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rfc:rfc1904

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

SNMPv2 Working Group Standards Track [Page 1] RFC 1904 Conformance Statements for SNMPv2 January 1996

 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.

SNMPv2 Working Group Standards Track [Page 2] RFC 1904 Conformance Statements for SNMPv2 January 1996

 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 ::=

SNMPv2 Working Group Standards Track [Page 3] RFC 1904 Conformance Statements for SNMPv2 January 1996

                value(Name ObjectName)
  Status ::=
                "current"
              | "deprecated"
              | "obsolete"
  ReferPart ::=
                "REFERENCE" Text
              | empty
  1. - 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
  1. - uses the NVT ASCII character set

Text ::= """" string """"

SNMPv2 Working Group Standards Track [Page 4] RFC 1904 Conformance Statements for SNMPv2 January 1996

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 "}"

SNMPv2 Working Group Standards Track [Page 5] RFC 1904 Conformance Statements for SNMPv2 January 1996

              | 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
  1. - must be a refinement for object's SYNTAX clause

SyntaxPart ::=

                "SYNTAX" type(SYNTAX)
              | empty
  1. - 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"

SNMPv2 Working Group Standards Track [Page 6] RFC 1904 Conformance Statements for SNMPv2 January 1996

              | "read-create"
  1. - 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 ::=

SNMPv2 Working Group Standards Track [Page 7] RFC 1904 Conformance Statements for SNMPv2 January 1996

                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
  1. - must be a refinement for object's SYNTAX clause

SyntaxPart ::=

                "SYNTAX" type(SYNTAX)
              | empty
  1. - 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"

SNMPv2 Working Group Standards Track [Page 8] RFC 1904 Conformance Statements for SNMPv2 January 1996

              | "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
  1. - 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].

SNMPv2 Working Group Standards Track [Page 9] RFC 1904 Conformance Statements for SNMPv2 January 1996

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.

SNMPv2 Working Group Standards Track [Page 10] RFC 1904 Conformance Statements for SNMPv2 January 1996

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

SNMPv2 Working Group Standards Track [Page 11] RFC 1904 Conformance Statements for SNMPv2 January 1996

 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.

SNMPv2 Working Group Standards Track [Page 12] RFC 1904 Conformance Statements for SNMPv2 January 1996

 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

SNMPv2 Working Group Standards Track [Page 13] RFC 1904 Conformance Statements for SNMPv2 January 1996

 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.

SNMPv2 Working Group Standards Track [Page 14] RFC 1904 Conformance Statements for SNMPv2 January 1996

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.

SNMPv2 Working Group Standards Track [Page 15] RFC 1904 Conformance Statements for SNMPv2 January 1996

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

SNMPv2 Working Group Standards Track [Page 16] RFC 1904 Conformance Statements for SNMPv2 January 1996

 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.

SNMPv2 Working Group Standards Track [Page 17] RFC 1904 Conformance Statements for SNMPv2 January 1996

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.

SNMPv2 Working Group Standards Track [Page 18] RFC 1904 Conformance Statements for SNMPv2 January 1996

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".

SNMPv2 Working Group Standards Track [Page 19] RFC 1904 Conformance Statements for SNMPv2 January 1996

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"

SNMPv2 Working Group Standards Track [Page 20] RFC 1904 Conformance Statements for SNMPv2 January 1996

  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.

SNMPv2 Working Group Standards Track [Page 21] RFC 1904 Conformance Statements for SNMPv2 January 1996

 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.

SNMPv2 Working Group Standards Track [Page 22] RFC 1904 Conformance Statements for SNMPv2 January 1996

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)

SNMPv2 Working Group Standards Track [Page 23] RFC 1904 Conformance Statements for SNMPv2 January 1996

   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.

SNMPv2 Working Group Standards Track [Page 24]

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