Network Working Group J. Strassner Internet Draft Huawei Technologies Intended status: Standard Track Expires: October 26, 2015 April 26, 2015 Generic Policy Model for Simplified Use of Policy Abstractions (SUPA) draft-strassner-supa-generic-policy-info-model-00 Abstract The Simplified Use of Policy Abstractions (SUPA) addresses the needs of operators and application developers to represent multiple types of policy rules. This document defines a common structure for policy rules that is independent of language, protocol, and the level of abstraction of the content of the policy rule. This enables multiple policy rule data models to be constructed from it. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on October 26, 2015. Strassner, et al. Expires September 18, 2015 [Page 1] Internet-Draft SUPA Generic Policy Model Apr 2015 Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction ................................................. 5 2. Conventions used in this document ............................ 5 3. Terminology .................................................. 5 3.1. Acronyms................................................. 5 3.2. Definitions ............................................. 6 3.2.1. Core Terminology .................................. 6 3.2.1.1. Information Model ............................. 6 3.2.1.2. Data Model .................................... 6 3.2.1.3. Container ..................................... 6 3.2.1.4. PolicyContainer ............................... 7 3.2.2. Policy Terminology ................................. 7 3.2.2.1. SUPAPolicy .................................... 7 3.2.2.2. SUPAPolicyStatement ........................... 7 3.2.2.3. SUPAECAPolicyRule ............................. 8 3.2.2.4. SUPAGoalPredicate ............................. 9 3.2.2.5. SUPAMetadata .................................. 9 3.2.2.6. SUPAPolicyTarget .............................. 9 3.2.2.7. SUPAPolicySubject ............................ 10 3.2.3. Modeling Terminology .............................. 10 3.2.3.1. Inheritance .................................. 10 3.2.3.2. Relationship ................................. 10 3.2.3.3. Association .................................. 10 3.2.3.4. Aggregation .................................. 11 3.2.3.5. Composition .................................. 11 3.2.3.6. Association Class ............................ 11 3.2.3.7. Multiplicity ................................. 11 3.2.3.8. Navigability ................................. 11 3.3. Symbology .............................................. 11 4. Policy Abstraction Architecture ............................. 12 4.1. Motivation ............................................. 13 4.2. SUPA Approach .......................................... 13 4.3. Structure of SUPA Policies ............................. 14 Strassner, et al. Expires September 18, 2015 [Page 2] Internet-Draft SUPA Generic Policy Model Apr 2015 Table of Contents (continued) 4.4. SUPA Generic Policy Information Model Overview ......... 15 4.4.1. Architectural Objectives .......................... 15 4.4.2. Scope of Previous Work ............................ 15 4.4.3. SGPIM Assumptions ................................. 16 5. SGPIM Model ................................................. 17 5.1. Overview ............................................... 17 5.2. The Abstract Class "SUPAPolicy" ........................ 18 5.2.1. SUPAPolicy Attributes ............................. 19 5.2.1.1. The Attribute "supaObjectIDContent" .......... 19 5.2.1.2. The Attribute "supaObjectIDFormat" ........... 19 5.2.1.3. The Attribute "supaPolicyName" ............... 20 5.2.2. SUPAPolicy Relationships .......................... 20 5.2.2.1. The Relationship "HasSUPAPolicies" ........... 20 5.2.2.2. The Association Class "HasSUPAPolicyDetail" .. 20 5.3. The Abstract Class "SUPAPolicyAtomic" .................. 20 5.4. The Abstract Class "SUPAPolicyComposite" ............... 21 5.5. The Abstract Class "SUPAPolicyStatement" ............... 21 5.5.1. SUPAPolicyStatement Attributes .................... 22 5.5.1.1. The Attribute "supaPolicyStmtAdminStatus" .... 22 5.5.1.2. The Attribute "supaPolicyStmtExecStatus" ..... 23 5.5.2. SUPAPolicyStatement Subclasses .................... 24 5.5.2.1. The Concrete Class "SUPAEncodedClause" ....... 24 5.5.2.1.1. The Attribute "supaClauseContent" ....... 24 5.5.2.1.2. The Attribute "supaClauseFormat" ........ 24 5.5.2.1.3. The Attribute "supaClauseResponse" ...... 25 5.5.3. SUPAPolicyStatement Relationships ................. 25 5.5.3.1. The Aggregation "HasSUPAPolicyStatements" .... 25 5.5.3.2. The Association Class "HasSUPAPolicyStmtDetail" ................... 25 5.6. The Abstract Class "SUPAPolicySubject" ................. 25 5.6.1. SUPAPolicySubject Attributes ...................... 26 5.6.2. SUPAPolicySubject Relationships ....................27 5.6.2.1. The Relationship "HasSUPAPolicySubjects" ......27 5.6.2.2. The Association Class "HasSUPAPolicySubjDetail" ....................27 5.7. The Abstract Class "SUPAPolicyTarget" .................. 31 5.7.1. SUPAPolicyTarget Attributes ....................... 28 5.7.1.1. The Attribute "supaPolicyTargetEnabled" ...... 28 5.7.2. SUPAPolicyTarget Relationships .................... 28 5.7.2.1. The Relationship "HasSUPAPolicyTargets" ...... 28 5.7.2.2. The Association Class "HasSUPAPolicyTgtDetail" 28 5.8. The Abstract Class "SUPAPolicyMetadata" ................ 28 6. SUPA ECAPolicyRule Information Model ........................ 29 6.1. Overview ............................................... 29 6.2. Constructing a SUPAECAPolicyRule ....................... 29 6.3. Working With SUPAECAPolicyRules ........................ 30 6.4. The Concrete Class "SUPAECAPolicyRule" ................. 31 6.4.1. SUPAECAPolicyRule Attributes ...................... 31 Strassner, et al. Expires September 18, 2015 [Page 3] Internet-Draft SUPA Generic Policy Model Apr 2015 Table of Contents (continued) 6.4.1.1. The Attribute "supaECAPRDeployStatus"......... 31 6.4.1.2. The Attribute "supaECAPRExecStatus"........... 32 6.4.2. SUPAECAPolicyRule Relationships ................... 32 6.4.2.1. The Relationship "HasSUPAEvents" ............. 32 6.4.2.2. The Relationship "HasSUPAConditions" ......... 32 6.4.2.3. The Relationship "HasSUPAActions" ............ 33 6.5. SUPAPolicyStatement Subclasses ......................... 33 6.5.1. Designing SUPAPolicyStatements Using SUPABooleanClauses ............................... 33 6.6. The Abstract Class "SUPABooleanClause" ................. 34 6.6.1. SUPABooleanClause Attributes ...................... 35 6.6.1.1. The Attribute "supaBoolIsNegated" ............ 35 6.6.2. SUPABooleanClause Relationships ................... 35 6.6.2.1. The Relationship "HasSUPABooleanClauses" ..... 35 6.7. SUPABooleanClause Subclasses ........................... 35 6.7.1. The Abstract Class "SUPABooleanClauseAtomic" ...... 36 6.7.1.1. The Abstract Class "SUPAPolicyVariable" ...... 36 6.7.1.1.1. Problems with the RFC3460 Version of PolicyVariable ......................... 37 6.7.1.1.2. The Abstract Class "SUPAPolicyVariable" . 37 6.7.1.2. The Concrete Class "SUPAPolicyOperator" ...... 36 6.7.1.3. The Abstract Class "SUPAPolicyValue" ......... 38 6.7.1.3.1. Problems with the RFC3460 Version of PolicyValue ............................. 38 6.7.1.3.2. The Abstract Class "SUPAPolicyValue" .... 38 6.7.2. The Abstract Class "SUPABooleanClauseComposite" ... 38 6.7.2.1. SUPABooleanClauseComposite Attributes ........ 38 6.7.2.2. SUPABooleanClauseComposite Relationships ..... 38 7. SUPA Goal Predicate Information Model ....................... 39 7.1. Overview ............................................... 39 7.2. Constructing a SUPAGoalPredicate ....................... 39 7.3. Working With SUPAGoalPredicates ........................ 39 7.4. The Abstract Class "SUPAGoalPredicate" ................. 39 8. Security Considerations .................................... 39 9. IANA Considerations ......................................... 39 10. Acknowledgments ............................................ 39 11. References ................................................. 40 11.1. Normative References .................................. 40 11.2. Informative References ............................... 40 Authors' Addresses ............................................. 41 Strassner, et al. Expires September 18, 2015 [Page 4] Internet-Draft SUPA Generic Policy Model Apr 2015 1. Introduction The Shared Unified Policy Automation (SUPA) addresses the needs of operators and application developers to represent multiple types of policy rules. This document defines a common structure for policy rules that is independent of language, protocol, and the level of abstraction of the content of the policy rule. This enables multiple policy rule data models to be constructed from it. 2. Conventions used in this document 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 [RFC2119]. In this document, these words will appear with that interpretation only when in ALL CAPS. Lower case uses of these words are not to be interpreted as carrying [RFC2119] significance. 3. Terminology This section defines acronyms, terms, and symbology used in the rest of this document. 3.1. Acronyms CLI Command Line Interface ECA Event-Condition-Action EPRIM ECA Policy Rule Information Model FOL First Order Logic GPIM Goal Predicate Policy Information Model Netconf Network Configuration protocol OAM Operational, Administrative, and Management OID Object IDentifier PAP Policy Administration Point PDP Policy Decision Point PEP Policy Enforcement Point PIP Policy Information Point PR Policy Repository PXP Policy Execution Point SGPIM SUPA Generic Policy Information Model SUPA Simplified Use of Policy Abstractions UML Unified Modeling Language URI Uniform Resource Identifier YANG A data definition language for use with Netconf. Strassner, et al. Expires September 18, 2015 [Page 5] Internet-Draft SUPA Generic Policy Model Apr 2015 3.2. Definitions This section defines important terms that are used in this document. 3.2.1. Core Terminology The following terms define the terms "information model" and "data model". 3.2.1.1. Information Model An information model is a representation of concepts of interest to an environment in a form that is independent of data repository, data definition language, query language, implementation language, and protocol. Note: this definition is different than that of [RFC3198]. A data model is defined in [RFC3198] as: "A mapping of the contents of an information model into a form that is specific to a particular type of data store or repository." The SUPA definition is more specific. For example, it takes into account differences between two implementations that use the same protocol, implementation language, and data repository, but which have different data definition and/or query protocols. 3.2.1.2. Data Model A data model is a representation of concepts of interest to an environment in a form that is dependent on data repository, data definition language, query language, implementation language, and protocol (typically, but not necessarily, all three). Note: this definition is different than that of [RFC3198]. A data model is defined in [RFC3198] as: "A mapping of the contents of an information model into a form that is specific to a particular type of data store or repository." The SUPA definition is more specific. For example, it takes into account differences between two implementations that use the same protocol, implementation language, and data repository, but which have different data definition and/or query protocols. 3.2.1.3. Container A container is an object whose instances may contain zero or more additional objects, including container objects. A container provides storage, query, and retrieval of its contained objects in a well-known, organized way. Strassner, et al. Expires September 18, 2015 [Page 6] Internet-Draft SUPA Generic Policy Model Apr 2015 3.2.1.4. PolicyContainer In this document, a PolicyContainer is a special type of container that provides at least the following three functions: 1. It uses metadata to define how its content is interpreted 2. It separates the content of the policy from the representation of the policy 3. It provides a convenient control point for OAMP operations The combination of these three features enables a PolicyContainer to define the behavior of how its constituent components will be accessed, queried, stored, retrieved, and how they operate. 3.2.2. Policy Terminology The following terms define different policy concepts used in the SUPA Generic Policy Information Model (SGPIM). Note that the prefix "SUPA" is used for all classes and relationships defined in the SGPIM in order to ensure name uniqueness. Similarly, the prefix "supa" is defined for all SUPA class attributes. 3.2.2.1. SUPAPolicy A SUPAPolicy is an abstract class that is a type of PolicyContainer. A SUPAPolicy MUST have one or more SUPAPolicyStatements that define the content of the Policy. SUPAPolicy is defined generically as a means to manage and control the changing and/or maintaining of the state of one or more managed objects [1]. In this context, "manage" means that at least create, read, query, update, and delete functions are supported. A SUPAPolicy MUST have at least one SUPAPolicyStatement. A SUPAPolicy MAY be qualified by a set of zero or more SUPAPolicySubjects, SUPAPolicyTargets, and/or SUPAPolicyMetadata objects (all of which are defined as abstract classes). When defined in an information model, the SUPAPolicy class MUST have separate aggregation relationships with the SUPAPolicySubject, SUPAPolicyTarget, and SUPAPolicyMetadata classes. When implemented in a data model, the set of SUPAPolicyStatement, SUPAPolicyTarget, SUPAPolicySubject, and SUPAPolicyMetadata object instances, SHOULD all be part of a single PolicyContainer object. 3.2.2.2. SUPAPolicyStatement A SUPAPolicyStatement is an abstract class that contains an individual or group of related functions; this set of functions defines a set of actions to take. Examples of actions include getting information, stating facts about the system being managed, writing a change to a configuration of one or more managed objects, and querying information about a set of managed objects. Strassner, et al. Expires September 18, 2015 [Page 7] Internet-Draft SUPA Generic Policy Model Apr 2015 SUPAPolicyStatements are objects in their own right, which facilitates their reuse. SUPAPolicyStatements can also be combined in a whole-part (containment) relationship under a SUPAPolicy, thereby forming a SUPAECAPolicyRule or a SUPAGoalPredicate. When defined in an information model, a SUPAPolicyStatement MUST be represented as a separate object that aggregates its constituent components. However, a data model MAY map this definition to a more efficient form (e.g., flattening the SUPAPolicyStatement and its aggregated object instances into a single object instance). 3.2.2.3. SUPAECAPolicyRule An Event-Condition-Action (ECA) Policy (SUPAECAPolicyRule) is an abstract class that is made up of at least one SUPAPolicyStatement. In other words, a SUPAECAPolicyRule is a type of PolicyContainer whose content is defined by one or more SUPAPolicyStatements. A SUPAECAPolicyRule is a three-tuple, and MUST contain an event clause, a condition clause, and an action clause. Each of these three clauses MUST have at least one term corresponding to the type of clause that it is; it MAY have more than one. If there are more than one term, then they MUST be combined using Boolean AND, OR, and NOT operators. For example, a valid event clause could be: "three events of type A AND NOT an event of type B". These three clauses enable the semantics of a SUPAECAPolicyRule to be clearly differentiated from the semantics of other types of SUPAPolicies that use SUPAPolicyStatements (and other parts of the SPGIM), such as SUPAGoalPredicates. The semantics of a SUPAECAPolicyRule are defined as follows: o the event clause defines a Boolean statement that, if true, triggers the evaluation of the condition clause of the SUPAECAPolicyRule o the condition clause defines a Boolean statement that, if true, enables the actions of the SUPAECAPolicyRule to be executed o the action clause is an aggregation of actions that may be executed if the event and condition clauses so dictate; the behavior of the actions is defined using the SUPAMetadata that has been aggregated by the SUPAECAPolicyRule When defined in an information model, each of the event, condition, and action clauses MUST be represented as an aggregation between a SUPAECAPolicyRule (the aggregate) and a set of event, condition, or action objects (the components). However, a data model MAY map these definitions to a more efficient form (e.g., flattening these three types of object instances into a single object instance). Strassner, et al. Expires September 18, 2015 [Page 8] Internet-Draft SUPA Generic Policy Model Apr 2015 3.2.2.4. SUPAGoalPredicate A SUPAGoalPredicate is an abstract class that is made up of at least one SUPAPolicyStatement. In other words, a SUPAGoalPredicate is a type of PolicyContainer whose content is defined by one or more SUPAPolicyStatements. A SUPAGoalPredicate defines what actions to take, but not how to execute those actions. It is commonly called declarative, or intent-based, policy. If the SUPAGoalPredicate is expressed in first order logic (FOL), then a SUPAGoalPredicate MUST consist of a head clause, and MAY also contain a body clause. This enables the semantics of a SUPAGoalPredicate to be clearly differentiated from the semantics of other types of SUPAPolicies that use SUPAPolicyStatements (and other parts of the SPGIM), such as SUPAECAPolicyRules. While in principle higher order logics can be defined, this document is limited to defining a SUPAGoalPredicate using just FOL. When implemented in an information model, both the head and body clauses MUST be defined as objects (or sets of objects). However, a data model MAY map these definitions to a more efficient form (e.g., flattening the head and body objects into a single object). 3.2.2.5. SUPAMetadata Metadata is, literally, data about data. SUPAMetadata is an abstract class that contains prescriptive and/or descriptive information about the object(s) that it is attached to. While metadata can be attached to any information model element, this document only considers metadata attached to classes and relationships. When defined in an information model, each instance of the SUPAMetadata class MUST have its own aggregation relationship with the set of objects that it applies to. However, a data model MAY map these definitions to a more efficient form (e.g., flattening the object instances into a single object instance). 3.2.2.6. SUPAPolicyTarget SUPAPolicyTarget is an abstract class that defines a set of managed objects that may be affected by the actions of a SUPAPolicyStatement. A SUPAPolicyTarget may use one or more mechanisms to identify the set of managed objects that it affects; examples include OIDs and URIs. Strassner, et al. Expires September 18, 2015 [Page 9] Internet-Draft SUPA Generic Policy Model Apr 2015 When defined in an information model, each instance of the SUPAPolicyTarget class MUST have its own aggregation relationship with each SUPAPolicy that uses it. However, a data model MAY map these definitions to a more efficient form (e.g., flattening the SUPAPolicyTarget, SUPAMetadata, and SUPAPolicy object instances into a single object instance). 3.2.2.7. SUPAPolicySubject SUPAPolicySubject is an abstract class that defines a set of managed objects that authored this SUPAPolicyStatement. This is required for auditability. A SUPAPolicySubject may use one or more mechanisms to identify the set of managed objects that authored it; examples include OIDs and URIs. When defined in an information model, each instance of the SUPAPolicySubject class MUST have its own aggregation relationship with each Policy that uses it. However, a data model MAY map these definitions to a more efficient form (e.g., flattening the PolicySubject, Metadata, and Policy object instances into a single object instance). 3.2.3. Modeling Terminology The following terms define different types of relationships used in the information models of the SUPA Generic Policy Information Model (SGPIM). 3.2.3.1. Inheritance Inheritance makes an entity at a lower level of abstraction (e.g., the subclass) a type of an entity at a higher level of abstraction (e.g., the superclass). A subclass does NOT change the characteristics or behavior of the superclass that it inherits from. However, a subclass MAY add new attributes and relationships that distinguish it from the attributes and relationships defined by its superclass. 3.2.3.2. Relationship A relationship is a generic term that represents how a first set of entities interact with a second set of entities. A recursive relationship sets the first and second entity to the same entity. There are three basic types of relationships, as defined in the subsections below. 3.2.3.3. Association An association represents a generic dependency between a first and a second set of entities. Strassner, et al. Expires September 18, 2015 [Page 10] Internet-Draft SUPA Generic Policy Model Apr 2015 3.2.3.4. Aggregation An aggregation is a stronger type (i.e., more restricted semantically) of association, and represents a whole-part dependency between a first and a second set of entities. Three objects are defined by an aggregation: the first entity, the second entity, and a new third entity that represents the combination of the first and second entities. The entity owning the aggregation is referred to as the "aggregate", and the entity that is aggregated is referred to as the "part". 3.2.3.5. Composition A composition is a stronger type (i.e., more restricted semantically) of aggregation, and represents a whole-part dependency with two important behaviors. First, an instance of the part is included in at most one instance of the aggregate at a time. Second, any action performed on the composite entity (i.e., the aggregate) is propagated to its constituent part objects. For example, if the composite entity is deleted, then all of its constituent part entities are also deleted. This is not true of aggregations or associations - in both, only the entity being deleted is actually removed, and the other entities are unaffected. 3.2.3.6. Multiplicity A specification of the range of allowable cardinalities that a set of entities may assume. This is always a pair of ranges, such as 1 - 1 or 0..n - 2..5. 3.3. Symbology To be Done Strassner, et al. Expires September 18, 2015 [Page 11] Internet-Draft SUPA Generic Policy Model Apr 2015 4. Policy Abstraction Architecture This section describes the motivation for the policy abstractions that are used in SUPA. In summary, the following abstractions are provided: o The SGPIM defines a technology-neutral information model that can express the concept of Policy. o This version of this document restricts the expression of Policy to either an event-condition-action tuple, a FOL predicate, or a combination of these statements. o Since these two representations are very different in syntax and content, the content of a Policy is abstracted from its representation: o Both SUPAECAPolicyRules and SUPAGoalPredicates are types of SUPAPolicies o Both SUPAECAPolicyRules and SUPAGoalPredicates are constructed from SUPAPolicyStatements o The syntax of a SUPAECAPolicyRule, and hence its representation, is different from that of a SUPAGoalPredicate o A SUPAPolicy MAY use SUPAECAPolicyRules and/or SUPAGoalPredicates o A SUPAPolicy consists of one or more SUPAPolicyStatements, one or more SUPAPolicyTargets, an optional SUPAPolicySubject, and optional SUPAPolicyMetadata o A SUPAPolicy MUST contain at least one SUPAPolicyStatement; it MAY contain more than one. o A SUPAECAPolicyRule defines the set of events and conditions that are responsible for executing its actions; it MUST have an event clause, a condition clause, and an action clause. o A SUPAGoalPredicate expresses facts that it believes to be true without defining how those facts are computed, and provides an efficient query mechanism for retrieving facts. Each SUPAPolicyStatement MUST be expressed as a function-free Horn clause; there are a number of additional restrictions that are covered in Section 7. o SUPAMetadata MAY be defined for any type of SUPAPolicyStatement (as well as for individual objects that make up a SUPAPolicyStatement). o SUPAMetadata MAY be prescriptive and/or descriptive in nature. o A SUPAPolicyTarget is a set of managed objects that the actions of the SUPAPolicy are applied to. o A SUPAPolicySubject is a set of managed objects that authored the SUPAPolicy. Strassner, et al. Expires September 18, 2015 [Page 12] Internet-Draft SUPA Generic Policy Model Apr 2015 4.1. Motivation The power of policy management is its applicability to many different types of systems. There are many different actors that can use a policy management system, including end-users, operators, application developers, and administrators. Each of these constituencies have different concepts and skills, and use different terminology. For example, an operator may want to express an operational rule that states that only Platinum and Gold users can use streaming multimedia applications. As a second example, a network administrator may want to define a more concrete policy rule that looks at the number of dropped packets and, if that number exceeds a programmable threshold, changes the queuing and dropping algorithms used. Both of these examples are commonly referred to as "policy rules", but they take very different forms, since they are at very different levels of abstraction and likely authored by different actors. The first was very abstract, and did not contain any technology-specific terms, while the second was more concrete, and likely used technical terms of a general (e.g., IP address range, port numbers) as well as a vendor-specific nature (e.g., specific algorithms implemented in a particular device). Note that these two policy rules could affect each other. For example, Gold and Platinum users might need different device configurations to give the proper QoS markings to their streaming multimedia traffic. This is very difficult to do if a common policy model does not exist. More importantly, the users of these two policies likely have different job responsibilities. They may have no idea of the concepts used in each policy. Yet, their policies need to interact in order for the business to provide the desired service. Hence, the need for a common policy framework. 4.2. SUPA Approach The purpose of the SUPA Generic Policy Information Model (SGPIM) is to define a common framework for expressing policies at different levels of abstraction. SUPA uses the SGPIM as a common vocabulary for representing concepts that are common to expressing policy, but which are independent of language, protocol, repository, and level of abstraction. This enables different policies at different levels of abstraction to form a continuum, where more abstract policies can be translated into more concrete policies, and vice-versa. Strassner, et al. Expires September 18, 2015 [Page 13] Internet-Draft SUPA Generic Policy Model Apr 2015 It may be necessary to translate the form of a PolicyRule from a general to a more specific form (while keeping the abstraction level the same). For example, the declarative policy "Every network attached to a VM must be a private network owned by someone in the same group as the owner of the VM" may be translated to more formal form (e.g., Datalog, or the Congress version of Datalog). It may also be necessary to translate a Policy to a different level of abstraction. For example, the previous Policy may need to be translated to a form that network devices understand. A common framework for expressing policies that is independent of the level of abstraction is required in order to form such a continuum. 4.3. Structure of SUPA Policies Figure 1 illustrates the approach for representing policy rules in SUPA. The top two layers are defined in this document; the bottom layer (Data Models) are defined in separate documents. +-----------------------------------------------+ | SUPA Generic Policy Information Model (SGPIM) | +-----------------------------------------------+ / \ | | +-------------+------------+ | | | | +---------------+-----------+ +-----------+--------------+ | SUPAECAPolicyRule | | SUPAGoalPredicate | | Information Model (EPRIM) | | Information Model (GPRIM)| +---------------------------+ +--------------------------+ / \ / \ | | | | +-----------+-----------+ +-----------+------------+ | ECAPolicyRule | | GoalPredicate | | Data Model | | Data Model | +-----------------------+ +------------------------+ Figure 1: Overview of SUPA Policy Rule Abstractions Conceptually, the SGPIM defines a set of objects that define the key elements of a Policy independent of how it is represented or its content. As will be shown, there is a significant difference between SUPAECAPolicyRules (see Section 6) and SUPAGoalPredicates (see Section 7). In principle, other types of SUPAPolicies could be defined, but the current charter is restricted to using these two types of SUPAPolicies as exemplars. Strassner, et al. Expires September 18, 2015 [Page 14] Internet-Draft SUPA Generic Policy Model Apr 2015 The SGPIM defines a SUPAPolicy object as a PolicyContainer that specifies the structure, content, and metadata of a collection of policies. The content of a SUPAPolicy is made up of one or more SUPAPolicyStatements. A SUPAPolicyStatement may, in this release of SUPA, take one of two forms: SUPAECAPolicyRules (see Section 6) and SUPAGoalPredicates (see Section 7). 4.4. SUPA Generic Policy Information Model Overview This section describes the overall design of the SGPIM. 4.4.1. Architectural Objectives The purpose of the SGPIM is to define the common characteristics and behavior of Policy independent of how Policy is written. Specifically, the SGPIM generalizes the concept of Policy to enable different forms of Policy to be defined that refine its definition. The implementation of Policy by SGPIM is called SUPA Policy. For this document, two exemplar forms of SUPAPolicy are defined: SUPAECAPolicyRules and SUPAGoalPredicates. 4.4.2. Scope of the Previous Work To be done. Section will include: o Description of, and problems with, [RFC3060] o Description of, and problems with, [RFC3460] o Should this section also talk about CIM or SID? I personally think that this should be in the gap analysis... Strassner, et al. Expires September 18, 2015 [Page 15] Internet-Draft SUPA Generic Policy Model Apr 2015 4.4.3. SGPIM Assumptions SUPA DOES NOT assume that it is the "root class of everything". Rather, the design of this information model assumes that the SUPA classes are inserted into another model at a given point in the other model. However, most models do not have a capability to integrate different namespaces. One of the goals of SUPA is to be able to generate different data models that support different types of protocols and repositories. This means that the notion of an object ID must be generic. In this way, different naming schemes, such as those depending on URIs, FQDNs, primary key - foreign key relationships, and UUIDs can all be accommodated. This is shown in Figure 2: +------------------------------------------+ | Root Class of an Existing Model | +------------------------------------------+ / \ | | +-----------------+--------------+ | | | | +-----------+-----------+ +-----------+------------+ | A Subclass of the | | A Subclass of the | | Existing Model | | Existing Model | +-----------------------+ +------------------------+ / \ | | ... | | +-----------+------------+ | SUPA Class Hierarchy | | (SGPIM plus EPRIM | | and/or GPRIM) | +------------------------+ Figure 2: Integrating SUPA into an Existing Model Strassner, et al. Expires September 18, 2015 [Page 16] Internet-Draft SUPA Generic Policy Model Apr 2015 5. SGPIM Model This section defines the classes and relationships of the SGPIM. 5.1. Overview The overall class definition is shown in Figure 3. SUPAPolicy is the root of the SUPA class hierarchy. For implementations, it is assumed that SUPAPolicy is subclassed from a class from another model. In Figure 3, indentation represents subclassing. (Class of another model that SUPA is integrating into) | +---SUPAPolicy (see Section 5.2) | | | +---SUPAPolicyAtomic (see Section 5.3) | | | +---SUPAPolicyComposite (see Section 5.4) | | | +---SUPAPolicyStatement (see Section 5.5) | | | +---SUPAPolicySubject (see Section 5.6) | | | +---SUPAPolicyTarget (see Section 5.7) | | | +---SUPAPolicyMetadata (see Section 5.8) | ... Figure 3: Integrating SUPA into an Existing Model The following subsections define the classes of the SGPIM. If a class has attributes, those attributes are also defined. Relationships are defined according to the class that is the "owner", or primary actor, participating in the relationship. Strassner, et al. Expires September 18, 2015 [Page 17] Internet-Draft SUPA Generic Policy Model Apr 2015 5.2. The Abstract Class "SUPAPolicy" This is a mandatory abstract class. This class is the root of the SUPA class hierarchy. It defines the common attributes and relationships that all SUPA subclasses inherit. Figure 4 shows the SUPAPolicy class, and two of its subclasses (SUPAPolicyAtomic and SUPAPolicyComposite). This is an implementation of the composite pattern [3], which enables a SUPAPolicy to be made up of a stand-alone object (an instance of a SUPAPolicyAtomic class) or a hierarchy of objects (i.e., instances of one or more SUPAPolicyAtomic and SUPAPolicyComposite classes). The use of this software pattern enables SUPA Policies to be designed as individual objects and/or hierarchies of objects. +-------------------------------+ | Parent Class of another Model | +-------------------------------+ / \ +---------------------+ | | HasSUPAPolicyDetail | | +-----+---------------+ | | | | 1..n +---------------+----------------+ | \| | +----+--------| SUPAPolicy | | /| | | +--------------------------------+ | / \ | HasSUPAPolicies | | | | +-----------+----------+ | | | | | | | 0..1 +----------+----------+ +---------+--------+ | / \| | | | +--- A | SUPAPolicyComposite | | SUPAPolicyAtomic | \ /| | | | +---------------------+ +------------------+ Figure 4: The SUPAPolicy Class Hierarchy Note that a SUPAPolicy is a PolicyContainer object. A SUPAPolicyAtomic as well as a SUPAPolicyComposite are also PolicyContainer objects. Strassner, et al. Expires September 18, 2015 [Page 18] Internet-Draft SUPA Generic Policy Model Apr 2015 In figure 4: o Both SUPAPolicyComposite and SUPAPolicyAtomic inherit from SUPAPolicy o The diamond with an enclosed "A" represents an aggregation (see Section 3.2.3.4) o The HasSUPAPolicies aggregation is implemented as an association class (see Section 3.2.3.6) o The multiplicity of the HasSUPAPolicies aggregation is 0..1 - 1..n (zero or one SUPAPolicyComposite object instances can aggregate one or more SUPAPolicy object instances, see Section 3.2.3.7) o The arrow pointing at SUPAPolicy restricts the navigability of this aggregation (see Section 3.2.3.8) 5.2.1. SUPAPolicy Attributes This section defines the attributes of the SUPAPolicy class. These attributes are inherited by all subclasses of the SUPAPolicy class. 5.2.1.1. The Attribute "supaObjectIDContent" This is a mandatory attribute that represents part of the object identifier of an instance of this class. It is a string attribute, and defines the content of the object identifier. It works with another class attribute, called supaObjectIDFormat, which defines how to interpret this attribute. These two attributes form a tuple, and together enable a machine to understand the syntax and value of an object identifier for the object instance of this class. This is based on the DEN-ng class design [2]. 5.2.1.2. The Attribute "supaObjectIDFormat" This is a mandatory attribute that represents part of the object identifier of an instance of this class. It is a string attribute, and defines the format of the object identifier. It works with another class attribute, called supaObjectIDContent, which defines the content of the object ID. These two attributes form a tuple, and together enable a machine to understand the syntax and value of an object identifier for the object instance of this class. This is based on the DEN-ng class design [2]. Strassner, et al. Expires September 18, 2015 [Page 19] Internet-Draft SUPA Generic Policy Model Apr 2015 5.2.1.3. The Attribute "supaPolicyName" This is an optional string attribute that defines the name of this Policy. This enables any existing generic naming attribute to be used for generic naming, while allowing this attribute to be used to name Policy entities in a common manner. Note that this is NOT the same as the commonName attribute of the Policy class defined in RFC3060 [RFC3060], as that attribute is intended to be used with just X.500 cn attributes. 5.2.2. SUPAPolicy Relationships This section defines the relationships of the SUPAPolicy class. 5.2.2.1. The Relationship "HasSUPAPolicies" This is a mandatory aggregation that defines the set of SUPAPolicies that are contained in the instance of this particular SUPAPolicyComposite object. The multiplicity of this relationship is defined as 0..1 on the aggregate (SUPAPolicyComposite) side, and 1..n on the part (SUPAPolicy) side. This means that this relationship is optional, but if it is instantiated, then one or more SUPAPolicy objects are contained in this particular SUPAPolicyComposite object. The semantics of this aggregation are implemented using the HasSUPAPolicyDetail association class. 5.2.2.2. The Association Class "HasSUPAPolicyDetail" This is a mandatory concrete association class that defines the semantics of the HasSUPAPolicies aggregation. This enables the attributes and relationships of the HasSUPAPolicyDetail class to be used to constrain which SUPAPolicy objects can be aggregated by this particular SUPAPolicyComposite object instance. Attributes will be added to this class at a later time. 5.3. The Abstract Class "SUPAPolicyAtomic" This is a mandatory abstract class. This class is a type of PolicyContainer. A SUPAPolicyAtomic class represents a SUPA Policy that can operate as a single, stand-alone, manageable object. Put another way, a SUPAPolicyAtomic object can NOT be modeled as a set of hierarchical SUPAPolicy objects; if this functionality is required, then a SUPAPolicyComposite object must be used. Strassner, et al. Expires September 18, 2015 [Page 20] Internet-Draft SUPA Generic Policy Model Apr 2015 No attributes are currently defined for the SUPAPolicyAtomic class. It serves as a superclass for the different types of SUPA Policies that are defined. In this release, both a SUPAECAPolicyRule (see Section 6) as well as a SUPAGoalPredicate (see Section 7) are defined as subclasses of the SUPAPolicyAtomic class. 5.4. The Abstract Class "SUPAPolicyComposite" This is a mandatory abstract class. This class is a type of PolicyContainer. A SUPAPolicyComposite class represents a SUPA Policy as a hierarchy of Policy objects, where the hierarchy contains instances of a SUPAPolicyAtomic and/or SUPAPolicyComposite object. Each of the SUPA Policy objects, including the outermost SUPAPolicyComposite object, are separately manageable. No attributes are currently defined for the SUPAPolicyAtomic class. It is used to create hierarchical SUPA Policies. 5.5. The Abstract Class "SUPAPolicyStatement" This is a mandatory abstract class that separates the representation of a SUPAPolicy from its implementation. Its subclasses enable the developer to define a SUPAPolicy as either a completely reusable set of SUPAPolicy objects or as an efficient encoding made up of attributes. Both SUPAECAPolicyRules (see Section 6) and SUPAGoalPredicates (see section 7) MAY use a SUPAEncodedClause (see Section 5.5.1); the former MAY also use a SUPABooleanClause (see Section 6.4), while the latter MAY also use a SUPAFOLClause (see Section 7.4). A class diagram showing SUPAPolicyStatement is shown in Figure 5. Note that in this figure: o SUPAPolicyStatement, SUPAPolicyAtomic, and SUPAPolicyComposite are subclasses of SUPAPolicy o A SUPAEncodedClause is a subclass of SUPAPolicyStatement, and may be used by either a SUPAECAPolicyRule or a SUPAGoalPredicate o Both the HasSUPAPolicyStatements and the HasSUPAPolicies aggregations are implemented as association classes Strassner, et al. Expires September 18, 2015 [Page 21] Internet-Draft SUPA Generic Policy Model Apr 2015 +-------------------------+ +---------------------+ | HasSUPAPolicyStmtDetail | | HasSUPAPolicyDetail | +-----+-------------------+ +----------+----------+ | | | 1 +-----------------+ | | / \| |/ | +-------+-------- A | SUPAPolicy |--------+-----------+ | \ /| |\ | | +-----------------+ 1..n | | / \ | | HasSUPAPolicyStatements | HasSUPAPolicies | | | | | +------+------+--------+ | | | | | | | 1..n +----------+----------+ | | | | \| | | | | +---------| SUPAPolicyStatement | | | | /| | | | | +---------------------+ | | | / \ | | | | +-----------+------+ | | | | SUPAPolicyAtomic | | | | +------------------+ | | | | | +-----------+-------+ +--------------+------+ | | SUPAEncodedClause | | |/ \ | +-------------------+ | SUPAPolicyComposite | A ----+ | |\ / +---------------------+ 0..1 Figure 5: SUPAPolicyStatements and SUPAPolicy Classes 5.5.1. SUPAPolicyStatement Attributes This section defines the attributes of the SUPAPolicyStatement class. These attributes are inherited by all subclasses of the SUPAPolicyStatement class. 5.5.1.1. The Attribute "supaPolicyStmtAdminStatus" This is an optional attribute, which is an enumerated non-negative integer. It defines the current administrative status of this SUPAPolicyStatement. Strassner, et al. Expires September 18, 2015 [Page 22] Internet-Draft SUPA Generic Policy Model Apr 2015 This attribute can be used to place this particular SUPAPolicyStatement into a specific administrative state, such as enabled, disabled, or in test. Note that since a SUPAPolicy (e.g., a SUPAECAPolicyRule or a SUPAGoalPredicate) is made up of SUPAPolicyStatements, this enables all or part of a SUPAPolicy to be administratively controlled. Values include: 0: Unknown (an error state) 1: Enabled 2: Disabled 3: In Test (i.e., no operational traffic can be passed) Value 0 denotes an error that prevents this SUPAPolicyStatement from being used. Values 1 and 2 mean that this SUPAPolicyStatement is administratively enabled or disabled, respectively. A value of 4 means that this SUPAPolicyStatement is in a special test mode. 5.5.1.2. The Attribute "supaPolicyStmtExecStatus" This is an optional attribute, which is an enumerated non-negative integer. It defines whether this SUPAPolicyStatement is currently in use and, if so, what its status is. This attribute can be used to place this particular SUPAPolicyStatement into a specific execution state, such as enabled, disabled, or in test. Note that since a SUPAPolicy (e.g., a SUPAECAPolicyRule or a SUPAGoalPredicate) is made up of SUPAPolicyStatements, this enables all or part of a SUPAPolicy to be administratively controlled. Values include: 0: Unknown (an error state) 1: Working (i.e., in use and no errors reported) 2: Not Working (i.e., in use, but errors have been reported) 3: In Test (i.e., no operational traffic can be passed) 4: Available (i.e., could be used, but currently isn't) 5: Not Available (i.e., not available for use) Value 0 denotes an error that prevents this SUPAPolicyStatement from being used. Values 1-3 mean that this SUPAPolicyStatement is in use; in addition, this SUPAPolicyStatement is working correctly, not working correctly, or in a special test state, respectively. Values 4-5 mean that this SUPAPolicyStatement is not currently in use; a value of 4 means that it is available and could be used, while a value of 5 means that it is unavailable. Strassner, et al. Expires September 18, 2015 [Page 23] Internet-Draft SUPA Generic Policy Model Apr 2015 5.5.2. SUPAPolicyStatement Subclasses As stated before, the primary purpose of SUPAPolicyStatement is to define a common type of Policy statement that can be used to represent policy content regardless of the type of SUPAPolicy that is being used (e.g., it is independent of the requirements of a SUPAECAPolicyRule or a SUPAGoalPredicate). The SGPIM defines one common subclass of SUPAPolicyStatement, called a SUPAEncodedClause, that can be used by both SUPAECAPolicyRules as well as SUPAGoalPredicates. Clauses dedicated to the specific use of a SUPAECAPolicyRule and a SUPAGoalPredicate are defined in Sections 6 and 7, respectively. 5.5.2.1. The Concrete Class "SUPAEncodedClause" This is a mandatory concrete class that specializes (i.e., is a subclass of) a SUPAPolicyStatement. It defines a generalized extension mechanism for representing SUPAPolicyStatements that have not been modeled with other SUPAPolicy objects. Rather, the Policy Clause is directly encoded into the attributes of the SUPAEncodedClause. Note that other subclasses of SUPAPolicyStatement use SUPAPolicy objects to define their content. This class uses two of its attributes (supaPolicyClauseContent and supaPolicyClauseFormat) for defining the content and format of a vendor-specific policy statement. This allows direct encoding of the policy statement, without having the "overhead" of using other objects. However, note that while this method is efficient, it does not reuse other SUPAPolicy objects. Rather, it can be thought of as a direct encoding of the policy statement. 5.5.2.1.1. The Attribute "supaClauseContent" This is a mandatory string attribute, and defines the content of this encoded clause of this clause. It works with another attribute of the SUPAEncodedClause class, called supaClauseFormat, which defines how to interpret this attribute. These two attributes form a tuple, and together enable a machine to understand the syntax and value of the encoded clause for the object instance of this class. This is based on the DEN-ng class design [2]. 5.5.2.1.2. The Attribute "supaClauseFormat" This is a mandatory string attribute, and defines the format of this encoded clause. It works with another attribute of the SUPAEncodedClause class, called supaClauseContent, which defines the content (i.e., the value) of the encoded clause. These two attributes form a tuple, and together enable a machine to understand the syntax and value of the encoded clause for the object instance of this class. This is based on the DEN-ng class design [2]. Strassner, et al. Expires September 18, 2015 [Page 24] Internet-Draft SUPA Generic Policy Model Apr 2015 5.5.2.1.3. The Attribute "supaClauseResponse" This is an optional Boolean attribute that emulates a Boolean response of this clause, so that it may be combined with other subclasses of the SUPAPolicyStatement that provide a status as to their correctness and/or evaluation state. 5.5.3. SUPAPolicyStatement Relationships This section defines the relationships of SUPAPolicyStatement. 5.5.3.1. The Aggregation "HasSUPAPolicyStatements" This is a mandatory aggregation that defines the set of SUPAPolicyStatements that are contained in the instance of this particular SUPAPolicy object. This defines a SUPAPolicy object as being made up of at least one SUPAPolicyStatement. The multiplicity of this relationship is defined as 1 on the aggregate (SUPAPolicy) side, and 1..n on the part (SUPAPolicyStatement) side. This means that this relationship is mandatory, and each SUPAPolicy object is made up of at least one SUPAPolicyStatement object. The semantics of this aggregation are implemented using the HasSUPAPolicyStmtDetail association class. 5.5.3.2. The Association Class "HasSUPAPolicyStmtDetail" This is a mandatory concrete association class that defines the semantics of the HasSUPAPolicyStatements aggregation. This enables the attributes and relationships of the HasSUPAPolicyStmtDetail class to be used to constrain which SUPAPolicyStatement objects can be aggregated by this particular SUPAPolicy object instance. Attributes will be added to this class at a later time. 5.6. The Abstract Class "SUPAPolicySubject" This is an optional class that defines the set of managed entities that authored, or are otherwise responsible for, this SUPAPolicyStatement. Note that a SUPAPolicySubject does NOT evaluate or execute SUPAPolicies. Its primary use is for auditability. A SUPAPolicySubject SHOULD be mapped to a role (e.g., using the role-object pattern, as DEN-ng does). A class diagram is shown in Figure 6. Strassner, et al. Expires September 18, 2015 [Page 25] Internet-Draft SUPA Generic Policy Model Apr 2015 +------------------------+ | HasSUPAPolicyTgtDetail | +-----------+------------+ | | 0..1 +------------+ | / \| | +------------+-------------- A | | | HasSUPAPolicyTargets \ /| | | | SUPAPolicy | | 0..1 | | | HasSUPAPolicySubjects / \| | | +------------+------------ A | | | | | \ /| | | | | +------------+ | | | / \ | | +----------+--------------+ | | | | HasSUPAPolicySubjDetail | | | | +-------------------------+ | | | | | | +--------------------+----+--------------+ | | | | | | | | | | | | 0..n +-------+---------+ 0..n +--------+-------+ (other | | \| | \| | SUPAPolicy | +------|SUPAPolicySubject| +---|SUPAPolicyTarget| subclasses) | /| | | /| | | +-----------------+ | +----------------+ | | +-----------------------------+ Figure 6. SUPAPolicySubject and SUPAPolicyTarget In Figure 6: o SUPAPolicySubject and SUPAPolicyTarget are both subclasses of SUPAPolicy o Both the HasSUPAPolicyTargets amd the HasSUPAPolicySubjects aggregations are implemented as association classes o The multiplicity of both of the above aggregations are 0..1 on the aggregate (SUPAPolicy) side and 0..n on the target (i.e., SUPAPolicySubject and SUPAPolicyTarget, respectively) side. This means that both aggregations are optional. If either is instantiated, then a SUPAPolicy MAY contain zero or more SUPAPolicySubject object instances and MAY contain zero or more SUPAPolicyTarget object instances. 5.6.1. SUPAPolicySubject Attributes Attributes will be added to this class at a later time. Strassner, et al. Expires September 18, 2015 [Page 26] Internet-Draft SUPA Generic Policy Model Apr 2015 5.6.2. SUPAPolicySubject Relationships This section defines the relationships of the SUPAPolicySubject class. 5.6.2.1. The Relationship "HasSUPAPolicySubjects" This is an optional aggregation that defines the set of SUPAPolicySubjects that are contained in the instance of this particular SUPAPolicy object. This defines the set of entities that authored this particular SUPAPolicy object. The multiplicity of this relationship is defined as 0..1 on the aggregate (SUPAPolicy) side, and 0..n on the part (SUPAPolicySubject) side. This means that this relationship is optional, but if it is implemented, then this particular SUPAPolicy object was authored by this set of SUPAPolicySubjects. The semantics of this aggregation are implemented using the HasSUPAPolicySubjDetail association class. 5.6.2.2. The Association Class "HasSUPAPolicySubjDetail" This is an optional concrete association class that defines the semantics of the HasSUPAPolicySubjects aggregation. This enables the attributes and relationships of the HasSUPAPolicySubjDetail class to be used to constrain which SUPAPolicySubject objects can be used to author this particular SUPAPolicy object instance. Attributes will be added to this class at a later time. 5.7. The Abstract Class "SUPAPolicyTarget" A PolicyTarget is a set of managed entities that a SUPAPolicy is applied to. This is determined by two conditions. First, the set of managed entities that are to be affected by the SUPAPolicy must all agree to play the role of a SUPAPolicyTarget. In general, a managed entity may or may not be in a state that enables SUPAPolicies to be applied to it to change its state; hence, a negotiation process may need to occur between the SUPAPolicySubject and the SUPAPolicyTarget, wherein the SUPAPolicyTarget consents to have SUPAPolicies applied to it. Second, a SUPAPolicyTarget must be able to either process (either directly or with the aid of a proxy) SUPAPolicies or receive the results of a processed SUPAPolicy and apply those results to itself. If a proposed SUPAPolicyTarget meets both of these conditions, it SHOULD set its supaPolicyTargetEnabled Boolean attribute to a value of TRUE. A SUPAPolicySubject SHOULD be mapped to a role (e.g., using the role-object pattern). Figure 6 shows a class diagram of the SUPAPolicyTarget. Strassner, et al. Expires September 18, 2015 [Page 27] Internet-Draft SUPA Generic Policy Model Apr 2015 5.7.1. SUPAPolicyTarget Attributes The following subsections define the attributes of a SUPAPolicyTarget. 5.7.1.1. The Attribute "supaPolicyTargetEnabled" This is an optional Boolean attribute. If its value is TRUE, then this indicates that this SUPAPolicyTarget is currently able to have SUPAPolicies applied to it. Otherwise, this SUPAPolicyTarget is not able to have SUPAPolicies applied to it. 5.7.2. SUPAPolicyTarget Relationships This section defines the relationships of the SUPAPolicyTarget class. 5.7.2.1. The Relationship "HasSUPAPolicyTargets" This is an optional aggregation that defines the set of SUPAPolicyTargets that are contained in the instance of this particular SUPAPolicy object. This defines the set of entities that will be operated on by this particular SUPAPolicy object. The multiplicity of this relationship is defined as 0..1 on the aggregate (SUPAPolicy) side, and 0..n on the part (SUPAPolicyTarget) side. This means that this relationship is optional, but if it is implemented, then this particular SUPAPolicy object will operate on this set of SUPAPolicyTargets. The semantics of this aggregation are implemented using the HasSUPAPolicyTgtDetail association class. 5.7.2.2. The Association Class "HasSUPAPolicyTgtDetail" This is an optional concrete association class that defines the semantics of the HasSUPAPolicyTargets aggregation. This enables the attributes and relationships of the HasSUPAPolicyTgtDetail class to be used to constrain which SUPAPolicyTarget objects can be operated on by this particular SUPAPolicy object instance. Attributes will be added to this class at a later time. 5.8. The Abstract Class "SUPAPolicyMetadata" This will be defined in the next version of this document. Strassner, et al. Expires September 18, 2015 [Page 28] Internet-Draft SUPA Generic Policy Model Apr 2015 6. SUPA ECAPolicyRule Information Model This section defines the classes, attributes, and relationships of the SUPA ECAPolicyRule Information Model (EPRIM). 6.1. Overview Conceptually, the EPRIM is a set of subclasses that specialize the concepts defined in the SGPIM for representing the components of a Policy that uses ECA semantics. Specifically, the EPRIM specializes the SUPAPolicyAtomic class to create a SUPAECAPolicyRule; it also specializes a SUPAPolicyStatement to create a SUPAECAComponent. The SUPAECAPolicyRule uses the rest of the SGPIM infrastructure to define a complete Policy model according to ECA semantics. Specifically: o Event, condition, and action clauses are subclasses of SUPAPolicyStatement o An optional set of SUPAPolicySubjects can be defined to represent the authoring of a SUPAECAPolicyRule o An optional set of SUPAPolicyTargets can be defined to represent the set of managed entities that will be affected by this SUPAECAPolicyRule o An optional set of SUPAPolicyMetadata can be defined for any of the objects that make up a SUPAECAPolicyRule 6.2. Constructing a SUPAECAPolicyRule A SUPAECAPolicyRule is constructed as follows: o Define three types of SUPABooleanClauses (see Section 6.4), one each for the event, condition, and action clauses that make up a SUPAECAPolicyRule (see Section 6.3) o Define a set of SUPAEvent objects (see Section 6.5.2), and associate them with the SUPABooleanClause that represents the event clause of the SUPAECAPolicyRule o Define a set of SUPACondition objects (see Section 6.5.3), and associate them with the SUPABooleanClause that represents the condition clause of the SUPAECAPolicyRule o Define a set of SUPAAction objects (see Section 6.5.4), and associate them with the SUPABooleanClause that represents the action clause of the SUPAECAPolicyRule o Define a SUPAECAPolicyRule, which is a subclass of the SGPIM SUPAPolicyAtomic class (see Section 5.3) o Aggregate the three SUPABooleanClauses into the SUPAECAPolicyRule o Optionally, define a set of SUPAPolicySubjects and SUPAPolicyTargets, and aggregate them into the SUPAECAPolicyRule o Optionally, define SUPAPolicyMetadata for any of the above objects, and aggregate them to the SUPAPolicy objects that the SUPAPolicyMetadata applies to Strassner, et al. Expires September 18, 2015 [Page 29] Internet-Draft SUPA Generic Policy Model Apr 2015 6.3. Working With SUPAECAPolicyRules A SUPAECAPolicyRule is a type of SUPAPolicy. It is a tuple that has three clauses, defined as follows: o The event clause defines a Boolean expression that, if TRUE, triggers the evaluation of its condition clause (if the event clause is not TRUE, then no further action for this policy rule takes place). o The condition clause defines a Boolean expression that, if TRUE, enables the actions in the action clause to be executed (if the condition clause is not TRUE, then no further action for this policy rule takes place). o The action clause is a set of actions, whose execution MAY be controlled by the SUPAMmetadata of the policy rule. Each of the three clauses is constructed from one or more SUPABooleanClauses. Since a SUPABooleanClause is a subclass of SUPAPolicyStatement (see Section 5.5), and a SUPABooleanClause can aggregate SUPAEncodedClauses (see Sections 5.5.2 and 6.3.2.2), a SUPAECAPolicyRule is built entirely from components defined in the SGPIM. As will be shown in Section 7.3, this is also true for SUPAGoalPredicates. The construction of a SUPAECAPolicyRule is shown in Figure 7, and is explained in Section 6.4. +----------------------+ +---------------------+ | SUPAPolicyAtomic | | SUPAPolicyStatement | +----------------------+ +---------------------+ / \ / \ | | | | +------------+------------+ +------------+------------+ | SUPAECAPolicyRule | | SUPABooleanClause | +-------------------------+ +-------------------------+ 0..1/ \ 0..1/ \ 0..1/ \ 1..n/ \ 1..n/ \ 1..n/ \ \ / \ / \ / | | | | | | | | | | | | HasSUPAEvents | | | | | +------------------+ | | | | HasSUPAConditions | | | +----------------------------------+ | | HasSUPAActions | +--------------------------------------------------+ Figure 7. SUPAECAPolicyRule Clauses Strassner, et al. Expires September 18, 2015 [Page 30] Internet-Draft SUPA Generic Policy Model Apr 2015 6.4. The Concrete Class "SUPAECAPolicyRule" This is a concrete mandatory class. In keeping with the original DEN-ng model [1], this class is a PolicyContainer that contains PolicyEvents, PolicyConditions, PolicyActions, and optionally, PolicyMetadata. As such, it doesn't have an inherent relationship with PolicySubject or PolicyTarget; these all represent the specific semantics for a particular SUPAECAPolicyRule. Hence, these semantics are defined in an instance of the SUPAPolicyComposite class if they are required. The semantics of a SUPAECAPolicyRule may be conceptualized as follows: ON RECEIPT OF IF EVALUATES TO TRUE THEN EXECUTE END END In the above, a policy-event-clause, policy-condition-clause, and a policy-action-clause are each instances of a SUPABooleanClause (see Section 6.4). 6.4.1. SUPAECAPolicyRule Attributes Currently, the SUPAECAPolicyRule defines two attributes, as described in the following subsections. 6.4.1.1. The Attribute "supaECAPRDeployStatus" This is an optional attribute, which is an enumerated, non-negative integer. It defines the current deployment status of this SUPAECAPolicyRule. Both operational and test mode values are included in its definition. Values include: 0: undefined 1: deployed and enabled 2: deployed and in test 3: deployed but not enabled 4: ready to be deployed 5: not deployed Strassner, et al. Expires September 18, 2015 [Page 31] Internet-Draft SUPA Generic Policy Model Apr 2015 6.4.1.2. The Attribute "supaECAPRExecStatus" This is an optional attribute, which is an enumerated, non-negative integer that defines the current execution status of this SUPAECAPolicyRule. Both operational and test mode values are included in its definition. Values include: 0: undefined 1: executed and SUCEEDED (operational mode) 2: executed and FAILED (operational mode) 3: currently executing (operational mode) 4: executed and SUCEEDED (test mode) 5: executed and FAILED (test mode) 6: currently executing (test mode) 6.4.2. SUPAECAPolicyRule Relationships Currently, the SUPAECAPolicyRule defines three relationships, as described in the following subsections. 6.4.2.1. The Relationship "HasSUPAEvents" This is a mandatory aggregation that defines the set of SUPABooleanClauses that are aggregated by this SUPAECAPolicyRule to form an Event clause. The multiplicity of this relationship is 0..1 on the aggregate (SUPAECAPolicyRule) side, and 1..n on the part (SUPABooleanClause) side. This means that one or more SUPABooleanClauses are aggregated and used to define this SUPAECAPolicyRule. The 0..1 cardinality on the SUPAECAPolicyRule side is necessary to enable SUPABooleanClauses to exist (e.g., in a PolicyRepository) before they are used by a SUPAECAPolicyRule. 6.4.2.2. The Relationship "HasSUPAConditions" This is a mandatory aggregation that defines the set of SUPABooleanClauses that are aggregated by this SUPAECAPolicyRule to form a Condition clause. The multiplicity of this relationship is 0..1 on the aggregate (SUPAECAPolicyRule) side, and 1..n on the part (SUPABooleanClause) side. This means that one or more SUPABooleanClauses are aggregated and used to define this SUPAECAPolicyRule. The 0..1 cardinality on the SUPAECAPolicyRule side is necessary to enable SUPABooleanClauses to exist (e.g., in a PolicyRepository) before they are used by a SUPAECAPolicyRule. Strassner, et al. Expires September 18, 2015 [Page 32] Internet-Draft SUPA Generic Policy Model Apr 2015 6.4.2.3. The Relationship "HasSUPAActions" This is a mandatory aggregation that defines the set of SUPABooleanClauses that are aggregated by this SUPAECAPolicyRule to form an Action clause. The multiplicity of this relationship is 0..1 on the aggregate (SUPAECAPolicyRule) side, and 1..n on the part (SUPABooleanClause) side. This means that one or more SUPABooleanClauses are aggregated and used to define this SUPAECAPolicyRule. The 0..1 cardinality on the SUPAECAPolicyRule side is necessary to enable SUPABooleanClauses to exist (e.g., in a PolicyRepository) before they are used by a SUPAECAPolicyRule. 6.5. SUPAPolicyStatement Subclasses Section 5.5.2 defines a common subclass of SUPAPolicyStatement, called SUPAEncodedClause, which any SUPAPolicy (rule or predicate) can use. This section describes another specialization of the SGPIM SUPAPolicyStatement class for use in constructing (only) SUPAECAPolicyRule objects. 6.5.1. Designing SUPAPolicyStatements Using SUPABooleanClauses A SUPABooleanClause specializes a SUPAPolicyClause, and defines a Boolean statement consisting of a standard structure in the form of a PolicyVariable, a PolicyOperator, and a PolicyValue. This design is based on the DEN-ng model [2]. For example, this enables the following Boolean clause to be defined: Foo >= Bar where Foo is a PolicyVariable, >= is a PolicyOperator, and Bar is a PolicyValue. Note that in this approach, each of these three terms (i.e., the PolicyVariable, PolicyOperator, and PolicyValue) are subclasses of the EPRIM (specifically, of the SUPABooleanClauseAtomic class, which is defined in Section 6.7.1). This enables the EPRIM, in conjunction with the SGPIM, to be used as a reusable class library. Put another way, this encourages interoperability, since each element of the clause is itself an object defined by SUPA. The addition of a negation in the above statement is provided by the supaTermIsNegated Boolean class attribute. Strassner, et al. Expires September 18, 2015 [Page 33] Internet-Draft SUPA Generic Policy Model Apr 2015 The construction of more complex clauses, which consist of a set of simple clauses in conjunctive or disjunctive normal form (as shown in the above example), is provided by using the composite pattern [3] to construct two subclasses of SUPABooleanClause. These are called SUPABooleanClauseAtomic and SUPABooleanClauseComposite, and are defined in Sections 6.7.1 and 6.7.2, respectively. This enables instances of either a SUPABooleanClauseAtomic and/or a SUPABooleanClauseComposite to be aggregated into a SUPABooleanClauseComposite object. 6.6. The Abstract Class "SUPABooleanClause" This is a mandatory abstract class that defines a clause as the following three-tuple: {PolicyVariable, PolicyOperator, PolicyValue} The composite pattern [3] is used in order to construct complex Boolean clauses from a set of SUPABooleanClause objects. This is why SUPABooleanClause is defined to be abstract - only instances of the SUPABooleanAtomic and/or SUPABooleanComposite classes can be used to construct a SUPABooleanClause. Figure 8 below shows the composite pattern applied to the SUPABooleanClause class. 1..n +-------------------+ \| | +--------------- | SUPABooleanClause | | /| | | +-------------------+ | / \ | HasSUPABooleanClauses | | | | +----------------+---------+ / \ | | A | | 0..1 \ / | | +----------------+---------+ +-----------+-----------+ |SUPABooleanClauseComposite| |SUPABooleanClauseAtomic| +--------------------------+ +-----------------------+ Figure 8. The Composite Pattern Applied to a SUPABooleanClause Strassner, et al. Expires September 18, 2015 [Page 34] Internet-Draft SUPA Generic Policy Model Apr 2015 The advantage of a SUPABooleanClause is that it is formed entirely from SUPAPolicy objects. This enhances both reusability as well as interoperability. Since this involves compositing a number of objects, data model implementations MAY optimize a SUPABooleanClause according to their application-specific needs (e.g., by flattening the set of classes that make up a SUPABooleanClause object into a single object). 6.6.1. SUPABooleanClause Attributes The following sections define attributes of a SUPABooleanClause. 6.6.1.1. The Attribute "supaBoolIsNegated" This is a mandatory Boolean attribute. If the value of this attribute is TRUE, then this SUPABooleanClause is negated. 6.6.2. SUPABooleanClause Relationships The following subsections define the relationships of a SUPABooleanClause. 6.6.2.1. The Relationship "HasSUPABooleanClauses" This is a mandatory aggregation that defines the set of SUPABooleanClauses that are aggregated by this SUPABooleanClauseComposite to form a complete SUPABooleanClause from multiple clauses (which can be made up of SUPABooleanClauseAtomic and/or SUPABooleanClauseComposite object instances. The multiplicity of this relationship is 0..1 on the aggregate (SUPABooleanClauseComposite) side, and 1..n on the part (SUPABooleanClause) side. This means that one or more SUPABooleanClauses are aggregated and used to define this SUPABooleanClauseComposite object. The 0..1 cardinality on the SUPABooleanClauseComposite side is necessary to enable SUPABooleanClauses to exist (e.g., in a PolicyRepository) before they are used by a SUPABooleanClauseComposite. 6.7. SUPABooleanClause Subclasses SUPABooleanClause defines two subclasses, as shown in Figure 8. They are both described in the following subsections. Strassner, et al. Expires September 18, 2015 [Page 35] Internet-Draft SUPA Generic Policy Model Apr 2015 6.7.1. The Abstract Class "SUPABooleanClauseAtomic" This is a mandatory abstract class that represents a SUPABooleanClause that can operate as a single, stand-alone, manageable object. Put another way, a SUPABooleanClauseAtomic object can NOT be modeled as a set of hierarchical clauses; if this functionality is required, then a SUPABooleanClauseComposite object must be used. No attributes are currently defined for the SUPABooleanClauseAtomic class. Its primary purpose is to aggregate SUPAPolicyVariable, SUPAPolicyOperator, and SUPAPolicyValue objects to form a complete SUPABoolean clause. As such, this class is defined as abstract to simplify data model optimization and mapping. The three primary subclasses of the SUPABooleanClauseAtomic class are shown in Figure 9. +-------------------------+ | SUPABooleanClauseAtomic | +-------------------------+ / \ | | +-------------+--+-----------+ | | | | | | +----------+---------+ | | | SUPAPolicyVariable | | | +--------------------+ | | | | +----------+---------+ | | SUPAPolicyOperator | | +------------------- + | | +--------+--------+ | SUPAPolicyValue | +---------------- + Figure 9. SUPABooleanClauseAtomic Subclasses 6.7.1.1. The Abstract Class "SUPAPolicyVariable" This is a mandatory abstract class. It is similar to the PolicyVariable class of [RFC3460], but there are some important differences in the SUPA version of this class that make the SUPA version more generic than the version defined in [RFC3460]. The problems in the definition of the [RFC3460] version of this class are discussed in Section 6.7.1.1.1, and the SUPAPolicyVariable class definition is defined in Section 6.7.1.1.2. Strassner, et al. Expires September 18, 2015 [Page 36] Internet-Draft SUPA Generic Policy Model Apr 2015 6.7.1.1.1. Problems with the RFC3460 Version of PolicyVariable First, [RFC3460] says: "Variables are used for building individual conditions". While this is true, variables can also be used for building individual actions. This is reflected in the SUPAPolicyVariable definition. Second, [RFC3460] says: "The variable specifies the property of a flow or an event that should be matched when evaluating the condition." While this is true, variables can be used to test many broader things than "just" a flow or an event. This is reflected in the SUPAPolicyVariable definition. Third, in [RFC3460], defining constraints for a variable is limited to associating the variable with a PolicyValue. This is both cumbersome (because associations are costly), and not scalable, because it is prone to proliferating PolicyValue classes for every constraint (or range of constraints) that is possible. Therefore, in SUPA, this mechanism is replaced with using an association to a generic SUPAConstraint object. Fourth, [RFC3460] is tightly bound to the DMTF CIM schema [4]. The CIM is a data model (despite its name), because: o It uses keys and weak relationships, which are both concepts from relational algebra and thus, not technology-independent o It has its own proprietary modeling language o It contains a number of concepts that are not defined in UML (including overriding keys for subclasses) 6.7.1.1.2. The Abstract Class "SUPAPolicyVariable" To be finished in the next version of this document. The big question to be answered is whether to keep the PolicyImplicitVariable and PolicyExplicitVariable subclasses of [RFC3460] or not. 6.7.1.2. The Concrete Class "SUPAPolicyOperator" This is a mandatory abstract class. Note that there is no equivalent to this class in [RFC3460], which causes a number of problems in the overloading of the semantics of an operator for defining clauses in an ECA policy rule. This will be defined in the next version of this document. Strassner, et al. Expires September 18, 2015 [Page 37] Internet-Draft SUPA Generic Policy Model Apr 2015 6.7.1.3. The Abstract Class "SUPAPolicyValue" This is a mandatory abstract class. It is similar to the PolicyValue class of [RFC3460], but there are some important differences in the SUPA version of this class that make the SUPA version more generic than the version defined in [RFC3460]. The problems in the definition of the [RFC3460] version of this class are discussed in Section 6.7.1.3.1, and the SUPAPolicyVariable class definition is defined in Section 6.7.1.3.2. 6.7.1.3.1. Problems with the RFC3460 Version of PolicyValue This will be defined in the next version of this document. 6.7.1.3.2. The Abstract Class "SUPAPolicyValue" This will be defined in the next version of this document. 6.7.2. The Abstract Class "SUPABooleanClauseComposite" This will be defined in the next version of this document. 6.7.2.1. SUPABooleanClauseComposite Attributes This will be defined in the next version of this document. 6.7.2.2. SUPABooleanClauseComposite Relationships This will be defined in the next version of this document. Strassner, et al. Expires September 18, 2015 [Page 38] Internet-Draft SUPA Generic Policy Model Apr 2015 7. SUPA GoalPredicate Information Model This section defines the classes, attributes, and relationships of the GPIM. 7.1. Overview A Goal policy rule (also called a declarative policy rule, or an intent-based policy rule) is a declarative statement that defines what the policy should do, but not how to implement the policy. In this draft, such rules are called SUPAGoalPredicates. 7.2. Constructing a SUPAGoalPredicate This will be defined in the next version of this document. 7.3. Working With SUPAGoalPredicates This will be defined in the next version of this document. 7.4. The Abstract Class "SUPAGoalPredicate" This will be defined in the next version of this document. 8. Security Considerations This will be defined in the next version of this document. 9. IANA Considerations This document has no actions for IANA. 10. Acknowledgments This document has benefited from reviews, suggestions, comments and proposed text provided by the following members, listed in alphabetical order: TBD. Strassner, et al. Expires September 18, 2015 [Page 39] Internet-Draft SUPA Generic Policy Model Apr 2015 11. References This section defines normative and informative references for this document. 11.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3060] Moore, B., Ellesson, E., Strassner, J., Westerinen, A., "Policy Core Information Model -- Version 1 Specification", RFC 3060, February 2001 [RFC3198] Westerinen, A., Schnizlein, J., Strassner, J., Scherling, M., Quinn, B., Herzog, S., Huynh, A., Carlson, M., Perry, J., Waldbusser, S., "Terminology for Policy-Based Management", RFC 3198, November, 2001 [RFC3460] Moore, B., ed., "Policy Core Information Model (PCIM) Extensions, RFC 3460, January 2003 [RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, October 2010. [RFC6021] Schoenwaelder, J., "Common YANG Data Types", RFC 6021, October 2010. 11.2. Informative References [1] Strassner, J., "Policy-Based Network Management", Morgan Kaufman, ISBN 978-1558608597, Sep 2003 [2] Strassner, J., ed., the DEN-ng Information Model, add stable URI [3] Riehle, D., "Composite Design Patterns", Proceedings of the 1997 Conference on Object-Oriented Programming Systems, Languages and Applications (OOPSLA '97). ACM Press, 1997. Page 218-228 [4] DMTF, CIM Schema, v2.43, http://dmtf.org/standards/cim/cim_schema_v2430 Strassner, et al. Expires September 18, 2015 [Page 40] Internet-Draft SUPA Generic Policy Model Apr 2015 Authors' Addresses John Strassner Huawei Technologies 2330 Central Expressway Santa Clara, CA 95138 USA Email: john.sc.strassner@huawei.com Strassner, et al. Expires September 18, 2015 [Page 41]