Conformance Statements for SMIv2
RFC 2580
| Document | Type |
RFC - Internet Standard
(April 1999; No errata)
Obsoletes RFC 1904
Also known as STD 58
Was draft-ops-smiv2-conf (individual)
|
|
|---|---|---|---|
| Authors | Keith McCloghrie , Jürgen Schönwälder , David Perkins , Keith McCloghrie | ||
| Last updated | 2013-03-02 | ||
| Stream | Legacy stream | ||
| Formats | plain text html pdf htmlized bibtex | ||
| Stream | Legacy state | (None) | |
| Consensus Boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | RFC 2580 (Internet Standard) | |
| Telechat date | |||
| Responsible AD | (None) | ||
| Send notices to | (None) | ||
Network Working Group Editors of this version:
Request for Comments: 2580 K. McCloghrie
STD: 58 Cisco Systems
Obsoletes: 1904 D. Perkins
Category: Standards Track SNMPinfo
J. Schoenwaelder
TU Braunschweig
Authors of previous version:
J. Case
SNMP Research
K. McCloghrie
Cisco Systems
M. Rose
First Virtual Holdings
S. Waldbusser
International Network Services
April 1999
Conformance Statements for SMIv2
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
Table of Contents
1 Introduction .....................................................3
1.1 A Note on Terminology ..........................................3
2 Definitions ......................................................3
2.1 The OBJECT-GROUP macro .........................................3
2.2 The NOTIFICATION-GROUP macro ...................................4
2.3 The MODULE-COMPLIANCE macro ....................................5
2.4 The AGENT-CAPABILITIES macro ...................................7
3 Mapping of the OBJECT-GROUP macro ...............................10
3.1 Mapping of the OBJECTS clause .................................10
3.2 Mapping of the STATUS clause ..................................11
3.3 Mapping of the DESCRIPTION clause .............................11
3.4 Mapping of the REFERENCE clause ...............................11
McCloghrie, et al. Standards Track [Page 1]
RFC 2580 Conformance Statements for SMIv2 April 1999
3.5 Mapping of the OBJECT-GROUP value .............................11
3.6 Usage Example .................................................12
4 Mapping of the NOTIFICATION-GROUP macro .........................12
4.1 Mapping of the NOTIFICATIONS clause ...........................12
4.2 Mapping of the STATUS clause ..................................13
4.3 Mapping of the DESCRIPTION clause .............................13
4.4 Mapping of the REFERENCE clause ...............................13
4.5 Mapping of the NOTIFICATION-GROUP value .......................13
4.6 Usage Example .................................................13
5 Mapping of the MODULE-COMPLIANCE macro ..........................14
5.1 Mapping of the STATUS clause ..................................14
5.2 Mapping of the DESCRIPTION clause .............................14
5.3 Mapping of the REFERENCE clause ...............................15
5.4 Mapping of the MODULE clause ..................................15
5.4.1 Mapping of the MANDATORY-GROUPS clause ......................15
5.4.2 Mapping of the GROUP clause .................................15
5.4.3 Mapping of the OBJECT clause ................................16
5.4.3.1 Mapping of the SYNTAX clause ..............................16
5.4.3.2 Mapping of the WRITE-SYNTAX clause ........................16
5.4.3.3 Mapping of the MIN-ACCESS clause ..........................16
5.4.4 Mapping of the DESCRIPTION clause ...........................17
5.5 Mapping of the MODULE-COMPLIANCE value ........................17
5.6 Usage Example .................................................17
6 Mapping of the AGENT-CAPABILITIES macro .........................19
6.1 Mapping of the PRODUCT-RELEASE clause .........................19
6.2 Mapping of the STATUS clause ..................................19
6.3 Mapping of the DESCRIPTION clause .............................20
6.4 Mapping of the REFERENCE clause ...............................20
6.5 Mapping of the SUPPORTS clause ................................20
6.5.1 Mapping of the INCLUDES clause ..............................20
6.5.2 Mapping of the VARIATION clause .............................20
6.5.2.1 Mapping of the SYNTAX clause ..............................21
6.5.2.2 Mapping of the WRITE-SYNTAX clause ........................21
6.5.2.3 Mapping of the ACCESS clause ..............................21
6.5.2.4 Mapping of the CREATION-REQUIRES clause ...................22
6.5.2.5 Mapping of the DEFVAL clause ..............................22
6.5.2.6 Mapping of the DESCRIPTION clause .........................22
6.6 Mapping of the AGENT-CAPABILITIES value .......................22
6.7 Usage Example .................................................23
7 Extending an Information Module .................................25
7.1 Conformance Groups ............................................25
7.2 Compliance Definitions ........................................26
7.3 Capabilities Definitions ......................................26
8 Security Considerations .........................................27
9 Editors' Addresses ..............................................27
10 References .....................................................28
11 Full Copyright Statement .......................................29
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RFC 2580 Conformance Statements for SMIv2 April 1999
1. Introduction
Management information is viewed as a collection of managed objects,
residing in a virtual information store, termed the Management
Information Base (MIB). Collections of related objects are defined
in MIB modules. These modules are written using an adapted subset of
OSI's Abstract Syntax Notation One, ASN.1 (1988) [1], termed the
Structure of Management Information (SMI) [2].
It may be useful to define the acceptable lower-bounds of
implementation, along with the actual level of implementation
achieved. It is the purpose of this document to define the notation
used for these purposes.
1.1. A Note on Terminology
For the purpose of exposition, the original Structure of Management
Information, as described in RFCs 1156 (STD 16), 1212 (STD 16), and
RFC 1215, is termed the SMI version 1 (SMIv1). The current version
of the Structure of Management Information is termed SMI version 2
(SMIv2).
2. Definitions
SNMPv2-CONF DEFINITIONS ::= BEGIN
IMPORTS ObjectName, NotificationName, ObjectSyntax
FROM SNMPv2-SMI;
-- definitions for conformance groups
OBJECT-GROUP MACRO ::=
BEGIN
TYPE NOTATION ::=
ObjectsPart
"STATUS" Status
"DESCRIPTION" Text
ReferPart
VALUE NOTATION ::=
value(VALUE OBJECT IDENTIFIER)
ObjectsPart ::=
"OBJECTS" "{" Objects "}"
Objects ::=
Object
| Objects "," Object
Object ::=
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value(ObjectName)
Status ::=
"current"
| "deprecated"
| "obsolete"
ReferPart ::=
"REFERENCE" Text
| empty
-- a character string as defined in [2]
Text ::= value(IA5String)
END
-- more definitions for conformance groups
NOTIFICATION-GROUP MACRO ::=
BEGIN
TYPE NOTATION ::=
NotificationsPart
"STATUS" Status
"DESCRIPTION" Text
ReferPart
VALUE NOTATION ::=
value(VALUE OBJECT IDENTIFIER)
NotificationsPart ::=
"NOTIFICATIONS" "{" Notifications "}"
Notifications ::=
Notification
| Notifications "," Notification
Notification ::=
value(NotificationName)
Status ::=
"current"
| "deprecated"
| "obsolete"
ReferPart ::=
"REFERENCE" Text
| empty
-- a character string as defined in [2]
Text ::= value(IA5String)
END
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-- definitions for compliance statements
MODULE-COMPLIANCE MACRO ::=
BEGIN
TYPE NOTATION ::=
"STATUS" Status
"DESCRIPTION" Text
ReferPart
ModulePart
VALUE NOTATION ::=
value(VALUE OBJECT IDENTIFIER)
Status ::=
"current"
| "deprecated"
| "obsolete"
ReferPart ::=
"REFERENCE" Text
| empty
ModulePart ::=
Modules
Modules ::=
Module
| Modules Module
Module ::=
-- name of module --
"MODULE" ModuleName
MandatoryPart
CompliancePart
ModuleName ::=
-- identifier must start with uppercase letter
identifier ModuleIdentifier
-- must not be empty unless contained
-- in MIB Module
| empty
ModuleIdentifier ::=
value(OBJECT IDENTIFIER)
| empty
MandatoryPart ::=
"MANDATORY-GROUPS" "{" Groups "}"
| empty
Groups ::=
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Group
| Groups "," Group
Group ::=
value(OBJECT IDENTIFIER)
CompliancePart ::=
Compliances
| empty
Compliances ::=
Compliance
| Compliances Compliance
Compliance ::=
ComplianceGroup
| Object
ComplianceGroup ::=
"GROUP" value(OBJECT IDENTIFIER)
"DESCRIPTION" Text
Object ::=
"OBJECT" value(ObjectName)
SyntaxPart
WriteSyntaxPart
AccessPart
"DESCRIPTION" Text
-- must be a refinement for object's SYNTAX clause
SyntaxPart ::= "SYNTAX" Syntax
| empty
-- must be a refinement for object's SYNTAX clause
WriteSyntaxPart ::= "WRITE-SYNTAX" Syntax
| empty
Syntax ::= -- Must be one of the following:
-- a base type (or its refinement),
-- a textual convention (or its refinement), or
-- a BITS pseudo-type
type
| "BITS" "{" NamedBits "}"
NamedBits ::= NamedBit
| NamedBits "," NamedBit
NamedBit ::= identifier "(" number ")" -- number is nonnegative
AccessPart ::=
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"MIN-ACCESS" Access
| empty
Access ::=
"not-accessible"
| "accessible-for-notify"
| "read-only"
| "read-write"
| "read-create"
-- a character string as defined in [2]
Text ::= value(IA5String)
END
-- definitions for capabilities statements
AGENT-CAPABILITIES MACRO ::=
BEGIN
TYPE NOTATION ::=
"PRODUCT-RELEASE" Text
"STATUS" Status
"DESCRIPTION" Text
ReferPart
ModulePart
VALUE NOTATION ::=
value(VALUE OBJECT IDENTIFIER)
Status ::=
"current"
| "obsolete"
ReferPart ::=
"REFERENCE" Text
| empty
ModulePart ::=
Modules
| empty
Modules ::=
Module
| Modules Module
Module ::=
-- name of module --
"SUPPORTS" ModuleName
"INCLUDES" "{" Groups "}"
VariationPart
ModuleName ::=
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-- identifier must start with uppercase letter
identifier ModuleIdentifier
ModuleIdentifier ::=
value(OBJECT IDENTIFIER)
| empty
Groups ::=
Group
| Groups "," Group
Group ::=
value(OBJECT IDENTIFIER)
VariationPart ::=
Variations
| empty
Variations ::=
Variation
| Variations Variation
Variation ::=
ObjectVariation
| NotificationVariation
NotificationVariation ::=
"VARIATION" value(NotificationName)
AccessPart
"DESCRIPTION" Text
ObjectVariation ::=
"VARIATION" value(ObjectName)
SyntaxPart
WriteSyntaxPart
AccessPart
CreationPart
DefValPart
"DESCRIPTION" Text
-- must be a refinement for object's SYNTAX clause
SyntaxPart ::= "SYNTAX" Syntax
| empty
WriteSyntaxPart ::= "WRITE-SYNTAX" Syntax
| empty
Syntax ::= -- Must be one of the following:
-- a base type (or its refinement),
-- a textual convention (or its refinement), or
-- a BITS pseudo-type
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type
| "BITS" "{" NamedBits "}"
NamedBits ::= NamedBit
| NamedBits "," NamedBit
NamedBit ::= identifier "(" number ")" -- number is nonnegative
AccessPart ::=
"ACCESS" Access
| empty
Access ::=
"not-implemented"
-- only "not-implemented" for notifications
| "accessible-for-notify"
| "read-only"
| "read-write"
| "read-create"
-- following is for backward-compatibility only
| "write-only"
CreationPart ::=
"CREATION-REQUIRES" "{" Cells "}"
| empty
Cells ::=
Cell
| Cells "," Cell
Cell ::=
value(ObjectName)
DefValPart ::= "DEFVAL" "{" Defvalue "}"
| empty
Defvalue ::= -- must be valid for the object's syntax
-- in this macro's SYNTAX clause, if present,
-- or if not, in object's OBJECT-TYPE macro
value(ObjectSyntax)
| "{" BitsValue "}"
BitsValue ::= BitNames
| empty
BitNames ::= BitName
| BitNames "," BitName
BitName ::= identifier
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-- a character string as defined in [2]
Text ::= value(IA5String)
END
END
3. Mapping of the OBJECT-GROUP macro
For conformance purposes, it is useful to define a collection of
related managed objects. The OBJECT-GROUP macro is used to define
each such collection of related objects. It should be noted that the
expansion of the OBJECT-GROUP macro is something which conceptually
happens during implementation and not during run-time.
To "implement" an object, an agent must return a reasonably accurate
value for management protocol retrieval operations; similarly, if the
object is writable, then in response to a management protocol set
operation, an agent must accordingly be able to reasonably influence
the underlying managed entity. If an agent can not implement an
object, the management protocol provides for it to return an
exception or error, e.g, noSuchObject [4]. Under no circumstances
shall an agent return a value for objects which it does not implement
-- it must always return the appropriate exception or error, as
described in the protocol specification [4].
Note that the OBJECT-GROUP macro itself provides no conformance
information. Rather, conformance information is specified through
the inclusion of defined groups in a MODULE-COMPLIANCE macro.
3.1. Mapping of the OBJECTS clause
The OBJECTS clause, which must be present, is used to specify each
object contained in the conformance group. Each of the specified
objects must be defined in the same information module as the
OBJECT-GROUP macro appears, and must have a MAX-ACCESS clause value
of "accessible-for-notify", "read-only", "read-write", or "read-
create".
It is required that every object defined in an information module
with a MAX-ACCESS clause other than "not-accessible" be contained in
at least one object group. This avoids the common error of adding a
new object to an information module and forgetting to add the new
object to a group.
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3.2. Mapping of the STATUS clause
The STATUS clause, which must be present, indicates whether this
definition is current or historic.
The value "current" means that the definition is current and valid.
The value "obsolete" means the definition is obsolete and the group
should no longer be used for defining conformance. While the value
"deprecated" also indicates an obsolete definition, it permits
new/continued use of conformance definitions using this group.
3.3. Mapping of the DESCRIPTION clause
The DESCRIPTION clause, which must be present, contains a textual
definition of that group, along with a description of any relations
to other groups. Note that generic compliance requirements should
not be stated in this clause. However, implementation relationships
between this group and other groups may be defined in this clause.
3.4. Mapping of the REFERENCE clause
The REFERENCE clause, which need not be present, contains a textual
cross-reference to some other document, either another information
module which defines a related assignment, or some other document
which provides additional information relevant to this definition.
3.5. Mapping of the OBJECT-GROUP value
The value of an invocation of the OBJECT-GROUP macro is the name of
the group, which is an OBJECT IDENTIFIER, an administratively
assigned name.
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3.6. Usage Example
The SNMP Group [3] is described:
snmpGroup OBJECT-GROUP
OBJECTS { snmpInPkts,
snmpInBadVersions,
snmpInASNParseErrs,
snmpBadOperations,
snmpSilentDrops,
snmpProxyDrops,
snmpEnableAuthenTraps }
STATUS current
DESCRIPTION
"A collection of objects providing basic instrumentation
and control of an agent."
::= { snmpMIBGroups 8 }
According to this invocation, the conformance group named
{ snmpMIBGroups 8 }
contains 7 objects.
4. Mapping of the NOTIFICATION-GROUP macro
For conformance purposes, it is useful to define a collection of
notifications. The NOTIFICATION-GROUP macro serves this purpose. It
should be noted that the expansion of the NOTIFICATION-GROUP macro is
something which conceptually happens during implementation and not
during run-time.
4.1. Mapping of the NOTIFICATIONS clause
The NOTIFICATIONS clause, which must be present, is used to specify
each notification contained in the conformance group. Each of the
specified notifications must be defined in the same information
module as the NOTIFICATION-GROUP macro appears.
It is required that every notification defined in an information
module be contained in at least one notification group.
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4.2. Mapping of the STATUS clause
The STATUS clause, which must be present, indicates whether this
definition is current or historic.
The value "current" means that the definition is current and valid.
The value "obsolete" means the definition is obsolete and this group
should no longer be used for defining conformance. While the value
"deprecated" also indicates an obsolete definition, it permits
new/continued use of conformance definitions using this group.
4.3. Mapping of the DESCRIPTION clause
The DESCRIPTION clause, which must be present, contains a textual
definition of the group, along with a description of any relations to
other groups. Note that generic compliance requirements should not
be stated in this clause. However, implementation relationships
between this group and other groups may be defined in this clause.
4.4. Mapping of the REFERENCE clause
The REFERENCE clause, which need not be present, contains a textual
cross-reference to some other document, either another information
module which defines a related assignment, or some other document
which provides additional information relevant to this definition.
4.5. Mapping of the NOTIFICATION-GROUP value
The value of an invocation of the NOTIFICATION-GROUP macro is the
name of the group, which is an OBJECT IDENTIFIER, an administratively
assigned name.
4.6. Usage Example
The SNMP Basic Notifications Group [3] is described:
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snmpBasicNotificationsGroup NOTIFICATION-GROUP
NOTIFICATIONS { coldStart, authenticationFailure }
STATUS current
DESCRIPTION
"The two notifications which an agent is required to
implement."
::= { snmpMIBGroups 7 }
According to this invocation, the conformance group named
{ snmpMIBGroups 7 }
contains 2 notifications.
5. Mapping of the MODULE-COMPLIANCE macro
The MODULE-COMPLIANCE macro is used to convey a minimum set of
requirements with respect to implementation of one or more MIB
modules. It should be noted that the expansion of the MODULE-
COMPLIANCE macro is something which conceptually happens during
implementation and not during run-time.
A requirement on all "standard" MIB modules is that a corresponding
MODULE-COMPLIANCE specification is also defined, either in the same
information module or in a companion information module.
5.1. Mapping of the STATUS clause
The STATUS clause, which must be present, indicates whether this
definition is current or historic.
The value "current" means that the definition is current and valid.
The value "obsolete" means the definition is obsolete, and this
MODULE-COMPLIANCE specification no longer specifies a valid
definition of conformance. While the value "deprecated" also
indicates an obsolete definition, it permits new/continued use of the
MODULE-COMPLIANCE specification.
5.2. Mapping of the DESCRIPTION clause
The DESCRIPTION clause, which must be present, contains a textual
definition of this compliance statement and should embody any
information which would otherwise be communicated in any ASN.1
commentary annotations associated with the statement.
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5.3. Mapping of the REFERENCE clause
The REFERENCE clause, which need not be present, contains a textual
cross-reference to some other document, either another information
module which defines a related assignment, or some other document
which provides additional information relevant to this definition.
5.4. Mapping of the MODULE clause
The MODULE clause, which must be present, is repeatedly used to name
each MIB module for which compliance requirements are being
specified. Each MIB module is named by its module name, and
optionally, by its associated OBJECT IDENTIFIER as well. The module
name can be omitted when the MODULE-COMPLIANCE invocation occurs
inside a MIB module, to refer to the encompassing MIB module.
5.4.1. Mapping of the MANDATORY-GROUPS clause
The MANDATORY-GROUPS clause, which need not be present, names the one
or more object or notification groups within the correspondent MIB
module which are unconditionally mandatory for implementation. If an
agent claims compliance to the MIB module, then it must implement
each and every object and notification within each conformance group
listed. That is, if an agent returns a noSuchObject exception in
response to a management protocol get operation [4] for any object
within any mandatory conformance group for every possible MIB view,
or if the agent cannot generate each notification listed in any
conformance group under the appropriate circumstances, then that
agent is not a conformant implementation of the MIB module.
5.4.2. Mapping of the GROUP clause
The GROUP clause, which need not be present, is repeatedly used to
name each object and notification group which is conditionally
mandatory for compliance to the MIB module. The GROUP clause can
also be used to name unconditionally optional groups. A group named
in a GROUP clause must be absent from the correspondent MANDATORY-
GROUPS clause.
Conditionally mandatory groups include those which are mandatory only
if a particular protocol is implemented, or only if another group is
implemented. A GROUP clause's DESCRIPTION specifies the conditions
under which the group is conditionally mandatory.
A group which is named in neither a MANDATORY-GROUPS clause nor a
GROUP clause, is unconditionally optional for compliance to the MIB
module.
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5.4.3. Mapping of the OBJECT clause
The OBJECT clause, which need not be present, is repeatedly used to
specify each MIB object for which compliance has a refined
requirement with respect to the MIB module definition. The MIB
object must be present in one of the conformance groups named in the
correspondent MANDATORY-GROUPS clause or GROUP clauses.
By definition, each object specified in an OBJECT clause follows a
MODULE clause which names the information module in which that object
is defined. Therefore, the use of an IMPORTS statement, to specify
from where such objects are imported, is redundant and is not
required in an information module.
5.4.3.1. Mapping of the SYNTAX clause
The SYNTAX clause, which need not be present, is used to provide a
refined SYNTAX for the object named in the correspondent OBJECT
clause. Note that if this clause and a WRITE-SYNTAX clause are both
present, then this clause only applies when instances of the object
named in the correspondent OBJECT clause are read.
Consult Section 9 of [2] for more information on refined syntax.
5.4.3.2. Mapping of the WRITE-SYNTAX clause
The WRITE-SYNTAX clause, which need not be present, is used to
provide a refined SYNTAX for the object named in the correspondent
OBJECT clause when instances of that object are written.
Consult Section 9 of [2] for more information on refined syntax.
5.4.3.3. Mapping of the MIN-ACCESS clause
The MIN-ACCESS clause, which need not be present, is used to define
the minimal level of access for the object named in the correspondent
OBJECT clause. If this clause is absent, the minimal level of access
is the same as the maximal level specified in the correspondent
invocation of the OBJECT-TYPE macro. If present, this clause must
not specify a greater level of access than is specified in the
correspondent invocation of the OBJECT-TYPE macro.
The level of access for certain types of objects is fixed according
to their syntax definition. These types include: conceptual tables
and rows, auxiliary objects, and objects with the syntax of
Counter32, Counter64 (and possibly, certain types of textual
conventions). A MIN-ACCESS clause should not be present for such
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objects.
An implementation is compliant if the level of access it provides is
greater or equal to the minimal level in the MODULE-COMPLIANCE macro
and less or equal to the maximal level in the OBJECT-TYPE macro.
5.4.4. Mapping of the DESCRIPTION clause
The DESCRIPTION clause must be present for each use of the GROUP or
OBJECT clause. For an OBJECT clause, it contains a textual
description of the refined compliance requirement. For a GROUP
clause, it contains a textual description of the conditions under
which the group is conditionally mandatory or unconditionally
optional.
5.5. Mapping of the MODULE-COMPLIANCE value
The value of an invocation of the MODULE-COMPLIANCE macro is an
OBJECT IDENTIFIER. As such, this value may be authoritatively used
when referring to the compliance statement embodied by that
invocation of the macro.
5.6. Usage Example
The compliance statement contained in the (hypothetical) XYZv2-MIB
might be:
xyzMIBCompliance MODULE-COMPLIANCE
STATUS current
DESCRIPTION
"The compliance statement for XYZv2 entities which
implement the XYZv2 MIB."
MODULE -- compliance to the containing MIB module
MANDATORY-GROUPS { xyzSystemGroup,
xyzStatsGroup, xyzTrapGroup,
xyzSetGroup,
xyzBasicNotificationsGroup }
GROUP xyzV1Group
DESCRIPTION
"The xyzV1 group is mandatory only for those
XYZv2 entities which also implement XYZv1."
::= { xyzMIBCompliances 1 }
According to this invocation, to claim alignment with the compliance
statement named
{ xyzMIBCompliances 1 }
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a system must implement the XYZv2-MIB's xyzSystemGroup,
xyzStatsGroup, xyzTrapGroup, and xyzSetGroup object conformance
groups, as well as the xyzBasicNotificationsGroup notifications
group. Furthermore, if the XYZv2 entity also implements XYZv1, then
it must also support the XYZv1Group group, if compliance is to be
claimed.
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6. Mapping of the AGENT-CAPABILITIES macro
The AGENT-CAPABILITIES macro is used to convey a set of capabilities
present in an agent. It should be noted that the expansion of the
AGENT-CAPABILITIES macro is something which conceptually happens
during implementation and not during run-time.
When a MIB module is written, it is divided into units of conformance
termed groups. If an agent claims to implement a group, then it must
implement each and every object, or each and every notification,
within that group. Of course, for whatever reason, an agent might
implement only a subset of the groups within a MIB module. In
addition, the definition of some MIB objects/notifications leave some
aspects of the definition to the discretion of an implementor.
Practical experience has demonstrated a need for concisely describing
the capabilities of an agent with respect to one or more MIB modules.
The AGENT-CAPABILITIES macro allows an agent implementor to describe
the precise level of support which an agent claims in regards to a
MIB group, and to bind that description to the value of an instance
of sysORID [3]. In particular, some objects may have restricted or
augmented syntax or access-levels.
If the AGENT-CAPABILITIES invocation is given to a management-station
implementor, then that implementor can build management applications
which optimize themselves when communicating with a particular agent.
For example, the management-station can maintain a database of these
invocations. When a management-station interacts with an agent, it
retrieves from the agent the values of all instances of sysORID [3].
Based on this, it consults the database to locate each entry matching
one of the retrieved values of sysORID. Using the located entries,
the management application can now optimize its behavior accordingly.
Note that the AGENT-CAPABILITIES macro specifies refinements or
variations with respect to OBJECT-TYPE and NOTIFICATION-TYPE macros
in MIB modules, NOT with respect to MODULE-COMPLIANCE macros in
compliance statements.
6.1. Mapping of the PRODUCT-RELEASE clause
The PRODUCT-RELEASE clause, which must be present, contains a textual
description of the product release which includes this set of
capabilities.
6.2. Mapping of the STATUS clause
The STATUS clause, which must be present, indicates whether this
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definition is current or historic.
The value "current" means that the definition is current and valid.
The value "obsolete" means the definition is obsolete and this
capabilities statement is no longer in use.
6.3. Mapping of the DESCRIPTION clause
The DESCRIPTION clause, which must be present, contains a textual
description of this set of capabilities.
6.4. Mapping of the REFERENCE clause
The REFERENCE clause, which need not be present, contains a textual
cross-reference to some other document, either another information
module which defines a related assignment, or some other document
which provides additional information relevant to this definition.
6.5. Mapping of the SUPPORTS clause
The SUPPORTS clause, which need not be present, is repeatedly used to
name each MIB module for which the agent claims a complete or partial
implementation. Each MIB module is named by its module name, and
optionally, by its associated OBJECT IDENTIFIER (as registered by the
MODULE-IDENTITY macro, see [2]) as well.
6.5.1. Mapping of the INCLUDES clause
The INCLUDES clause, which must follow each and every use of the
SUPPORTS clause, is used to name each MIB group associated with the
SUPPORTS clause, which the agent claims to implement.
6.5.2. Mapping of the VARIATION clause
The VARIATION clause, which need not be present, is repeatedly used
to name each object or notification which the agent implements in
some variant or refined fashion with respect to the correspondent
invocation of the OBJECT-TYPE or NOTIFICATION-TYPE macro.
Note that the variation concept is meant for generic implementation
restrictions, e.g., if the variation for an object depends on the
values of other objects, then this should be noted in the appropriate
DESCRIPTION clause.
By definition, each object specified in a VARIATION clause follows a
SUPPORTS clause which names the information module in which that
object is defined. Therefore, the use of an IMPORTS statement, to
specify from where such objects are imported, is redundant and is not
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required in an information module.
6.5.2.1. Mapping of the SYNTAX clause
The SYNTAX clause, which need not be present, is used to provide a
refined SYNTAX for the object named in the correspondent VARIATION
clause. Note that if this clause and a WRITE-SYNTAX clause are both
present, then this clause only applies when instances of the object
named in the correspondent VARIATION clause are read.
Consult Section 9 of [2] for more information on refined syntax.
Note that for enumerated INTEGERs and for the BITS construct, the
changes allowed when updating a MIB module include the addition of
enumerations and/or changing the labels of existing enumerations (see
Section 10.2 of [2]). This type of change can cause problems for an
AGENT-CAPABILITIES macro written against the old revision of a MIB
module. One way to avoid such problems is to explicitly list all
objects having an enumerated syntax in a VARIATION clause, even when
all enumerations are currently supported.
6.5.2.2. Mapping of the WRITE-SYNTAX clause
The WRITE-SYNTAX clause, which need not be present, is used to
provide a refined SYNTAX for the object named in the correspondent
VARIATION clause when instances of that object are written.
Consult Section 9 of [2] for more information on refined syntax.
6.5.2.3. Mapping of the ACCESS clause
The ACCESS clause, which need not be present, is used to indicate the
agent provides less than the maximal level of access to the object or
notification named in the correspondent VARIATION clause.
The only value applicable to notifications is "not-implemented".
The value "not-implemented" indicates the agent does not implement
the object or notification, and in the ordering of possible values is
equivalent to "not-accessible".
The value "write-only" is provided solely for backward compatibility,
and shall not be used for newly-defined object types. In the
ordering of possible values, "write-only" is less than "not-
accessible".
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6.5.2.4. Mapping of the CREATION-REQUIRES clause
The CREATION-REQUIRES clause, which need not be present, is used to
name the columnar objects of a conceptual row to which values must be
explicitly assigned, by a management protocol set operation, before
the agent will allow the instance of the status column of that row to
be set to `active'. (Consult the definition of RowStatus [5].)
If the conceptual row does not have a status column (i.e., the
objects corresponding to the conceptual table were defined using the
mechanisms in [6,7]), then the CREATION-REQUIRES clause, which need
not be present, is used to name the columnar objects of a conceptual
row to which values must be explicitly assigned, by a management
protocol set operation, before the agent will create new instances of
objects in that row.
This clause must not be present unless the object named in the
correspondent VARIATION clause is a conceptual row, i.e., has a
syntax which resolves to a SEQUENCE containing columnar objects. The
objects named in the value of this clause usually will refer to
columnar objects in that row. However, objects unrelated to the
conceptual row may also be specified.
All objects which are named in the CREATION-REQUIRES clause for a
conceptual row, and which are columnar objects of that row, must have
an access level of "read-create".
6.5.2.5. Mapping of the DEFVAL clause
The DEFVAL clause, which need not be present, is used to provide a
alternate DEFVAL value for the object named in the correspondent
VARIATION clause. The semantics of this value are identical to those
of the OBJECT-TYPE macro's DEFVAL clause.
6.5.2.6. Mapping of the DESCRIPTION clause
The DESCRIPTION clause, which must be present for each use of the
VARIATION clause, contains a textual description of the variant or
refined implementation of the object or notification.
6.6. Mapping of the AGENT-CAPABILITIES value
The value of an invocation of the AGENT-CAPABILITIES macro is an
OBJECT IDENTIFIER, which names the value of sysORID [3] for which
this capabilities statement is valid.
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6.7. Usage Example
Consider how a capabilities statement for an agent might be
described:
exampleAgent AGENT-CAPABILITIES
PRODUCT-RELEASE "ACME Agent release 1.1 for 4BSD."
STATUS current
DESCRIPTION "ACME agent for 4BSD."
SUPPORTS SNMPv2-MIB
INCLUDES { systemGroup, snmpGroup, snmpSetGroup,
snmpBasicNotificationsGroup }
VARIATION coldStart
DESCRIPTION "A coldStart trap is generated on all
reboots."
SUPPORTS IF-MIB
INCLUDES { ifGeneralGroup, ifPacketGroup }
VARIATION ifAdminStatus
SYNTAX INTEGER { up(1), down(2) }
DESCRIPTION "Unable to set test mode on 4BSD."
VARIATION ifOperStatus
SYNTAX INTEGER { up(1), down(2) }
DESCRIPTION "Information limited on 4BSD."
SUPPORTS IP-MIB
INCLUDES { ipGroup, icmpGroup }
VARIATION ipDefaultTTL
SYNTAX INTEGER (255..255)
DESCRIPTION "Hard-wired on 4BSD."
VARIATION ipInAddrErrors
ACCESS not-implemented
DESCRIPTION "Information not available on 4BSD."
VARIATION ipNetToMediaEntry
CREATION-REQUIRES { ipNetToMediaPhysAddress }
DESCRIPTION "Address mappings on 4BSD require
both protocol and media addresses."
SUPPORTS TCP-MIB
INCLUDES { tcpGroup }
VARIATION tcpConnState
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ACCESS read-only
DESCRIPTION "Unable to set this on 4BSD."
SUPPORTS UDP-MIB
INCLUDES { udpGroup }
SUPPORTS EVAL-MIB
INCLUDES { functionsGroup, expressionsGroup }
VARIATION exprEntry
CREATION-REQUIRES { evalString, evalStatus }
DESCRIPTION "Conceptual row creation is supported."
::= { acmeAgents 1 }
According to this invocation, an agent with a sysORID value of
{ acmeAgents 1 }
supports objects defined in six MIB modules.
From SNMPv2-MIB, five conformance groups are supported.
From IF-MIB, the ifGeneralGroup and ifPacketGroup groups are
supported. However, the objects ifAdminStatus and ifOperStatus have
a restricted syntax.
From IP-MIB, all objects in the ipGroup and icmpGroup are supported
except ipInAddrErrors, while ipDefaultTTL has a restricted range, and
when creating a new instance in the ipNetToMediaTable, the set-
request must create an instance of ipNetToMediaPhysAddress.
From TCP-MIB, the tcpGroup is supported except that tcpConnState is
available only for reading.
From UDP-MIB, the udpGroup is fully supported.
From the EVAL-MIB, all the objects contained in the functionsGroup
and expressionsGroup conformance groups are supported, without
variation. In addition, creation of new instances in the expr table
is supported, and requires both of the objects: evalString and
evalStatus, to be assigned a value.
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7. Extending an Information Module
As experience is gained with a published information module, it may
be desirable to revise that information module.
Section 10 of [2] defines the rules for extending an information
module. The remainder of this section defines how conformance
groups, compliance statements, and capabilities statements may be
extended.
7.1. Conformance Groups
It may be desirable to revise the definition of a conformance group
(an OBJECT-GROUP or a NOTIFICATION-GROUP) after experience is gained
with it. However, conformance groups can be referenced by compliance
and/or capabilities definitions. Therefore, a change to a
conformance group is not allowed if it has the potential to cause a
reference to the group's original definition to be different from a
reference to the updated definition. Such changes can only be
accommodated by defining a new conformance group with a new
descriptor and a new OBJECT IDENTIFIER value.
The following revisions are allowed:
(1) A STATUS clause value of "current" may be revised as "deprecated"
or "obsolete". Similarly, a STATUS clause value of "deprecated"
may be revised as "obsolete". When making such a change, the
DESCRIPTION clause should be updated to explain the rationale.
(2) A REFERENCE clause may be added or updated.
(3) Clarifications and additional information may be included in the
DESCRIPTION clause.
(4) Any editorial change.
It is not necessary to change the STATUS value of a conformance group
when the status of a member of the group is changed.
7.2. Compliance Definitions
It may be desirable to revise the definition of a compliance
definition (MODULE-COMPLIANCE) after experience is gained with it.
However, changes are not allowed if they cause the requirements
specified by the original definition to be different from the
requirements of the updated definition. Such changes can only be
accommodated by defining a new compliance definition with a new
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descriptor and a new OBJECT IDENTIFIER value.
The following revisions are allowed:
(1) A STATUS clause value of "current" may be revised as "deprecated"
or "obsolete". Similarly, a STATUS clause value of "deprecated"
may be revised as "obsolete". When making such a change, the
DESCRIPTION clause should be updated to explain the rationale.
(2) A REFERENCE clause may be added or updated.
(3) Clarifications and additional information may be included in the
DESCRIPTION clause(s).
(4) Any editorial change.
It is not necessary to change the STATUS value of a compliance
definition due to a change in the STATUS value of a definition it
references.
7.3. Capabilities Definitions
It may be desirable to revise the definition of a capabilities
definition (AGENT-CAPABILITIES) after experience is gained with it.
However, changes are not allowed if they cause the capabilities
specified by the original specification to be different from the
capabilities of the updated specification. Such changes can only be
accommodated by defining a new capabilities definition with a new
descriptor and a new OBJECT IDENTIFIER value.
The following revisions are allowed:
(1) A STATUS clause value of "current" may be revised as "obsolete".
When making such a change, the DESCRIPTION clause should be updated
to explain the rationale.
(2) A REFERENCE clause may be added or updated.
(3) Clarifications and additional information may be included in the
DESCRIPTION clause(s).
(4) Any editorial change.
It is not necessary to change the STATUS value of a capabilities
definition due to a change in the STATUS value of a definition it
references.
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8. Security Considerations
This document defines the means to define conformance requirements
for implementing on documents describing management information.
This method of defining conformance requirements has no security
impact on the Internet.
9. Editors' Addresses
Keith McCloghrie
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
USA
Phone: +1 408 526 5260
EMail: kzm@cisco.com
David Perkins
SNMPinfo
3763 Benton Street
Santa Clara, CA 95051
USA
Phone: +1 408 221-8702
Email: dperkins@snmpinfo.com
Juergen Schoenwaelder
TU Braunschweig
Bueltenweg 74/75
38106 Braunschweig
Germany
Phone: +49 531 391-3283
EMail: schoenw@ibr.cs.tu-bs.de
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10. References
[1] Information processing systems - Open Systems Interconnection -
Specification of Abstract Syntax Notation One (ASN.1),
International Organization for Standardization. International
Standard 8824, (December, 1987).
[2] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M.
and S. Waldbusser, "Structure of Management Information Version 2
(SMIv2)", STD 58, RFC 2578, April 1999.
[3] The SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M. and
S. Waldbusser, "Management Information Base for Version 2 of the
Simple Network Management Protocol (SNMPv2)", RFC 1907, January
1996.
[4] The SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M. and
S. Waldbusser, "Protocol Operations for Version 2 of the Simple
Network Management Protocol (SNMPv2)", RFC 1905, January 1996.
[5] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M.
and S. Waldbusser, "Textual Conventions for SMIv2", STD 58,
RFC 2579, April 1999.
[6] Rose, M. and K. McCloghrie, "Structure and Identification of
Management Information for TCP/IP-based internets", STD 16, RFC
1155, May 1990.
[7] Rose, M. and K. McCloghrie, "Concise MIB Definitions", STD 16, RFC
1212, March 1991.
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11. Full Copyright Statement
Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."
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