or Diffserv and Intserv may each be thought of as functional
scopes. These scoping decisions are represented by the structure of
the submodels derived from PCIM and PCIMe, and may be reflected in
the number and types of PEP policy client(s), services, and the
interaction between policies. Policies in different functional
scopes are organized into disjoint sets of policy rules. Different
functional domains may share some roles, some conditions, and even
some actions. The rules from different functional domains may even
be enforced at the same managed resource, but for the purposes of
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policy evaluation they are separate. See section 5.5.3 for more
information.
The functional scopes MAY be reflected in administrative scopes.
That is, deployments of policy may have different administrative
scopes for different functional scopes, but there is no requirement
to do so.
5.2. 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 PDP
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 6 and 7 are the result
of this item:
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 ContainedDomain is defined.
o PCIM's PolicyRepositoryInPolicyRepository aggregation is
deprecated.
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5.3. Policy Sets
A "policy" can be thought of as a coherent set of rules to
administer, manage, and control access to network resources ("Policy
Terminology", reference [10]). The structuring of these coherent
sets of rules into subsets is enhanced in this document. In Section
5.4, 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 structural flexibility and
semantic capability of both subclasses.
Two properties are defined in PolicySet: PolicyDecisionStrategy and
PolicyRoles. The PolicyDecisionStrategy property is included in
PolicySet to define the evaluation relationship among the rules in
the policy set. See Section 5.5 for more information. The
PolicyRoles property is included in PolicySet to characterize the
resources to which the PolicySet applies. See Section 5.6 for more
information.
Along with the definition of the PolicySet class, a new concrete
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 in a PolicySet. PolicySetComponent replaces the two PCIM
aggregations PolicyGroupInPolicyGroup and PolicyRuleInPolicyGroup, so
these two aggregations are deprecated.
A PolicySet's relationship to an AdminDomain or other administrative
scoping system (for example, a ComputerSystem) is represented by the
PolicySetInSystem abstract association. This new association is
derived from PolicyInSystem, and the PolicyGroupInSystem and
PolicyRuleInSystem associations are now derived from
PolicySetInSystem instead of directly from PolicyInSystem. The
PolicySetInSystem.Priority property is discussed in Section 5.5.3.
5.4. 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. The aggregation PolicySetComponent is used
to represent the nesting of a policy rule in another policy rule.
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5.4.1. 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 condition for evaluation
of all nested rules; that is, the conditions of the parent are
logically ANDed to the conditions of the sub-rules. If the parent
rule's condition clause evaluates to FALSE, sub-rules MAY be
skipped since they also evaluate to FALSE.
o If the parent rule's condition evaluates to TRUE, the set of sub-
rules SHALL BE evaluated according to the decision strategy and
priorities as discussed in Section 5.5.
o If the parent rule's condition evaluates to TRUE, the parent
rule's set of actions is executed BEFORE execution of the sub-
rules actions. 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 parent-condition then parent rule's action
if condA then actA
if condB then ActB
if True then default action
Such a default action functions as a default when FirstMatching
decision strategies are in effect (see section 5.5). If
AllMatching applies, the "default" action is always performed.
o Policy rules have a context in which they are executed. The rule
engine evaluates and applies the policy rules in the context of
the managed resource(s) that are identified by the policy roles
(or by an explicit association). Submodels MAY add additional
context to policy rules based on rule structure; any such
additional context is defined by the semantics of the action
classes of the submodel.
5.4.2. Motivation
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.
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These enhancements ease the policy management tools' task, allowing
policy rules to be expressed in a way closer to how humans think.
Although rule nesting can be used to suggest optimizations in the way
policy rules are evaluated, as discussed in section 5.5.2 "Side
Effects," nesting does not specify nor does it require any particular
order of evaluation of conditions. Optimization of rule evaluation
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 may be able to
influence the evaluation of the policy rules for execution using rule
nesting.
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.
5.5. 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 only
actions enforced on a given examination of the PolicySet are those
for the first rule (that is, the rule with the highest priority) that
has its conditions evaluate to TRUE. The AllMatching strategy is
used to cause the evaluation of all rules in a set; for all of the
rules whose conditions evaluate to TRUE, the actions are enforced.
Implementations MUST support the FirstMatching decision strategy;
implementations MAY support the AllMatching decision strategy.
As previously discussed, the PolicySet subclasses are PolicyGroup and
PolicyRule: 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 aggregation.
The relative priority within a PolicySet is established by the
Priority property of the PolicySetComponent aggregation of the
contained PolicyGroup and PolicyRule instances. 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
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two advantages. First, it generalizes the concept of priority, so
that it can be used for both groups and rules. 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.
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 same aggregating PolicySet. Thus, the
evaluation of rules within a set is deterministically specified.
For a FirstMatching decision strategy, the first rule (that is, 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, all of the matching rules are
enforced. The relative priority of the rules is used to determine
the order in which the actions are to be executed by the enforcement
point: the actions of the higher priority rules are executed first.
Since the actions of higher priority rules are executed first, lower
priority rules that also match may get the "last word," and thus
produce a counter-intuitive result. 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 action of the
lower priority rule will be executed later and, therefore, will
"win," in this example, setting the DSCP to 4. Thus, conflicts
between rules are resolved by this execution order.
An implementation of the rule engine need not provide the action
sequencing but the actions MUST be sequenced by the PEP or PDP on its
behalf. So, for example, the rule engine may provide an ordered list
of actions to be executed by the PEP and any required serialization
is then provided by the service configured by the rule engine. See
Section 5.5.2 for a discussion of side effects.
5.5.1. Structuring Decision Strategies
As discussed in Sections 5.3 and 5.4, PolicySet instances may be
nested arbitrarily. For a FirstMatching decision strategy on a
PolicySet, any contained PolicySet that matches satisfies the
termination criteria for the FirstMatching strategy. A PolicySet is
considered to match if it is a PolicyRule and its conditions evaluate
to True, or if the PolicySet is a PolicyGroup and at least one of its
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contained PolicyGroups or PolicyRules match. The priority associated
with contained PolicySets, then, determines when to terminate rule
evaluation in the structured set of rules.
In the example shown in Figure 3, the relative priorities for the
nested rules, high to low, are 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, which
rules are enforced is also dependent on which rules, if any, match.
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
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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.
5.5.2. Side Effects
Although evaluation of conditions is sometimes discussed as an
ordered set of operations, the rule engine need not be implemented as
a procedural language interpreter. Any side effects of condition
evaluation or the execution of actions MUST NOT affect the result of
the evaluation of other conditions evaluated by the rule engine in
the same evaluation pass. That is, an implementation of a rule
engine MAY evaluate all conditions in any order before applying the
priority and determining which actions are to be executed.
So, regardless of how a rule engine is implemented, it MUST NOT
include any side effects of condition evaluation in the evaluation of
conditions for either of the decision strategies. For both the
AllMatching decision strategy and for the nesting of rules within
rules (either directly or indirectly) where the actions of more than
one rule may be enforced, any side effects of the enforcement of
actions MUST NOT be included in condition evaluation on the same
evaluation pass.
5.5.3. 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
aggregation instances between them. Each PolicySet tree has a
defined set of decision strategies and evaluation priorities. In
section 5.6 we discuss some improvements in the use of PolicyRoles
that cause the parent PolicySet.PolicyRoles to be applied to all
contained PolicySet instances. However, a given resource may still
have multiple, disjoint PolicySet trees regardless of how they are
collected. These top-level PolicySet instances are called "unrooted"
relative to the given resource.
So, a PolicySet instance is defined to be rooted or unrooted in the
context of a particular managed element; the relationship to the
managed element is usually established by the policy roles of the
PolicySet instance and of the managed element (see 5.6 "Policy
Roles"). A PolicySet instance is unrooted in that context if and
only if there is no PolicySetComponent association to a parent
PolicySet that is also related to the same managed element. These
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PolicySetComponent aggregations are traversed up the tree without
regard to how a PolicySet instance came to be related with the
ManagedElement. Figure 4. shows an example where instance A has role
A, instance B has role B and so on. In this example, in the context
of interface X, instances B, and C are unrooted and instances D, E,
and F are all rooted. In the context of interface Y, instance A is
unrooted and instances B, C, D, E and F are all rooted.
+---+ +-----------+ +-----------+
| A | | I/F X | | I/F Y |
+---+ | has roles | | has roles |
/ \ | B & C | | A & B |
/ \ +-----------+ +-----------+
+---+ +---+
| B | | C |
+---+ +---+
/ \ \
/ \ \
+---+ +---+ +---+
| D | | E | | F |
+---+ +---+ +---+
Figure 4. Unrooted PolicySet Instances
For those cases where there are multiple unrooted PolicySet instances
that apply to the same managed resource (i.e., not in a common
PolicySetComponent tree), the decision strategy among these disjoint
PolicySet instances is the FirstMatching strategy. The priority used
with this FirstMatching strategy is defined in the PolicySetInSystem
association. The PolicySetInSystem subclass instances are present
for all PolicySet instances (it is a required association) but the
priority is only used as a default for unrooted PolicySet instances
in a given ManagedElement context.
The FirstMatching strategy is used among all unrooted PolicySet
instances that apply to a given resource for a given functional
domain. So, for example, the PolicySet instances that are used for
QoS policy and the instances that are used for IKE policy, although
they are disjoint, are not joined in a FirstMatching decision
strategy. Instead, they are evaluated independently of one another.
5.5.4. Deterministic Decisions
As previously discussed, PolicySetComponent.Priority values MUST be
unique within a containing PolicySet and PolicySetInSystem.Priority
values MUST be unique for an associated System. Each PolicySet,
then, has a deterministic behavior based upon the decision strategy
and uniquely defined priority.
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There are certainly cases where rules need not have a unique priority
value (i.e., where evaluation and execution priority is not
important). However, it is believed that the flexibility gained by
this capability is not sufficiently beneficial to justify the
possible variations in implementation behavior and the resulting
confusion that might occur.
5.6. Policy Roles
A policy role is defined in [10] 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 document, 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.
5.6.1. Comparison of Roles in PCIM with Roles in snmpconf
In the Configuration Management with SNMP (snmpconf) working group's
Policy Based Management MIB [14], 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 [14] 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 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 [14], however, no special processing is required for
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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 [14] this is done via the
use of the Role tables (pmRoleESTable and pmRoleSETable). The Role
tables associate Role values with elements.
5.6.2. Addition of PolicyRoleCollection to PCIMe
In order to remedy the latter shortcoming in PCIM (the lack of a way
of associating a role with an object instance), PCIMe has a new class
PolicyRoleCollection derived from the CIM Collection class.
Resources that share a common role are aggregated by a
PolicyRoleCollection instance, via the ElementInPolicyRoleCollection
aggregation. The role is specified in the PolicyRole property of the
aggregating PolicyRoleCollection instance.
A PolicyRoleCollection always exists in the context of a system. As
was done in PCIM for PolicyRules and PolicyGroups, an association,
PolicyRoleCollectionInSystem, captures this relationship. Remember
that in CIM, System is a base class for describing network devices
and administrative domains.
The association between a PolicyRoleCollection and a system should be
consistent with the associations that scope the policy rules/groups
that are applied to the resources in that collection. Specifically,
a PolicyRoleCollection should be 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".
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
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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).
5.6.3. 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.
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.
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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:
+------------------------------+
| PolicyGroup PG1 |
| PolicyRoles = Ethernet, Fast |
+------------------------------+
|
| +------------------------+
| | PolicyRule PR1 |
|--------| PolicyRoles = Ethernet |
| +------------------------+
|
| +--------------------------+
| | PolicyRule PR2 |
|--------| PolicyRoles = <undefined>|
| +--------------------------+
|
| +------------------------+
| | PolicyRule PR3 |
|--------| PolicyRoles = Slow |
+------------------------+
Figure 5. 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.
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5.7. Compound Policy Conditions and Compound Policy Actions
Compound policy conditions and compound policy actions are introduced
to provide additional reusable "chunks" of policy.
5.7.1. 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 6.4), 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
PolicyConditionStructure, 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 6.
5.7.2. 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
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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 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 PolicyActionStructure, from which the
existing aggregation PolicyActionInPolicyRule and a new
aggregation PolicyActionInPolicyAction are derived.
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 6.
5.8. Variables and Values
The following subsections introduce several related concepts,
including PolicyVariables and PolicyValues (and their numerous
subclasses), SimplePolicyConditions, and SimplePolicyActions.
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5.8.1. Simple Policy Conditions
The SimplePolicyCondition class models elementary Boolean expressions
of the form: "(<variable> MATCH <value>)". The relationship 'MATCH',
which is implicit in the model, is interpreted based on the variable
and the value. Section 5.8.3 explains the semantics of the 'MATCH'
operator. 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 5.7.1).
For example, the expression "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 5.8.5 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>,
<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 model,
this object could represent the flow that is being conditioned. A
set of predefined variables that cover network attributes commonly
used for filtering is introduced 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).
The bound variable is matched against a value to produce the Boolean
result. For example, in the condition "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.
5.8.2. 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
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friendliest, from a user point-of-view) way to do this 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 6. depicts a SimplePolicyCondition with its associated
variable and value. Also shown are two PolicyValue instances that
identify the values that the variable can assume.
+-----------------------+
| SimplePolicyCondition |
+-----------------------+
* @
* @
+------------------+ * @ +---------------+
| (PolicyVariable) |*** @@@| (PolicyValue) |
+------------------+ +---------------+
# #
# ooo #
# #
+---------------+ +---------------+
| (PolicyValue) | ooo | (PolicyValue) |
+---------------+ +---------------+
Aggregation Legend:
**** PolicyVariableInSimplePolicyCondition
@@@@ PolicyValueInSimplePolicyCondition
#### ExpectedPolicyValuesForVariable
Figure 6. SimplePolicyCondition
Note: The class names in parenthesis denote subclasses. The classes
named in the figure are abstract, and thus cannot themselves be
instantiated.
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5.8.3. The Simple Condition Operator
A simple condition models an elementary Boolean expression of the
form "variable MATCHes value". However, the formal notation of the
SimplePolicyCondition, together with its associations, models only a
pair, (<variable>, <value>). The 'MATCH' operator is not directly
modeled -- it is implied. Furthermore, this implied 'MATCH' operator
carries overloaded semantics.
For example, in the simple condition "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 "DestinationPort MATCH {'80', '8080'}" -- operator is 'IS SET
MEMBER'
o "DestinationPort MATCH {'1 to 255'}" -- operator is 'IN INTEGER
RANGE'
o "SourceIPAddress MATCH 'MyCompany.com'" -- operator is 'IP ADDRESS
AS RESOLVED BY DNS'
The examples above illustrate the implicit, context-dependent nature
of the 'MATCH' operator. The interpretation depends on the actual
variable and value instances in the simple condition. The
interpretation is always derived from the bound variable and the
value instance associated with the simple condition. Text
accompanying the value class and implicit variable definition is used
for interpreting the semantics of the 'MATCH' relationship. In the
following list, we define generic (type-independent) matching.
PolicyValues may be multi-fielded, where each field may contain a
range of values. The same equally holds for PolicyVariables.
Basically, we have to deal with single values (singleton), ranges
([lower bound .. upper bound]), and sets (a,b,c). So independent of
the variable and value type, the following set of generic matching
rules for the 'MATCH' operator are defined.
o singleton matches singleton -> the matching rule is defined in the
type
o singleton matches range [lower bound .. upper bound] -> the
matching evaluates to true, if the singleton matches the lower
bound or the upper bound or a value in between
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o singleton matches set -> the matching evaluates to true, if the
value of the singleton matches one of the components in the set,
where a component may be a singleton or range again
o ranges [A..B] matches singleton -> is true if A matches B matches
singleton
o range [A..B] matches range [X..Y] -> the matching evaluates to
true, if all values of the range [A..B] are also in the range
[X..Y]. For instance, [3..5] match [1..6] evaluates to true,
whereas [3..5] match [4..6] evaluates to false.
o range [A..B] matches set (a,b,c, ...) -> the matching evaluates to
true, if all values in the range [A..B] are part of the set. For
instance, range [2..3] match set ([1..2],3) evaluates to true, as
well as range [2..3] match set (2,3), and range [2..3] match set
([1..2],[3..5]).
o set (a,b,c, ...) match singleton -> is true if a match b match c
match ... match singleton
o set match range -> the matching evaluates to true, if all values
in the set are part of the range. For example, set (2,3) match
range [1..4] evaluates to true.
o set (a,b,c,...) match set (x,y,z,...) -> the matching evaluates to
true, if all values in the set (a,b,c,...) are part of the set
(x,y,z,...). For example, set (1,2,3) match set (1,2,3,4)
evaluates to true. Set (1,2,3) match set (1,2) evaluates to
false.
Variables may contain various types (Section 6.11.1). When not
stated otherwise, the type of the value bound to the variable at
condition evaluation time and the value type of the PolicyValue
instance need to be of the same type. If they differ, then the
condition evaluates to FALSE.
The ExpectedPolicyValuesForVariable association specifies an expected
set of values that can be matched with a variable within a simple
condition. Using this association, a source or destination port can
be limited to the range 0-200, a source or destination IP address can
be limited to a specified list of IPv4 address values, etc.
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+-----------------------+
| SimplePolicyCondition |
+-----------------------+
* @
* @
* @
+-----------------------------------+ +--------------------------+
| Name=SmallSourcePorts | | Name=Port300 |
| Class=PolicySourcePortVariable | | Class=PolicyIntegerValue |
| ValueTypes=[PolicyIntegerValue] | | IntegerList = [300] |
+-----------------------------------+ +--------------------------+
#
#
#
+-------------------------+
|Name=SmallPortsValues |
|Class=PolicyIntegerValue |
|IntegerList=[1..200] |
+-------------------------+
Aggregation Legend:
**** PolicyVariableInSimplePolicyCondition
@@@@ PolicyValueInSimplePolicyCondition
#### ExpectedPolicyValuesForVariable
Figure 7. An Invalid SimplePolicyCondition
The ability to express these limitations appears in the model to
support validation of a SimplePolicyCondition prior to its deployment
to an enforcement point. A Policy Management Tool, for example
SHOULD NOT accept the SimplePolicyCondition shown in Figure 7. If,
however, a policy rule containing this condition does appear at an
enforcement point, the expected values play no role in the
determination of whether the condition evaluates to True or False.
Thus in this example, the SimplePolicyCondition evaluates to True if
the source port for the packet under consideration is 300, and it
evaluates to False otherwise.
5.8.4. SimplePolicyActions
The SimplePolicyAction class models the elementary set operation.
"SET <variable> TO <value>". The set operator MUST overwrite an old
value of the variable. In the case where the variable to be updated
is multi- valued, the only update operation defined is a complete
replacement of all previous values with a new set. In other words,
there are no Add or Remove [to/from the set of values] operations
defined for SimplePolicyActions.
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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.
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. The value of this
attribute is set to the value specified in <value>. Selection of the
object is a function of the type of variable involved. See Sections
5.8.6 and 5.8.7, respectively, for details on object selection for
explicitly bound and implicitly bound policy variables.
SimplePolicyActions can be used in policy rules directly, or as
building blocks for creating CompoundPolicyActions.
The set operation is only valid if the list of types of the variable
(ValueTypes property of PolicyImplicitVariable) includes the
specified type of the value. Conversion of values from one
representation into another is not defined. For example, a variable
of IPv4Address type may not be set to a string containing a DNS name.
Conversions are part of an implementation-specific mapping of the
model.
As was the case with SimplePolicyConditions, the role of expected
values for the variables that appear in SimplePolicyActions is for
validation, prior to the time when an action is executed. Expected
values play no role in action execution.
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 8. depicts a SimplePolicyAction with its associated variable
and value.
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+-----------------------+
| SimplePolicyAction |
| |
+-----------------------+
* @
* @
+------------------+ * @ +---------------+
| (PolicyVariable) |*** @@@| (PolicyValue) |
+------------------+ +---------------+
# #
# ooo #
# #
+---------------+ +---------------+
| (PolicyValue) | ooo | (PolicyValue) |
+---------------+ +---------------+
Aggregation Legend:
**** PolicyVariableInSimplePolicyAction
@@@@ PolicyValueInSimplePolicyAction
#### ExpectedPolicyValuesForVariable
Figure 8. SimplePolicyAction
5.8.5. 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, PolicyImplicitVariables
and PolicyExplicitVariables. 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. For example, one can imagine a
PolicyCondition testing whether a CIM ManagedSystemElement's Status
property has the value "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 or modification of a packet's source
address.
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5.8.6. 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 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 instance. If PolicyExplicitVariables were tied to
instances (either via associations or by an object identification
property in the class itself), then we would be 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>, <value>) pair) that defines CIM LogicalDevice
DeviceID="12345". Alternately, if a PolicyRule's PolicyRoles is
"edge device" and the condition ((<variable>, <value>) pair) is
Status="Error", then a general rule results for all edge devices in
error.
Currently, the only binding for a PolicyExplicitVariable defined in
PCIMe is to the instances selected by policy roles. For each such
instance, a SimplePolicyCondition that aggregates the
PolicyExplicitVariable evaluates to True if and only if ALL of the
following are true:
o The instance selected is of the class identified by the variable's
ModelClass property, or of a subclass of this class.
o The instance selected has the property identified by the
variable's ModelProperty property.
o The value of this property in the instance matches the value
specified in the PolicyValue aggregated by the condition.
In all other cases, the SimplePolicyCondition evaluates to False.
For the case where a SimplePolicyAction aggregates a
PolicyExplicitVariable, the indicated property in the selected
instance is set to the value represented by the PolicyValue that the
SimplePolicyAction also aggregates. However, if the selected
instance is not of the class identified by the variable's ModelClass
property, or of a subclass of this class, then the action is not
performed. In this case the SimplePolicyAction is not treated either
as a successfully executed action (for the execution strategy Do
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Until Success) or as a failed action (for the execution strategy Do
Until Failure). Instead, the remaining actions for the policy rule,
if any, are executed as if this SimplePolicyAction were not present
at all in the list of actions aggregated by the rule.
Explicit variables would be more powerful if they could reach beyond
the instances selected by policy roles, to related instances.
However, to represent a policy rule involving such variables in any
kind of general way requires something that starts to resemble very
much a complete policy language. Clearly such a language is outside
the scope of PCIMe, although it might be the subject of a future
document.
By restricting much of the generality, it would be possible for
explicit variables in PCIMe to reach slightly beyond a selected
instance. For example, if a selected instance were related to
exactly one instance of another class via a particular association
class, and if the goal of the policy rule were both to test a
property of this related instance and to set a property of that same
instance, then it would be possible to represent the condition and
action of the rule using PolicyExplicitVariables. Rather than
handling this one specific case with explicit variables, though, it
was decided to lump them with the more general case, and deal with
them if and when a policy language is defined.
Refer to Section 6.10 for the formal definition of the class
PolicyExplicitVariable.
5.8.7. 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 or an action. Further instructions are provided for
specifying data type and/or value constraints for implicitly bound
variables.
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 5.8.9.
A domain-specific policy information model that extends PCIMe may
define additional implicitly bound variables either by deriving them
directly from the class PolicyImplicitVariable, or by further
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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.
5.8.8. 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 have 'SourcePort' in
its name.
PCIMe defines one association and one general-purpose mechanism that
together characterize each of the implicitly bound variables that it
introduces:
1. The ExpectedPolicyValuesForVariable 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
ExpectedPolicyValuesForVariable association provide a consistent and
extensible set of metadata that define the semantics of variables
that are used to form policy conditions. Since the
ExpectedPolicyValuesForVariable association points to a PolicyValue
instance, any of the values expressible 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.
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o The ExpectedPolicyValuesForVariable 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).
5.8.9. 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 wouldn't 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 derived from this
information model may be more difficult to optimize for
applications. This argument is rejected on the grounds that
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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 model can be mapped
correctly to the definitions specified in this document.
5.8.10. 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 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 6.14 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 6.14 of this document.
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5.9. Packet Filtering
PCIMe contains two mechanisms for representing packet filters. The
more general of these, termed here the domain-level model, expresses
packet filters in terms of policy variables and policy values. The
other mechanism, termed here the device-level model, expresses packet
filters in a way that maps more directly to the packet fields to
which the filters are being applied. While it is possible to map
between these two representations of packet filters, no mapping is
provided in PCIMe itself.
5.9.1. Domain-Level Packet Filters
In addition to filling in the holes in the overall Policy
infrastructure, PCIMe proposes a single mechanism for expressing
domain-level 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 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 9. Packet Filtering in Policy Conditions
In Figure 9., 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
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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
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.
5.9.2. Device-Level Packet Filters
At the device level, packet header filters are represented by two
subclasses of the abstract class FilterEntryBase: IpHeadersFilter and
8021Filter. Submodels of PCIMe may define other subclasses of
FilterEntryBase in addition to these two; ICPM [12], for example,
defines subclasses for IPsec-specific filters.
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Instances of the subclasses of FilterEntryBase are not used directly
as filters. They are always aggregated into a FilterList, by the
aggregation EntriesInFilterList. For PCIMe and its submodels, the
EntrySequence property in this aggregation always takes its default
value '0', indicating that the aggregated filter entries are ANDed
together.
The FilterList class includes an enumeration property Direction,
representing the direction of the traffic flow to which the
FilterList is to be applied. The value Mirrored(4) for Direction
represents exactly the same thing as the IsMirrored boolean does in
CompoundFilterCondition. See Section 5.9.1 for details.
5.10. Conformance to PCIM and PCIMe
Because PCIM and PCIMe provide the core classes for modeling
policies, they are not in general sufficient by themselves for
representing actual policy rules. Submodels, such as QPIM and ICPM,
provide the means for expressing policy rules, by defining subclasses
of the classes defined in PCIM and PCIMe, and/or by indicating how
the PolicyVariables and PolicyValues defined in PCIMe can be used to
express conditions and actions applicable to the submodel.
A particular submodel will not, in general, need to use every element
defined in PCIM and PCIMe. For the elements it does not use, a
submodel SHOULD remain silent on whether its implementations must
support the element, must not support the element, should support the
element, etc. For the elements it does use, a submodel SHOULD
indicate which elements its implementations must support, which
elements they should support, and which elements they may support.
PCIM and PCIMe themselves simply define elements that may be of use
to submodels. These documents remain silent on whether
implementations are required to support an element, should support
it, etc.
This model (and derived submodels) defines conditions and actions
that are used by policy rules. While the conditions and actions
defined herein are straightforward and may be presumed to be widely
supported, as submodels are developed it is likely that situations
will arise in which specific conditions or actions are not supported
by some part of the policy execution system. Similarly, situations
may also occur where rules contain syntactic or semantic errors.
It should be understood that the behavior and effect of undefined or
incorrectly defined conditions or actions is not prescribed by this
information model. While it would be helpful if it were prescribed,
the variations in implementation restrict the ability for this
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information model to control the effect. For example, if an
implementation only detected that a PEP could not enforce a given
action on that PEP, it would be very difficult to declare that such a
failure should affect other PEPs, or the PDP process. On the other
hand, if the PDP determines that it cannot properly evaluate a
condition, that failure may well affect all applications of the
containing rules.
6. 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.
6.1. 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;
All Matching 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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6.2. Update PCIM's Class "PolicyGroup"
The PolicyGroup class is moved, so that it is now derived from
PolicySet.
NAME PolicyGroup
DESCRIPTION A container for a set of related PolicyRules and
PolicyGroups.
DERIVED FROM PolicySet
ABSTRACT FALSE
PROPERTIES (none)
6.3. Update PCIM's Class "PolicyRule"
The PolicyRule class is moved, so that it is now derived from
PolicySet. The Priority property is also deprecated in PolicyRule,
and 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
AND FOR PolicySetInSystem.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
document defines three execution strategies:
Do Until Success - 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.
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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
PolicyRule.
SYNTAX uint16 (ENUM, {1=Do Until Success, 2=Do All, 3=Do
Until Failure} )
DEFAULT VALUE Do All (2)
6.4. 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)
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6.5. 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
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)
6.6. 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:
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NAME IsMirrored
DESCRIPTION Indicates whether packets that mirror the specified
filter are to be treated as matching the filter.
SYNTAX boolean
DEFAULT VALUE FALSE
6.7. 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 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)
6.8. 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.
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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 document defines three
execution strategies:
Do Until Success - 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.
Do Until Failure - execute actions according to predefined order,
until the first failure in execution of a single
sub-action.
Since a CompoundPolicyAction may itself be aggregated either by a
PolicyRule or by another CompoundPolicyAction, its success or failure
will be an input to the aggregating entity's execution strategy.
Consequently, the following rules are specified, for determining
whether a CompoundPolicyAction succeeds or fails:
If the CompoundPolicyAction's ExecutionStrategy is Do Until Success,
then:
o If one component action succeeds, then the CompoundPolicyAction
succeeds.
o If all component actions fail, then the CompoundPolicyAction
fails.
If the CompoundPolicyAction's ExecutionStrategy is Do All, then:
o If all component actions succeed, then the CompoundPolicyAction
succeeds.
o If at least one component action fails, then the
CompoundPolicyAction fails.
If the CompoundPolicyAction's ExecutionStrategy is Do Until Failure,
then:
o If all component actions succeed, then the CompoundPolicyAction
succeeds.
o If at least one component action fails, then the
CompoundPolicyAction fails.
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The definition of the ExecutionStrategy property 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=Do Until Success, 2=Do All, 3=Do
Until Failure} )
DEFAULT VALUE Do All (2)
6.9. 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 ExpectedPolicyValuesForVariable 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)
6.10. 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. See Section 5.8.6 for a complete
discussion of what happens when the values of the ModelClass and
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ModelProperty properties in an instance of this class do not
correspond to the characteristics of the model construct being
evaluated or updated.
The class definition is as follows:
NAME PolicyExplicitVariable
DERIVED FROM PolicyVariable
ABSTRACT False
PROPERTIES ModelClass, ModelProperty
6.10.1. 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
6.10.2. 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
6.11. 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[ ]
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6.11.1. 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.
The property is defined as follows:
NAME ValueTypes
SYNTAX String
6.12. Subclasses of "PolicyImplicitVariable" Specified in PCIMe
The following subclasses of PolicyImplicitVariable are defined in
PCIMe.
6.12.1. The Class "PolicySourceIPv4Variable"
NAME PolicySourceIPv4Variable
DESCRIPTION The source IPv4 address. of the outermost IP packet
header. "Outermost" here refers to the IP packet as
it flows on the wire, before any headers have been
stripped from it.
ALLOWED VALUE TYPES:
- PolicyIPv4AddrValue
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.2. The Class "PolicySourceIPv6Variable"
NAME PolicySourceIPv6Variable
DESCRIPTION The source IPv6 address of the outermost IP packet
header. "Outermost" here refers to the IP packet as
it flows on the wire, before any headers have been
stripped from it.
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ALLOWED VALUE TYPES:
- PolicyIPv6AddrValue
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.3. The Class "PolicyDestinationIPv4Variable"
NAME PolicyDestinationIPv4Variable
DESCRIPTION The destination IPv4 address of the outermost IP
packet header. "Outermost" here refers to the IP
packet as it flows on the wire, before any headers
have been stripped from it.
ALLOWED VALUE TYPES:
- PolicyIPv4AddrValue
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.4. The Class "PolicyDestinationIPv6Variable"
NAME PolicyDestinationIPv6Variable
DESCRIPTION The destination IPv6 address of the outermost IP
packet header. "Outermost" here refers to the IP
packet as it flows on the wire, before any headers
have been stripped from it.
ALLOWED VALUE TYPES:
- PolicyIPv6AddrValue
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
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6.12.5. 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 of the
outermost UDP or TCP packet header. "Outermost"
here refers to the IP packet as it flows on the
wire, before any headers have been stripped from
it.
ALLOWED VALUE TYPES:
- PolicyIntegerValue (0..65535)
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.6. 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 of the
outermost UDP or TCP packet header. "Outermost"
here refers to the IP packet as it flows on the
wire, before any headers have been stripped from it.
ALLOWED VALUE TYPES:
- PolicyIntegerValue (0..65535)
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.7. The Class "PolicyIPProtocolVariable"
NAME PolicyIPProtocolVariable
DESCRIPTION The IP protocol number.
ALLOWED VALUE TYPES:
- PolicyIntegerValue (0..255)
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DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.8. The Class "PolicyIPVersionVariable"
NAME PolicyIPVersionVariable
DESCRIPTION The IP version number. The well-known values are 4
and 6.
ALLOWED VALUE TYPES:
- PolicyIntegerValue (0..15)
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.9. The Class "PolicyIPToSVariable"
NAME PolicyIPToSVariable
DESCRIPTION The IP TOS octet.
ALLOWED VALUE TYPES:
- PolicyIntegerValue (0..255)
- PolicyBitStringValue (8 bits)
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.10. The Class "PolicyDSCPVariable"
NAME PolicyDSCPVariable
DESCRIPTION The 6 bit Differentiated Service Code Point.
ALLOWED VALUE TYPES:
- PolicyIntegerValue (0..63)
- PolicyBitStringValue (6 bits)
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
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6.12.11. The Class "PolicyFlowIdVariable"
NAME PolicyFlowIdVariable
DESCRIPTION The flow identifier of the outermost IPv6 packet
header. "Outermost" here refers to the IP packet as
it flows on the wire, before any headers have been
stripped from it.
ALLOWED VALUE TYPES:
- PolicyIntegerValue (0..1048575
- PolicyBitStringValue (20 bits)
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.12. The Class "PolicySourceMACVariable"
NAME PolicySourceMACVariable
DESCRIPTION The source MAC address.
ALLOWED VALUE TYPES:
- PolicyMACAddrValue
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.13. The Class "PolicyDestinationMACVariable"
NAME PolicyDestinationMACVariable
DESCRIPTION The destination MAC address.
ALLOWED VALUE TYPES:
- PolicyMACAddrValue
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.14. 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.
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ALLOWED VALUE TYPES:
- PolicyIntegerValue (0..4095)
- PolicyBitStringValue (12 bits)
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.15. 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 (0..7)
- PolicyBitStringValue (3 bits)
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.16. The Class "PolicyEthertypeVariable"
NAME PolicyEthertypeVariable
DESCRIPTION The Ethertype protocol number of Ethernet frames.
ALLOWED VALUE TYPES:
- PolicyIntegerValue (0..65535)
- PolicyBitStringValue (16 bits)
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.17. The Class "PolicySourceSAPVariable"
NAME PolicySourceSAPVariable
DESCRIPTION The Source Service Access Point (SAP) number of the
IEEE 802.2 LLC header.
ALLOWED VALUE TYPES:
- PolicyIntegerValue (0..255)
- PolicyBitStringValue (8 bits)
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DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.18. The Class "PolicyDestinationSAPVariable"
NAME PolicyDestinationSAPVariable
DESCRIPTION The Destination Service Access Point (SAP) number of
the IEEE 802.2 LLC header.
ALLOWED VALUE TYPES:
- PolicyIntegerValue (0..255)
- PolicyBitStringValue (8 bits)
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.19. The Class "PolicySNAPOUIVariable"
NAME PolicySNAPOUIVariable
DESCRIPTION The value of the first three octets of the Sub-
Network Access Protocol (SNAP) Protocol Identifier
field for 802.2 SNAP encapsulation, containing an
Organizationally Unique Identifier (OUI). The value
00-00-00 indicates the encapsulation of Ethernet
frames (RFC 1042). OUI value 00-00-F8 indicates the
special encapsulation of Ethernet frames by certain
types of bridges (IEEE 802.1H). Other values are
supported, but are not further defined here. These
OUI values are to be interpreted according to the
endian-notation conventions of IEEE 802. For either
of the two Ethernet encapsulations, the remainder of
the Protocol Identifier field is represented by the
PolicySNAPTypeVariable.
ALLOWED VALUE TYPES:
- PolicyIntegerValue (0..16777215)
- PolicyBitStringValue (24 bits)
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
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6.12.20. The Class "PolicySNAPTypeVariable"
NAME PolicySNAPTypeVariable
DESCRIPTION The value of the 4th and 5th octets of the Sub-
Network Access Protocol (SNAP) Protocol Identifier
field for IEEE 802 SNAP encapsulation when the
PolicySNAPOUIVariable indicates one of the two
Encapsulated Ethernet frame formats. This value is
undefined for other values of PolicySNAPOUIVariable.
ALLOWED VALUE TYPES:
- PolicyIntegerValue (0..65535)
- PolicyBitStringValue (16 bits)
DERIVED FROM PolicyImplicitVariable
ABSTRACT FALSE
PROPERTIES (none)
6.12.21. 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 ('IN", "OUT")
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".
6.13. 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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6.14. 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.
6.14.1. 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 [6] 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 [4])
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.
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5. A single Hostname. The Hostname format follows the guidelines and
restrictions specified in [4]. Example: www.bigcompany.com.
Conditions matching IPv4AddrValues evaluate to true according to the
generic matching rules. Additionally, a hostname is matched against
another valid IPv4address representation by resolving the hostname
into an IPv4 address first, and then comparing the addresses
afterwards. Matching hostnames against each other is done using a
string comparison of the two names.
The property definition is as follows:
NAME IPv4AddrList
SYNTAX String
FORMAT IPv4address | IPv4prefix | IPv4range |
IPv4maskedaddress | hostname
6.14.2. 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 [7]. The ABNF definition [6] as specified in [7] 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 [4].
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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.
Conditions matching IPv6AddrValues evaluate to true according to the
generic matching rules. Additionally, a hostname is matched against
another valid IPv6address representation by resolving the hostname
into an IPv6 address first, and then comparing the addresses
afterwards. Matching hostnames against each other is done using a
string comparison of the two names.
6.14.3. 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 [6] 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.
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The property definition is as follows:
NAME MACAddrList
SYNTAX String
FORMAT MACaddress | MACmaskedaddress
6.14.4. 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 [5]. If the asterisk character
is required as part of the string value itself, it MUST be quoted as
described in Section 4.3 of [5].
The property definition is as follows:
NAME StringList
SYNTAX String
6.14.5. 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
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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
6.14.6. 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
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.
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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. In addition to ordinary integer matches,
INFINITY matches INFINITY and -INFINITY matches -INFINITY.
The ABNF definition [6] 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
6.14.7. 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
SYNTAX boolean
6.15. 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.
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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
6.15.1. 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
6.16. 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)
6.17. Deprecate 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.
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.
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DERIVED FROM AdminDomain
ABSTRACT FALSE
PROPERTIES (none)
6.18. The Abstract Class "FilterEntryBase"
FilterEntryBase is the abstract base class from which all filter
entry classes are derived. It serves as the endpoint for the
EntriesInFilterList aggregation, which groups filter entries into
filter lists. Its properties include CIM naming attributes and an
IsNegated boolean property (to easily "NOT" the match information
specified in an instance of one of its subclasses).
The class definition is as follows:
NAME FilterEntryBase
DESCRIPTION An abstract class representing a single
filter that is aggregated into a
FilterList via the aggregation
EntriesInFilterList.
DERIVED FROM LogicalElement
TYPE Abstract
PROPERTIES IsNegated
6.19. The Class "IpHeadersFilter"
This concrete class contains the most commonly required properties
for performing filtering on IP, TCP or UDP headers. Properties not
present in an instance of IPHeadersFilter are treated as 'all
values'. A property HdrIpVersion identifies whether the IP addresses
in an instance are IPv4 or IPv6 addresses. Since the source and
destination IP addresses come from the same packet header, they will
always be of the same type.
The class definition is as follows:
NAME IpHeadersFilter
DESCRIPTION A class representing an entire IP
header filter, or any subset of one.
DERIVED FROM FilterEntryBase
TYPE Concrete
PROPERTIES HdrIpVersion, HdrSrcAddress,
HdrSrcAddressEndOfRange, HdrSrcMask,
HdrDestAddress, HdrDestAddressEndOfRange,
HdrDestMask, HdrProtocolID,
HdrSrcPortStart, HdrSrcPortEnd,
HdrDestPortStart, HdrDestPortEnd, HdrDSCP[ ],
HdrFlowLabel
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6.19.1. The Property HdrIpVersion
This property is an 8-bit unsigned integer, identifying the version
of the IP addresses to be filtered on. IP versions are identified as
they are in the Version field of the IP packet header - IPv4 = 4,
IPv6 = 6. These two values are the only ones defined for this
property.
The value of this property determines the sizes of the OctetStrings
in the six properties HdrSrcAddress, HdrSrcAddressEndOfRange,
HdrSrcMask, HdrDestAddress, HdrDestAddressEndOfRange, and
HdrDestMask, as follows:
o IPv4: OctetString(SIZE (4))
o IPv6: OctetString(SIZE (16|20)), depending on whether a scope
identifier is present
If a value for this property is not provided, then the filter does
not consider IP version in selecting matching packets, i.e., IP
version matches for all values. In this case, the HdrSrcAddress,
HdrSrcAddressEndOfRange, HdrSrcMask, HdrDestAddress,
HdrDestAddressEndOfRange, and HdrDestMask must also not be present.
6.19.2. The Property HdrSrcAddress
This property is an OctetString, of a size determined by the value of
the HdrIpVersion property, representing a source IP address. When
there is no HdrSrcAddressEndOfRange value, this value is compared to
the source address in the IP header, subject to the mask represented
in the HdrSrcMask property. (Note that the mask is ANDed with the
address.) When there is a HdrSrcAddressEndOfRange value, this value
is the start of the specified range (i.e., the HdrSrcAddress is lower
than the HdrSrcAddressEndOfRange) that is compared to the source
address in the IP header and matches on any value in the range.
If a value for this property is not provided, then the filter does
not consider HdrSrcAddress in selecting matching packets, i.e.,
HdrSrcAddress matches for all values.
6.19.3. The Property HdrSrcAddressEndOfRange
This property is an OctetString, of a size determined by the value of
the HdrIpVersion property, representing the end of a range of source
IP addresses (inclusive), where the start of the range is the
HdrSrcAddress property value.
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If a value for HdrSrcAddress is not provided, then this property also
MUST NOT be provided. If a value for this property is provided, then
HdrSrcMask MUST NOT be provided.
6.19.4. The Property HdrSrcMask
This property is an OctetString, of a size determined by the value of
the HdrIpVersion property, representing a mask to be used in
comparing the source address in the IP header with the value
represented in the HdrSrcAddress property.
If a value for this property is not provided, then the filter does
not consider HdrSrcMask in selecting matching packets, i.e., the
value of HdrSrcAddress or the source address range must match the
source address in the packet exactly. If a value for this property
is provided, then HdrSrcAddressEndOfRange MUST NOT be provided.
6.19.5. The Property HdrDestAddress
This property is an OctetString, of a size determined by the value of
the HdrIpVersion property, representing a destination IP address.
When there is no HdrDestAddressEndOfRange value, this value is
compared to the destination address in the IP header, subject to the
mask represented in the HdrDestMask property. (Note that the mask is
ANDed with the address.) When there is a HdrDestAddressEndOfRange
value, this value is the start of the specified range (i.e., the
HdrDestAddress is lower than the HdrDestAddressEndOfRange) that is
compared to the destination address in the IP header and matches on
any value in the range.
If a value for this property is not provided, then the filter does
not consider HdrDestAddress in selecting matching packets, i.e.,
HdrDestAddress matches for all values.
6.19.6. The Property HdrDestAddressEndOfRange
This property is an OctetString, of a size determined by the value of
the HdrIpVersion property, representing the end of a range of
destination IP addresses (inclusive), where the start of the range is
the HdrDestAddress property value.
If a value for HdrDestAddress is not provided, then this property
also MUST NOT be provided. If a value for this property is provided,
then HdrDestMask MUST NOT be provided.
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6.19.7. The Property HdrDestMask
This property is an OctetString, of a size determined by the value of
the HdrIpVersion property, representing a mask to be used in
comparing the destination address in the IP header with the value
represented in the HdrDestAddress property.
If a value for this property is not provided, then the filter does
not consider HdrDestMask in selecting matching packets, i.e., the
value of HdrDestAddress or the destination address range must match
the destination address in the packet exactly. If a value for this
property is provided, then HdrDestAddressEndOfRange MUST NOT be
provided.
6.19.8. The Property HdrProtocolID
This property is an 8-bit unsigned integer, representing an IP
protocol type. This value is compared to the Protocol field in the
IP header.
If a value for this property is not provided, then the filter does
not consider HdrProtocolID in selecting matching packets, i.e.,
HdrProtocolID matches for all values.
6.19.9. The Property HdrSrcPortStart
This property is a 16-bit unsigned integer, representing the lower
end of a range of UDP or TCP source ports. The upper end of the
range is represented by the HdrSrcPortEnd property. The value of
HdrSrcPortStart MUST be no greater than the value of HdrSrcPortEnd.
A single port is indicated by equal values for HdrSrcPortStart and
HdrSrcPortEnd.
A source port filter is evaluated by testing whether the source port
identified in the IP header falls within the range of values between
HdrSrcPortStart and HdrSrcPortEnd, including these two end points.
If a value for this property is not provided, then the filter does
not consider HdrSrcPortStart in selecting matching packets, i.e.,
there is no lower bound in matching source port values.
6.19.10. The Property HdrSrcPortEnd
This property is a 16-bit unsigned integer, representing the upper
end of a range of UDP or TCP source ports. The lower end of the
range is represented by the HdrSrcPortStart property. The value of
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HdrSrcPortEnd MUST be no less than the value of HdrSrcPortStart. A
single port is indicated by equal values for HdrSrcPortStart and
HdrSrcPortEnd.
A source port filter is evaluated by testing whether the source port
identified in the IP header falls within the range of values between
HdrSrcPortStart and HdrSrcPortEnd, including these two end points.
If a value for this property is not provided, then the filter does
not consider HdrSrcPortEnd in selecting matching packets, i.e., there
is no upper bound in matching source port values.
6.19.11. The Property HdrDestPortStart
This property is a 16-bit unsigned integer, representing the lower
end of a range of UDP or TCP destination ports. The upper end of the
range is represented by the HdrDestPortEnd property. The value of
HdrDestPortStart MUST be no greater than the value of HdrDestPortEnd.
A single port is indicated by equal values for HdrDestPortStart and
HdrDestPortEnd.
A destination port filter is evaluated by testing whether the
destination port identified in the IP header falls within the range
of values between HdrDestPortStart and HdrDestPortEnd, including
these two end points.
If a value for this property is not provided, then the filter does
not consider HdrDestPortStart in selecting matching packets, i.e.,
there is no lower bound in matching destination port values.
6.19.12. The Property HdrDestPortEnd
This property is a 16-bit unsigned integer, representing the upper
end of a range of UDP or TCP destination ports. The lower end of the
range is represented by the HdrDestPortStart property. The value of
HdrDestPortEnd MUST be no less than the value of HdrDestPortStart. A
single port is indicated by equal values for HdrDestPortStart and
HdrDestPortEnd.
A destination port filter is evaluated by testing whether the
destination port identified in the IP header falls within the range
of values between HdrDestPortStart and HdrDestPortEnd, including
these two end points.
If a value for this property is not provided, then the filter does
not consider HdrDestPortEnd in selecting matching packets, i.e.,
there is no upper bound in matching destination port values.
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6.19.13. The Property HdrDSCP
The property HdrDSCP is defined as an array of uint8's, restricted to
the range 0..63. Since DSCPs are defined as discrete code points,
with no inherent structure, there is no semantically significant
relationship between different DSCPs. Consequently, there is no
provision for specifying a range of DSCPs in this property. However,
a list of individual DSCPs, which are ORed together to form a filter,
is supported by the array syntax.
If a value for this property is not provided, then the filter does
not consider HdrDSCP in selecting matching packets, i.e., HdrDSCP
matches for all values.
6.19.14. The Property HdrFlowLabel
The 20-bit Flow Label field in the IPv6 header may be used by a
source to label sequences of packets for which it requests special
handling by IPv6 devices, such as non-default quality of service or
'real-time' service. This property is an octet string of size 3
(that is, 24 bits), in which the 20-bit Flow Label appears in the
rightmost 20 bits, padded on the left with b'0000'.
If a value for this property is not provided, then the filter does
not consider HdrFlowLabel in selecting matching packets, i.e.,
HdrFlowLabel matches for all values.
6.20. The Class "8021Filter"
This concrete class allows 802.1.source and destination MAC
addresses, as well as the 802.1 protocol ID, priority, and VLAN
identifier fields, to be expressed in a single object
The class definition is as follows:
NAME 8021Filter
DESCRIPTION A class that allows 802.1 source
and destination MAC address and
protocol ID, priority, and VLAN
identifier filters to be
expressed in a single object.
DERIVED FROM FilterEntryBase
TYPE Concrete
PROPERTIES 8021HdrSrcMACAddr, 8021HdrSrcMACMask,
8021HdrDestMACAddr, 8021HdrDestMACMask,
8021HdrProtocolID, 8021HdrPriorityValue,
8021HDRVLANID
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6.20.1. The Property 8021HdrSrcMACAddr
This property is an OctetString of size 6, representing a 48-bit
source MAC address in canonical format. This value is compared to
the SourceAddress field in the MAC header, subject to the mask
represented in the 8021HdrSrcMACMask property.
If a value for this property is not provided, then the filter does
not consider 8021HdrSrcMACAddr in selecting matching packets, i.e.,
8021HdrSrcMACAddr matches for all values.
6.20.2. The Property 8021HdrSrcMACMask
This property is an OctetString of size 6, representing a 48-bit mask
to be used in comparing the SourceAddress field in the MAC header
with the value represented in the 8021HdrSrcMACAddr property.
If a value for this property is not provided, then the filter does
not consider 8021HdrSrcMACMask in selecting matching packets, i.e.,
the value of 8021HdrSrcMACAddr must match the source MAC address in
the packet exactly.
6.20.3. The Property 8021HdrDestMACAddr
This property is an OctetString of size 6, representing a 48-bit
destination MAC address in canonical format. This value is compared
to the DestinationAddress field in the MAC header, subject to the
mask represented in the 8021HdrDestMACMask property.
If a value for this property is not provided, then the filter does
not consider 8021HdrDestMACAddr in selecting matching packets, i.e.,
8021HdrDestMACAddr matches for all values.
6.20.4. The Property 8021HdrDestMACMask
This property is an OctetString of size 6, representing a 48-bit mask
to be used in comparing the DestinationAddress field in the MAC
header with the value represented in the 8021HdrDestMACAddr property.
If a value for this property is not provided, then the filter does
not consider 8021HdrDestMACMask in selecting matching packets, i.e.,
the value of 8021HdrDestMACAddr must match the destination MAC
address in the packet exactly.
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6.20.5. The Property 8021HdrProtocolID
This property is a 16-bit unsigned integer, representing an Ethernet
protocol type. This value is compared to the Ethernet Type field in
the 802.3 MAC header.
If a value for this property is not provided, then the filter does
not consider 8021HdrProtocolID in selecting matching packets, i.e.,
8021HdrProtocolID matches for all values.
6.20.6. The Property 8021HdrPriorityValue
This property is an 8-bit unsigned integer, representing an 802.1Q
priority. This value is compared to the Priority field in the 802.1Q
header. Since the 802.1Q Priority field consists of 3 bits, the
values for this property are limited to the range 0..7.
If a value for this property is not provided, then the filter does
not consider 8021HdrPriorityValue in selecting matching packets,
i.e., 8021HdrPriorityValue matches for all values.
6.20.7. The Property 8021HdrVLANID
This property is a 32-bit unsigned integer, representing an 802.1Q
VLAN Identifier. This value is compared to the VLAN ID field in the
802.1Q header. Since the 802.1Q VLAN ID field consists of 12 bits,
the values for this property are limited to the range 0..4095.
If a value for this property is not provided, then the filter does
not consider 8021HdrVLANID in selecting matching packets, i.e.,
8021HdrVLANID matches for all values.
6.21. The Class FilterList
This is a concrete class that aggregates instances of (subclasses of)
FilterEntryBase via the aggregation EntriesInFilterList. It is
possible to aggregate different types of filters into a single
FilterList - for example, packet header filters (represented by the
IpHeadersFilter class) and security filters (represented by
subclasses of FilterEntryBase defined by IPsec).
The aggregation property EntriesInFilterList.EntrySequence is always
set to 0, to indicate that the aggregated filter entries are ANDed
together to form a selector for a class of traffic.
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The class definition is as follows:
NAME FilterList
DESCRIPTION A concrete class representing
the aggregation of multiple filters.
DERIVED FROM LogicalElement
TYPE Concrete
PROPERTIES Direction
6.21.1. The Property Direction
This property is a 16-bit unsigned integer enumeration, representing
the direction of the traffic flow to which the FilterList is to be
applied. Defined enumeration values are
o NotApplicable(0)
o Input(1)
o Output(2)
o Both(3) - This value is used to indicate that the direction is
immaterial, e.g., to filter on a source subnet regardless of
whether the flow is inbound or outbound
o Mirrored(4) - This value is also applicable to both inbound and
outbound flow processing, but it indicates that the filter
criteria are applied asymmetrically to traffic in both directions
and, thus, specifies the reversal of source and destination
criteria (as opposed to the equality of these criteria as
indicated by "Both"). The match conditions in the aggregated
FilterEntryBase subclass instances are defined from the
perspective of outbound flows and applied to inbound flows as well
by reversing the source and destination criteria. So, for
example, consider a FilterList with 3 filter entries indicating
destination port = 80, and source and destination addresses of a
and b, respectively. Then, for the outbound direction, the filter
entries match as specified and the 'mirror' (for the inbound
direction) matches on source port = 80 and source and destination
addresses of b and a, respectively.
7. 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.
7.1. The Aggregation "PolicySetComponent"
PolicySetComponent is a new aggregation class that collects instances
of PolicySet subclasses (PolicyGroups and PolicyRules) into coherent
sets of policies.
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NAME PolicySetComponent
DESCRIPTION A concrete class representing the components of a
policy set that have the same decision strategy, and
are prioritized within the set.
DERIVED FROM PolicyComponent
ABSTRACT FALSE
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
7.2. Deprecate PCIM's Aggregation "PolicyGroupInPolicyGroup"
The new aggregation PolicySetComponent is used directly to represent
aggregation of PolicyGroups by a higher-level PolicyGroup. Thus the
aggregation PolicyGroupInPolicyGroup is no longer needed, and can be
deprecated.
NAME PolicyGroupInPolicyGroup
DEPRECATED FOR PolicySetComponent
DESCRIPTION A class representing the aggregation of PolicyGroups
by a higher-level PolicyGroup.
DERIVED FROM PolicyComponent
ABSTRACT FALSE
PROPERTIES GroupComponent[ref PolicyGroup[0..n]]
PartComponent[ref PolicyGroup[0..n]]
7.3. Deprecate PCIM's Aggregation "PolicyRuleInPolicyGroup"
The new aggregation PolicySetComponent is used directly to represent
aggregation of PolicyRules by a PolicyGroup. Thus the aggregation
PolicyRuleInPolicyGroup is no longer needed, and can be deprecated.
NAME PolicyRuleInPolicyGroup
DEPRECATED FOR PolicySetComponent
DESCRIPTION A class representing the aggregation of PolicyRules
by a PolicyGroup.
DERIVED FROM PolicyComponent
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ABSTRACT FALSE
PROPERTIES GroupComponent[ref PolicyGroup[0..n]]
PartComponent[ref PolicyRule[0..n]]
7.4. The Abstract Association "PolicySetInSystem"
PolicySetInSystem is a new association that defines a relationship
between a System and a PolicySet used in the administrative scope of
that system (e.g., AdminDomain, ComputerSystem). The Priority
property is used to assign a relative priority to a PolicySet within
the administrative scope in contexts where it is not a component of
another PolicySet.
NAME PolicySetInSystem
DESCRIPTION An abstract class representing the relationship
between a System and a PolicySet that is used in the
administrative scope of the System.
DERIVED FROM PolicyInSystem
ABSTRACT TRUE
PROPERTIES Antecedent[ref System[0..1]]
Dependent [ref PolicySet[0..n]]
Priority
The Priority property is used to specify the relative priority of the
referenced PolicySet when there are more than one PolicySet instances
applied to a managed resource that are not PolicySetComponents and,
therefore, have no other relative priority defined.
NAME Priority
DESCRIPTION A non-negative integer for prioritizing the
referenced PolicySet among other PolicySet
instances that are not components of a common
PolicySet. A larger value indicates a higher
priority.
SYNTAX uint16
DEFAULT VALUE 0
7.5. Update PCIM's Weak Association "PolicyGroupInSystem"
Regardless of whether it a component of another PolicySet, a
PolicyGroup is itself defined within the scope of a System. This
association links a PolicyGroup to the System in whose scope the
PolicyGroup is defined. It is a subclass of the abstract
PolicySetInSystem association. The class definition for the
association is as follows:
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NAME PolicyGroupInSystem
DESCRIPTION A class representing the fact that a PolicyGroup is
defined within the scope of a System.
DERIVED FROM PolicySetInSystem
ABSTRACT FALSE
PROPERTIES Antecedent[ref System[1..1]]
Dependent [ref PolicyGroup[weak]]
The Reference "Antecedent" is inherited from PolicySetInSystem, 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
PolicyGroups. Since this is a weak association, the cardinality for
this object reference is always 1, that is, a PolicyGroup is always
defined within the scope of exactly one System.
The Reference "Dependent" is inherited from PolicySetInSystem, and
overridden to become an object reference to a PolicyGroup defined
within the scope of a System. Note that for any single instance of
the association class PolicyGroupInSystem, 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
PolicyGroups defined within its scope.
7.6. Update PCIM's Weak Association "PolicyRuleInSystem"
Regardless of whether it a component of another PolicySet, a
PolicyRule is itself defined within the scope of a System. This
association links a PolicyRule to the System in whose scope the
PolicyRule is defined. It is a subclass of the abstract
PolicySetInSystem association. The class definition for the
association is as follows:
NAME PolicyRuleInSystem
DESCRIPTION A class representing the fact that a PolicyRule is
defined within the scope of a System.
DERIVED FROM PolicySetInSystem
ABSTRACT FALSE
PROPERTIES Antecedent[ref System[1..1]]
Dependent[ref PolicyRule[weak]]
The Reference "Antecedent" is inherited from PolicySetInSystem, 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
PolicyRules. Since this is a weak association, the cardinality for
this object reference is always 1, that is, a PolicyRule is always
defined within the scope of exactly one System.
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The Reference "Dependent" is inherited from PolicySetInSystem, and
overridden to become an object reference to a PolicyRule defined
within the scope of a System. Note that for any single instance of
the association class PolicyRuleInSystem, 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
PolicyRules defined within its scope.
7.7. The Abstract Aggregation "PolicyConditionStructure"
NAME PolicyConditionStructure
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
7.8. Update PCIM's Aggregation "PolicyConditionInPolicyRule"
The PCIM aggregation "PolicyConditionInPolicyRule" is updated, to
make it a subclass of the new abstract aggregation
PolicyConditionStructure. 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 PolicyConditionStructure
ABSTRACT FALSE
PROPERTIES GroupComponent[ref PolicyRule[0..n]]
7.9. The Aggregation "PolicyConditionInPolicyCondition"
A second subclass of PolicyConditionStructure 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 PolicyConditionStructure
ABSTRACT FALSE
PROPERTIES GroupComponent[ref CompoundPolicyCondition[0..n]]
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7.10. The Abstract Aggregation "PolicyActionStructure"
NAME PolicyActionStructure
DESCRIPTION A class representing the aggregation of
PolicyActions by an aggregating instance.
DERIVED FROM PolicyComponent
ABSTRACT TRUE
PROPERTIES PartComponent[ref PolicyAction[0..n]]
ActionOrder
The definition of the ActionOrder property appears in Section 7.8.3
of PCIM [1].
7.11. Update PCIM's Aggregation "PolicyActionInPolicyRule"
The PCIM aggregation "PolicyActionInPolicyRule" is updated, to make
it a subclass of the new abstract aggregation PolicyActionStructure.
The 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 PolicyActionStructure
ABSTRACT FALSE
PROPERTIES GroupComponent[ref PolicyRule[0..n]]
7.12. The Aggregation "PolicyActionInPolicyAction"
A second subclass of PolicyActionStructure 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 PolicyActionStructure
ABSTRACT FALSE
PROPERTIES GroupComponent[ref CompoundPolicyAction[0..n]]
7.13. 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.
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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 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.
7.14. 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
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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.
7.15. 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:
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.
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7.16. 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, 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.
7.17. 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.
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DERIVED FROM PolicyInSystem
ABSTRACT FALSE
PROPERTIES Antecedent[ref ReusablePolicyContainer[0..1]]
7.18. 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]]
7.19. 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]]
7.20. The Association ExpectedPolicyValuesForVariable
This association links a PolicyValue object to a PolicyVariable
object, modeling the set of expected values for that PolicyVariable.
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 with it the set
of values (integers) representing the allowed enumeration, using
appropriate number of instances of the
ExpectedPolicyValuesForVariable 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 purpose of this association is to support validation of simple
policy conditions and simple policy actions, prior to their
deployment to an enforcement point. This association, and the
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PolicyValue object that it refers to, plays no role when a PDP or a
PEP is evaluating a simple policy condition, or executing a simple
policy action. See Section 5.8.3 for more details on this point.
The class definition for the association is as follows:
NAME ExpectedPolicyValuesForVariable
DESCRIPTION A class representing the association of a set of
expected values 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
representing 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 set(s)
of values that the policy variable can take.
7.21. The Aggregation "ContainedDomain"
The aggregation ContainedDomain provides a means of nesting of one
ReusablePolicyContainer inside another one. The aggregation is
defined at the level of ReusablePolicyContainer's superclass,
AdminDomain, to give it applicability to areas other than Core
Policy.
NAME ContainedDomain
DESCRIPTION A class representing the aggregation of lower level
administrative domains by a higher-level
AdminDomain.
DERIVED FROM SystemComponent
ABSTRACT FALSE
PROPERTIES GroupComponent[ref AdminDomain [0..n]]
PartComponent[ref AdminDomain [0..n]]
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7.22. Deprecate PCIM's "PolicyRepositoryInPolicyRepository"
NAME PolicyRepositoryInPolicyRepository
DEPRECATED FOR ContainedDomain
DESCRIPTION A class representing the aggregation of
PolicyRepositories by a higher-level
PolicyRepository.
DERIVED FROM SystemComponent
ABSTRACT FALSE
PROPERTIES GroupComponent[ref PolicyRepository[0..n]]
PartComponent[ref PolicyRepository[0..n]]
7.23. The Aggregation "EntriesInFilterList"
This aggregation is a specialization of the Component aggregation; it
is used to define a set of filter entries (subclasses of
FilterEntryBase) that are aggregated by a FilterList.
The cardinalities of the aggregation itself are 0..1 on the
FilterList end, and 0..n on the FilterEntryBase end. Thus in the
general case, a filter entry can exist without being aggregated into
any FilterList. However, the only way a filter entry can figure in
the PCIMe model is by being aggregated into a FilterList by this
aggregation.
The class definition for the aggregation is as follows:
NAME EntriesInFilterList
DESCRIPTION An aggregation used to define a set of
filter entries (subclasses of
FilterEntryBase) that are aggregated by
a particular FilterList.
DERIVED FROM Component
ABSTRACT False
PROPERTIES GroupComponent[ref
FilterList[0..1]],
PartComponent[ref
FilterEntryBase[0..n],
EntrySequence
7.23.1. The Reference GroupComponent
This property is overridden in this aggregation to represent an
object reference to a FilterList object (instead of to the more
generic ManagedSystemElement object defined in its superclass). It
also restricts the cardinality of the aggregate to 0..1 (instead of
the more generic 0-or-more), representing the fact that a filter
entry always exists within the context of at most one FilterList.
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7.23.2. The Reference PartComponent
This property is overridden in this aggregation to represent an
object reference to a FilterEntryBase object (instead of to the more
generic ManagedSystemElement object defined in its superclass). This
object represents a single filter entry, which may be aggregated with
other filter entries to form the FilterList.
7.23.3. The Property EntrySequence
An unsigned 16-bit integer indicating the order of the filter entry
relative to all others in the FilterList. The default value '0'
indicates that order is not significant, because the entries in this
FilterList are ANDed together.
7.24. 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]]
7.25. 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:
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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 become an object reference to a System, and 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
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.
8. 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.
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9. Acknowledgements
The starting point for this document was PCIM itself [1], and the
first three submodels derived from it [11], [12], [13]. The authors
of these documents created the extensions to PCIM, and asked the
questions about PCIM, that are reflected in PCIMe.
10. Contributors
This document includes text written by a number of authors (including
the editor), that was subsequently merged by the editor. The
following people contributed text to this document:
Lee Rafalow
IBM Corporation, BRQA/501
4205 S. Miami Blvd.
Research Triangle Park, NC 27709
Phone: +1 919-254-4455
Fax: +1 919-254-6243
EMail: 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
EMail: yramberg@cisco.com
Yoram Snir
Cisco Systems
4 Maskit Street
Herzliya Pituach, Israel 46766
Phone: +972-9-970-0085
Fax: +972-9-970-0366
EMail: ysnir@cisco.com
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RFC 3460 PCIM Extensions January 2003
Andrea Westerinen
Cisco Systems
Building 20
725 Alder Drive
Milpitas, CA 95035
Phone: +1-408-853-8294
Fax: +1-408-527-6351
EMail: 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
EMail: chadha@research.telcordia.com
Marcus Brunner
NEC Europe Ltd.
C&C Research Laboratories
Adenauerplatz 6
D-69115 Heidelberg, Germany
Phone: +49 (0)6221 9051129
Fax: +49 (0)6221 9051155
EMail: brunner@ccrle.nec.de
Ron Cohen
Ntear LLC
EMail: ronc@ntear.com
John Strassner
INTELLIDEN, Inc.
90 South Cascade Avenue
Colorado Springs, CO 80903
Phone: +1-719-785-0648
EMail: john.strassner@intelliden.com
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11. Security Considerations
The Policy Core Information Model (PCIM) [1] 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.
12. Normative References
[1] Moore, B., Ellesson, E., Strassner, J. and A. Westerinen,
"Policy Core Information Model -- Version 1 Specification", RFC
3060, February 2001.
[2] Distributed Management Task Force, Inc., "DMTF Technologies: CIM
Standards CIM Schema: Version 2.5", available at
http://www.dmtf.org/standards/cim_schema_v25.php.
[3] Distributed Management Task Force, Inc., "Common Information
Model (CIM) Specification: Version 2.2", June 14, 1999,
available at
http://www.dmtf.org/standards/documents/CIM/DSP0004.pdf.
[4] Mockapetris, P., "Domain Names - implementation and
specification", STD 13, RFC 1035, November 1987.
[5] Wahl, M., Coulbeck, A., Howes, T. and S. Kille, "Lightweight
Directory Access Protocol (v3): Attribute Syntax Definitions",
RFC 2252, December 1997.
[6] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[7] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, July 1998.
[8] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
13. Informative References
[9] Hovey, R. and S. Bradner, "The Organizations Involved in the
IETF Standards Process", BCP 11, RFC 2028, October 1996.
[10] Westerinen, A., Schnizlein, J., Strassner, J., Scherling, M.,
Quinn, B., Herzog, S., Huynh, A., Carlson, M., Perry, J. and
Waldbusser, "Terminology for Policy-Based Management", RFC 3198,
November 2001.
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RFC 3460 PCIM Extensions January 2003
[11] Snir, Y., and Y. Ramberg, J. Strassner, R. Cohen, "Policy QoS
Information Model", Work in Progress.
[12] Jason, J., and L. Rafalow, E. Vyncke, "IPsec Configuration
Policy Model", Work in Progress.
[13] 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.
[14] S. Waldbusser, and J. Saperia, T. Hongal, "Policy Based
Management MIB", Work in Progress.
[15] B. Moore, and D. Durham, J. Halpern, J. Strassner, A.
Westerinen, W. Weiss, "Information Model for Describing Network
Device QoS Datapath Mechanisms", Work in Progress.
Author's Address
Bob Moore
IBM Corporation, BRQA/501
4205 S. Miami Blvd.
Research Triangle Park, NC 27709
Phone: +1 919-254-4436
Fax: +1 919-254-6243
EMail: remoore@us.ibm.com
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Full Copyright Statement
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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