    Network Working Group                               SNMPv2 Working Group
    Request for Comments: 1904                                       J. Case
    Obsoletes: 1444                                      SNMP Research, Inc.
    Category: Standards Track                                  K. McCloghrie
                                                         Cisco Systems, Inc.
                                                                     M. Rose
                                                Dover Beach Consulting, Inc.
                                                               S. Waldbusser
                                              International Network Services
                                                                January 1996

                  Conformance Statements for Version 2 of the
                  Simple Network Management Protocol (SNMPv2)

    Status of this Memo

       This document specifies an Internet standards track protocol for the
       Internet community, and requests discussion and suggestions for
       improvements.  Please refer to the current edition of the "Internet
       Official Protocol Standards" (STD 1) for the standardization state
       and status of this protocol.  Distribution of this memo is unlimited.

    Table of Contents

       1. Introduction ................................................    2
       1.1 A Note on Terminology ......................................    3
       2. Definitions .................................................    3
       2.1 The OBJECT-GROUP macro .....................................    3
       2.2 The NOTIFICATION-GROUP macro ...............................    4
       2.3 The MODULE-COMPLIANCE macro ................................    5
       2.4 The AGENT-CAPABILITIES macro ...............................    7
       3. Mapping of the OBJECT-GROUP macro ...........................    9
       3.1 Mapping of the OBJECTS clause ..............................   10
       3.2 Mapping of the STATUS clause ...............................   10
       3.3 Mapping of the DESCRIPTION clause ..........................   10
       3.4 Mapping of the REFERENCE clause ............................   10
       3.5 Mapping of the OBJECT-GROUP value ..........................   10
       3.6 Usage Example ..............................................   11
       4. Mapping of the NOTIFICATION-GROUP macro .....................   11
       4.1 Mapping of the NOTIFICATIONS clause ........................   11
       4.2 Mapping of the STATUS clause ...............................   11
       4.3 Mapping of the DESCRIPTION clause ..........................   12
       4.4 Mapping of the REFERENCE clause ............................   12
       4.5 Mapping of the NOTIFICATION-GROUP value ....................   12
       4.6 Usage Example ..............................................   12
       5. Mapping of the MODULE-COMPLIANCE macro ......................   12
       5.1 Mapping of the STATUS clause ...............................   13

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       5.2 Mapping of the DESCRIPTION clause ..........................   13
       5.3 Mapping of the REFERENCE clause ............................   13
       5.4 Mapping of the MODULE clause ...............................   13
       5.4.1 Mapping of the MANDATORY-GROUPS clause ...................   13
       5.4.2 Mapping of the GROUP clause ..............................   14
       5.4.3 Mapping of the OBJECT clause .............................   14
       5.4.3.1 Mapping of the SYNTAX clause ...........................   14
       5.4.3.2 Mapping of the WRITE-SYNTAX clause .....................   15
       5.4.3.3 Mapping of the MIN-ACCESS clause .......................   15
       5.4.4 Mapping of the DESCRIPTION clause ........................   15
       5.5 Mapping of the MODULE-COMPLIANCE value .....................   15
       5.6 Usage Example ..............................................   16
       6. Mapping of the AGENT-CAPABILITIES macro .....................   16
       6.1 Mapping of the PRODUCT-RELEASE clause ......................   17
       6.2 Mapping of the STATUS clause ...............................   17
       6.3 Mapping of the DESCRIPTION clause ..........................   17
       6.4 Mapping of the REFERENCE clause ............................   17
       6.5 Mapping of the SUPPORTS clause .............................   18
       6.5.1 Mapping of the INCLUDES clause ...........................   18
       6.5.2 Mapping of the VARIATION clause ..........................   18
       6.5.2.1 Mapping of the SYNTAX clause ...........................   18
       6.5.2.2 Mapping of the WRITE-SYNTAX clause .....................   18
       6.5.2.3 Mapping of the ACCESS clause ...........................   19
       6.5.2.4 Mapping of the CREATION-REQUIRES clause ................   19
       6.5.2.5 Mapping of the DEFVAL clause ...........................   20
       6.5.2.6 Mapping of the DESCRIPTION clause ......................   20
       6.6 Mapping of the AGENT-CAPABILITIES value ....................   20
       6.7 Usage Example ..............................................   20
       7. Extending an Information Module .............................   22
       7.1 Conformance Groups .........................................   22
       7.2 Compliance Definitions .....................................   22
       7.3 Capabilities Definitions ...................................   22
       8. Security Considerations .....................................   23
       9. Editor's Address ............................................   23
       10. Acknowledgements ...........................................   23
       11. References .................................................   24

    1.  Introduction

       A management system contains:  several (potentially many) nodes, each
       with a processing entity, termed an agent, which has access to
       management instrumentation; at least one management station; and, a
       management protocol, used to convey management information between
       the agents and management stations.  Operations of the protocol are
       carried out under an administrative framework which defines
       authentication, authorization, access control, and privacy policies.

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       Management stations execute management applications which monitor and
       control managed elements.  Managed elements are devices such as
       hosts, routers, terminal servers, etc., which are monitored and
       controlled via access to their management information.

       Management information is viewed as a collection of managed objects,
       residing in a virtual information store, termed the Management
       Information Base (MIB).  Collections of related objects are defined
       in MIB modules.  These modules are written using a subset of OSI's
       Abstract Syntax Notation One (ASN.1) [1], termed the Structure of
       Management Information (SMI) [2].

       It may be useful to define the acceptable lower-bounds of
       implementation, along with the actual level of implementation
       achieved.  It is the purpose of this document to define the notation
       used for these purposes.

    1.1.  A Note on Terminology

       For the purpose of exposition, the original Internet-standard Network
       Management Framework, as described in RFCs 1155 (STD 16), 1157 (STD
       15), and 1212 (STD 16), is termed the SNMP version 1 framework
       (SNMPv1).  The current framework is termed the SNMP version 2
       framework (SNMPv2).

    2.  Definitions

    SNMPv2-CONF DEFINITIONS ::= BEGIN

    -- definitions for conformance groups

    OBJECT-GROUP MACRO ::=
    BEGIN
        TYPE NOTATION ::=
                      ObjectsPart
                      "STATUS" Status
                      "DESCRIPTION" Text
                      ReferPart

        VALUE NOTATION ::=
                      value(VALUE OBJECT IDENTIFIER)

        ObjectsPart ::=
                      "OBJECTS" "{" Objects "}"
        Objects ::=
                      Object
                    | Objects "," Object
        Object ::=

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                      value(Name ObjectName)

        Status ::=
                      "current"
                    | "deprecated"
                    | "obsolete"

        ReferPart ::=
                      "REFERENCE" Text
                    | empty

        -- uses the NVT ASCII character set
        Text ::= """" string """"
    END

    -- more definitions for conformance groups

    NOTIFICATION-GROUP MACRO ::=
    BEGIN
        TYPE NOTATION ::=
                      NotificationsPart
                      "STATUS" Status
                      "DESCRIPTION" Text
                      ReferPart

        VALUE NOTATION ::=
                      value(VALUE OBJECT IDENTIFIER)

        NotificationsPart ::=
                      "NOTIFICATIONS" "{" Notifications "}"
        Notifications ::=
                      Notification
                    | Notifications "," Notification
        Notification ::=
                      value(Name NotificationName)

        Status ::=
                      "current"
                    | "deprecated"
                    | "obsolete"

        ReferPart ::=
                      "REFERENCE" Text
                    | empty

        -- uses the NVT ASCII character set
        Text ::= """" string """"

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    END

    -- definitions for compliance statements

    MODULE-COMPLIANCE MACRO ::=
    BEGIN
        TYPE NOTATION ::=
                      "STATUS" Status
                      "DESCRIPTION" Text
                      ReferPart
                      ModulePart

        VALUE NOTATION ::=
                      value(VALUE OBJECT IDENTIFIER)

        Status ::=
                      "current"
                    | "deprecated"
                    | "obsolete"

        ReferPart ::=
                    "REFERENCE" Text
                  | empty

        ModulePart ::=
                      Modules
                    | empty
        Modules ::=
                      Module
                    | Modules Module
        Module ::=
                      -- name of module --
                      "MODULE" ModuleName
                      MandatoryPart
                      CompliancePart

        ModuleName ::=
                      modulereference ModuleIdentifier
                    -- must not be empty unless contained
                    -- in MIB Module
                    | empty
        ModuleIdentifier ::=
                      value(ModuleID OBJECT IDENTIFIER)
                    | empty

        MandatoryPart ::=
                      "MANDATORY-GROUPS" "{" Groups "}"

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                    | empty

        Groups ::=
                      Group
                    | Groups "," Group
        Group ::=
                      value(Group OBJECT IDENTIFIER)

        CompliancePart ::=
                      Compliances
                    | empty

        Compliances ::=
                      Compliance
                    | Compliances Compliance
        Compliance ::=
                      ComplianceGroup
                    | Object

        ComplianceGroup ::=
                      "GROUP" value(Name OBJECT IDENTIFIER)
                      "DESCRIPTION" Text

        Object ::=
                      "OBJECT" value(Name ObjectName)
                      SyntaxPart
                      WriteSyntaxPart
                      AccessPart
                      "DESCRIPTION" Text

        -- must be a refinement for object's SYNTAX clause
        SyntaxPart ::=
                      "SYNTAX" type(SYNTAX)
                    | empty

        -- must be a refinement for object's SYNTAX clause
        WriteSyntaxPart ::=
                      "WRITE-SYNTAX" type(WriteSYNTAX)
                    | empty

        AccessPart ::=
                      "MIN-ACCESS" Access
                    | empty
        Access ::=
                      "not-accessible"
                    | "accessible-for-notify"
                    | "read-only"
                    | "read-write"

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                    | "read-create"

        -- uses the NVT ASCII character set
        Text ::= """" string """"
    END

    -- definitions for capabilities statements

    AGENT-CAPABILITIES MACRO ::=
    BEGIN
        TYPE NOTATION ::=
                      "PRODUCT-RELEASE" Text
                      "STATUS" Status
                      "DESCRIPTION" Text
                      ReferPart
                      ModulePart

        VALUE NOTATION ::=
                      value(VALUE OBJECT IDENTIFIER)

        Status ::=
                      "current"
                    | "obsolete"

        ReferPart ::=
                    "REFERENCE" Text
                  | empty

        ModulePart ::=
                      Modules
                    | empty
        Modules ::=
                      Module
                    | Modules Module
        Module ::=
                      -- name of module --
                      "SUPPORTS" ModuleName
                      "INCLUDES" "{" Groups "}"
                      VariationPart

        ModuleName ::=
                      identifier ModuleIdentifier
        ModuleIdentifier ::=
                      value(ModuleID OBJECT IDENTIFIER)
                    | empty

        Groups ::=

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                      Group
                    | Groups "," Group
        Group ::=
                      value(Name OBJECT IDENTIFIER)

        VariationPart ::=
                      Variations
                    | empty
        Variations ::=
                      Variation
                    | Variations Variation

        Variation ::=
                      ObjectVariation
                    | NotificationVariation

        NotificationVariation ::=
                      "VARIATION" value(Name NotificationName)
                      AccessPart
                      "DESCRIPTION" Text

        ObjectVariation ::=
                      "VARIATION" value(Name ObjectName)
                      SyntaxPart
                      WriteSyntaxPart
                      AccessPart
                      CreationPart
                      DefValPart
                      "DESCRIPTION" Text

        -- must be a refinement for object's SYNTAX clause
        SyntaxPart ::=
                      "SYNTAX" type(SYNTAX)
                    | empty

        -- must be a refinement for object's SYNTAX clause
        WriteSyntaxPart ::=
                      "WRITE-SYNTAX" type(WriteSYNTAX)
                    | empty

        AccessPart ::=
                      "ACCESS" Access
                    | empty

        Access ::=
                      "not-implemented"
                    -- only "not-implemented" for notifications
                    | "accessible-for-notify"

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                    | "read-only"
                    | "read-write"
                    | "read-create"
                    -- following is for backward-compatibility only
                    | "write-only"

        CreationPart ::=
                      "CREATION-REQUIRES" "{" Cells "}"
                    | empty

        Cells ::=
                      Cell
                    | Cells "," Cell

        Cell ::=
                      value(Cell ObjectName)

        DefValPart ::=
                      "DEFVAL" "{" value(Defval ObjectSyntax) "}"
                    | empty

        -- uses the NVT ASCII character set
        Text ::= """" string """"
    END

    END

    3.  Mapping of the OBJECT-GROUP macro

       For conformance purposes, it is useful to define a collection of
       related managed objects.  The OBJECT-GROUP macro is used to define
       each such collection of related objects.  It should be noted that the
       expansion of the OBJECT-GROUP macro is something which conceptually
       happens during implementation and not during run-time.

       To "implement" an object, a SNMPv2 entity acting in an agent role
       must return a reasonably accurate value for management protocol
       retrieval operations; similarly, if the object is writable, then in
       response to a management protocol set operation, a SNMPv2 entity must
       accordingly be able to reasonably influence the underlying managed
       entity.  If a SNMPv2 entity acting in an agent role can not implement
       an object, the management protocol provides for the SNMPv2 entity to
       return an exception or error, e.g, noSuchObject [4].  Under no
       circumstances shall a SNMPv2 entity return a value for objects which
       it does not implement -- it must always return the appropriate
       exception or error, as described in the protocol specification [4].

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    3.1.  Mapping of the OBJECTS clause

       The OBJECTS clause, which must be present, is used to name each
       object contained in the conformance group.  Each of the named objects
       must be defined in the same information module as the OBJECT-GROUP
       macro appears, and must have a MAX-ACCESS clause value of
       "accessible-for-notify", "read-only", "read-write", or "read-create".

       It is required that every object defined in an information module
       with a MAX-ACCESS clause other than "not-accessible" be contained in
       at least one object group.  This avoids the common error of adding a
       new object to an information module and forgetting to add the new
       object to a group.

    3.2.  Mapping of the STATUS clause

       The STATUS clause, which must be present, indicates whether this
       definition is current or historic.

       The values "current", and "obsolete" are self-explanatory.  The
       "deprecated" value indicates that the definition is obsolete, but
       that an implementor may wish to support the group to foster
       interoperability with older implementations.

    3.3.  Mapping of the DESCRIPTION clause

       The DESCRIPTION clause, which must be present, contains a textual
       definition of that group, along with a description of any relations
       to other groups.  Note that generic compliance requirements should
       not be stated in this clause.  However, implementation relationships
       between this group and other groups may be defined in this clause.

    3.4.  Mapping of the REFERENCE clause

       The REFERENCE clause, which need not be present, contains a textual
       cross-reference to a group  defined in some other information module.
       This is useful when de-osifying a MIB module produced by some other
       organization.

    3.5.  Mapping of the OBJECT-GROUP value

       The value of an invocation of the OBJECT-GROUP macro is the name of
       the group, which is an OBJECT IDENTIFIER, an administratively
       assigned name.

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    3.6.  Usage Example

       The SNMP Group [3] is described:

    snmpGroup OBJECT-GROUP
        OBJECTS { snmpInPkts,
                  snmpInBadVersions,
                  snmpInASNParseErrs,
                  snmpBadOperations,
                  snmpSilentDrops,
                  snmpProxyDrops,
                  snmpEnableAuthenTraps }
        STATUS  current
        DESCRIPTION
                "A collection of objects providing basic instrumentation and
                control of an SNMPv2 entity."
        ::= { snmpMIBGroups 8 }

    According to this invocation, the conformance group named

         { snmpMIBGroups 8 }

    contains 7 objects.

    4.  Mapping of the NOTIFICATION-GROUP macro

       For conformance purposes, it is useful to define a collection of
       notifications.  The NOTIFICATION-GROUP macro serves this purpose.  It
       should be noted that the expansion of the NOTIFICATION-GROUP macro is
       something which conceptually happens during implementation and not
       during run-time.

    4.1.  Mapping of the NOTIFICATIONS clause

       The NOTIFICATIONS clause, which must be present, is used to name each
       notification contained in the conformance group.  Each of the named
       notifications must be defined in the same information module as the
       NOTIFICATION-GROUP macro appears.

    4.2.  Mapping of the STATUS clause

       The STATUS clause, which must be present, indicates whether this
       definition is current or historic.

       The values "current", and "obsolete" are self-explanatory.  The
       "deprecated" value indicates that the definition is obsolete, but
       that an implementor may wish to support the group to foster

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       interoperability with older implementations.

    4.3.  Mapping of the DESCRIPTION clause

       The DESCRIPTION clause, which must be present, contains a textual
       definition of the group, along with a description of any relations to
       other groups.  Note that generic compliance requirements should not
       be stated in this clause.  However, implementation relationships
       between this group and other groups may be defined in this clause.

    4.4.  Mapping of the REFERENCE clause

       The REFERENCE clause, which need not be present, contains a textual
       cross-reference to a group defined in some other information module.
       This is useful when de-osifying a MIB module produced by some other
       organization.

    4.5.  Mapping of the NOTIFICATION-GROUP value

       The value of an invocation of the NOTIFICATION-GROUP macro is the
       name of the group, which is an OBJECT IDENTIFIER, an administratively
       assigned name.

    4.6.  Usage Example

       The SNMP Basic Notifications Group [3] is described:

    snmpBasicNotificationsGroup NOTIFICATION-GROUP
        NOTIFICATIONS { coldStart, authenticationFailure }
        STATUS        current
        DESCRIPTION
                "The two notifications which an SNMPv2 entity is required to
                implement."
        ::= { snmpMIBGroups 7 }

    According to this invocation, the conformance group named

         { snmpMIBGroups 1 }

    contains 2 notifications.

    5.  Mapping of the MODULE-COMPLIANCE macro

       The MODULE-COMPLIANCE macro is used to convey a minimum set of
       requirements with respect to implementation of one or more MIB
       modules.  It should be noted that the expansion of the MODULE-
       COMPLIANCE macro is something which conceptually happens during
       implementation and not during run-time.

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       A requirement on all "standard" MIB modules is that a corresponding
       MODULE-COMPLIANCE specification is also defined, either in the same
       information module or in a companion information module.

    5.1.  Mapping of the STATUS clause

       The STATUS clause, which must be present, indicates whether this
       definition is current or historic.

       The values "current", and "obsolete" are self-explanatory.  The
       "deprecated" value indicates that the specification is obsolete, but
       that an implementor may wish to support that object to foster
       interoperability with older implementations.

    5.2.  Mapping of the DESCRIPTION clause

       The DESCRIPTION clause, which must be present, contains a textual
       definition of this compliance statement and should embody any
       information which would otherwise be communicated in any ASN.1
       commentary annotations associated with the statement.

    5.3.  Mapping of the REFERENCE clause

       The REFERENCE clause, which need not be present, contains a textual
       cross-reference to a compliance statement defined in some other
       information module.

    5.4.  Mapping of the MODULE clause

       The MODULE clause, which must be present, is repeatedly used to name
       each MIB module for which compliance requirements are being
       specified.  Each MIB module is named by its module name, and
       optionally, by its associated OBJECT IDENTIFIER as well.  The module
       name can be omitted when the MODULE-COMPLIANCE invocation occurs
       inside a MIB module, to refer to the encompassing MIB module.

    5.4.1.  Mapping of the MANDATORY-GROUPS clause

       The MANDATORY-GROUPS clause, which need not be present, names the one
       or more object or notification groups within the correspondent MIB
       module which are unconditionally mandatory for implementation.  If a
       SNMPv2 entity acting in an agent role claims compliance to the MIB
       module, then it must implement each and every object and notification
       within each conformance group listed.  That is, if a SNMPv2 entity
       returns a noSuchObject exception in response to a management protocol
       get operation [4] for any object within any mandatory conformance
       group for every MIB view, or if the SNMPv2 entity cannot generate
       each notification listed in any conformance group under the

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       appropriate circumstances, then that SNMPv2 entity is not a
       conformant implementation of the MIB module.

    5.4.2.  Mapping of the GROUP clause

       The GROUP clause, which need not be present, is repeatedly used to
       name each object and notification group which is conditionally
       mandatory or unconditionally optional for compliance to the MIB
       module.  A group named in a GROUP clause must be absent from the
       correspondent MANDATORY-GROUPS clause.

       Conditionally mandatory groups include those which are mandatory only
       if a particular protocol is implemented, or only if another group is
       implemented.  A GROUP clause's DESCRIPTION specifies the conditions
       under which the group is conditionally mandatory.

       A group which is named in neither a MANDATORY-GROUPS clause nor a
       GROUP clause, is unconditionally optional for compliance to the MIB
       module.

    5.4.3.  Mapping of the OBJECT clause

       The OBJECT clause, which need not be present, is repeatedly used to
       name each MIB object for which compliance has a refined requirement
       with respect to the MIB module definition.  The MIB object must be
       present in one of the conformance groups named in the correspondent
       MANDATORY-GROUPS clause or GROUP clauses.

       By definition, each object specified in an OBJECT clause follows a
       MODULE clause which names the information module in which that object
       is defined.  Therefore, the use of an IMPORTS statement, to specify
       from where such objects are imported, is redundant and is not
       required in an information module.

    5.4.3.1.  Mapping of the SYNTAX clause

       The SYNTAX clause, which need not be present, is used to provide a
       refined SYNTAX for the object named in the correspondent OBJECT
       clause.  Note that if this clause and a WRITE-SYNTAX clause are both
       present, then this clause only applies when instances of the object
       named in the correspondent OBJECT clause are read.

       Consult Section 9 of [2] for more information on refined syntax.

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    5.4.3.2.  Mapping of the WRITE-SYNTAX clause

       The WRITE-SYNTAX clause, which need not be present, is used to
       provide a refined SYNTAX for the object named in the correspondent
       OBJECT clause when instances of that object are written.

       Consult Section 9 of [2] for more information on refined syntax.

    5.4.3.3.  Mapping of the MIN-ACCESS clause

       The MIN-ACCESS clause, which need not be present, is used to define
       the minimal level of access for the object named in the correspondent
       OBJECT clause.  If this clause is absent, the minimal level of access
       is the same as the maximal level specified in the correspondent
       invocation of the OBJECT-TYPE macro.  If present, this clause must
       not specify a greater level of access than is specified in the
       correspondent invocation of the OBJECT-TYPE macro.

       The level of access for certain types of objects is fixed according
       to their syntax definition.  These types include: conceptual tables
       and rows, auxiliary objects, and objects with the syntax of
       Counter32, Counter64 (and possibly, certain types of textual
       conventions).  A MIN-ACCESS clause should not be present for such
       objects.

       An implementation is compliant if the level of access it provides is
       greater or equal to the minimal level in the MODULE-COMPLIANCE macro
       and less or equal to the maximal level in the OBJECT-TYPE macro.

    5.4.4.  Mapping of the DESCRIPTION clause

       The DESCRIPTION clause must be present for each use of the GROUP or
       OBJECT clause.  For an OBJECT clause, it contains a textual
       description of the refined compliance requirement.  For a GROUP
       clause, it contains a textual description of the conditions under
       which the group is conditionally mandatory or unconditionally
       optional.

    5.5.  Mapping of the MODULE-COMPLIANCE value

       The value of an invocation of the MODULE-COMPLIANCE macro is an
       OBJECT IDENTIFIER.  As such, this value may be authoritatively used
       when referring to the compliance statement embodied by that
       invocation of the macro.

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    5.6.  Usage Example

       The compliance statement contained in the (hypothetical) XYZv2-MIB
       might be:

    xyzMIBCompliance MODULE-COMPLIANCE
        STATUS  current
        DESCRIPTION
                "The compliance statement for XYZv2 entities which implement
                the XYZv2 MIB."
        MODULE  -- compliance to the containing MIB module
            MANDATORY-GROUPS { xyzSystemGroup,
                               xyzStatsGroup, xyzTrapGroup,
                               xyzSetGroup,
                               xyzBasicNotificationsGroup }

            GROUP   xyzV1Group
            DESCRIPTION
                "The xyzV1 group is mandatory only for those
                 XYZv2 entities which also implement XYZv1."
    ::= { xyzMIBCompliances 1 }

       According to this invocation, to claim alignment with the compliance
       statement named

         { xyzMIBCompliances 1 }

       a system must implement the XYZv2-MIB's xyzSystemGroup,
       xyzStatsGroup, xyzTrapGroup, and xyzSetGroup object conformance
       groups, as well as the xyzBasicNotificationsGroup notifications
       group.  Furthermore, if the XYZv2 entity also implements XYZv1, then
       it must also support the XYZv1Group group, if compliance is to be
       claimed.

    6.  Mapping of the AGENT-CAPABILITIES macro

       The AGENT-CAPABILITIES macro is used to convey a set of capabilities
       present in a SNMPv2 entity acting in an agent role.  It should be
       noted that the expansion of the AGENT-CAPABILITIES macro is something
       which conceptually happens during implementation and not during run-
       time.

       When a MIB module is written, it is divided into units of conformance
       termed groups.  If a SNMPv2 entity acting in an agent role claims to
       implement a group, then it must implement each and every object
       within that group.  Of course, for whatever reason, a SNMPv2 entity
       might implement only a subset of the groups within a MIB module.  In
       addition, the definition of some MIB objects leave some aspects of

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       the definition to the discretion of an implementor.

       Practical experience has demonstrated a need for concisely describing
       the capabilities of an agent with respect to one or more MIB modules.
       The AGENT-CAPABILITIES macro allows an agent implementor to describe
       the precise level of support which an agent claims in regards to a
       MIB group, and to bind that description to the value of an instance
       of sysORID [3].  In particular, some objects may have restricted or
       augmented syntax or access-levels.

       If the AGENT-CAPABILITIES invocation is given to a management-station
       implementor, then that implementor can build management applications
       which optimize themselves when communicating with a particular agent.
       For example, the management-station can maintain a database of these
       invocations.  When a management-station interacts with an agent, it
       retrieves from the agent the values of all instances of sysORID [3].
       Based on this, it consults the database to locate each entry matching
       one of the retrieved values of sysORID.  Using the located entries,
       the management application can now optimize its behavior accordingly.

       Note that the AGENT-CAPABILITIES macro specifies refinements or
       variations with respect to OBJECT-TYPE and NOTIFICATION-TYPE macros
       in MIB modules, NOT with respect to MODULE-COMPLIANCE macros in
       compliance statements.

    6.1.  Mapping of the PRODUCT-RELEASE clause

       The PRODUCT-RELEASE clause, which must be present, contains a textual
       description of the product release which includes this set of
       capabilities.

    6.2.  Mapping of the STATUS clause

       The STATUS clause, which must be present, indicates whether this
       definition is current ("current") or historic ("obsolete").

    6.3.  Mapping of the DESCRIPTION clause

       The DESCRIPTION clause, which must be present, contains a textual
       description of this set of capabilities.

    6.4.  Mapping of the REFERENCE clause

       The REFERENCE clause, which need not be present, contains a textual
       cross-reference to a capability statement defined in some other
       information module.

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    6.5.  Mapping of the SUPPORTS clause

       The SUPPORTS clause, which need not be present, is repeatedly used to
       name each MIB module for which the agent claims a complete or partial
       implementation.  Each MIB module is named by its module name, and
       optionally, by its associated OBJECT IDENTIFIER as well.

    6.5.1.  Mapping of the INCLUDES clause

       The INCLUDES clause, which must be present for each use of the
       SUPPORTS clause, is used to name each MIB group associated with the
       SUPPORTS clause, which the agent claims to implement.

    6.5.2.  Mapping of the VARIATION clause

       The VARIATION clause, which need not be present, is repeatedly used
       to name each object or notification which the agent implements in
       some variant or refined fashion with respect to the correspondent
       invocation of the OBJECT-TYPE or NOTIFICATION-TYPE macro.

       Note that the variation concept is meant for generic implementation
       restrictions, e.g., if the variation for an object depends on the
       values of other objects, then this should be noted in the appropriate
       DESCRIPTION clause.

       By definition, each object specified in a VARIATION clause follows a
       SUPPORTS clause which names the information module in which that
       object is defined.  Therefore, the use of an IMPORTS statement, to
       specify from where such objects are imported, is redundant and is not
       required in an information module.

    6.5.2.1.  Mapping of the SYNTAX clause

       The SYNTAX clause, which need not be present, is used to provide a
       refined SYNTAX for the object named in the correspondent VARIATION
       clause.  Note that if this clause and a WRITE-SYNTAX clause are both
       present, then this clause only applies when instances of the object
       named in the correspondent VARIATION clause are read.

       Consult Section 9 of [2] for more information on refined syntax.

    6.5.2.2.  Mapping of the WRITE-SYNTAX clause

       The WRITE-SYNTAX clause, which need not be present, is used to
       provide a refined SYNTAX for the object named in the correspondent
       VARIATION clause when instances of that object are written.

       Consult Section 9 of [2] for more information on refined syntax.

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    6.5.2.3.  Mapping of the ACCESS clause

       The ACCESS clause, which need not be present, is used to indicate the
       agent provides less than the maximal level of access to the object or
       notification named in the correspondent VARIATION clause.

       The only value applicable to notifications is "not-implemented".

       The value "not-implemented" indicates the agent does not implement
       the object or notification, and in the ordering of possible values is
       equivalent to "not-accessible".

       The value "write-only" is provided solely for backward compatibility,
       and shall not be used for newly-defined object types.  In the
       ordering of possible values, "write-only" is less than "not-
       accessible".

    6.5.2.4.  Mapping of the CREATION-REQUIRES clause

       The CREATION-REQUIRES clause, which need not be present, is used to
       name the columnar objects of a conceptual row to which values must be
       explicitly assigned, by a management protocol set operation, before
       the agent will allow the instance of the status column of that row to
       be set to `active'.  (Consult the definition of RowStatus [5].)

       If the conceptual row does not have a status column (i.e., the
       objects corresponding to the conceptual table were defined using the
       mechanisms in [6,7]), then the CREATION-REQUIRES clause, which need
       not be present, is used to name the columnar objects of a conceptual
       row to which values must be explicitly assigned, by a management
       protocol set operation, before the agent will create new instances of
       objects in that row.

       This clause must not present unless the object named in the
       correspondent VARIATION clause is a conceptual row, i.e., has a
       syntax which resolves to a SEQUENCE containing columnar objects.  The
       objects named in the value of this clause usually will refer to
       columnar objects in that row.  However, objects unrelated to the
       conceptual row may also be specified.

       All objects which are named in the CREATION-REQUIRES clause for a
       conceptual row, and which are columnar objects of that row, must have
       an access level of "read-create".

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    6.5.2.5.  Mapping of the DEFVAL clause

       The DEFVAL clause, which need not be present, is used to provide a
       refined DEFVAL value for the object named in the correspondent
       VARIATION clause.  The semantics of this value are identical to those
       of the OBJECT-TYPE macro's DEFVAL clause.

    6.5.2.6.  Mapping of the DESCRIPTION clause

       The DESCRIPTION clause, which must be present for each use of the
       VARIATION clause, contains a textual description of the variant or
       refined implementation of the object or notification.

    6.6.  Mapping of the AGENT-CAPABILITIES value

       The value of an invocation of the AGENT-CAPABILITIES macro is an
       OBJECT IDENTIFIER, which names the value of sysORID [3] for which
       this capabilities statement is valid.

    6.7.  Usage Example

       Consider how a capabilities statement for an agent might be
       described:

    exampleAgent AGENT-CAPABILITIES
        PRODUCT-RELEASE      "ACME Agent release 1.1 for 4BSD"
        STATUS               current
        DESCRIPTION          "ACME agent for 4BSD"

        SUPPORTS             SNMPv2-MIB
            INCLUDES         { systemGroup, snmpGroup, snmpSetGroup,
                               snmpBasicNotificationsGroup }

            VARIATION        coldStart
                DESCRIPTION  "A coldStart trap is generated on all
                             reboots."

        SUPPORTS             IF-MIB
            INCLUDES         { ifGeneralGroup, ifPacketGroup }

            VARIATION        ifAdminStatus
                SYNTAX       INTEGER { up(1), down(2) }
                DESCRIPTION  "Unable to set test mode on 4BSD"

            VARIATION        ifOperStatus
                SYNTAX       INTEGER { up(1), down(2) }
                DESCRIPTION  "Information limited on 4BSD"

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        SUPPORTS             IP-MIB
            INCLUDES         { ipGroup, icmpGroup }

            VARIATION        ipDefaultTTL
                SYNTAX       INTEGER (255..255)
                DESCRIPTION  "Hard-wired on 4BSD"

            VARIATION        ipInAddrErrors
                ACCESS       not-implemented
                DESCRIPTION  "Information not available on 4BSD"

            VARIATION        ipNetToMediaEntry
                CREATION-REQUIRES { ipNetToMediaPhysAddress }
                DESCRIPTION  "Address mappings on 4BSD require
                             both protocol and media addresses"

        SUPPORTS             TCP-MIB
            INCLUDES         { tcpGroup }
            VARIATION        tcpConnState
                ACCESS       read-only
                DESCRIPTION  "Unable to set this on 4BSD"

        SUPPORTS             UDP-MIB
            INCLUDES         { udpGroup }

        SUPPORTS             EVAL-MIB
            INCLUDES         { functionsGroup, expressionsGroup }
            VARIATION        exprEntry
                CREATION-REQUIRES { evalString }
                DESCRIPTION "Conceptual row creation supported"

        ::= { acmeAgents 1 }

       According to this invocation, an agent with a sysORID value of

         { acmeAgents 1 }

       supports six MIB modules.

       From SNMPv2-MIB, five conformance groups are supported.

       From IF-MIB, the ifGeneralGroup and ifPacketGroup groups are
       supported.  However, the objects ifAdminStatus and ifOperStatus have
       a restricted syntax.

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       From IP-MIB, all objects in the ipGroup and icmpGroup are supported
       except ipInAddrErrors, while ipDefaultTTL has a restricted range, and
       when creating a new instance in the ipNetToMediaTable, the set-
       request must create an instance of atPhysAddress.

       From TCP-MIB, the tcpGroup is supported except that tcpConnState is
       available only for reading.

       From UDP-MIB, the udpGroup is fully supported.

       From the EVAL-MIB, all the objects contained in the functionsGroup
       and expressionsGroup conformance groups are supported, without
       variation.  In addition, creation of new instances in the expr table
       is supported.

    7.  Extending an Information Module

       As experience is gained with a published information module, it may
       be desirable to revise that information module.

       Section 10 of [2] defines the rules for extending an information
       module.  The remainder of this section defines how conformance
       groups, compliance statements, and capabilities statements may be
       extended.

    7.1.  Conformance Groups

       If any non-editorial change is made to any clause of an object group
       then the OBJECT IDENTIFIER value associated with that object group
       must also be changed, along with its associated descriptor.

    7.2.  Compliance Definitions

       If any non-editorial change is made to any clause of a compliance
       definition, then the OBJECT IDENTIFIER value associated with that
       compliance definition must also be changed, along with its associated
       descriptor.

    7.3.  Capabilities Definitions

       If any non-editorial change is made to any clause of a capabilities
       definition, then the OBJECT IDENTIFIER value associated with that
       capabilities definition must also be changed, along with its
       associated descriptor.

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    8.  Security Considerations

       Security issues are not discussed in this memo.

    9.  Editor's Address

       Keith McCloghrie
       Cisco Systems, Inc.
       170 West Tasman Drive
       San Jose, CA  95134-1706
       US

       Phone: +1 408 526 5260
       EMail: kzm@cisco.com

    10.  Acknowledgements

       This document is the result of significant work by the four major
       contributors:

       Jeffrey D. Case (SNMP Research, case@snmp.com)
       Keith McCloghrie (Cisco Systems, kzm@cisco.com)
       Marshall T. Rose (Dover Beach Consulting, mrose@dbc.mtview.ca.us)
       Steven Waldbusser (International Network Services, stevew@uni.ins.com)

       In addition, the contributions of the SNMPv2 Working Group are
       acknowledged.  In particular, a special thanks is extended for the
       contributions of:

         Alexander I. Alten (Novell)
         Dave Arneson (Cabletron)
         Uri Blumenthal (IBM)
         Doug Book (Chipcom)
         Kim Curran (Bell-Northern Research)
         Jim Galvin (Trusted Information Systems)
         Maria Greene (Ascom Timeplex)
         Iain Hanson (Digital)
         Dave Harrington (Cabletron)
         Nguyen Hien (IBM)
         Jeff Johnson (Cisco Systems)
         Michael Kornegay (Object Quest)
         Deirdre Kostick (AT&T Bell Labs)
         David Levi (SNMP Research)
         Daniel Mahoney (Cabletron)
         Bob Natale (ACE*COMM)
         Brian O'Keefe (Hewlett Packard)
         Andrew Pearson (SNMP Research)
         Dave Perkins (Peer Networks)

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         Randy Presuhn (Peer Networks)
         Aleksey Romanov (Quality Quorum)
         Shawn Routhier (Epilogue)
         Jon Saperia (BGS Systems)
         Bob Stewart (Cisco Systems, bstewart@cisco.com), chair
         Kaj Tesink (Bellcore)
         Glenn Waters (Bell-Northern Research)
         Bert Wijnen (IBM)

    11.  References

    [1]  Information processing systems - Open Systems Interconnection -
         Specification of Abstract Syntax Notation One (ASN.1),
         International Organization for Standardization.  International
         Standard 8824, (December, 1987).

    [2]  SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and
         S. Waldbusser, "Structure of Management Information for Version 2
         of the Simple Network Management Protocol (SNMPv2)", RFC 1902,
         January 1996.

    [3]  SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and
         S. Waldbusser, "Management Information Base for Version 2 of the
         Simple Network Management Protocol (SNMPv2)", RFC 1907,
         January 1996.

    [4]  SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and
         S. Waldbusser, "Protocol Operations for Version 2 of the Simple
         Network Management Protocol (SNMPv2)", RFC 1905, January 1996.

    [5]  SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and
         S. Waldbusser, "Textual Conventions for Version 2 of the Simple
         Network Management Protocol (SNMPv2)", RFC 1903, January 1996.

    [6]  Rose, M., and K. McCloghrie, "Structure and Identification of
         Management Information for TCP/IP-based internets", STD 16, RFC
         1155, May 1990.

    [7]  Rose, M., and K. McCloghrie, "Concise MIB Definitions", STD 16,
         RFC 1212, March 1991.

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