

Network Working Group                 Editors of this version:
Request for Comments: 2580                                 K. McCloghrie
STD: 58                                                    Cisco Systems
Obsoletes: 1904                                               D. Perkins
Category: Standards Track                                       SNMPinfo
                                                        J. Schoenwaelder
                                                         TU Braunschweig
                                      Authors of previous version:
                                                                 J. Case
                                                           SNMP Research
                                                           K. McCloghrie
                                                           Cisco Systems
                                                                 M. Rose
                                                  First Virtual Holdings
                                                           S. Waldbusser
                                          International Network Services
                                                              April 1999


                    Conformance Statements for SMIv2


Status of this Memo

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

Copyright Notice

   Copyright (C) The Internet Society (1999).  All Rights Reserved.


Table of Contents

   1 Introduction .....................................................3
   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 ...............................10
   3.1 Mapping of the OBJECTS clause .................................10
   3.2 Mapping of the STATUS clause ..................................11
   3.3 Mapping of the DESCRIPTION clause .............................11
   3.4 Mapping of the REFERENCE clause ...............................11


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   3.5 Mapping of the OBJECT-GROUP value .............................11
   3.6 Usage Example .................................................12
   4 Mapping of the NOTIFICATION-GROUP macro .........................12
   4.1 Mapping of the NOTIFICATIONS clause ...........................12
   4.2 Mapping of the STATUS clause ..................................13
   4.3 Mapping of the DESCRIPTION clause .............................13
   4.4 Mapping of the REFERENCE clause ...............................13
   4.5 Mapping of the NOTIFICATION-GROUP value .......................13
   4.6 Usage Example .................................................13
   5 Mapping of the MODULE-COMPLIANCE macro ..........................14
   5.1 Mapping of the STATUS clause ..................................14
   5.2 Mapping of the DESCRIPTION clause .............................14
   5.3 Mapping of the REFERENCE clause ...............................15
   5.4 Mapping of the MODULE clause ..................................15
   5.4.1 Mapping of the MANDATORY-GROUPS clause ......................15
   5.4.2 Mapping of the GROUP clause .................................15
   5.4.3 Mapping of the OBJECT clause ................................16
   5.4.3.1 Mapping of the SYNTAX clause ..............................16
   5.4.3.2 Mapping of the WRITE-SYNTAX clause ........................16
   5.4.3.3 Mapping of the MIN-ACCESS clause ..........................16
   5.4.4 Mapping of the DESCRIPTION clause ...........................17
   5.5 Mapping of the MODULE-COMPLIANCE value ........................17
   5.6 Usage Example .................................................17
   6 Mapping of the AGENT-CAPABILITIES macro .........................19
   6.1 Mapping of the PRODUCT-RELEASE clause .........................19
   6.2 Mapping of the STATUS clause ..................................19
   6.3 Mapping of the DESCRIPTION clause .............................20
   6.4 Mapping of the REFERENCE clause ...............................20
   6.5 Mapping of the SUPPORTS clause ................................20
   6.5.1 Mapping of the INCLUDES clause ..............................20
   6.5.2 Mapping of the VARIATION clause .............................20
   6.5.2.1 Mapping of the SYNTAX clause ..............................21
   6.5.2.2 Mapping of the WRITE-SYNTAX clause ........................21
   6.5.2.3 Mapping of the ACCESS clause ..............................21
   6.5.2.4 Mapping of the CREATION-REQUIRES clause ...................22
   6.5.2.5 Mapping of the DEFVAL clause ..............................22
   6.5.2.6 Mapping of the DESCRIPTION clause .........................22
   6.6 Mapping of the AGENT-CAPABILITIES value .......................22
   6.7 Usage Example .................................................23
   7 Extending an Information Module .................................25
   7.1 Conformance Groups ............................................25
   7.2 Compliance Definitions ........................................26
   7.3 Capabilities Definitions ......................................26
   8 Security Considerations .........................................27
   9 Editors' Addresses ..............................................27
   10 References .....................................................28
   11 Full Copyright Statement .......................................29


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1.  Introduction

   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 an adapted subset of
   OSI's Abstract Syntax Notation One, ASN.1 (1988) [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 Structure of Management
   Information, as described in RFCs 1156 (STD 16), 1212 (STD 16), and
   RFC 1215, is termed the SMI version 1 (SMIv1).  The current version
   of the Structure of Management Information is termed SMI version 2
   (SMIv2).

2.  Definitions

SNMPv2-CONF DEFINITIONS ::= BEGIN

IMPORTS ObjectName, NotificationName, ObjectSyntax
                                               FROM SNMPv2-SMI;

-- 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(ObjectName)

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

    ReferPart ::=
                  "REFERENCE" Text
                | empty

    -- a character string as defined in [2]
    Text ::= value(IA5String)
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(NotificationName)

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

    ReferPart ::=
                  "REFERENCE" Text
                | empty

    -- a character string as defined in [2]
    Text ::= value(IA5String)
END


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

    ModuleName ::=
                  -- identifier must start with uppercase letter
                  identifier ModuleIdentifier
                  -- must not be empty unless contained
                  -- in MIB Module
                | empty
    ModuleIdentifier ::=
                  value(OBJECT IDENTIFIER)
                | empty

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

    Groups ::=


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

    CompliancePart ::=
                  Compliances
                | empty

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

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

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

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

    -- must be a refinement for object's SYNTAX clause
    WriteSyntaxPart ::= "WRITE-SYNTAX" Syntax
                | empty

    Syntax ::=    -- Must be one of the following:
                       -- a base type (or its refinement),
                       -- a textual convention (or its refinement), or
                       -- a BITS pseudo-type
                  type
                | "BITS" "{" NamedBits "}"

    NamedBits ::= NamedBit
                | NamedBits "," NamedBit

    NamedBit ::= identifier "(" number ")" -- number is nonnegative

    AccessPart ::=


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

    -- a character string as defined in [2]
    Text ::= value(IA5String)
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 ::=


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                  -- identifier must start with uppercase letter
                  identifier ModuleIdentifier
    ModuleIdentifier ::=
                  value(OBJECT IDENTIFIER)
                | empty

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

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

    Variation ::=
                  ObjectVariation
                | NotificationVariation

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

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

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

    WriteSyntaxPart ::= "WRITE-SYNTAX" Syntax
                | empty

    Syntax ::=    -- Must be one of the following:
                       -- a base type (or its refinement),
                       -- a textual convention (or its refinement), or
                       -- a BITS pseudo-type


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                  type
                | "BITS" "{" NamedBits "}"

    NamedBits ::= NamedBit
                | NamedBits "," NamedBit

    NamedBit ::= identifier "(" number ")" -- number is nonnegative

    AccessPart ::=
                  "ACCESS" Access
                | empty

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

    DefValPart ::= "DEFVAL" "{" Defvalue "}"
                | empty

    Defvalue ::=  -- must be valid for the object's syntax
                  -- in this macro's SYNTAX clause, if present,
                  -- or if not, in object's OBJECT-TYPE macro
                  value(ObjectSyntax)
                | "{" BitsValue "}"

    BitsValue ::= BitNames
                | empty

    BitNames ::=  BitName
                | BitNames "," BitName

    BitName ::= identifier


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    -- a character string as defined in [2]
    Text ::= value(IA5String)
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, an agent 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, an agent must accordingly be able to reasonably influence
   the underlying managed entity.  If an agent can not implement an
   object, the management protocol provides for it to return an
   exception or error, e.g, noSuchObject [4].  Under no circumstances
   shall an agent 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].

   Note that the OBJECT-GROUP macro itself provides no conformance
   information.  Rather, conformance information is specified through
   the inclusion of defined groups in a MODULE-COMPLIANCE macro.

3.1.  Mapping of the OBJECTS clause

   The OBJECTS clause, which must be present, is used to specify each
   object contained in the conformance group.  Each of the specified
   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.


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3.2.  Mapping of the STATUS clause

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

   The value "current" means that the definition is current and valid.
   The value "obsolete" means the definition is obsolete and the group
   should no longer be used for defining conformance.  While the value
   "deprecated" also indicates an obsolete definition, it permits
   new/continued use of conformance definitions using this group.

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 some other document, either another information
   module which defines a related assignment, or some other document
   which provides additional information relevant to this definition.

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 agent."
      ::= { 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 specify
   each notification contained in the conformance group.  Each of the
   specified notifications must be defined in the same information
   module as the NOTIFICATION-GROUP macro appears.

   It is required that every notification defined in an information
   module be contained in at least one notification group.


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4.2.  Mapping of the STATUS clause

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

   The value "current" means that the definition is current and valid.
   The value "obsolete" means the definition is obsolete and this group
   should no longer be used for defining conformance.  While the value
   "deprecated" also indicates an obsolete definition, it permits
   new/continued use of conformance definitions using this group.

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 some other document, either another information
   module which defines a related assignment, or some other document
   which provides additional information relevant to this definition.

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:


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

   According to this invocation, the conformance group named

        { snmpMIBGroups 7 }

   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.

   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 value "current" means that the definition is current and valid.
   The value "obsolete" means the definition is obsolete, and this
   MODULE-COMPLIANCE specification no longer specifies a valid
   definition of conformance.  While the value "deprecated" also
   indicates an obsolete definition, it permits new/continued use of the
   MODULE-COMPLIANCE specification.

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.


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5.3.  Mapping of the REFERENCE clause

   The REFERENCE clause, which need not be present, contains a textual
   cross-reference to some other document, either another information
   module which defines a related assignment, or some other document
   which provides additional information relevant to this definition.

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 an
   agent claims compliance to the MIB module, then it must implement
   each and every object and notification within each conformance group
   listed.  That is, if an agent returns a noSuchObject exception in
   response to a management protocol get operation [4] for any object
   within any mandatory conformance group for every possible MIB view,
   or if the agent cannot generate each notification listed in any
   conformance group under the appropriate circumstances, then that
   agent 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 for compliance to the MIB module.  The GROUP clause can
   also be used to name unconditionally optional groups.  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.


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5.4.3.  Mapping of the OBJECT clause

   The OBJECT clause, which need not be present, is repeatedly used to
   specify 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.

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


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   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.

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 }


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   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.


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6.  Mapping of the AGENT-CAPABILITIES macro

   The AGENT-CAPABILITIES macro is used to convey a set of capabilities
   present in an agent.  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 an agent claims to implement a group, then it must
   implement each and every object, or each and every notification,
   within that group.  Of course, for whatever reason, an agent might
   implement only a subset of the groups within a MIB module.  In
   addition, the definition of some MIB objects/notifications leave some
   aspects of 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


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   definition is current or historic.

   The value "current" means that the definition is current and valid.
   The value "obsolete" means the definition is obsolete and this
   capabilities statement is no longer in use.

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 some other document, either another information
   module which defines a related assignment, or some other document
   which provides additional information relevant to this definition.

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 registered by the
   MODULE-IDENTITY macro, see [2]) as well.

6.5.1.  Mapping of the INCLUDES clause

   The INCLUDES clause, which must follow each and every 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


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   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.

   Note that for enumerated INTEGERs and for the BITS construct, the
   changes allowed when updating a MIB module include the addition of
   enumerations and/or changing the labels of existing enumerations (see
   Section 10.2 of [2]).  This type of change can cause problems for an
   AGENT-CAPABILITIES macro written against the old revision of a MIB
   module.  One way to avoid such problems is to explicitly list all
   objects having an enumerated syntax in a VARIATION clause, even when
   all enumerations are currently supported.

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.

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".


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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 be 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".

6.5.2.5.  Mapping of the DEFVAL clause

   The DEFVAL clause, which need not be present, is used to provide a
   alternate 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.


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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."

       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


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               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, evalStatus }
               DESCRIPTION  "Conceptual row creation is supported."

       ::= { acmeAgents 1 }


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

        { acmeAgents 1 }

   supports objects defined in 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.

   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 ipNetToMediaPhysAddress.

   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, and requires both of the objects:  evalString and
   evalStatus, to be assigned a value.


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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

   It may be desirable to revise the definition of a conformance group
   (an OBJECT-GROUP or a NOTIFICATION-GROUP) after experience is gained
   with it.  However, conformance groups can be referenced by compliance
   and/or capabilities definitions.  Therefore, a change to a
   conformance group is not allowed if it has the potential to cause a
   reference to the group's original definition to be different from a
   reference to the updated definition.  Such changes can only be
   accommodated by defining a new conformance group with a new
   descriptor and a new OBJECT IDENTIFIER value.

   The following revisions are allowed:

(1)  A STATUS clause value of "current" may be revised as "deprecated"
     or "obsolete".  Similarly, a STATUS clause value of "deprecated"
     may be revised as "obsolete".  When making such a change, the
     DESCRIPTION clause should be updated to explain the rationale.

(2)  A REFERENCE clause may be added or updated.

(3)  Clarifications and additional information may be included in the
     DESCRIPTION clause.

(4)  Any editorial change.

   It is not necessary to change the STATUS value of a conformance group
   when the status of a member of the group is changed.

7.2.  Compliance Definitions

   It may be desirable to revise the definition of a compliance
   definition (MODULE-COMPLIANCE) after experience is gained with it.
   However, changes are not allowed if they cause the requirements
   specified by the original definition to be different from the
   requirements of the updated definition.  Such changes can only be
   accommodated by defining a new compliance definition with a new


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   descriptor and a new OBJECT IDENTIFIER value.

   The following revisions are allowed:

(1)  A STATUS clause value of "current" may be revised as "deprecated"
     or "obsolete".  Similarly, a STATUS clause value of "deprecated"
     may be revised as "obsolete".  When making such a change, the
     DESCRIPTION clause should be updated to explain the rationale.

(2)  A REFERENCE clause may be added or updated.

(3)  Clarifications and additional information may be included in the
     DESCRIPTION clause(s).

(4)  Any editorial change.

   It is not necessary to change the STATUS value of a compliance
   definition due to a change in the STATUS value of a definition it
   references.

7.3.  Capabilities Definitions

   It may be desirable to revise the definition of a capabilities
   definition (AGENT-CAPABILITIES) after experience is gained with it.
   However, changes are not allowed if they cause the capabilities
   specified by the original specification to be different from the
   capabilities of the updated specification.  Such changes can only be
   accommodated by defining a new capabilities definition with a new
   descriptor and a new OBJECT IDENTIFIER value.

   The following revisions are allowed:

(1)  A STATUS clause value of "current" may be revised as "obsolete".
     When making such a change, the DESCRIPTION clause should be updated
     to explain the rationale.

(2)  A REFERENCE clause may be added or updated.

(3)  Clarifications and additional information may be included in the
     DESCRIPTION clause(s).

(4)  Any editorial change.

   It is not necessary to change the STATUS value of a capabilities
   definition due to a change in the STATUS value of a definition it
   references.


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8.  Security Considerations

   This document defines the means to define conformance requirements
   for implementing on documents describing management information.
   This method of defining conformance requirements has no security
   impact on the Internet.


9.  Editors' Addresses

   Keith McCloghrie
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA  95134-1706
   USA
   Phone: +1 408 526 5260
   EMail: kzm@cisco.com

   David Perkins
   SNMPinfo
   3763 Benton Street
   Santa Clara, CA 95051
   USA
   Phone: +1 408 221-8702
   Email: dperkins@snmpinfo.com

   Juergen Schoenwaelder
   TU Braunschweig
   Bueltenweg 74/75
   38106 Braunschweig
   Germany
   Phone: +49 531 391-3283
   EMail: schoenw@ibr.cs.tu-bs.de


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10.  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]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M.
     and S. Waldbusser, "Structure of Management Information Version 2
     (SMIv2)", STD 58, RFC 2578, April 1999.

[3]  The 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]  The 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]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M.
     and S. Waldbusser, "Textual Conventions for SMIv2", STD 58,
     RFC 2579, April 1999.

[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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11.  Full Copyright Statement

   Copyright (C) The Internet Society (1999).  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."


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