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Versions: 00 01 RFC 2580

Network Working Group                 Editors of this version:
Internet Draft                                             K. McCloghrie
                                                           Cisco Systems
                                                              D. Perkins
                                             Desktalk Systems & 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
                                                         30 January 1999


                    Conformance Statements for SMIv2
                      draft-ops-smiv2-conf-01.txt


Status of this Memo

This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.  Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, and
its working groups.  Note that other groups may also distribute working
documents as Internet-Drafts.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time.  It is inappropriate to use Internet-Drafts as reference material
or to cite them other than as ``work in progress.''

To view the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in an Internet-Drafts Shadow
Directory, see http://www.ietf.org/shadow.html.

Copyright Notice

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







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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).





























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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 ::=
                  value(ObjectName)

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

    ReferPart ::=
                  "REFERENCE" Text
                | empty

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










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-- 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 "}"





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                | empty

    Groups ::=
                  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 "}"






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    NamedBits ::= NamedBit
                | NamedBits "," NamedBit

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

    AccessPart ::=
                  "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
































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

    Groups ::=
                  Group
                | Groups "," Group
    Group ::=





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

    NamedBits ::= NamedBit
                | NamedBits "," NamedBit

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





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    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

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

END





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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.


3.2.  Mapping of the STATUS clause

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







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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























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group, which is an OBJECT IDENTIFIER, an administratively assigned name.


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.























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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.


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





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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:


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.





















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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.


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.










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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.






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

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


5.4.4.  Mapping of the DESCRIPTION clause

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


5.5.  Mapping of the MODULE-COMPLIANCE value

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
























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5.6.  Usage Example

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

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

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

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

     { xyzMIBCompliances 1 }

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


















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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.






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6.2.  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 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





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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.

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.









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6.5.2.3.  Mapping of the ACCESS clause

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

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

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

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


6.5.2.4.  Mapping of the CREATION-REQUIRES clause

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

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

This clause must not 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".








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6.5.2.5.  Mapping of the DEFVAL clause

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


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."





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        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
            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.







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>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





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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 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).






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(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
     Desktalk Systems & 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 Waldbusser, S.  "Structure of Management Information Version 2
     (SMIv2)", draft-ops-smiv2-smi-01.txt, January 1999.

[3]  The SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and
     Waldbusser, S., "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
     Waldbusser, S., "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 Waldbusser, S.  "Textual Conventions for SMIv2", draft-ops-
     smiv2-tc-01.txt, January 1999.

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

[7]  Rose, M., and McCloghrie, K., "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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Table of Contents


1 Introduction ....................................................    2
1.1 A Note on Terminology .........................................    2
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 ..................................    8
3 Mapping of the OBJECT-GROUP macro ...............................   11
3.1 Mapping of the OBJECTS clause .................................   11
3.2 Mapping of the STATUS clause ..................................   11
3.3 Mapping of the DESCRIPTION clause .............................   12
3.4 Mapping of the REFERENCE clause ...............................   12
3.5 Mapping of the OBJECT-GROUP value .............................   12
3.6 Usage Example .................................................   13
4 Mapping of the NOTIFICATION-GROUP macro .........................   14
4.1 Mapping of the NOTIFICATIONS clause ...........................   14
4.2 Mapping of the STATUS clause ..................................   14
4.3 Mapping of the DESCRIPTION clause .............................   14
4.4 Mapping of the REFERENCE clause ...............................   14
4.5 Mapping of the NOTIFICATION-GROUP value .......................   15
4.6 Usage Example .................................................   15
5 Mapping of the MODULE-COMPLIANCE macro ..........................   16
5.1 Mapping of the STATUS clause ..................................   16
5.2 Mapping of the DESCRIPTION clause .............................   16
5.3 Mapping of the REFERENCE clause ...............................   16
5.4 Mapping of the MODULE clause ..................................   17
5.4.1 Mapping of the MANDATORY-GROUPS clause ......................   17
5.4.2 Mapping of the GROUP clause .................................   17
5.4.3 Mapping of the OBJECT clause ................................   18
5.4.3.1 Mapping of the SYNTAX clause ..............................   18
5.4.3.2 Mapping of the WRITE-SYNTAX clause ........................   18
5.4.3.3 Mapping of the MIN-ACCESS clause ..........................   18
5.4.4 Mapping of the DESCRIPTION clause ...........................   19
5.5 Mapping of the MODULE-COMPLIANCE value ........................   19
5.6 Usage Example .................................................   20
6 Mapping of the AGENT-CAPABILITIES macro .........................   21
6.1 Mapping of the PRODUCT-RELEASE clause .........................   21
6.2 Mapping of the STATUS clause ..................................   22
6.3 Mapping of the DESCRIPTION clause .............................   22
6.4 Mapping of the REFERENCE clause ...............................   22
6.5 Mapping of the SUPPORTS clause ................................   22
6.5.1 Mapping of the INCLUDES clause ..............................   22





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6.5.2 Mapping of the VARIATION clause .............................   22
6.5.2.1 Mapping of the SYNTAX clause ..............................   23
6.5.2.2 Mapping of the WRITE-SYNTAX clause ........................   23
6.5.2.3 Mapping of the ACCESS clause ..............................   24
6.5.2.4 Mapping of the CREATION-REQUIRES clause ...................   24
6.5.2.5 Mapping of the DEFVAL clause ..............................   25
6.5.2.6 Mapping of the DESCRIPTION clause .........................   25
6.6 Mapping of the AGENT-CAPABILITIES value .......................   25
6.7 Usage Example .................................................   25
7 Extending an Information Module .................................   28
7.1 Conformance Groups ............................................   28
7.2 Compliance Definitions ........................................   28
7.3 Capabilities Definitions ......................................   29
8 Security Considerations .........................................   31
9 Editors' Addresses ..............................................   31
10 References .....................................................   32
11 Full Copyright Statement .......................................   33

































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