Internet Engineering Task Force John Strassner INTERNET DRAFT Cisco Systems 8 February 1999 Ed Ellesson IBM Policy Framework Core Information Model draft-ietf-policy-core-schema-01.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim). Copyright Notice Copyright (C) The Internet Society (1998). All Rights Reserved. Abstract This document defines an object-oriented information model for representing policy information. This model defines structural information of objects that comprise and control policy (the 'schema', or class inheritance hierarchy) as well as information that describes how different objects are related to other objects (the relationship hierarchy). In general, both of these class hierarchies will need to be mapped to a particular data store. This draft targets a directory that uses LDAP as its access protocol. As such, the class inheritance hierarchy can be directly mapped, but the relationship hierarchy will in general need to be mapped to a form suitable for directory implementation. This is because it contains concepts that are usually not directly translatable to the underlying data store. This document defines a schema and one such mapping of relationships for implementation in directories using LDAPv3 as their access protocol. Strassner, et. al Expires 8 August 1999 [Page 1] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 The information model described in this document consists of five very general classes: policyGroup, policyRule, policyCondition, policyValidityPeriodCondition, and policyAction. While structural information is represented very well in LDAP schemas, relationships between objects are not. This document also defines how to map more abstract concepts, such as relationships, into LDAP schemas. One mechanism to do this mapping is to use auxiliary classes. This document defines one such class, the policyRuleContainmentAuxClass. While these classes are general, they are not abstract: they can all be directly instantiated. Policy solutions for specific areas, such as DiffServ and IPSec, may use the policyGroup, policyRule, policyValidityPeriodCondition, and policyRuleContainmentAuxClass classes directly, while creating their own subclasses derived from policyCondition and policyAction in order to represent their own application-specific needs. Table of Contents 1.0 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 2.0 Modeling Policies . . . . . . . . . . . . . . . . . . . . . 5 2.1 Policy Scope . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.0 Overview of the Schema . . . . . . . . . . . . . . . . . . . 8 3.1 Relationships . . . . . . . . . . . . . . . . . . . . . . . . 9 3.2 Associations . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.3 Aggregations . . . . . . . . . . . . . . . . . . . . . . . . 9 3.4 Key Relationships of the Policy Framework Core Information Model 9 4.0 Inheritance Hierarchy . . . . . . . . . . . . . . . . . . . 11 5.0 Class Definitions . . . . . . . . . . . . . . . . . . . . . 11 5.1 Naming Attributes in the Core Schema . . . . . . . . . . . . 11 5.2 The Class policyGroup . . . . . . . . . . . . . . . . . . . 12 5.2.1 The Attribute cn . . . . . . . . . . . . . . . . . . . . . 13 5.2.2 The Attribute policyGroupName . . . . . . . . . . . . . . 13 5.2.3 The Attribute containedPolicyGroups . . . . . . . . . . . . 13 5.2.4 The Attribute policyGroupType . . . . . . . . . . . . . . . 14 5.3 The Class policyRuleContainmentAuxClass . . . . . . . . . . 14 5.3.1 The Attribute policyRulesAuxContainedSet . . . . . . . . . . 15 5.4 The Class policyRule . . . . . . . . . . . . . . . . . . . . 15 5.4.1 The Attribute cn . . . . . . . . . . . . . . . . . . . . . 17 5.4.2 The Attribute policyRuleName. . . . . . . . . . . . . . . . 17 5.4.3 The Attribute policyRuleEnabled . . . . . . . . . . . . . . . 17 5.4.4 The Attribute policyRuleValidityPeriodRef . . . . . . . . . . 18 5.4.5 The Attribute policyRuleConditionList . . . . . . . . . . . . 18 5.4.6 The Attribute policyRuleActionList. . . . . . . . . . . . . . 20 5.4.7 The Attribute policyRuleKeywords . . . . . . . . . . . . . . 21 5.4.8 The Attribute policyRuleType . . . . . . . . . . . . . . . . 21 5.4.9 The Attribute policyRuleUsage . . . . . . . . . . . . . . . 22 Strassner, et. al Expires 8 August 1999 [Page 2] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 5.4.10 The Attribute policyRulePriority . . . . . . . . . . . . . . 22 5.4.11 The Attribute policyRuleMandatory . . . . . . . . . . . . . 22 5.4.12 The Attribute policyRuleDebugMode . . . . . . . . . . . . . 23 5.4.13 The Attribute policyRuleSequencedActions . . . . . . . . . . 23 5.5 The Class policyValidityPeriodCondition . . . . . . . . . . . 24 5.5.1 The Attribute cn . . . . . . . . . . . . . . . . . . . . . . 25 5.5.2 The Attribute pvpConditionName . . . . . . . . . . . . . . . 26 5.5.3 The Attribute pvpConditionTime . . . . . . . . . . . . . . . 26 5.5.4 The Attribute pvpConditionMonthOfYearMask . . . . . . .. . . 27 5.5.5 The Attribute pvpConditionDayOfMonthMask . . . . . . . . . . 28 5.5.6 The Attribute pvpConditionDayOfWeekMask . . . . . . . . . . . 29 5.5.7 The Attribute pvpConditionTimeOfDayMask . . . . . . . . . . . 27 5.5.8 The Attribute pvpConditionTimeZone . . . . . . . . . . . . . 29 5.6 The Class policyCondition . . . . . . . . . . . . . . . . . . 29 5.6.1 The Attribute cn . . . . . . . . . . . . . . . . . . . . . . 31 5.6.2 The Attribute policyConditionName . . . . . . . . . . . . . . 31 5.7 The Class vendorPolicyCondition . . . . . . . . . . . . . . . . 31 5.7.1 The Attribute vendorPolicyConditionData . . . . . . . . . . 32 5.7.2 The Attribute vendorPolicyConditionEncoding . . . . . . . . . 32 5.8 The Class policyAction. . . . . . . . . . . . . . . . . . . . . 33 5.8.1 The Attribute cn . . . . . . . . . . . . . . . . . . . . . . 33 5.8.2 The Attribute policyActionName . . . . . . . . . . . . . . . 33 5.9 The Class vendorPolicyAction . . . . . . . . . . . . . . . . . 34 5.9.1 The Attribute vendorPolicyActionData . . . . . . . . . . . . 34 5.9.2 The Attribute vendorPolicyActionEncoding . . . . . . . . . . 35 6.0 Extending the Core Schema . . . . . . . . . . . . . . . . . . 35 6.1 Subclassing policyCondition and policyAction. . . . . . . . . 35 6.2 Subclassing policyRule . . . . . . . . . . . . . . . . . . . 36 6.2.1 Refining the Semantics of policyRule . . . . . . . . . . . 36 6.2.2 Optimizing the computation of a policyRule . . . . . . . . . 36 6.3 Using the Vendor Policy Encoding Attributes . . . . . . . . . 36 6.4 Using Time Validity Periods . . . . . . . . . . . . . . . . . 37 7.0 Security Considerations . . . . . . . . . . . . . . . . . . . 37 8.0 Intellectual Property . . . . . . . . . . . . . . . . . . . . 37 9.0 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 38 10.0 References . . . . . . . . . . . . . . . . . . . . . . . . . 38 11.0 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 39 12.0 Full Copyright Statement . . . . . . . . . . . . . . . . . . 39 Strassner, et. al Expires 8 August 1999 [Page 3] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 1.0 Introduction This document defines an information model, containing a schema (represented as a class inheritance hierarchy) and a relationship model. The schema contains five core classes for representing policies: policyGroup, policyRule, policyCondtion, policyAction, and policyValidityPeriodCondition. This schema can be mapped to many different data store implementations. This document concentrates on a mapping of the data store to a directory that uses LDAP as its access protocol. However, the relationship class hierarchy needs to be mapped to a specific data store implementation. This document defines a mapping for the relationships of this information model to a directory that uses LDAPv3 as its access protocol. A sixth core class, policyRuleContainmentAuxClass, is used as part of this mapping. The use of an information model enables the schema and the relationship class hierarchy to be extensible, such that other types of policy repositories, such as relational databases, can use this information. These six classes and their relationships are sufficiently generic to allow them to represent policies related to anything. However, their initial application will be for representing policies related to QoS (DiffServ and IntServ) and to IPSec. Policy models for application-specific areas such as these may extend the core schema in several ways. The preferred way is to use the policyGroup, policyRule, policyValidityPeriodCondition, and policyRuleContainmentAuxClass classes directly, as a foundation for representing and communicating policy information. Then, specific subclasses derived from policyCondition and policyAction can capture application-specific definitions of conditions and actions of policies. These subclasses will then fit naturally within the policy framework of the above four classes. This will be explored more thoroughly in Section 6.0, "Extending the Core Schema". Two subclasses vendorPolicyCondition and vendorPolicyAction are also included in this document, to provide a standard escape mechanism for vendor-specific extensions to the core policy schema. This document fits into the overall framework for representing, deploying, and managing policies being developed by the Policy Framework Working Group. The initial work to define this framework is in reference [1]. More specifically, this document builds on the core policy classes first introduced in references [2] and [3]. It also draws on the work done for the Directory-enabled Networks (DEN) specification, reference [4]. Work on the DEN specification by the DEN Ad-Hoc Working Group itself has been completed. Further work to standardize the models contained in it will be the responsibility of selected working groups of the CIM (Common Information Model) effort in the Desktop Management Task Force (DMTF). Standardization of the core policy model is the responsibility of the SLA Policy working group. Strassner, et. al Expires 8 August 1999 [Page 4] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119, reference [5]. 2.0 Modeling Policies The classes comprising the Policy Framework Core Information Model Class Hierarchy are intended to serve as an extensible class hierarchy (through specialization) for defining policy objects that enable application developers, network administrators, and policy administrators to represent policies of different types. The simplest way to think of a policy-controlled network is to first model the network as a state machine and then use policy to control which state a policy-controlled device should be in or is allowed to be in at any given time. Given this approach, policy is applied using a set of policy rules. Each policy rule consists of a set of conditions and a set of actions. Policy rules may be aggregated into policy groups. These groups may be nested, to represent a hierarchy of policies. The set of conditions associated with a policy rule specifies when the policy rule is applicable. The set of conditions can be expressed as either an ORed set of ANDed sets of condition statements or an ANDed set of ORed sets of statements. These combinations are termed, respectively, Disjunctive Normal Form (DNF) and Conjunctive Normal Form (CNF) for the conditions. Please note that it is explicitly NOT a goal of this specification to represent more complicated conditions (such as those that may be found in a procedural language) at this time. If the set of conditions associated with a policy rule evaluates to TRUE, then a set of actions that either maintain the current state of the object or transition the object to a new state may be executed. For the set of actions associated with a policy rule, it is possible to specify an order of execution, as well as an indication of whether the order is required or merely recommended. It is also possible to indicate that the order in which the actions are executed does not matter. Actions can be prioritized so as to avoid conflicts. However, this release of the core schema draft does not specify conditional handling of the actions to be executed, nor does it specify the handling of generalized error conditions. This is because if this feature is implemented, then policies immediately become much more complex. It is considered better to gain implementation experience with simpler policies and use this experience to then build more complex policies. Policy rules themselves can be prioritized. One common reason for doing this is to express an overall policy that has a general case with a few specific exceptions. Strassner, et. al Expires 8 August 1999 [Page 5] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 For example, a general QoS policy rule might specify that traffic originating from members of the engineering group is to get Bronze Service. A second policy rule might express an exception: traffic originating from John, a specific member of the engineering group, is to get Gold Service. Since traffic originating from John satisfies the conditions of both policy rules, and the actions associated with the two rules are incompatible, a priority needs to be established. By giving the second rule (the exception) a higher priority than the first rule (the general case), a policy administrator can get the desired effect: traffic originating from John gets Gold Service, and traffic originating from all the other members of the engineering group gets Bronze Service. Policies can either be used in a stand-alone fashion or aggregated into policy groups to perform more elaborate functions. Stand-alone policies are called policy rules. Policy groups are aggregations of policy rules, or aggregations of policy groups, but not both. Policy groups can model intricate interactions between objects that have complex interdependencies. Examples of this include a sophisticated user logon policy that sets up application access, security, and reconfigures network connections based on a combination of user identity, network location, logon method and time of day. A policy group represents a unit of reusability and manageability in that its management is handled by an identifiable group of administrators and its policyRules apply equally to the scope of the policyGroup. Stand-alone policies are those that can be expressed in a simple statement. They can be represented effectively in schemas or MIBs. Examples of this are VLAN assignments, simple YES/NO QoS requests, and IP address allocations. A specific design goal of this schema is to support both stand-alone and aggregated policies. Policy groups and rules can be classified by their purpose and intent. This classification is useful in querying or grouping policy rules. It indicates whether the policy is used to motivate when or how an action occurs, or to characterize services (that can then be used, for example, to bind clients to network services). Describing each of these concepts in more detail, - Motivational Policies are solely targeted at whether or how a policy's goal is accomplished. Configuration and Usage Policies are specific kinds of Motivational Policies. Another example is the scheduling of file backup based on disk write activity from 8am to 3pm, M-F. - Configuration Policies define the default (or generic) setup of a managed entity (for example, a network service). Examples of Configuration Policies are the setup of a network forwarding service or a network-hosted print queue. Strassner, et. al Expires 8 August 1999 [Page 6] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 - Installation Policies define what can and can't be put on a system or component, as well as the configuration of the mechanisms that perform the install. Installation policies typically represent specific administrative permissions, and can also represent dependencies between different components (e.g., to complete the installation of component A, components B and C must be previously successfully installed or uninstalled). - Error and Event Policies. For example, if a device fails between 8am and 9pm, call the system administrator, else call the Help Desk. - Usage Policies control the selection and configuration of entities based on specific "usage" data. Configuration Policies can be modified or simply re-applied by Usage Policies. Examples of Usage Policies include upgrading network forwarding services after a user is verified to be a member of a "gold" service group, or reconfiguring a printer to be able to handle the next job in its queue. - Security Policies deal with verifying that the client is actually who the client purports to be, permitting or denying access to resources, selecting and applying appropriate authentication mechanisms, and performing accounting and auditing of resources. - Service Policies characterize network and other services (not use them). For example, all wide-area backbone interfaces shall use a specific type of queuing. Service policies describe services available in the network. Usage policies describe the particular binding of a client of the network to services available in the network. 2.1 Policy Scope Policies represent business goals and objectives. A translation must be made between these goals and objectives and their realization in the network. An example of this could be a Service Level Agreement (SLA), and its objectives and metrics (Service Level Objectives, or SLOs), that are used to specify services that the network will provide for a given client [8]. The SLA will usually be written in high-level business terminology. SLOs address more specific metrics in support of the SLA. These high-level descriptions of network services and metrics must be translated into lower-level, but also vendor- and device-independent specifications. The core policy schema classes are intended to be used as part of the definition of this specification. This translation is domain-independent. That is, it applies equally to Quality of Service (QoS) as defined in the Differentiated Services working group of the IETF) as it does to signaled QoS, as specified in the Integrated Services working group of the IETF. Strassner, et. al Expires 8 August 1999 [Page 7] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 Furthermore, it is envisioned that the definition of policy in this draft is generic in nature and is suitable for non-QoS networking applications (e.g., DHCP and IPSEC) as well as non-networking applications (e.g., backup policies, auditing access, etc.). 3.0 Overview of the Schema The following diagram provides an overview of the five classes that comprise the CIM core schema, and their relationships to each other. Note that the two extension classes vendorPolicyCondition and vendorPolicyAction are not shown. ************** * * 0..n * * ContainedPolicyGroups +------v------+ * | policyGroup <****** | | 0..n +------^------+ 0..n * * ContainedPolicyRules 0..n * +-----v-------+ | | | policyRule | | | ContainedPolicyConditions (ORed set of ANDed | <************************* conditions, or | | 0..n * vice-versa) | | * 0..n | | +---------v------------+ | | | policyCondition | | | +----------------------+ | | ^ | | I | | I | | ^ | | +------------------------------ + | | | policyValidityPeriodCondition | | | +------------------------------ + | | | | ContainedPolicyActions | <************************* | | 0..n * | | * 0..n | | +---------v------------+ | | | policyAction | +-------------+ +----------------------+ Figure 1. An Overview of the CIM Policy Classes and Their Relationships Strassner, et. al Expires 8 August 1999 [Page 8] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 3.1 Relationships Relationships are a central feature of information models. A relationship represents a physical or conceptual connection between objects. CIM and DEN define the general concept of an association between two (or more) objects. Two types of associations are aggregations (which express whole-part relationships) and other relationships, such as those that express dependency. Both are used in this model. 3.2 Associations An association is a class that contains two or more references, where each reference identifies another object. An association is defined using a class. Associations can be defined between classes without affecting any of the related classes. That is, addition of an association does not affect the interface of the related classes. 3.3 Aggregations An aggregation is a strong form of an association. An aggregation is usually used to represent a "whole-part" relationship. This type of relationship defines the containment relationship between a system and the components that make up the system. Aggregation often implies, but does not require, that the aggregated objects have mutual dependencies. 3.4 Key Relationships of the Policy Framework Core Information Model The following relationships are shown in the preceding figure: - The ContainedPolicyGroups relationship enables policyGroups to be nested. This is critical for scalability and manageability, as it enables complex policies to be constructed from multiple simpler policies for administrative convenience. For example, a policyGroup representing policies for the US might have nested within it policy groups for the Eastern and Western US. For LDAP schemata, the ContainedPolicyGroups relation is mapped to the containedPolicyGroups attribute (note that other data stores may define a different mapping). This attribute enables a policyGroup to identify another policyGroup as its offspring. - A policy group may also aggregate one or more policy rules. Grouping of policy rules into a policy group is again for administrative convenience; a policy rule may also be used by itself, without belonging to a policy group. Strassner, et. al Expires 8 August 1999 [Page 9] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 - A policyRule may also be aggregated by an instance of any class to which the policyRuleContainmentAuxClass class has been attached. Once again, this is for administrative convenience. If the directory entry to which the policyRuleContainmentAuxClass has been attached is a policy group, then the pointer in the policyRuleContainmentAuxClass realizes the relationship discussed above between the group and a policyRule; a separate attribute is not needed in the policyGroup class. - A condition of a policyRule may specify one or more time validity periods. This can be used for several purposes. Two important uses include representing time as an additional condition (e.g., use one policy in the morning and use a different policy in the afternoon) and to enable scheduled activation and deactivation of the policyRule. A policy validity period may be aggregated by multiple policyRules. A rule that does not point to a policy validity period is, from the point of view of scheduling, always active. It may, however, be inactive for other reasons. Time validity periods are a general concept that can be used in other applications. However, they are mentioned explicitly here in this specification since they are frequently used in policy applications. - A policyRule aggregates zero or more instances of the policyCondition class. For all policy rules, at least one condition MUST be specified, either via the containedPolicyConditions aggregation, or defined explicitly within a subclass of policyRule. These conditions are grouped into two levels of lists: either an ORed set of ANDed sets of conditions (DNF, the default) or an ANDed set of ORed sets of conditions (CNF). The attribute policyRuleConditionListType specifies which of these two grouping schemes applies to a particular policyRule. Since conditions may be defined explicitly in a subclass of policyRule, the AND/OR mechanism to combine these conditions with other (associated) policyConditions MUST be specified by the policyRule's subclass. In either case, the conditions are used to determine whether to perform the actions associated with the policyRule. For LDAP schemata, pointers to PolicyCondition objects (or subclasses of this class) are used. - A policyRule may aggregate zero or more policy actions. For all policy rules, at least one action MUST be specified, either via the containedPolicyActions aggregation, or defined explicitly within a subclass of policyRule. The actions associated with a policyRule may be given a required order, a recommended order, or no order at all. For actions represented as separate objects, the containedPolicyActions aggregation can be used to express an order. For actions defined explicitly in a subclass of policyRule, the ordering mechanism must be specified in the subclass definition. Strassner, et. al Expires 8 August 1999 [Page 10] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 4.0 Inheritance Hierarchy for the LDAP Schema The following diagram illustrates the class hierarchy for the LDAP policy schema classes: top | +---policyGroup | +---policyRuleContainmentAuxClass | +---policyRule | +---policyCondition | ^ | | | +---policyValidityPeriodCondition | | | +---vendorPolicyCondition | +---policyAction ^ | +---vendorPolicyAction 5.0 Class Definitions for the LDAP Schema The classes described below contain certain optimizations for a directory that uses LDAP as its access protocol. One example of this is the use of an auxiliary class to represent CIM relationships. Other data stores might need to implement these relationships differently. 5.1 Naming Attributes in the Core Schema Instances in a directory are identified by distinguished names (DNs), which provide the same type of hierarchical organization that a file system provides in a computer system. A distinguished name is a sequence of relative distinguished names (RDNs), where an RDN provides a unique identifier for an instance within the context of its immediate superior in the same way that a filename provides a unique identifier for a file within the context of the folder in which it resides. To preserve maximum naming flexibility for policy administrators, each of the classes defined in this schema has its own naming attribute. Since the naming attributes are different, the policy administrator is guaranteed that there will be no name collisions between instances of different classes, even if the same VALUE is assigned to the instances' respective naming attributes. To fit in with existing directory practice, each of the classes uses the commonName (cn) attribute as its naming attribute. Strassner, et. al Expires 8 August 1999 [Page 11] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 5.2 The Class policyGroup This class is a generalized aggregation container. It enables either policyRules or policyGroups, but not both, to be aggregated in a single container. Loops, including the degenerate case of a policyGroup that contains itself, are not allowed when policyGroups contain other policyGroups. PolicyGroups and their nesting capabilities are shown in Figure 2 below. Note that a policyGroup can nest other policyGroups, and there is no restriction on the depth of the nesting in sibling policyGroups. --------------------------------------------------- | policyGroup | | | | -------------------- ----------------- | | | policyGroup A | | policyGroup X | | | | | | | | | | ---------------- | บบบ | | | | | | policyGroup A1 | | | | | | | ---------------- | | | | | -------------------- ----------------- | --------------------------------------------------- Figure 2. Overview of the policyGroup class As a simple example, think of the highest level policyGroup shown in Figure 2 above as a logon policy for US employees of a company. This policyGroup may be called USEmployeeLogonPolicy, and may aggregate several policyGroups that provide specialized rules per location. Hence, policyGroupA in Figure 2 above may define logon rules for employees on the West Coast, while another policyGroup might define logon rules for the Midwest (e.g., policyGroupX), and so forth. Note also that the depth of each policyGroup does not need to be the same. Thus, the WestCoast policyGroup might have several additional layers of policyGroups defined for any of several reasons (different locales, number of subnets, etc.). The policyRules are therefore contained at n levels from the USEmployeeLogonPolicyGroup. Compare this to the Midwest policyGroup (policyGroupX), which might directly contain policyRules. The class definition for policyGroup is as follows. Note that this class definition does not include an attribute to realize the ContainedPolicyRules association from the object model, since a policyGroup object points to instances of policyRule via the pointer in policyRuleContainmentAuxClass. Strassner, et. al Expires 8 August 1999 [Page 12] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 NAME policyGroup DESCRIPTION A container for either a set of related policyRules or a set of related policyGroups DERIVED FROM top TYPE structural AUXILIARY CLASSES policyRuleContainmentAuxClass POSSIBLE SUPERIORS container, organization, organizationalUnit, policyGroup OID MUST cn, policyGroupName MAY containedPolicyGroups, policyGroupType 5.2.1 The attribute cn The cn, or commonName, attribute is an X.500 attribute. It stands for commonName. It specifies a user-friendly name by which the object is commonly known. This name may be ambiguous by itself. This name is used in a limited scope (such as an organization). It conforms to the naming conventions of the country or culture with which it is associated. CN is used universally in DEN as the naming attribute for a class. NAME cn DESCRIPTION Naming attribute of this class SYNTAX DirectoryString OID 2.4.5.3 EQUALITY caseExactMatch SINGLE-VALUED 5.2.2 The Attribute policyGroupName This attribute provides a user-friendly name for a policy group, and is normally what will be displayed to the end-user as the name of this class. It is defined as follows: NAME policyGroupName DESCRIPTION The user-friendly name of this policy group. SYNTAX IA5String OID EQUALITY caseExactIA5Match SINGLE-VALUED 5.2.3 The Attribute containedPolicyGroups This attribute provides an unordered set of DN pointers to zero or more other policyGroup objects, representing nested policyGroups contained by this policyGroup. The attribute definition is as follows: Strassner, et. al Expires 8 August 1999 [Page 13] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 NAME containedPolicyGroups DESCRIPTION Distinguished names of other policyGroup objects aggregated by this policy group. There is no order implied among the members of the set. SYNTAX DN OID EQUALITY distinguishedNameMatch MULTI-VALUED 5.2.4 The Attribute policyGroupType This attribute is used to specify the type of policy that this policyGroup represents. This can be used for classification (for example, service policy or usage policy) or categorization (the type of service or usage policy that this policy is). The attribute definition is as follows: NAME policyGroupType DESCRIPTION Defines a policyGroup classification and categorization. When multiple classifications are possible, the one that "best" describes the policyGroup's type should be used. SYNTAX INTEGER OID EQUALITY integerMatch SINGLE-VALUED DEFAULT VALUE 0 The defined values for this attribute are: Unknown (0), Configuration (1), Usage (2), Security (3), Service (4), Motivational (5), Installation (6), and Event (7). These concepts were defined in Section 2.0. 5.3 The Class policyRuleContainmentAuxClass This auxiliary class provides a single, multi-valued attribute that points to a set of policyRules. By attaching this attribute to instances of various other classes, a policy administrator has a flexible way of providing an entry point into the directory that allows a client to locate and retrieve the policyRules relevant to it. A policy administrator might have several different pointers to a policyRule in the overall directory structure. For example, there might be pointers to all policyRules for traffic originating in a particular subnet from a directory entry that represents that subnet. At the same time, there might be pointers to all policyRules related to a particular DiffServ setting from an instance of a policyGroup explicitly introduced as a container for DiffServ-related policyRules. The policyRuleContainmentAuxClass is the mechanism that makes it possible for the policy administrator to define all these pointers. Strassner, et. al Expires 8 August 1999 [Page 14] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 Note that the cn attribute does NOT need to be defined for this class. This is because an auxiliary class is used as a means to collect common attributes and treat them as properties of an object. A good analogy is a #include file, except that since an auxiliary class is a class, all the benefits of a class (e.g., inheritance) can be applied to an auxiliary class. The class definition is as follows: NAME policyRuleContainmentAuxClass DESCRIPTION An auxiliary class used to bind policyRules to an appropriate container object. DERIVED FROM top TYPE auxiliary AUXILIARY CLASSES none POSSIBLE SUPERIORS container, organization, organizationalUnit, policyGroup OID MUST policyRulesAuxContainedSet 5.3.1 The Attribute policyRulesAuxContainedSet This attribute provides an unordered set of DN pointers to one or more policyRules associated with the instance of a structural class to which this attribute has been appended. The attribute definition is: NAME policyRulesAuxContainedSet DESCRIPTION Distinguished names of policyRules associated in some way with the instance to which this attribute has been appended. No order is implied. SYNTAX DN OID EQUALITY distinguishedNameMatch MULTI-VALUED 5.4 The Class policyRule This class represents the "If Condition then Action" semantics associated with a policy. A policyRule condition, in the most general sense, is represented as either an ORed set of ANDed conditions (Disjunctive Normal Form, or DNF) or an ANDed set of ORed conditions (Conjunctive Normal Form, or CNF). The actions specified by a policyRule are to be performed if and only if the policyRule condition (whether it is represented in DNF or CNF) evaluates to TRUE. Both the conditions and the actions are identified by DN pointers and/or by specific attributes introduced in subclasses of policyRule. Strassner, et. al Expires 8 August 1999 [Page 15] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 This is illustrated conceptually in Figure 3 below. ------------------------------------------------ | PolicyRule | | | | -------------------- ----------------- | | | PolicyCondition(s)| | PolicyAction(s) | | | -------------------- ----------------- | | | ------------------------------------------------ Figure 3. Overview of the PolicyRule Class The policyRule class uses the attribute policyRuleConditionListType, to indicate whether the conditions for the rule are in DNF or CNF. The DN pointers from a policyRule to its associated policyConditions also contain an integer to partition the referenced conditions into one or more sets. An example shows how the attribute and the grouping integer provide a unique representation of a set of conditions in either DNF or CNF. Suppose we have pointers to five policyConditions from an instance of policyRule, grouped as follows: (C1: groupNumber = 1, C2: groupNumber = 1, C3: groupNumber = 1, C4: groupNumber = 2, C5: groupNumber = 2) If policyRuleConditionListType = DNF, then the overall condition for the policyRule is: (C1 AND C2 AND C3) OR (C4 AND C5) On the other hand, if policyRuleConditionListType = CNF, then the overall condition for the policyRule is: (C1 OR C2 OR C3) AND (C4 OR C5) In both cases there is an unambiguous specification of the overall condition that is tested to determine whether to perform the actions associated with the policyRule. This class also contains several attributes designed to help directory clients locate the policy rules applicable to them. The class definition is as follows: Strassner, et. al Expires 8 August 1999 [Page 16] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 NAME policyRule DESCRIPTION The central class for representing the "If Condition then Action" semantics associated with a policy rule. DERIVED FROM top TYPE structural AUXILIARY CLASSES none POSSIBLE SUPERIORS policyGroup OID MUST cn policyRuleName MAY policyRuleEnabled policyRuleConditionListType policyRuleConditionList policyRuleActionList policyRuleKeywords policyRuleType policyRuleUsage policyRulePriority policyRuleMandatory policyRuleDebugMode policyRuleSequencedActions 5.4.1 The Attribute cn This is the exact same definition as in Section 5.2.1. It is included in this class for the reasons enumerated there. 5.4.2 The Attribute policyRuleName This attribute provides a user-friendly name for a policy rule. The attribute definition is as follows: NAME policyRuleName DESCRIPTION The user-friendly name of this policy rule. SYNTAX IA5String OID EQUALITY caseExactIA5Match SINGLE-VALUED 5.4.3 The Attribute policyRuleEnabled This flag indicates whether a policy rule is currently enabled, from an ADMINISTRATIVE point of view. Its purpose is to allow a policy administrator to enable or disable a policy rule without having to add it to, or remove it from, the directory. The attribute definition is as follows: Strassner, et. al Expires 8 August 1999 [Page 17] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 NAME policyRuleEnabled DESCRIPTION A flag indicating whether this policy rule is enabled from an administrative point of view. SYNTAX Boolean OID EQUALITY booleanMatch SINGLE-VALUED DEFAULT VALUE TRUE 5.4.4 The Attribute policyRuleConditionListType This attribute is used to specify whether the list of policy conditions associated with this policy rule is in disjunctive normal form (DNF) or conjunctive normal form (CNF). If this attribute is not present, the list type defaults to DNF. The attribute definition is as follows: NAME policyRuleConditionListType DESCRIPTION Indicates whether the list of policy conditions associated with this policy rule is in disjunctive normal form (DNF) or conjunctive normal form (CNF). Defined values are 'DNF (1)' and 'CNF (2)'. SYNTAX INTEGER OID EQUALITY integerMatch SINGLE-VALUED DEFAULT VALUE 1 (DNF) 5.4.5 The Attribute policyRuleConditionList This attribute provides an unordered list of DN pointers that identify a set of policy conditions associated with this policy rule. There is an integer associated with each pointer, to provide the grouping of the conditions into first-level groups for the DNF or CNF representation of the overall policyRule condition. To accommodate this grouping, the syntax of this attribute is a string of the form 'groupNumber:DN'. Existing matching rules are built to operate on a single data type. This attribute is conceptually comprised of two data types, an Integer (groupNumber) and DistinguishedName (DN). There are three ways to address this. Strassner, et. al Expires 8 August 1999 [Page 18] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 1. Collapse the two attribute types into a single structured IA5 string with the format 'groupNumber:DN'. This approach has the advantage of not requiring any new support in the directory server implementations, since these servers already support an IA5 string matching rule. Its disadvantage is that an IA5 string match works somewhat differently from a DN match with respect to subtleties such as preserving versus ignoring versus removing repeated whitespace characters. Thus DNs that would match with the distinguishedNameMatch matching rule might fail to be found as substrings of 'groupNumber:DN' strings by the IA% matching rules, or vice versa. 2. Define a new syntax ':', with its own matching rules. With this approach the matching problems introduced by the IA5 string could be avoided, since the new type would have its own matching rules. The disadvantage of defining a new type in this way is that a directory server must add new code that recognizes the type and implements its matching rules. A directory server would thus be unable to support the Core Policy Schema until it had added this new code. 3. Use two objects in the directory to represent the two data types, and relate the objects with the Families of Entries model currently being discussed in the LDAP Extensions working group. This approach has the same problem as the previous one: without the addition of new code to support Families of Entries, a directory server would be unable to support the Core Policy Schema at all. There is also the additional complication here, that the Families of Entries model itself may take some time to reach approved status in the LDAP Extensions (LDAPEXT) working group. For now, this document will move forward with the 'groupNumber:DN' structured IA5 string approach for containedPolicyConditions, as well as with an analogous 'n:DN' approach for containedPolicyActions. To minimize problems arising from differences in matching rules, this document will provide a series of guidelines for constructing DNs that behave identically with respect to the IA5 matching rules and the distinguishedNameMatch. These guidelines are in Appendix A. The attribute definition is as follows: NAME policyRuleConditionList DESCRIPTION An unordered list of strings of the form 'groupNumber:DN', indicating a set of policy conditions that determine when the policyRule is applicable. SYNTAX OctetString OID EQUALITY TBD MULTI-VALUED FORMAT groupNumber:DN Strassner, et. al Expires 8 August 1999 [Page 19] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 5.4.6 The Attribute policyRuleActionList This attribute provides an unordered list of strings of the form 'n:DN' that identify a set of policy actions associated with this policy rule. (See section 5.4.5 for a discussion of the issues surrounding the use of a syntax of this type.) When 'n' is a positive integer, it indicates a place in the sequence of actions to be performed, with smaller integers indicating earlier positions in the sequence. The special value '0' indicates "don't care," with one exception: all actions with positive sequence numbers are to be performed before any actions with sequence number '0'. Finally, if two or more actions have the same non-zero sequence number, they may be performed in any order, but they must all be performed at the appropriate place in the overall action sequence. A series of examples will make ordering of actions clearer: - If all actions have the same sequence number, regardless of whether it is '0' or non-zero, any order is acceptable. - The values 1:DN-A 2:DN-B 1:DN-C 3:DN-D indicate two acceptable orders: A,C,B,D or C,A,B.D, since A and C can be performed in either order, but only at the '1' position. - The values 0:DN-A 2:DN-B 0:DN-C 3:DN-D indicate either B,D,A,C or B,D,C,A, since the '0' actions A and C must be performed after the non-zero ones. Note that the non-zero sequence numbers need not start with '1', and they need not be consecutive. All that matters is their relative magnitude. This attribute indicates the actions of a policyRule and their order (or absence of order). However, another attribute, policyRuleSequencedActions, indicates whether the indicated order is required, recommended, or not to be used at all. All actions specified in the policyRuleActionList will be executed as long as the overall policy condition as defined by the policyRuleConditionListType and policyRuleConditionList attributes evaluates to TRUE. Strassner, et. al Expires 8 August 1999 [Page 20] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 The attribute definition is as follows: NAME policyRuleActionList DESCRIPTION An unordered list of strings of the form 'n:DN', indicating an ordered set of policy actions to be performed if the associated condition(s) of the policyRule evaluates to true. SYNTAX Octet String OID EQUALITY TBD MULTI-VALUED FORMAT n:DN 5.4.7 The Attribute policyRuleKeywords This attribute provides a set of one or more ad hoc keywords that a policy administrator may define to assist directory clients in locating the policy rules applicable to them. Values for this attribute are installation dependent, and thus are not specified in any schema document. The attribute definition is as follows: NAME policyRuleKeywords DESCRIPTION A set of ad hoc keywords to assist directory clients in locating the policy rules applicable to them. SYNTAX IA5String OID EQUALITY caseExactIA5Match MULTI-VALUED 5.4.8 The Attribute policyRuleType This attribute is used to specify the type of policy that this policy rule represents. This can be used for classification (for example, service policy or usage policy) or categorization (the type of service or usage policy that this policy is). The attribute definition is as follows: NAME policyRuleType DESCRIPTION Defines a policy classification and categorization. When multiple classifications are possible, the one that "best" describes the policy's type should be used. SYNTAX INTEGER OID EQUALITY integerMatch SINGLE-VALUED DEFAULT VALUE 0 Strassner, et. al Expires 8 August 1999 [Page 21] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 The defined values for this attribute are: Unknown (0), Configuration (1), Usage (2), Security (3), Service (4), Motivational (5), Installation (6), and Event (7). These concepts were defined in Section 2.0. 5.4.9 The Attribute policyRuleUsage This attribute is a free-form string that recommends how this policy should be used. The attribute definition is as follows: NAME policyRuleUsage DESCRIPTION This attribute is used to provide guidelines on how this policy should be used. SYNTAX DirectoryString OID EQUALITY caseIgnoreMatch SINGLE-VALUED 5.4.10 The Attribute policyRulePriority This attribute provides a positive integer for prioritizing policy rules relative to each other. For policy rules that have this attribute, smaller integer values indicate higher priority. Since one purpose of this attribute is to allow specific, ad hoc policy rules to temporarily override established policy rules, an instance that has this attribute set has a higher priority than all instances that lack it. Prioritization among policy rules provides a simple and efficient mechanism for resolving policy conflicts. The attribute definition is as follows: NAME policyRulePriority DESCRIPTION A positive integer for prioritizing this policyRule relative to other policyRules. A smaller value indicates a higher priority. SYNTAX INTEGER OID EQUALITY integerMatch SINGLE-VALUED DEFAULT VALUE 0 5.4.11 The Attribute policyRuleMandatory This attribute indicates whether evaluation (and possibly action execution) of a policyRule is mandatory or not. Its concept is similar to the ability to mark packets for delivery or possible discard, based on network traffic and device load. Strassner, et. al Expires 8 August 1999 [Page 22] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 The evaulation of a policyRule MUST be attempted if the policyRuleMandatory attribute value is True. If the policyRuleMandatory attribute value of a policyRule is False, then the evaluation of the rule is "best effort" and MAY be ignored. The attribute definition is as follows: NAME policyRuleMandatory DESCRIPTION A flag indicating that the evaluation of the policyConditions and execution of policyActions (if the condition list evaluates to True) is required. SYNTAX Boolean OID EQUALITY booleanMatch SINGLE-VALUED DEFAULT VALUE TRUE 5.4.12 The Attribute policyRuleDebugMode This attribute indicates that the policyRule should be evaluated, but no actions taken. It serves as a debug vehicle when attempting to determine what policies would execute in a particular scenario, but not to take any actions to change state due to that scenario. The attribute definition is as follows: NAME policyRuleDebugMode DESCRIPTION A flag indicating that the evaluation of the policyRule's policyConditions should occur, but the set of actions specified for the rule should not be executed. SYNTAX Boolean OID EQUALITY booleanMatch SINGLE-VALUED DEFAULT VALUE FALSE 5.4.13 The Attribute policyRuleSequencedActions This attrribute gives a policy administrator a way of specifying how the ordering of the policy actions associated with this policyRule is to be interpreted. Three values are supported: - mandatory (1): Do the actions in the indicated order, or don't do them at all. - recommended (2): Do the actions in the indicated order if you can, but if you can't do them in this order, do them in another order if you can. - dontCare (3): Do them -- I don't care about the order. Strassner, et. al Expires 8 August 1999 [Page 23] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 When error / event reporting is addressed for the Policy Framework, suitable codes will be defined for reporting that a set of actions could not be performed in an order specified as mandatory (and thus were not performed at all), that a set of actions could not be performed in a recommended order (and moreover could not be performed in any order), or that a set of actions could not be performed in a recommended order (but were performed in a different order). The attribute definition is as follows: NAME policyRuleSequencedActions DESCRIPTION An enumeration indicating how to interpret the action ordering indicated via the policyRuleActionList attribute. SYNTAX INTEGER OID EQUALITY integerMatch SINGLE-VALUED DEFAULT VALUE 3 The defined values for this attribute are mandatory(1), recommended(2), and dontCare(3). 5.5 The Class policyValidityPeriodCondition This class provides a means of representing the time periods during which a policy rule is valid, i.e., active. At all times that fall outside these time periods, the policy rule has no effect. A policy rule is treated as valid at all times if it does not specify a policyValidityPeriodCondition. PolicyValidityPeriodCondition is defined as a subclass of policyCondition. This is to allow the inclusion of time-based criteria in the AND/OR condition definitions for a policyRule. Instances of this class may have up to five attributes identifying time periods at different levels. The values of all the attributes present in an instance are ANDed together to determine the validity period(s) for the instance. For example, an instance with an overall validity range of January 1, 1999 through December 31, 1999; a month mask of "001100000000" (March and April); a day-of-the-week mask of "0000100" (Fridays); and a time of day range of 8 AM through 4 PM would represent the following validity periods: Friday, March 5, 1999, from 8 AM through 4 PM; Friday, March 12, 1999, from 8 AM through 4 PM; Friday, March 19, 1999, from 8 AM through 4 PM; Friday, March 26, 1999, from 8 AM through 4 PM; Friday, April 2, 1999, from 8 AM through 4 PM; Friday, April 9, 1999, from 8 AM through 4 PM; Friday, April 16, 1999, from 8 AM through 4 PM; Friday, April 23, 1999, from 8 AM through 4 PM; Friday, April 30, 1999, from 8 AM through 4 PM. Strassner, et. al Expires 8 August 1999 [Page 24] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 Attributes not present in an instance of policyValidityPeriodCondition are implicitly treated as having their value "always enabled". Thus, in the example above, the day-of-the-month mask is not present, and so the validity period for the instance implicitly includes a day-of-the-month mask containing 31 1's. If we apply this "missing attribute" rule to its fullest, we see that there is a second way to indicate that a policy rule is always enabled: have it point to an instance of policyValidityPeriodCondition whose only attributes are its naming attributes. The class definition is as follows. Note that instances of this class are named with the attributes cn and policyConditionName that they inherit from policyCondition. NAME policyValidityPeriodCondition DESCRIPTION A class that provides the capability of enabling / disabling a policy rule according to a pre-determined schedule. DERIVED FROM policyCondition TYPE structural AUXILIARY CLASSES none POSSIBLE SUPERIORS policyRule OID MUST MAY pvpConditionTime pvpConditionMonthOfYearMask pvpConditionDayOfMonthMask pvpConditionDayOfWeekMask pvpConditionTimeOfDayMask pvpConditionTimeZone 5.5.1 The Attribute pvpConditionTime This attribute identifies an overall range of calendar dates and times over which a policy rule is valid. It is formatted as a string consisting of a start date and time, then a colon (':'), and followed by an end date and time. The first date indicates the beginning of the range, while the second date indicates the end. Thus the second date and time must be later than the first. Dates are expressed as substrings of the form "yyyymmddhhmmss". For example: 19990101080000:19990131120000 January 1, 1999, 8 AM through January 31, 1999, noon Strassner, et. al Expires 8 August 1999 [Page 25] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 The attribute definition is as follows: NAME pvpConditionTime DESCRIPTION The range of calendar dates on which a policy rule is valid. SYNTAX PrintableString OID EQUALITY caseIgnoreMatch SINGLE-VALUED FORMAT yyyymmddhhmmss:yyyymmddhhmmss 5.5.2 The Attribute pvpConditionMonthOfYearMask The purpose of this attribute is to refine the definition of the valid time period that is defined by the pvpConditionTime attribute by explicitly specifying which months the policy is valid for. These attributes work together, with the pvpConditionTime used to specify the overall time period that the policy is valid for, and the pvpConditionMonthOfYearMask used to pick out which months of that time period the policy is valid for. This attribute is formatted as a string containing 12 ASCII '0's and '1's, where the '1's identify the months (beginning with January) in which the policy rule is valid. The value "000010010000", for example, indicates that a policy rule is valid only in the months May and August. If this attribute is omitted, then the policy assumes that it is valid for all twelve months. The attribute definition is as follows: NAME pvpConditionMonthOfYearMask DESCRIPTION A mask identifying the months of the year in which a policy rule is valid. SYNTAX Printable String OID EQUALITY caseIgnoreMatch SINGLE-VALUED FORMAT A string of 12 ASCII '0's and '1's. 5.5.3 The Attribute pvpConditionDayOfMonthMask The purpose of this attribute is to refine the definition of the valid time period that is defined by the pvpConditionTime attribute by explicitly specifying which days of the month the policy is valid for. These attributes work together, with the pvpConditionTime used to specify the overall time period that the policy is valid for, and the pvpConditionDayOfMonthMask used to pick out which days of the month that time period the policy is valid for. Strassner, et. al Expires 8 August 1999 [Page 26] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 This attribute is formatted as a string containing 31 ASCII '0's and '1's, where the '1's identify the days of the month (beginning with day 1 and going up through day 31) on which the policy rule is valid. The value "1110000000000000000000000000000", for example, indicates that a policy rule is valid only on the first three days of each month. For months with fewer than 31 days, the digits corresponding to days that the months do not have are ignored. The attribute definition is as follows: NAME pvpConditionDayOfMonthMask DESCRIPTION A mask identifying the days of the month on which a policy rule is valid. SYNTAX PrintableString OID EQUALITY caseIgnoreMatch SINGLE-VALUED FORMAT A string of 31 ASCII '0's and '1's. 5.5.4 The Attribute pvpConditionDayOfWeekMask The purpose of this attribute is to refine the definition of the valid time period that is defined by the pvpConditionTime attribute by explicitly specifying which days of the week the policy is valid for. These attributes work together, with the pvpConditionTime used to specify the overall time period that the policy is valid for, and the pvpConditionDayOfWeekMask used to pick out which days of the week of that time period the policy is valid for. This attribute is formatted as a string containing 7 ASCII '0's and '1's, where the '1's identify the days of the week (beginning with Monday and going up through Sunday) on which the policy rule is valid. The value "1111100", for example, indicates that a policy rule is valid Monday through Friday. The attribute definition is as follows: NAME pvpConditionDayOfWeekMask DESCRIPTION A mask identifying the days of the week on which a policy rule is valid. SYNTAX PrintableString OID EQUALITY caseIgnoreMatch SINGLE-VALUED FORMAT A string of 7 ASCII '0's and '1's. Strassner, et. al Expires 8 August 1999 [Page 27] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 5.5.5 The Attribute pvpConditionTimeOfDayMask The purpose of this attribute is to refine the definition of the valid time period that is defined by the pvpConditionTime attribute by explicitly specifying a range of times in a day the policy is valid for. These attributes work together, with the pvpConditionTime used to specify the overall time period that the policy is valid for, and the pvpConditionTimeOfDayMask used to pick out which range of time periods in a given day of the week of that time period the policy is valid for. This attribute is formatted as a string containing two times, separated by a colon (':'). The first time indicates the beginning of the range, while the second time indicates the end. Times are expressed as substrings of the form "hhmmss". The second substring always identifies a later time than the first substring. To allow for ranges that span midnight, however, the value of the second string may be smaller than the value of the first substring. Thus "080000:210000" identifies the range from 8 AM until 9 PM, while "210000:080000" identifies the range from 9 PM until 8 AM of the following day. When a range spans midnight, it by definition includes parts of two successive days. When one of these days is also selected by either the policyValidityMonthMask, policyValidityDayOfMonthMask, and/or policyValidityDayOfWeekMask, but the other day is not, then the policy is active only during the portion of the range that falls on the selected day. For example, if the range extends from 9 PM until 8 AM, and the day of week mask selects Monday and Tuesday, then the policy is active during the following three intervals: From midnight Sunday until 8 AM Monday; From 9 PM Monday until 8 AM Tuesday; From 9 PM Tuesday until 11:59:59 Tuesday. The attribute definition is as follows: NAME pvpConditionTimeOfDayMask DESCRIPTION The range of times at which a policy rule is valid. If the second time is earlier than the first, then the interval spans midnight. SYNTAX Printable String OID EQUALITY caseIgnoreMatch SINGLE-VALUED FORMAT hhmmss:hhmmss[:] Strassner, et. al Expires 8 August 1999 [Page 28] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 5.5.6 The Attribute pvpConditionTimeZone This attribute is used to explicitly define a time zone for use by the pvpConditionTime and the various Mask attributes. If this attribute is NULL, then local time is assumed. This attribute specifies time in UTC, using an offset indicator. The UTC offset indicator is either a 'Z', indicating UTC, or a substring of the following form: '+' or '-' direction from UTC: '+' = east, '-' = west plus: hh hours from UTC (00..13) mm minutes from UTC (00..59) The attribute definition is as follows: NAME pvpConditionTimeZone DESCRIPTION The definition of the time zone for use by the PolicyValidityCOndition. SYNTAX PrintableString OID EQUALITY caseIgnoreMatch SINGLE-VALUED FORMAT either 'Z' (UTC) or {'+' | '-'}'hhmm' 5.6 The Class policyCondition The purpose of a policy condition is to determine whether or not the set of actions (contained in the policyRule that the condition applies to) should be executed or not. For the purposes of the Core Policy Framework, all that matters about an individual policyCondition is that it evaluate to TRUE or FALSE. (The individual policyConditions associated with a policyRule are combined to form a compound expression in either DNF or CNF, but this is accomplished via the groupNumber component of the policyRuleConditionList string and by the policyRuleConditionListType attribute, both of which are discussed above.) A logical structure WITHIN an individual policyCondition may also be introduced, but this would have to be done in a suclass of policyCondition. Strassner, et. al Expires 8 August 1999 [Page 29] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 +---------------------------------------------------------------+ | Policy Conditions in DNF | | +-------------------------+ +-----------------------+ | | | AND list | | AND list | | | | +-------------------+ | | +-----------------+ | | | | | policyCondition | | | | policyCondition | | | | | +-------------------+ | | +-----------------+ | | | | +-------------------+ | | +-----------------+ | | | | | policyCondition | | ... | | policyCondition | | | | | +-------------------+ | ORed | +-----------------+ | | | | ... | | ... | | | | ANDed | | ANDed | | | | +-------------------+ | | +-----------------+ | | | | | policyCondition | | | | policyCondition | | | | | +-------------------+ | | +-----------------+ | | | +-------------------------+ +-----------------------+ | +---------------------------------------------------------------+ Figure 4. Overview of Policy Conditions in DNF This figure illustrates that when policy conditions are in DNF, there are one or more sets of conditions that are ANDed together to form AND lists. An AND list evaluates to TRUE if and only if all of its constituent conditions evaluate to TRUE. The overall condition then evaluates to TRUE if and only if at least one of its constituent AND lists evaluates to TRUE. +---------------------------------------------------------------+ | Policy Conditions in CNF | | +-------------------------+ +-----------------------+ | | | OR list | | OR list | | | | +-------------------+ | | +-----------------+ | | | | | policyCondition | | | | policyCondition | | | | | +-------------------+ | | +-----------------+ | | | | +-------------------+ | | +-----------------+ | | | | | policyCondition | | ... | | policyCondition | | | | | +-------------------+ | ANDed | +-----------------+ | | | | ... | | ... | | | | ORed | | ORed | | | | +-------------------+ | | +-----------------+ | | | | | policyCondition | | | | policyCondition | | | | | +-------------------+ | | +-----------------+ | | | +-------------------------+ +-----------------------+ | +---------------------------------------------------------------+ Figure 5. Overview of Policy Conditions in CNF In this figure the policy conditions are in CNF. Consequently, there are one or more OR lists, each of which evaluates to TRUE if and only if at least one of its constituent conditions evaluates to TRUE. The overall condition then evaluates to TRUE if and only if ALL of its constituent OR lists evaluate to TRUE. The class definition is as follows: Strassner, et. al Expires 8 August 1999 [Page 30] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 NAME policyCondition DESCRIPTION A class representing a condition to be evaluated in conjunction with a policy rule. DERIVED FROM top TYPE structural AUXILIARY CLASSES none POSSIBLE SUPERIORS policyRule OID MUST cn PolicyConditionName MAY 5.6.1 The Attribute cn This is the exact same definition as in Section 5.2.1. It is included in this class for the reasons enumerated there. 5.6.2 The Attribute policyConditionName This attribute provides a user-friendly name for a policy condition. The attribute definition is as follows: NAME policyConditionName DESCRIPTION The user-friendly name of this policy condition. SYNTAX IA5String OID EQUALITY caseExactIA5Match SINGLE-VALUED 5.7 The Class vendorPolicyCondition The purpose of this class is to provide a general escape mechanism for representing policy conditions that have not been modeled with specific attributes. Instead, the two attributes policyConstraintData and policyConstraintEncoding are used to define the content and format of the condition, as explained below. As its name suggests, this class is intended for vendor-specific extensions to the Core Policy Schema. Standardized extensions are not expected to use this class. Strassner, et. al Expires 8 August 1999 [Page 31] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 The class definition is as follows: NAME vendorPolicyCondition DESCRIPTION A class that defines a registered means to describe a policy condition. DERIVED FROM policyCondition TYPE structural AUXILIARY CLASSES none POSSIBLE SUPERIORS policyRule OID MUST vendorPolicyConditionConstraint vendorPolicyConditionEncoding MAY 5.7.1 The Attribute vendorPolicyConditionConstraint This attribute provides a general escape mechanism for representing policy conditions that have not been modeled with specific attributes. The format of the OctetString is left unspecified in this definition. It is determined by the OID value stored in the attribute vendorPolicyConditionEncoding. Since vendorPolicyConditionEncoding is single-valued, all the values of vendorPolicyConditionData share the same format and semantics. A policy decision point can readily determine whether it supports the values stored in an instance of vendorPolicyConditionData by checking the OID value from vendorPolicyConditionEncoding against the set of OIDs it recognizes. The action for the policy decision point to take in case it does not recognize the format of this data could itself be modeled as a policy rule, governing the behavior of the policy decision point. The attribute definition is as follows: NAME vendorPolicyConditionConstraint DESCRIPTION Escape mechanism for representing constraints that have not been modeled as specific attributes. The format of the values is identified by the OID stored in the attribute vendorPolicyConditionEncoding. SYNTAX OctetString OID EQUALITY octetStringMatch MULTI-VALUED 5.7.2 The Attribute vendorPolicyConditionEncoding This attribute identifies the encoding and semantics of the values of vendorPolicyConditionConstraint in this instance. The value of this attribute is a single OID. Strassner, et. al Expires 8 August 1999 [Page 32] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 The attribute definition is as follows: NAME vendorPolicyConditionEncoding DESCRIPTION An OID identifying the format and semantics for this instance's vendorPolicyConditionConstraint attribute. SYNTAX OID OID EQUALITY objectIdentifierMatch SINGLE-VALUED 5.8 The Class policyAction The purpose of a policy action is to execute one or more operations that will affect network traffic and/or systems, devices, etc. in order to achieve a desired policy state. This (new) policy state provides one or more (new) behaviors. A policy action ordinarily changes the configuration of one or more elements. A policyRule contains one or more policy actions. Unlike a condition, however, only one list of policy actions is contained in a PolicyRule. A policy administrator can assign an order to the actions associated with a policyRule, complete with an indication of whether the indicated order is mandatory, recommended, or of no significance. The actions associated with a PolicyRule are executed if and only if the overall condition(s) of the PolicyRule evaluates to TRUE. The class definition is as follows: NAME policyAction DESCRIPTION A class representing an action to be performed as a result of a policy rule. DERIVED FROM top TYPE structural AUXILIARY CLASSES none POSSIBLE SUPERIORS policyRule OID MUST cn PolicyActionName MAY 5.8.1 The Attribute cn This is the exact same definition as in Section 5.2.1. It is included in this class for the reasons enumerated there. 5.8.2 The Attribute policyActionName This attribute provides a user-friendly name for a policy action. The attribute definition is as follows: Strassner, et. al Expires 8 August 1999 [Page 33] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 NAME policyActionName DESCRIPTION The user-friendly name of this policy action. SYNTAX IA5String OID EQUALITY caseExactIA5Match SINGLE-VALUED 5.9 The Class vendorPolicyAction The purpose of this class is to provide a general escape mechanism for representing policy actions that have not been modeled with specific attributes. Instead, the two attributes vendorPolicyActionData and vendorPolicyActionEncoding are used to define the content and format of the condition, as explained below. As its name suggests, this class is intended for vendor-specific extensions to the Core Policy Schema. Standardized extensions are not expected to use this class. The class definition is as follows: NAME vendorPolicyAction DESCRIPTION A class that defines a registered means to describe a policy action. DERIVED FROM policyAction TYPE structural AUXILIARY CLASSES none POSSIBLE SUPERIORS policyRule OID MUST vendorPolicyActionData vendorPolicyActionEncoding MAY 5.9.1 The Attribute vendorPolicyActionData This attribute provides a general escape mechanism for representing policy actions that have not been modeled with specific attributes. The format of the OctetString is left unspecified in this definition. It is determined by the OID value stored in the attribute vendorPolicyActionEncoding. Since vendorPolicyActionEncoding is single-valued, all the values of vendorPolicyActionData share the same format and semantics. A policy decision point can readily determine whether it supports the values stored in an instance of vendorPolicyActionData, by checking the OID value from vendorPolicyActionEncoding against the set of OIDs it recognizes. The action for the policy decision point to take in case it does not recognize the format of this data could itself be modeled as a policy rule, governing the behavior of the policy decision point. The attribute definition is as follows: Strassner, et. al Expires 8 August 1999 [Page 34] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 NAME vendorPolicyActionData DESCRIPTION Escape mechanism for representing actions that have not been modeled as specific attributes. The format of the values is identified by the OID stored in the attribute vendorPolicyActionEncoding. SYNTAX OctetString OID EQUALITY octetStringMatch MULTI-VALUED 5.9.2 The Attribute vendorPolicyActionEncoding This attribute identifies the encoding and semantics of the values of vendorPolicyActionData in this instance. The value of this attribute is a single OID. The attribute definition is as follows: NAME vendorPolicyActionEncoding DESCRIPTION An OID identifying the format and semantics for this instance's vendorPolicyActionData attribute. SYNTAX OID OID EQUALITY objectIdentifierMatch SINGLE-VALUED 6.0 Extending the Core Schema There are three fundamental ways to extend the core schema. These are detailed in sections 6.1 - 6.3 below. A guideline for using the policyValidityPeriod class is discussed in Section 6.4. Each of these methods may be used separately or in conjunction with other methods. 6.1 Subclassing policyCondition and policyAction The simplest way of extending the core schema is to use the first four classes as they are, and simply subclass policyCondition and policyAction. An instance of policyRule ties everything together, with its very simple, invariant semantics: If the policyRule is active, then evaluate, possibly in a specified order, all conditions pointed to by policyConditionList. If all conditions evaluate to TRUE, then perform, possibly in a specified order, all actions pointed to by policyActionList. With this approach a new schema specifies the conditions it needs in subclasses of policyCondition (or, better still, reuses conditions that have already been specified in subclasses of policyCondition), and it specifies (or reuses) the actions it needs in subclasses of policyAction. Strassner, et. al Expires 8 August 1999 [Page 35] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 PolicyRules are used to aggregate policy conditions and actions, and policyGroups are used to aggregate policyRules. Of course, the policyRuleContainmentAuxClass and policyValidityPeriodCondition classes can still be used as previously described. Note that the subclassing of policyCondition and policyAction can also be used in combination with the other methods (discussed below) to extend the schema. 6.2 Subclassing policyRule There are two possible ways to subclass policyRule, as described below. 6.2.1 Refining the semantics of policyRule This approach refines the structural and possibly behavioral semantics of what it means to be a policy rule. For example, additional attributes and relationships could be defined in a subclass of policyRule. These attributes and relationships could provide extra meaning for how to interpret the set of conditions and actions that a policyRule aggregates. This method can be used in a stand-alone fashion by keeping the semantics of policyCondition and policyAction as specified and adding semantics to policyRule. These policyRule semantics can explicitly specify policyConditions and/or policyActions, or dictate how policyConditions and policyActions are used and interpreted. Finally, these methods can be used with the other methods discussed in this subsection to extend the schema. 6.2.2 Optimizing the computation of a policyRule All preceding mechanisms for extending the core schema will work in all cases, but they come at a price: in order to fully understand a policy rule, a client must retrieve at least three objects: a policy rule, at least one policy condition, and at least one policy action. A future version of this specification may define how to optimize the evaluation of a policy rule so as to reduce the number of classes that must be instantiated to define a policy. 6.3 Using the Vendor Policy Encoding Attributes As discussed in 5.7, "The Class vendorPolicyCondition", the attributes vendorPolicyConditionConstraint and vendorPolicyConditionEncoding are included in the vendorPolicyCondition to provide an escape mechanism for representing "exceptional" policy conditions. The attributes vendorPolicyActionData and vendorPolicyActionEncoding of the vendorPolicyAction class play the same role with respect to actions. This enables interoperability between different vendors. Strassner, et. al Expires 8 August 1999 [Page 36] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 For example, imagine a network comprised of access devices from vendor A, edge and core devices from vendor B, and a policy server from vendor C. It is desirable for the policy server to be able to configure and manage all of the devices from vendors A and B. Unfortunately, these devices will in general have little in common (e.g., different mechanisms, different ways for controlling those mechanisms, different operating systems, different commands, and so forth). The escape conditions provide a way for vendor-specific commands to be encoded as OctetStrings so that devices from different vendors can be commonly managed by a single policy server. 6.4 Using Time Validity Periods Time validity periods are defined as a subclass of policyCondition, called policyValidityPeriodCondition. This is to allow their inclusion in the AND/OR condition definitions for a policyRule. Care should be taken to not subclass policyValidityPeriodCondition to add domain-specific condition properties. For example, it would be incorrect to add IPSec- or QoS-specific condition properties to the policyValidityPeriodCondition class, just because IPSec or QoS includes time in its condition definition. The correct subclassing would be to create IPSec or QoS-specific subclasses of policyCondition and then combine instances of these domain-specific condition classes with the validity period criteria. This is accomplished using the AND/OR aggregation capabilities for policyConditions in policyRules. 7.0 Security Considerations Security and denial of service considerations are not explicitly considered in this memo, as they are appropriate for the underlying policy architecture. However, the policy architecture must be secure as far as the following aspects are concerned. First, the mechanisms proposed under the framework must minimize theft and denial of service threats. Second, it must be ensured that the entities (such as PEPs and PDPs) involved in policy control can verify each other's identity and establish necessary trust before communicating. The schema defined in this document MUST not compromise either of these goals. 8.0 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. Strassner, et. al Expires 8 August 1999 [Page 37] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 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. 9.0 Acknowledgments This document is closely aligned with the work being done in the Desktop Management Task Force (DMTF) Service Level Agreements and Networks working groups. As noted, the core schema described here was initially defined in references [2] and [3]. We would especially like to thank Bob Moore, Raju Rajan, Sanjay Kamat, Andrea Westerinen, Lee Rafalow, Raj Yavatkar, Glenn Waters, David Black, Michael Richardson, Mark Stevens, and David Jones for their helpful comments. 10.0 References [1] J. Strassner and E. Ellesson, "Terminology for describing network policy and services", draft-strassner-policy-terms-00.txt, August 1998. [2] Bhattacharya, P., and R. Adams, W. Dixon, R. Pereira, R. Rajan, "An LDAP Schema for Configuration and Administration of IPSec based Virtual Private Networks (VPNs)", Internet-Draft work in progress, October 1998 [3] Rajan, R., and J. C. Martin, S. Kamat, M. See, R. Chaudhury, D. Verma, G. Powers, R. Yavatkar, "Schema for Differentiated Services and Integrated Services in Networks", Internet-Draft work in progress, October 1998 [4] J. Strassner and S. Judd, "Directory-Enabled Networks", version 3.0c5 (August 1998). [5] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [6] Hovey, R., and S. Bradner, "The Organizations Involved in the IETF Standards Process", BCP 11, RFC 2028, October 1996. [7] Wahl, M., and S. Kille, T. Howes, "Lightweight Directory Access Protocol (v3): UTF-8 String Representation of Distinguished Names", RFC 2253, December 1997. Strassner, et. al Expires 8 August 1999 [Page 38] INTERNET DRAFT draft-ietf-policy-core-schema-01.txt 8 Feb 99 [8] J. Strassner, policy architecture BOF presentation, 42nd IETF Meeting, Chicago, Illinois, October, 1998 11.0 Authors' Addresses John Strassner Cisco Systems, Bldg 1 170 West Tasman Drive San Jose, CA 95134 Phone: +1-408-527-1069 Fax: +1-408-527-1722 E-mail: johns@cisco.com Ed Ellesson IBM Corporation, JDGA/501 4205 S. Miami Blvd. Research Triangle Park, NC 27709 Phone: +1-919-254-4115 Fax: +1-919-254-6243 E-mail: ellesson@raleigh.ibm.com 12.0 Full Copyright Statement Copyright (C) The Internet Society (1997). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Appendix A - Guidelines for Construction of DNs - To Be Provided Strassner, et. al Expires 8 August 1999 [Page 39]