Network Working Group Editors of this version:
Request for Comments: 2578 K. McCloghrie
STD: 58 Cisco Systems
Obsoletes: 1902 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
Structure of Management Information Version 2 (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 ......................................4
2 Definitions ..................................................4
2.1 The MODULE-IDENTITY macro ..................................5
2.2 Object Names and Syntaxes ..................................5
2.3 The OBJECT-TYPE macro ......................................8
2.5 The NOTIFICATION-TYPE macro ...............................10
2.6 Administrative Identifiers ................................11
3 Information Modules .........................................11
3.1 Macro Invocation ..........................................12
3.1.1 Textual Values and Strings ..............................13
McCloghrie, et al. Standards Track [Page 1]
RFC 2578 SMIv2 April 1999
3.2 IMPORTing Symbols .........................................14
3.3 Exporting Symbols .........................................14
3.4 ASN.1 Comments ............................................14
3.5 OBJECT IDENTIFIER values ..................................15
3.6 OBJECT IDENTIFIER usage ...................................15
3.7 Reserved Keywords .........................................16
4 Naming Hierarchy ............................................16
5 Mapping of the MODULE-IDENTITY macro ........................17
5.1 Mapping of the LAST-UPDATED clause ........................17
5.2 Mapping of the ORGANIZATION clause ........................17
5.3 Mapping of the CONTACT-INFO clause ........................18
5.4 Mapping of the DESCRIPTION clause .........................18
5.5 Mapping of the REVISION clause ............................18
5.5.1 Mapping of the DESCRIPTION sub-clause ...................18
5.6 Mapping of the MODULE-IDENTITY value ......................18
5.7 Usage Example .............................................18
6 Mapping of the OBJECT-IDENTITY macro ........................19
6.1 Mapping of the STATUS clause ..............................19
6.2 Mapping of the DESCRIPTION clause .........................20
6.3 Mapping of the REFERENCE clause ...........................20
6.4 Mapping of the OBJECT-IDENTITY value ......................20
6.5 Usage Example .............................................20
7 Mapping of the OBJECT-TYPE macro ............................20
7.1 Mapping of the SYNTAX clause ..............................21
7.1.1 Integer32 and INTEGER ...................................21
7.1.2 OCTET STRING ............................................21
7.1.3 OBJECT IDENTIFIER .......................................22
7.1.4 The BITS construct ......................................22
7.1.5 IpAddress ...............................................22
7.1.6 Counter32 ...............................................23
7.1.7 Gauge32 .................................................23
7.1.8 TimeTicks ...............................................24
7.1.9 Opaque ..................................................24
7.1.10 Counter64 ..............................................24
7.1.11 Unsigned32 .............................................25
7.1.12 Conceptual Tables ......................................25
7.1.12.1 Creation and Deletion of Conceptual Rows .............26
7.2 Mapping of the UNITS clause ...............................26
7.3 Mapping of the MAX-ACCESS clause ..........................26
7.4 Mapping of the STATUS clause ..............................27
7.5 Mapping of the DESCRIPTION clause .........................27
7.6 Mapping of the REFERENCE clause ...........................27
7.7 Mapping of the INDEX clause ...............................27
7.8 Mapping of the AUGMENTS clause ............................29
7.8.1 Relation between INDEX and AUGMENTS clauses .............30
7.9 Mapping of the DEFVAL clause ..............................30
7.10 Mapping of the OBJECT-TYPE value .........................31
7.11 Usage Example ............................................32
McCloghrie, et al. Standards Track [Page 2]
RFC 2578 SMIv2 April 1999
8 Mapping of the NOTIFICATION-TYPE macro ......................34
8.1 Mapping of the OBJECTS clause .............................34
8.2 Mapping of the STATUS clause ..............................34
8.3 Mapping of the DESCRIPTION clause .........................35
8.4 Mapping of the REFERENCE clause ...........................35
8.5 Mapping of the NOTIFICATION-TYPE value ....................35
8.6 Usage Example .............................................35
9 Refined Syntax ..............................................36
10 Extending an Information Module ............................37
10.1 Object Assignments .......................................37
10.2 Object Definitions .......................................38
10.3 Notification Definitions .................................39
11 Appendix A: Detailed Sub-typing Rules ......................40
11.1 Syntax Rules .............................................40
11.2 Examples .................................................41
12 Security Considerations ....................................41
13 Editors' Addresses .........................................41
14 References .................................................42
15 Full Copyright Statement ...................................43
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]. It is the
purpose of this document, the Structure of Management Information
(SMI), to define that adapted subset, and to assign a set of
associated administrative values.
The SMI is divided into three parts: module definitions, object
definitions, and, notification definitions.
(1) Module definitions are used when describing information modules.
An ASN.1 macro, MODULE-IDENTITY, is used to concisely convey the
semantics of an information module.
(2) Object definitions are used when describing managed objects. An
ASN.1 macro, OBJECT-TYPE, is used to concisely convey the syntax
and semantics of a managed object.
(3) Notification definitions are used when describing unsolicited
transmissions of management information. An ASN.1 macro,
NOTIFICATION-TYPE, is used to concisely convey the syntax and
semantics of a notification.
McCloghrie, et al. Standards Track [Page 3]
RFC 2578 SMIv2 April 1999
1.1. A Note on Terminology
For the purpose of exposition, the original Structure of Management
Information, as described in RFCs 1155 (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-SMI DEFINITIONS ::= BEGIN
-- the path to the root
org OBJECT IDENTIFIER ::= { iso 3 } -- "iso" = 1
dod OBJECT IDENTIFIER ::= { org 6 }
internet OBJECT IDENTIFIER ::= { dod 1 }
directory OBJECT IDENTIFIER ::= { internet 1 }
mgmt OBJECT IDENTIFIER ::= { internet 2 }
mib-2 OBJECT IDENTIFIER ::= { mgmt 1 }
transmission OBJECT IDENTIFIER ::= { mib-2 10 }
experimental OBJECT IDENTIFIER ::= { internet 3 }
private OBJECT IDENTIFIER ::= { internet 4 }
enterprises OBJECT IDENTIFIER ::= { private 1 }
security OBJECT IDENTIFIER ::= { internet 5 }
snmpV2 OBJECT IDENTIFIER ::= { internet 6 }
-- transport domains
snmpDomains OBJECT IDENTIFIER ::= { snmpV2 1 }
-- transport proxies
snmpProxys OBJECT IDENTIFIER ::= { snmpV2 2 }
-- module identities
snmpModules OBJECT IDENTIFIER ::= { snmpV2 3 }
-- Extended UTCTime, to allow dates with four-digit years
-- (Note that this definition of ExtUTCTime is not to be IMPORTed
-- by MIB modules.)
ExtUTCTime ::= OCTET STRING(SIZE(11 | 13))
-- format is YYMMDDHHMMZ or YYYYMMDDHHMMZ
McCloghrie, et al. Standards Track [Page 4]
RFC 2578 SMIv2 April 1999
-- where: YY - last two digits of year (only years
-- between 1900-1999)
-- YYYY - last four digits of the year (any year)
-- MM - month (01 through 12)
-- DD - day of month (01 through 31)
-- HH - hours (00 through 23)
-- MM - minutes (00 through 59)
-- Z - denotes GMT (the ASCII character Z)
--
-- For example, "9502192015Z" and "199502192015Z" represent
-- 8:15pm GMT on 19 February 1995. Years after 1999 must use
-- the four digit year format. Years 1900-1999 may use the
-- two or four digit format.
-- definitions for information modules
MODULE-IDENTITY MACRO ::=
BEGIN
TYPE NOTATION ::=
"LAST-UPDATED" value(Update ExtUTCTime)
"ORGANIZATION" Text
"CONTACT-INFO" Text
"DESCRIPTION" Text
RevisionPart
VALUE NOTATION ::=
value(VALUE OBJECT IDENTIFIER)
RevisionPart ::=
Revisions
| empty
Revisions ::=
Revision
| Revisions Revision
Revision ::=
"REVISION" value(Update ExtUTCTime)
"DESCRIPTION" Text
-- a character string as defined in section 3.1.1
Text ::= value(IA5String)
END
OBJECT-IDENTITY MACRO ::=
BEGIN
TYPE NOTATION ::=
"STATUS" Status
"DESCRIPTION" Text
McCloghrie, et al. Standards Track [Page 5]
RFC 2578 SMIv2 April 1999
ReferPart
VALUE NOTATION ::=
value(VALUE OBJECT IDENTIFIER)
Status ::=
"current"
| "deprecated"
| "obsolete"
ReferPart ::=
"REFERENCE" Text
| empty
-- a character string as defined in section 3.1.1
Text ::= value(IA5String)
END
-- names of objects
-- (Note that these definitions of ObjectName and NotificationName
-- are not to be IMPORTed by MIB modules.)
ObjectName ::=
OBJECT IDENTIFIER
NotificationName ::=
OBJECT IDENTIFIER
-- syntax of objects
-- the "base types" defined here are:
-- 3 built-in ASN.1 types: INTEGER, OCTET STRING, OBJECT IDENTIFIER
-- 8 application-defined types: Integer32, IpAddress, Counter32,
-- Gauge32, Unsigned32, TimeTicks, Opaque, and Counter64
ObjectSyntax ::=
CHOICE {
simple
SimpleSyntax,
-- note that SEQUENCEs for conceptual tables and
-- rows are not mentioned here...
application-wide
ApplicationSyntax
}
McCloghrie, et al. Standards Track [Page 6]
RFC 2578 SMIv2 April 1999
-- built-in ASN.1 types
SimpleSyntax ::=
CHOICE {
-- INTEGERs with a more restrictive range
-- may also be used
integer-value -- includes Integer32
INTEGER (-2147483648..2147483647),
-- OCTET STRINGs with a more restrictive size
-- may also be used
string-value
OCTET STRING (SIZE (0..65535)),
objectID-value
OBJECT IDENTIFIER
}
-- indistinguishable from INTEGER, but never needs more than
-- 32-bits for a two's complement representation
Integer32 ::=
INTEGER (-2147483648..2147483647)
-- application-wide types
ApplicationSyntax ::=
CHOICE {
ipAddress-value
IpAddress,
counter-value
Counter32,
timeticks-value
TimeTicks,
arbitrary-value
Opaque,
big-counter-value
Counter64,
unsigned-integer-value -- includes Gauge32
Unsigned32
}
-- in network-byte order
McCloghrie, et al. Standards Track [Page 7]
RFC 2578 SMIv2 April 1999
-- (this is a tagged type for historical reasons)
IpAddress ::=
[APPLICATION 0]
IMPLICIT OCTET STRING (SIZE (4))
-- this wraps
Counter32 ::=
[APPLICATION 1]
IMPLICIT INTEGER (0..4294967295)
-- this doesn't wrap
Gauge32 ::=
[APPLICATION 2]
IMPLICIT INTEGER (0..4294967295)
-- an unsigned 32-bit quantity
-- indistinguishable from Gauge32
Unsigned32 ::=
[APPLICATION 2]
IMPLICIT INTEGER (0..4294967295)
-- hundredths of seconds since an epoch
TimeTicks ::=
[APPLICATION 3]
IMPLICIT INTEGER (0..4294967295)
-- for backward-compatibility only
Opaque ::=
[APPLICATION 4]
IMPLICIT OCTET STRING
-- for counters that wrap in less than one hour with only 32 bits
Counter64 ::=
[APPLICATION 6]
IMPLICIT INTEGER (0..18446744073709551615)
-- definition for objects
OBJECT-TYPE MACRO ::=
BEGIN
TYPE NOTATION ::=
"SYNTAX" Syntax
UnitsPart
"MAX-ACCESS" Access
"STATUS" Status
"DESCRIPTION" Text
ReferPart
McCloghrie, et al. Standards Track [Page 8]
RFC 2578 SMIv2 April 1999
IndexPart
DefValPart
VALUE NOTATION ::=
value(VALUE ObjectName)
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
UnitsPart ::=
"UNITS" Text
| empty
Access ::=
"not-accessible"
| "accessible-for-notify"
| "read-only"
| "read-write"
| "read-create"
Status ::=
"current"
| "deprecated"
| "obsolete"
ReferPart ::=
"REFERENCE" Text
| empty
IndexPart ::=
"INDEX" "{" IndexTypes "}"
| "AUGMENTS" "{" Entry "}"
| empty
IndexTypes ::=
IndexType
| IndexTypes "," IndexType
IndexType ::=
"IMPLIED" Index
| Index
McCloghrie, et al. Standards Track [Page 9]
RFC 2578 SMIv2 April 1999
Index ::=
-- use the SYNTAX value of the
-- correspondent OBJECT-TYPE invocation
value(ObjectName)
Entry ::=
-- use the INDEX value of the
-- correspondent OBJECT-TYPE invocation
value(ObjectName)
DefValPart ::= "DEFVAL" "{" Defvalue "}"
| empty
Defvalue ::= -- must be valid for the type specified in
-- SYNTAX clause of same OBJECT-TYPE macro
value(ObjectSyntax)
| "{" BitsValue "}"
BitsValue ::= BitNames
| empty
BitNames ::= BitName
| BitNames "," BitName
BitName ::= identifier
-- a character string as defined in section 3.1.1
Text ::= value(IA5String)
END
-- definitions for notifications
NOTIFICATION-TYPE MACRO ::=
BEGIN
TYPE NOTATION ::=
ObjectsPart
"STATUS" Status
"DESCRIPTION" Text
ReferPart
VALUE NOTATION ::=
value(VALUE NotificationName)
ObjectsPart ::=
"OBJECTS" "{" Objects "}"
| empty
Objects ::=
Object
McCloghrie, et al. Standards Track [Page 10]
RFC 2578 SMIv2 April 1999
| Objects "," Object
Object ::=
value(ObjectName)
Status ::=
"current"
| "deprecated"
| "obsolete"
ReferPart ::=
"REFERENCE" Text
| empty
-- a character string as defined in section 3.1.1
Text ::= value(IA5String)
END
-- definitions of administrative identifiers
zeroDotZero OBJECT-IDENTITY
STATUS current
DESCRIPTION
"A value used for null identifiers."
::= { 0 0 }
END
3. Information Modules
An "information module" is an ASN.1 module defining information
relating to network management.
The SMI describes how to use an adapted subset of ASN.1 (1988) to
define an information module. Further, additional restrictions are
placed on "standard" information modules. It is strongly recommended
that "enterprise-specific" information modules also adhere to these
restrictions.
Typically, there are three kinds of information modules:
(1) MIB modules, which contain definitions of inter-related managed
objects, make use of the OBJECT-TYPE and NOTIFICATION-TYPE macros;
(2) compliance statements for MIB modules, which make use of the
MODULE-COMPLIANCE and OBJECT-GROUP macros [2]; and,
(3) capability statements for agent implementations which make use of
the AGENT-CAPABILITIES macros [2].
McCloghrie, et al. Standards Track [Page 11]
RFC 2578 SMIv2 April 1999
This classification scheme does not imply a rigid taxonomy. For
example, a "standard" information module will normally include
definitions of managed objects and a compliance statement.
Similarly, an "enterprise-specific" information module might include
definitions of managed objects and a capability statement. Of
course, a "standard" information module may not contain capability
statements.
The constructs of ASN.1 allowed in SMIv2 information modules include:
the IMPORTS clause, value definitions for OBJECT IDENTIFIERs, type
definitions for SEQUENCEs (with restrictions), ASN.1 type assignments
of the restricted ASN.1 types allowed in SMIv2, and instances of
ASN.1 macros defined in this document and its companion documents [2,
3]. Additional ASN.1 macros must not be defined in SMIv2 information
modules. SMIv1 macros must not be used in SMIv2 information modules.
The names of all standard information modules must be unique (but
different versions of the same information module should have the
same name). Developers of enterprise information modules are
encouraged to choose names for their information modules that will
have a low probability of colliding with standard or other enterprise
information modules. An information module may not use the ASN.1
construct of placing an object identifier value between the module
name and the "DEFINITIONS" keyword. For the purposes of this
specification, an ASN.1 module name begins with an upper-case letter
and continues with zero or more letters, digits, or hyphens, except
that a hyphen can not be the last character, nor can there be two
consecutive hyphens.
All information modules start with exactly one invocation of the
MODULE-IDENTITY macro, which provides contact information as well as
revision history to distinguish between versions of the same
information module. This invocation must appear immediately after
any IMPORTs statements.
3.1. Macro Invocation
Within an information module, each macro invocation appears as:
<descriptor> <macro> <clauses> ::= <value>
where <descriptor> corresponds to an ASN.1 identifier, <macro> names
the macro being invoked, and <clauses> and <value> depend on the
definition of the macro. (Note that this definition of a descriptor
applies to all macros defined in this memo and in [2].)
McCloghrie, et al. Standards Track [Page 12]
RFC 2578 SMIv2 April 1999
For the purposes of this specification, an ASN.1 identifier consists
of one or more letters or digits, and its initial character must be a
lower-case letter. Note that hyphens are not allowed by this
specification (except for use by information modules converted from
SMIv1 which did allow hyphens).
For all descriptors appearing in an information module, the
descriptor shall be unique and mnemonic, and shall not exceed 64
characters in length. (However, descriptors longer than 32
characters are not recommended.) This promotes a common language for
humans to use when discussing the information module and also
facilitates simple table mappings for user-interfaces.
The set of descriptors defined in all "standard" information modules
shall be unique.
Finally, by convention, if the descriptor refers to an object with a
SYNTAX clause value of either Counter32 or Counter64, then the
descriptor used for the object should denote plurality.
3.1.1. Textual Values and Strings
Some clauses in a macro invocation may take a character string as a
textual value (e.g., the DESCRIPTION clause). Other clauses take
binary or hexadecimal strings (in any position where a non-negative
number is allowed).
A character string is preceded and followed by the quote character
("), and consists of an arbitrary number (possibly zero) of:
- any 7-bit displayable ASCII characters except quote ("),
- tab characters,
- spaces, and
- line terminator characters (\n or \r\n).
The value of a character string is interpreted as ASCII.
A binary string consists of a number (possibly zero) of zeros and
ones preceded by a single (') and followed by either the pair ('B) or
('b), where the number is a multiple of eight.
A hexadecimal string consists of an even number (possibly zero) of
hexadecimal digits, preceded by a single (') and followed by either
the pair ('H) or ('h). Digits specified via letters can be in upper
or lower case.
Note that ASN.1 comments can not be enclosed inside any of these
types of strings.
McCloghrie, et al. Standards Track [Page 13]
RFC 2578 SMIv2 April 1999
3.2. IMPORTing Symbols
To reference an external object, the IMPORTS statement must be used
to identify both the descriptor and the module in which the
descriptor is defined, where the module is identified by its ASN.1
module name.
Note that when symbols from "enterprise-specific" information modules
are referenced (e.g., a descriptor), there is the possibility of
collision. As such, if different objects with the same descriptor
are IMPORTed, then this ambiguity is resolved by prefixing the
descriptor with the name of the information module and a dot ("."),
i.e.,
"module.descriptor"
(All descriptors must be unique within any information module.)
Of course, this notation can be used to refer to objects even when
there is no collision when IMPORTing symbols.
Finally, if any of the ASN.1 named types and macros defined in this
document, specifically:
Counter32, Counter64, Gauge32, Integer32, IpAddress, MODULE-
IDENTITY, NOTIFICATION-TYPE, Opaque, OBJECT-TYPE, OBJECT-
IDENTITY, TimeTicks, Unsigned32,
or any of those defined in [2] or [3], are used in an information
module, then they must be imported using the IMPORTS statement.
However, the following must not be included in an IMPORTS statement:
- named types defined by ASN.1 itself, specifically: INTEGER,
OCTET STRING, OBJECT IDENTIFIER, SEQUENCE, SEQUENCE OF type,
- the BITS construct.
3.3. Exporting Symbols
The ASN.1 EXPORTS statement is not allowed in SMIv2 information
modules. All items defined in an information module are
automatically exported.
3.4. ASN.1 Comments
ASN.1 comments can be included in an information module. However, it
is recommended that all substantive descriptions be placed within an
appropriate DESCRIPTION clause.
McCloghrie, et al. Standards Track [Page 14]
RFC 2578 SMIv2 April 1999
ASN.1 comments commence with a pair of adjacent hyphens and end with
the next pair of adjacent hyphens or at the end of the line,
whichever occurs first. Comments ended by a pair of hyphens have the
effect of a single space character.
3.5. OBJECT IDENTIFIER values
An OBJECT IDENTIFIER value is an ordered list of non-negative
numbers. For the SMIv2, each number in the list is referred to as a
sub-identifier, there are at most 128 sub-identifiers in a value, and
each sub-identifier has a maximum value of 2^32-1 (4294967295
decimal).
All OBJECT IDENTIFIER values have at least two sub-identifiers, where
the value of the first sub-identifier is one of the following well-
known names:
Value Name
0 ccitt
1 iso
2 joint-iso-ccitt
(Note that this SMI does not recognize "new" well-known names, e.g.,
as defined when the CCITT became the ITU.)
3.6. OBJECT IDENTIFIER usage
OBJECT IDENTIFIERs are used in information modules in two ways:
(1) registration: the definition of a particular item is registered as
a particular OBJECT IDENTIFIER value, and associated with a
particular descriptor. After such a registration, the semantics
thereby associated with the value are not allowed to change, the
OBJECT IDENTIFIER can not be used for any other registration, and
the descriptor can not be changed nor associated with any other
registration. The following macros result in a registration:
OBJECT-TYPE, MODULE-IDENTITY, NOTIFICATION-TYPE, OBJECT-GROUP,
OBJECT-IDENTITY, NOTIFICATION-GROUP, MODULE-COMPLIANCE,
AGENT-CAPABILITIES.
(2) assignment: a descriptor can be assigned to a particular OBJECT
IDENTIFIER value. For this usage, the semantics associated with
the OBJECT IDENTIFIER value is not allowed to change, and a
descriptor assigned to a particular OBJECT IDENTIFIER value cannot
subsequently be assigned to another. However, multiple descriptors
can be assigned to the same OBJECT IDENTIFIER value. Such
assignments are specified in the following manner:
McCloghrie, et al. Standards Track [Page 15]
RFC 2578 SMIv2 April 1999
mib OBJECT IDENTIFIER ::= { mgmt 1 } -- from RFC1156
mib-2 OBJECT IDENTIFIER ::= { mgmt 1 } -- from RFC1213
fredRouter OBJECT IDENTIFIER ::= { flintStones 1 1 }
barneySwitch OBJECT IDENTIFIER ::= { flintStones bedrock(2) 1 }
Note while the above examples are legal, the following is not:
dinoHost OBJECT IDENTIFIER ::= { flintStones bedrock 2 }
A descriptor is allowed to be associated with both a registration and
an assignment, providing both are associated with the same OBJECT
IDENTIFIER value and semantics.
3.7. Reserved Keywords
The following are reserved keywords which must not be used as
descriptors or module names:
ABSENT ACCESS AGENT-CAPABILITIES ANY APPLICATION AUGMENTS BEGIN
BIT BITS BOOLEAN BY CHOICE COMPONENT COMPONENTS CONTACT-INFO
CREATION-REQUIRES Counter32 Counter64 DEFAULT DEFINED
DEFINITIONS DEFVAL DESCRIPTION DISPLAY-HINT END ENUMERATED
ENTERPRISE EXPLICIT EXPORTS EXTERNAL FALSE FROM GROUP Gauge32
IDENTIFIER IMPLICIT IMPLIED IMPORTS INCLUDES INDEX INTEGER
Integer32 IpAddress LAST-UPDATED MANDATORY-GROUPS MAX MAX-ACCESS
MIN MIN-ACCESS MINUS-INFINITY MODULE MODULE-COMPLIANCE MODULE-
IDENTITY NOTIFICATION-GROUP NOTIFICATION-TYPE NOTIFICATIONS NULL
OBJECT OBJECT-GROUP OBJECT-IDENTITY OBJECT-TYPE OBJECTS OCTET OF
OPTIONAL ORGANIZATION Opaque PLUS-INFINITY PRESENT PRIVATE
PRODUCT-RELEASE REAL REFERENCE REVISION SEQUENCE SET SIZE STATUS
STRING SUPPORTS SYNTAX TAGS TEXTUAL-CONVENTION TRAP-TYPE TRUE
TimeTicks UNITS UNIVERSAL Unsigned32 VARIABLES VARIATION WITH
WRITE-SYNTAX
4. Naming Hierarchy
The root of the subtree administered by the Internet Assigned Numbers
Authority (IANA) for the Internet is:
internet OBJECT IDENTIFIER ::= { iso 3 6 1 }
That is, the Internet subtree of OBJECT IDENTIFIERs starts with the
prefix:
1.3.6.1.
Several branches underneath this subtree are used for network
management:
McCloghrie, et al. Standards Track [Page 16]
RFC 2578 SMIv2 April 1999
mgmt OBJECT IDENTIFIER ::= { internet 2 }
experimental OBJECT IDENTIFIER ::= { internet 3 }
private OBJECT IDENTIFIER ::= { internet 4 }
enterprises OBJECT IDENTIFIER ::= { private 1 }
However, the SMI does not prohibit the definition of objects in other
portions of the object tree.
The mgmt(2) subtree is used to identify "standard" objects.
The experimental(3) subtree is used to identify objects being
designed by working groups of the IETF. If an information module
produced by a working group becomes a "standard" information module,
then at the very beginning of its entry onto the Internet standards
track, the objects are moved under the mgmt(2) subtree.
The private(4) subtree is used to identify objects defined
unilaterally. The enterprises(1) subtree beneath private is used,
among other things, to permit providers of networking subsystems to
register models of their products.
5. Mapping of the MODULE-IDENTITY macro
The MODULE-IDENTITY macro is used to provide contact and revision
history for each information module. It must appear exactly once in
every information module. It should be noted that the expansion of
the MODULE-IDENTITY macro is something which conceptually happens
during implementation and not during run-time.
Note that reference in an IMPORTS clause or in clauses of SMIv2
macros to an information module is NOT through the use of the
'descriptor' of a MODULE-IDENTITY macro; rather, an information
module is referenced through specifying its module name.
5.1. Mapping of the LAST-UPDATED clause
The LAST-UPDATED clause, which must be present, contains the date and
time that this information module was last edited.
5.2. Mapping of the ORGANIZATION clause
The ORGANIZATION clause, which must be present, contains a textual
description of the organization under whose auspices this information
module was developed.
McCloghrie, et al. Standards Track [Page 17]
RFC 2578 SMIv2 April 1999
5.3. Mapping of the CONTACT-INFO clause
The CONTACT-INFO clause, which must be present, contains the name,
postal address, telephone number, and electronic mail address of the
person to whom technical queries concerning this information module
should be sent.
5.4. Mapping of the DESCRIPTION clause
The DESCRIPTION clause, which must be present, contains a high-level
textual description of the contents of this information module.
5.5. Mapping of the REVISION clause
The REVISION clause, which need not be present, is repeatedly used to
describe the revisions (including the initial version) made to this
information module, in reverse chronological order (i.e., most recent
first). Each instance of this clause contains the date and time of
the revision.
5.5.1. Mapping of the DESCRIPTION sub-clause
The DESCRIPTION sub-clause, which must be present for each REVISION
clause, contains a high-level textual description of the revision
identified in that REVISION clause.
5.6. Mapping of the MODULE-IDENTITY value
The value of an invocation of the MODULE-IDENTITY macro is an OBJECT
IDENTIFIER. As such, this value may be authoritatively used when
specifying an OBJECT IDENTIFIER value to refer to the information
module containing the invocation.
Note that it is a common practice to use the value of the MODULE-
IDENTITY macro as a subtree under which other OBJECT IDENTIFIER
values assigned within the module are defined. However, it is legal
(and occasionally necessary) for the other OBJECT IDENTIFIER values
assigned within the module to be unrelated to the OBJECT IDENTIFIER
value of the MODULE-IDENTITY macro.
5.7. Usage Example
Consider how a skeletal MIB module might be constructed: e.g.,
FIZBIN-MIB DEFINITIONS ::= BEGIN
IMPORTS
MODULE-IDENTITY, OBJECT-TYPE, experimental
McCloghrie, et al. Standards Track [Page 18]
RFC 2578 SMIv2 April 1999
FROM SNMPv2-SMI;
fizbin MODULE-IDENTITY
LAST-UPDATED "199505241811Z"
ORGANIZATION "IETF SNMPv2 Working Group"
CONTACT-INFO
" Marshall T. Rose
Postal: Dover Beach Consulting, Inc.
420 Whisman Court
Mountain View, CA 94043-2186
US
Tel: +1 415 968 1052
Fax: +1 415 968 2510
E-mail:
[email protected]"
DESCRIPTION
"The MIB module for entities implementing the xxxx
protocol."
REVISION "9505241811Z"
DESCRIPTION
"The latest version of this MIB module."
REVISION "9210070433Z"
DESCRIPTION
"The initial version of this MIB module, published in
RFC yyyy."
-- contact IANA for actual number
::= { experimental xx }
END
6. Mapping of the OBJECT-IDENTITY macro
The OBJECT-IDENTITY macro is used to define information about an
OBJECT IDENTIFIER assignment. All administrative OBJECT IDENTIFIER
assignments which define a type identification value (see
AutonomousType, a textual convention defined in [3]) should be
defined via the OBJECT-IDENTITY macro. It should be noted that the
expansion of the OBJECT-IDENTITY macro is something which
conceptually happens during implementation and not during run-time.
6.1. Mapping of the STATUS clause
The STATUS clause, which must be present, indicates whether this
definition is current or historic.
McCloghrie, et al. Standards Track [Page 19]
RFC 2578 SMIv2 April 1999
The value "current" means that the definition is current and valid.
The value "obsolete" means the definition is obsolete and should not
be implemented and/or can be removed if previously implemented.
While the value "deprecated" also indicates an obsolete definition,
it permits new/continued implementation in order to foster
interoperability with older/existing implementations.
6.2. Mapping of the DESCRIPTION clause
The DESCRIPTION clause, which must be present, contains a textual
description of the object assignment.
6.3. 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.
6.4. Mapping of the OBJECT-IDENTITY value
The value of an invocation of the OBJECT-IDENTITY macro is an OBJECT
IDENTIFIER.
6.5. Usage Example
Consider how an OBJECT IDENTIFIER assignment might be made: e.g.,
fizbin69 OBJECT-IDENTITY
STATUS current
DESCRIPTION
"The authoritative identity of the Fizbin 69 chipset."
::= { fizbinChipSets 1 }
7. Mapping of the OBJECT-TYPE macro
The OBJECT-TYPE macro is used to define a type of managed object. It
should be noted that the expansion of the OBJECT-TYPE macro is
something which conceptually happens during implementation and not
during run-time.
For leaf objects which are not columnar objects (i.e., not contained
within a conceptual table), instances of the object are identified by
appending a sub-identifier of zero to the name of that object.
Otherwise, the INDEX clause of the conceptual row object superior to
a columnar object defines instance identification information.
McCloghrie, et al. Standards Track [Page 20]
RFC 2578 SMIv2 April 1999
7.1. Mapping of the SYNTAX clause
The SYNTAX clause, which must be present, defines the abstract data
structure corresponding to that object. The data structure must be
one of the following: a base type, the BITS construct, or a textual
convention. (SEQUENCE OF and SEQUENCE are also possible for
conceptual tables, see section 7.1.12). The base types are those
defined in the ObjectSyntax CHOICE. A textual convention is a
newly-defined type defined as a sub-type of a base type [3].
An extended subset of the full capabilities of ASN.1 (1988) sub-
typing is allowed, as appropriate to the underlying ASN.1 type. Any
such restriction on size, range or enumerations specified in this
clause represents the maximal level of support which makes "protocol
sense". Restrictions on sub-typing are specified in detail in
Section 9 and Appendix A of this memo.
The semantics of ObjectSyntax are now described.
7.1.1. Integer32 and INTEGER
The Integer32 type represents integer-valued information between
-2^31 and 2^31-1 inclusive (-2147483648 to 2147483647 decimal). This
type is indistinguishable from the INTEGER type. Both the INTEGER
and Integer32 types may be sub-typed to be more constrained than the
Integer32 type.
The INTEGER type (but not the Integer32 type) may also be used to
represent integer-valued information as named-number enumerations.
In this case, only those named-numbers so enumerated may be present
as a value. Note that although it is recommended that enumerated
values start at 1 and be numbered contiguously, any valid value for
Integer32 is allowed for an enumerated value and, further, enumerated
values needn't be contiguously assigned.
Finally, a label for a named-number enumeration must consist of one
or more letters or digits, up to a maximum of 64 characters, and the
initial character must be a lower-case letter. (However, labels
longer than 32 characters are not recommended.) Note that hyphens
are not allowed by this specification (except for use by information
modules converted from SMIv1 which did allow hyphens).
7.1.2. OCTET STRING
The OCTET STRING type represents arbitrary binary or textual data.
Although the SMI-specified size limitation for this type is 65535
octets, MIB designers should realize that there may be implementation
and interoperability limitations for sizes in excess of 255 octets.
McCloghrie, et al. Standards Track [Page 21]
RFC 2578 SMIv2 April 1999
7.1.3. OBJECT IDENTIFIER
The OBJECT IDENTIFIER type represents administratively assigned
names. Any instance of this type may have at most 128 sub-
identifiers. Further, each sub-identifier must not exceed the value
2^32-1 (4294967295 decimal).
7.1.4. The BITS construct
The BITS construct represents an enumeration of named bits. This
collection is assigned non-negative, contiguous (but see below)
values, starting at zero. Only those named-bits so enumerated may be
present in a value. (Thus, enumerations must be assigned to
consecutive bits; however, see Section 9 for refinements of an object
with this syntax.)
As part of updating an information module, for an object defined
using the BITS construct, new enumerations can be added or existing
enumerations can have new labels assigned to them. After an
enumeration is added, it might not be possible to distinguish between
an implementation of the updated object for which the new enumeration
is not asserted, and an implementation of the object prior to the
addition. Depending on the circumstances, such an ambiguity could
either be desirable or could be undesirable. The means to avoid such
an ambiguity is dependent on the encoding of values on the wire;
however, one possibility is to define new enumerations starting at
the next multiple of eight bits. (Of course, this can also result in
the enumerations no longer being contiguous.)
Although there is no SMI-specified limitation on the number of
enumerations (and therefore on the length of a value), except as may
be imposed by the limit on the length of an OCTET STRING, MIB
designers should realize that there may be implementation and
interoperability limitations for sizes in excess of 128 bits.
Finally, a label for a named-number enumeration must consist of one
or more letters or digits, up to a maximum of 64 characters, and the
initial character must be a lower-case letter. (However, labels
longer than 32 characters are not recommended.) Note that hyphens
are not allowed by this specification.
7.1.5. IpAddress
The IpAddress type represents a 32-bit internet address. It is
represented as an OCTET STRING of length 4, in network byte-order.
McCloghrie, et al. Standards Track [Page 22]
RFC 2578 SMIv2 April 1999
Note that the IpAddress type is a tagged type for historical reasons.
Network addresses should be represented using an invocation of the
TEXTUAL-CONVENTION macro [3].
7.1.6. Counter32
The Counter32 type represents a non-negative integer which
monotonically increases until it reaches a maximum value of 2^32-1
(4294967295 decimal), when it wraps around and starts increasing
again from zero.
Counters have no defined "initial" value, and thus, a single value of
a Counter has (in general) no information content. Discontinuities
in the monotonically increasing value normally occur at re-
initialization of the management system, and at other times as
specified in the description of an object-type using this ASN.1 type.
If such other times can occur, for example, the creation of an object
instance at times other than re-initialization, then a corresponding
object should be defined, with an appropriate SYNTAX clause, to
indicate the last discontinuity. Examples of appropriate SYNTAX
clause include: TimeStamp (a textual convention defined in [3]),
DateAndTime (another textual convention from [3]) or TimeTicks.
The value of the MAX-ACCESS clause for objects with a SYNTAX clause
value of Counter32 is either "read-only" or "accessible-for-notify".
A DEFVAL clause is not allowed for objects with a SYNTAX clause value
of Counter32.
7.1.7. Gauge32
The Gauge32 type represents a non-negative integer, which may
increase or decrease, but shall never exceed a maximum value, nor
fall below a minimum value. The maximum value can not be greater
than 2^32-1 (4294967295 decimal), and the minimum value can not be
smaller than 0. The value of a Gauge32 has its maximum value
whenever the information being modeled is greater than or equal to
its maximum value, and has its minimum value whenever the information
being modeled is smaller than or equal to its minimum value. If the
information being modeled subsequently decreases below (increases
above) the maximum (minimum) value, the Gauge32 also decreases
(increases). (Note that despite of the use of the term "latched" in
the original definition of this type, it does not become "stuck" at
its maximum or minimum value.)
McCloghrie, et al. Standards Track [Page 23]
RFC 2578 SMIv2 April 1999
7.1.8. TimeTicks
The TimeTicks type represents a non-negative integer which represents
the time, modulo 2^32 (4294967296 decimal), in hundredths of a second
between two epochs. When objects are defined which use this ASN.1
type, the description of the object identifies both of the reference
epochs.
For example, [3] defines the TimeStamp textual convention which is
based on the TimeTicks type. With a TimeStamp, the first reference
epoch is defined as the time when sysUpTime [5] was zero, and the
second reference epoch is defined as the current value of sysUpTime.
The TimeTicks type may not be sub-typed.
7.1.9. Opaque
The Opaque type is provided solely for backward-compatibility, and
shall not be used for newly-defined object types.
The Opaque type supports the capability to pass arbitrary ASN.1
syntax. A value is encoded using the ASN.1 Basic Encoding Rules [4]
into a string of octets. This, in turn, is encoded as an OCTET
STRING, in effect "double-wrapping" the original ASN.1 value.
Note that a conforming implementation need only be able to accept and
recognize opaquely-encoded data. It need not be able to unwrap the
data and then interpret its contents.
A requirement on "standard" MIB modules is that no object may have a
SYNTAX clause value of Opaque.
7.1.10. Counter64
The Counter64 type represents a non-negative integer which
monotonically increases until it reaches a maximum value of 2^64-1
(18446744073709551615 decimal), when it wraps around and starts
increasing again from zero.
Counters have no defined "initial" value, and thus, a single value of
a Counter has (in general) no information content. Discontinuities
in the monotonically increasing value normally occur at re-
initialization of the management system, and at other times as
specified in the description of an object-type using this ASN.1 type.
If such other times can occur, for example, the creation of an object
instance at times other than re-initialization, then a corresponding
object should be defined, with an appropriate SYNTAX clause, to
indicate the last discontinuity. Examples of appropriate SYNTAX
McCloghrie, et al. Standards Track [Page 24]
RFC 2578 SMIv2 April 1999
clause are: TimeStamp (a textual convention defined in [3]),
DateAndTime (another textual convention from [3]) or TimeTicks.
The value of the MAX-ACCESS clause for objects with a SYNTAX clause
value of Counter64 is either "read-only" or "accessible-for-notify".
A requirement on "standard" MIB modules is that the Counter64 type
may be used only if the information being modeled would wrap in less
than one hour if the Counter32 type was used instead.
A DEFVAL clause is not allowed for objects with a SYNTAX clause value
of Counter64.
7.1.11. Unsigned32
The Unsigned32 type represents integer-valued information between 0
and 2^32-1 inclusive (0 to 4294967295 decimal).
7.1.12. Conceptual Tables
Management operations apply exclusively to scalar objects. However,
it is sometimes convenient for developers of management applications
to impose an imaginary, tabular structure on an ordered collection of
objects within the MIB. Each such conceptual table contains zero or
more rows, and each row may contain one or more scalar objects,
termed columnar objects. This conceptualization is formalized by
using the OBJECT-TYPE macro to define both an object which
corresponds to a table and an object which corresponds to a row in
that table. A conceptual table has SYNTAX of the form:
SEQUENCE OF <EntryType>
where <EntryType> refers to the SEQUENCE type of its subordinate
conceptual row. A conceptual row has SYNTAX of the form:
<EntryType>
where <EntryType> is a SEQUENCE type defined as follows:
<EntryType> ::= SEQUENCE { <type1>, ... , <typeN> }
where there is one <type> for each subordinate object, and each
<type> is of the form:
<descriptor> <syntax>
where <descriptor> is the descriptor naming a subordinate object, and
<syntax> has the value of that subordinate object's SYNTAX clause,
McCloghrie, et al. Standards Track [Page 25]
RFC 2578 SMIv2 April 1999
except that both sub-typing information and the named values for
enumerated integers or the named bits for the BITS construct, are
omitted from <syntax>.
Further, a <type> is always present for every subordinate object.
(The ASN.1 DEFAULT and OPTIONAL clauses are disallowed in the
SEQUENCE definition.) The MAX-ACCESS clause for conceptual tables
and rows is "not-accessible".
7.1.12.1. Creation and Deletion of Conceptual Rows
For newly-defined conceptual rows which allow the creation of new
object instances and/or the deletion of existing object instances,
there should be one columnar object with a SYNTAX clause value of
RowStatus (a textual convention defined in [3]) and a MAX-ACCESS
clause value of read-create. By convention, this is termed the
status column for the conceptual row.
7.2. Mapping of the UNITS clause
This UNITS clause, which need not be present, contains a textual
definition of the units associated with that object.
7.3. Mapping of the MAX-ACCESS clause
The MAX-ACCESS clause, which must be present, defines whether it
makes "protocol sense" to read, write and/or create an instance of
the object, or to include its value in a notification. This is the
maximal level of access for the object. (This maximal level of
access is independent of any administrative authorization policy.)
The value "read-write" indicates that read and write access make
"protocol sense", but create does not. The value "read-create"
indicates that read, write and create access make "protocol sense".
The value "not-accessible" indicates an auxiliary object (see Section
7.7). The value "accessible-for-notify" indicates an object which is
accessible only via a notification (e.g., snmpTrapOID [5]).
These values are ordered, from least to greatest: "not-accessible",
"accessible-for-notify", "read-only", "read-write", "read-create".
If any columnar object in a conceptual row has "read-create" as its
maximal level of access, then no other columnar object of the same
conceptual row may have a maximal access of "read-write". (Note that
"read-create" is a superset of "read-write".)
McCloghrie, et al. Standards Track [Page 26]
RFC 2578 SMIv2 April 1999
7.4. 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 should not
be implemented and/or can be removed if previously implemented.
While the value "deprecated" also indicates an obsolete definition,
it permits new/continued implementation in order to foster
interoperability with older/existing implementations.
7.5. Mapping of the DESCRIPTION clause
The DESCRIPTION clause, which must be present, contains a textual
definition of that object which provides all semantic definitions
necessary for implementation, and should embody any information which
would otherwise be communicated in any ASN.1 commentary annotations
associated with the object.
7.6. 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.
7.7. Mapping of the INDEX clause
The INDEX clause, which must be present if that object corresponds to
a conceptual row (unless an AUGMENTS clause is present instead), and
must be absent otherwise, defines instance identification information
for the columnar objects subordinate to that object.
The instance identification information in an INDEX clause must
specify object(s) such that value(s) of those object(s) will
unambiguously distinguish a conceptual row. The objects can be
columnar objects from the same and/or another conceptual table, but
must not be scalar objects. Multiple occurrences of the same object
in a single INDEX clause is strongly discouraged.
The syntax of the objects in the INDEX clause indicate how to form
the instance-identifier:
(1) integer-valued (i.e., having INTEGER as its underlying primitive
type): a single sub-identifier taking the integer value (this
works only for non-negative integers);
McCloghrie, et al. Standards Track [Page 27]
RFC 2578 SMIv2 April 1999
(2) string-valued, fixed-length strings (or variable-length preceded by
the IMPLIED keyword): `n' sub-identifiers, where `n' is the length
of the string (each octet of the string is encoded in a separate
sub-identifier);
(3) string-valued, variable-length strings (not preceded by the IMPLIED
keyword): `n+1' sub-identifiers, where `n' is the length of the
string (the first sub-identifier is `n' itself, following this,
each octet of the string is encoded in a separate sub-identifier);
(4) object identifier-valued (when preceded by the IMPLIED keyword):
`n' sub-identifiers, where `n' is the number of sub-identifiers in
the value (each sub-identifier of the value is copied into a
separate sub-identifier);
(5) object identifier-valued (when not preceded by the IMPLIED
keyword): `n+1' sub-identifiers, where `n' is the number of sub-
identifiers in the value (the first sub-identifier is `n' itself,
following this, each sub-identifier in the value is copied);
(6) IpAddress-valued: 4 sub-identifiers, in the familiar a.b.c.d
notation.
Note that the IMPLIED keyword can only be present for an object
having a variable-length syntax (e.g., variable-length strings or
object identifier-valued objects), Further, the IMPLIED keyword can
only be associated with the last object in the INDEX clause.
Finally, the IMPLIED keyword may not be used on a variable-length
string object if that string might have a value of zero-length.
Since a single value of a Counter has (in general) no information
content (see section 7.1.6 and 7.1.10), objects defined using the
syntax, Counter32 or Counter64, must not be specified in an INDEX
clause. If an object defined using the BITS construct is used in an
INDEX clause, it is considered a variable-length string.
Instances identified by use of integer-valued objects should be
numbered starting from one (i.e., not from zero). The use of zero as
a value for an integer-valued index object should be avoided, except
in special cases.
Objects which are both specified in the INDEX clause of a conceptual
row and also columnar objects of the same conceptual row are termed
auxiliary objects. The MAX-ACCESS clause for auxiliary objects is
"not-accessible", except in the following circumstances:
McCloghrie, et al. Standards Track [Page 28]
RFC 2578 SMIv2 April 1999
(1) within a MIB module originally written to conform to SMIv1, and
later converted to conform to SMIv2; or
(2) a conceptual row must contain at least one columnar object which is
not an auxiliary object. In the event that all of a conceptual
row's columnar objects are also specified in its INDEX clause, then
one of them must be accessible, i.e., have a MAX-ACCESS clause of
"read-only". (Note that this situation does not arise for a
conceptual row allowing create access, since such a row will have a
status column which will not be an auxiliary object.)
Note that objects specified in a conceptual row's INDEX clause need
not be columnar objects of that conceptual row. In this situation,
the DESCRIPTION clause of the conceptual row must include a textual
explanation of how the objects which are included in the INDEX clause
but not columnar objects of that conceptual row, are used in uniquely
identifying instances of the conceptual row's columnar objects.
7.8. Mapping of the AUGMENTS clause
The AUGMENTS clause, which must not be present unless the object
corresponds to a conceptual row, is an alternative to the INDEX
clause. Every object corresponding to a conceptual row has either an
INDEX clause or an AUGMENTS clause.
If an object corresponding to a conceptual row has an INDEX clause,
that row is termed a base conceptual row; alternatively, if the
object has an AUGMENTS clause, the row is said to be a conceptual row
augmentation, where the AUGMENTS clause names the object
corresponding to the base conceptual row which is augmented by this
conceptual row augmentation. (Thus, a conceptual row augmentation
cannot itself be augmented.) Instances of subordinate columnar
objects of a conceptual row augmentation are identified according to
the INDEX clause of the base conceptual row corresponding to the
object named in the AUGMENTS clause. Further, instances of
subordinate columnar objects of a conceptual row augmentation exist
according to the same semantics as instances of subordinate columnar
objects of the base conceptual row being augmented. As such, note
that creation of a base conceptual row implies the correspondent
creation of any conceptual row augmentations.
For example, a MIB designer might wish to define additional columns
in an "enterprise-specific" MIB which logically extend a conceptual
row in a "standard" MIB. The "standard" MIB definition of the
conceptual row would include the INDEX clause and the "enterprise-
specific" MIB would contain the definition of a conceptual row using
the AUGMENTS clause. On the other hand, it would be incorrect to use
the AUGMENTS clause for the relationship between RFC 2233's ifTable
McCloghrie, et al. Standards Track [Page 29]
RFC 2578 SMIv2 April 1999
and the many media-specific MIBs which extend it for specific media
(e.g., the dot3Table in RFC 2358), since not all interfaces are of
the same media.
Note that a base conceptual row may be augmented by multiple
conceptual row augmentations.
7.8.1. Relation between INDEX and AUGMENTS clauses
When defining instance identification information for a conceptual
table:
(1) If there is a one-to-one correspondence between the conceptual rows
of this table and an existing table, then the AUGMENTS clause
should be used.
(2) Otherwise, if there is a sparse relationship between the conceptual
rows of this table and an existing table, then an INDEX clause
should be used which is identical to that in the existing table.
For example, the relationship between RFC 2233's ifTable and a
media-specific MIB which extends the ifTable for a specific media
(e.g., the dot3Table in RFC 2358), is a sparse relationship.
(3) Otherwise, if no existing objects have the required syntax and
semantics, then auxiliary objects should be defined within the
conceptual row for the new table, and those objects should be used
within the INDEX clause for the conceptual row.
7.9. Mapping of the DEFVAL clause
The DEFVAL clause, which need not be present, defines an acceptable
default value which may be used at the discretion of an agent when an
object instance is created. That is, the value is a "hint" to
implementors.
During conceptual row creation, if an instance of a columnar object
is not present as one of the operands in the correspondent management
protocol set operation, then the value of the DEFVAL clause, if
present, indicates an acceptable default value that an agent might
use (especially for a read-only object).
Note that with this definition of the DEFVAL clause, it is
appropriate to use it for any columnar object of a read-create table.
It is also permitted to use it for scalar objects dynamically created
by an agent, or for columnar objects of a read-write table
dynamically created by an agent.
McCloghrie, et al. Standards Track [Page 30]
RFC 2578 SMIv2 April 1999
The value of the DEFVAL clause must, of course, correspond to the
SYNTAX clause for the object. If the value is an OBJECT IDENTIFIER,
then it must be expressed as a single ASN.1 identifier, and not as a
collection of sub-identifiers.
Note that if an operand to the management protocol set operation is
an instance of a read-only object, then the error `notWritable' [6]
will be returned. As such, the DEFVAL clause can be used to provide
an acceptable default value that an agent might use.
By way of example, consider the following possible DEFVAL clauses:
ObjectSyntax DEFVAL clause
---------------- ------------
Integer32 DEFVAL { 1 }
-- same for Gauge32, TimeTicks, Unsigned32
INTEGER DEFVAL { valid } -- enumerated value
OCTET STRING DEFVAL { 'ffffffffffff'H }
DisplayString DEFVAL { "SNMP agent" }
IpAddress DEFVAL { 'c0210415'H } -- 192.33.4.21
OBJECT IDENTIFIER DEFVAL { sysDescr }
BITS DEFVAL { { primary, secondary } }
-- enumerated values that are set
BITS DEFVAL { { } }
-- no enumerated values are set
A binary string used in a DEFVAL clause for an OCTET STRING must be
either an integral multiple of eight or zero bits in length;
similarly, a hexadecimal string must be an even number of hexadecimal
digits. The value of a character string used in a DEFVAL clause must
not contain tab characters or line terminator characters.
Object types with SYNTAX of Counter32 and Counter64 may not have
DEFVAL clauses, since they do not have defined initial values.
However, it is recommended that they be initialized to zero.
7.10. Mapping of the OBJECT-TYPE value
The value of an invocation of the OBJECT-TYPE macro is the name of
the object, which is an OBJECT IDENTIFIER, an administratively
assigned name.
When an OBJECT IDENTIFIER is assigned to an object:
(1) If the object corresponds to a conceptual table, then only a single
assignment, that for a conceptual row, is present immediately
beneath that object. The administratively assigned name for the
conceptual row object is derived by appending a sub-identifier of
McCloghrie, et al. Standards Track [Page 31]
RFC 2578 SMIv2 April 1999
"1" to the administratively assigned name for the conceptual table.
(2) If the object corresponds to a conceptual row, then at least one
assignment, one for each column in the conceptual row, is present
beneath that object. The administratively assigned name for each
column is derived by appending a unique, positive sub-identifier to
the administratively assigned name for the conceptual row.
(3) Otherwise, no other OBJECT IDENTIFIERs which are subordinate to the
object may be assigned.
Note that the final sub-identifier of any administratively assigned
name for an object shall be positive. A zero-valued final sub-
identifier is reserved for future use.
7.11. Usage Example
Consider how one might define a conceptual table and its
subordinates. (This example uses the RowStatus textual convention
defined in [3].)
evalSlot OBJECT-TYPE
SYNTAX Integer32 (0..2147483647)
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The index number of the first unassigned entry in the
evaluation table, or the value of zero indicating that
all entries are assigned.
A management station should create new entries in the
evaluation table using this algorithm: first, issue a
management protocol retrieval operation to determine the
value of evalSlot; and, second, issue a management
protocol set operation to create an instance of the
evalStatus object setting its value to createAndGo(4) or
createAndWait(5). If this latter operation succeeds,
then the management station may continue modifying the
instances corresponding to the newly created conceptual
row, without fear of collision with other management
stations."
::= { eval 1 }
evalTable OBJECT-TYPE
SYNTAX SEQUENCE OF EvalEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
McCloghrie, et al. Standards Track [Page 32]
RFC 2578 SMIv2 April 1999
"The (conceptual) evaluation table."
::= { eval 2 }
evalEntry OBJECT-TYPE
SYNTAX EvalEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"An entry (conceptual row) in the evaluation table."
INDEX { evalIndex }
::= { evalTable 1 }
EvalEntry ::=
SEQUENCE {
evalIndex Integer32,
evalString DisplayString,
evalValue Integer32,
evalStatus RowStatus
}
evalIndex OBJECT-TYPE
SYNTAX Integer32 (1..2147483647)
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The auxiliary variable used for identifying instances of
the columnar objects in the evaluation table."
::= { evalEntry 1 }
evalString OBJECT-TYPE
SYNTAX DisplayString
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The string to evaluate."
::= { evalEntry 2 }
evalValue OBJECT-TYPE
SYNTAX Integer32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The value when evalString was last evaluated, or zero if
no such value is available."
DEFVAL { 0 }
::= { evalEntry 3 }
evalStatus OBJECT-TYPE
McCloghrie, et al. Standards Track [Page 33]
RFC 2578 SMIv2 April 1999
SYNTAX RowStatus
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The status column used for creating, modifying, and
deleting instances of the columnar objects in the
evaluation table."
DEFVAL { active }
::= { evalEntry 4 }
8. Mapping of the NOTIFICATION-TYPE macro
The NOTIFICATION-TYPE macro is used to define the information
contained within an unsolicited transmission of management
information (i.e., within either a SNMPv2-Trap-PDU or InformRequest-
PDU). It should be noted that the expansion of the NOTIFICATION-TYPE
macro is something which conceptually happens during implementation
and not during run-time.
8.1. Mapping of the OBJECTS clause
The OBJECTS clause, which need not be present, defines an ordered
sequence of MIB object types. One and only one object instance for
each occurrence of each object type must be present, and in the
specified order, in every instance of the notification. If the same
object type occurs multiple times in a notification's ordered
sequence, then an object instance is present for each of them. An
object type specified in this clause must not have an MAX-ACCESS
clause of "not-accessible". The notification's DESCRIPTION clause
must specify the information/meaning conveyed by each occurrence of
each object type in the sequence. The DESCRIPTION clause must also
specify which object instance is present for each object type in the
notification.
Note that an agent is allowed, at its own discretion, to append as
many additional objects as it considers useful to the end of the
notification (i.e., after the objects defined by the OBJECTS clause).
8.2. 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 should not
be implemented and/or can be removed if previously implemented.
While the value "deprecated" also indicates an obsolete definition,
it permits new/continued implementation in order to foster
McCloghrie, et al. Standards Track [Page 34]
RFC 2578 SMIv2 April 1999
interoperability with older/existing implementations.
8.3. Mapping of the DESCRIPTION clause
The DESCRIPTION clause, which must be present, contains a textual
definition of the notification which provides all semantic
definitions necessary for implementation, and should embody any
information which would otherwise be communicated in any ASN.1
commentary annotations associated with the notification. In
particular, the DESCRIPTION clause should document which instances of
the objects mentioned in the OBJECTS clause should be contained
within notifications of this type.
8.4. 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.
8.5. Mapping of the NOTIFICATION-TYPE value
The value of an invocation of the NOTIFICATION-TYPE macro is the name
of the notification, which is an OBJECT IDENTIFIER, an
administratively assigned name. In order to achieve compatibility
with SNMPv1 traps, both when converting SMIv1 information modules
to/from this SMI, and in the procedures employed by multi-lingual
systems and proxy forwarding applications, the next to last sub-
identifier in the name of any newly-defined notification must have
the value zero.
Sections 4.2.6 and 4.2.7 of [6] describe how the NOTIFICATION-TYPE
macro is used to generate a SNMPv2-Trap-PDU or InformRequest-PDU,
respectively.
8.6. Usage Example
Consider how a configuration change notification might be described:
entityMIBTraps OBJECT IDENTIFIER ::= { entityMIB 2 }
entityMIBTrapPrefix OBJECT IDENTIFIER ::= { entityMIBTraps 0 }
entConfigChange NOTIFICATION-TYPE
STATUS current
DESCRIPTION
"An entConfigChange trap is sent when the value of
entLastChangeTime changes. It can be utilized by an NMS to
trigger logical/physical entity table maintenance polls.
McCloghrie, et al. Standards Track [Page 35]
RFC 2578 SMIv2 April 1999
An agent must not generate more than one entConfigChange
'trap-event' in a five second period, where a 'trap-event'
is the transmission of a single trap PDU to a list of
trap destinations. If additional configuration changes
occur within the five second 'throttling' period, then
these trap-events should be suppressed by the agent. An
NMS should periodically check the value of
entLastChangeTime to detect any missed entConfigChange
trap-events, e.g. due to throttling or transmission loss."
::= { entityMIBTrapPrefix 1 }
According to this invocation, the notification authoritatively
identified as
{ entityMIBTrapPrefix 1 }
is used to report a particular type of configuration change.
9. Refined Syntax
Some macros have clauses which allows syntax to be refined,
specifically: the SYNTAX clause of the OBJECT-TYPE macro, and the
SYNTAX/WRITE-SYNTAX clauses of the MODULE-COMPLIANCE and AGENT-
CAPABILITIES macros [2]. However, not all refinements of syntax are
appropriate. In particular, the object's primitive or application
type must not be changed.
Further, the following restrictions apply:
Restrictions to Refinement of
object syntax range enumeration size
----------------- ----- ----------- ----
INTEGER (1) (2) -
Integer32 (1) - -
Unsigned32 (1) - -
OCTET STRING - - (3)
OBJECT IDENTIFIER - - -
BITS - (2) -
IpAddress - - -
Counter32 - - -
Counter64 - - -
Gauge32 (1) - -
TimeTicks - - -
where:
McCloghrie, et al. Standards Track [Page 36]
RFC 2578 SMIv2 April 1999
(1) the range of permitted values may be refined by raising the lower-
bounds, by reducing the upper-bounds, and/or by reducing the
alternative value/range choices;
(2) the enumeration of named-values may be refined by removing one or
more named-values (note that for BITS, a refinement may cause the
enumerations to no longer be contiguous); or,
(3) the size in octets of the value may be refined by raising the
lower-bounds, by reducing the upper-bounds, and/or by reducing the
alternative size choices.
No other types of refinements can be specified in the SYNTAX clause.
However, the DESCRIPTION clause is available to specify additional
restrictions which can not be expressed in the SYNTAX clause.
Further details on (and examples of) sub-typing are provided in
Appendix A.
10. Extending an Information Module
As experience is gained with an information module, it may be
desirable to revise that information module. However, changes are
not allowed if they have any potential to cause interoperability
problems "over the wire" between an implementation using an original
specification and an implementation using an updated
specification(s).
For any change, the invocation of the MODULE-IDENTITY macro must be
updated to include information about the revision: specifically,
updating the LAST-UPDATED clause, adding a pair of REVISION and
DESCRIPTION clauses (see section 5.5), and making any necessary
changes to existing clauses, including the ORGANIZATION and CONTACT-
INFO clauses.
Note that any definition contained in an information module is
available to be IMPORT-ed by any other information module, and is
referenced in an IMPORTS clause via the module name. Thus, a module
name should not be changed. Specifically, the module name (e.g.,
"FIZBIN-MIB" in the example of Section 5.7) should not be changed
when revising an information module (except to correct typographical
errors), and definitions should not be moved from one information
module to another.
Also note that obsolete definitions must not be removed from MIB
modules since their descriptors may still be referenced by other
information modules, and the OBJECT IDENTIFIERs used to name them
must never be re-assigned.
McCloghrie, et al. Standards Track [Page 37]
RFC 2578 SMIv2 April 1999
10.1. Object Assignments
If any non-editorial change is made to any clause of a object
assignment, then the OBJECT IDENTIFIER value associated with that
object assignment must also be changed, along with its associated
descriptor.
10.2. Object Definitions
An object definition may be revised in any of the following ways:
(1) A SYNTAX clause containing an enumerated INTEGER may have new
enumerations added or existing labels changed. Similarly, named
bits may be added or existing labels changed for the BITS
construct.
(2) The value of a SYNTAX clause may be replaced by a textual
convention, providing the textual convention is defined to use the
same primitive ASN.1 type, has the same set of values, and has
identical semantics.
(3) 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.
(4) A DEFVAL clause may be added or updated.
(5) A REFERENCE clause may be added or updated.
(6) A UNITS clause may be added.
(7) A conceptual row may be augmented by adding new columnar objects at
the end of the row, and making the corresponding update to the
SEQUENCE definition.
(8) Clarifications and additional information may be included in the
DESCRIPTION clause.
(9) Entirely new objects may be defined, named with previously
unassigned OBJECT IDENTIFIER values.
Otherwise, if the semantics of any previously defined object are
changed (i.e., if a non-editorial change is made to any clause other
than those specifically allowed above), then the OBJECT IDENTIFIER
value associated with that object must also be changed.
McCloghrie, et al. Standards Track [Page 38]
RFC 2578 SMIv2 April 1999
Note that changing the descriptor associated with an existing object
is considered a semantic change, as these strings may be used in an
IMPORTS statement.
10.3. Notification Definitions
A notification definition may be revised in any of the following
ways:
(1) A REFERENCE clause may be added or updated.
(2) 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.
(3) A DESCRIPTION clause may be clarified.
Otherwise, if the semantics of any previously defined notification
are changed (i.e., if a non-editorial change is made to any clause
other those specifically allowed above), then the OBJECT IDENTIFIER
value associated with that notification must also be changed.
Note that changing the descriptor associated with an existing
notification is considered a semantic change, as these strings may be
used in an IMPORTS statement.
McCloghrie, et al. Standards Track [Page 39]
RFC 2578 SMIv2 April 1999
11. Appendix A: Detailed Sub-typing Rules
11.1. Syntax Rules
The syntax rules for sub-typing are given below. Note that while
this syntax is based on ASN.1, it includes some extensions beyond
what is allowed in ASN.1, and a number of ASN.1 constructs are not
allowed by this syntax.
<integerSubType>
::= <empty>
| "(" <range> ["|" <range>]... ")"
<octetStringSubType>
::= <empty>
| "(" "SIZE" "(" <range> ["|" <range>]... ")" ")"
<range>
::= <value>
| <value> ".." <value>
<value>
::= "-" <number>
| <number>
| <hexString>
| <binString>
where:
<empty> is the empty string
<number> is a non-negative integer
<hexString> is a hexadecimal string (e.g., '0F0F'H)
<binString> is a binary string (e.g, '1010'B)
<range> is further restricted as follows:
- any <value> used in a SIZE clause must be non-negative.
- when a pair of values is specified, the first value
must be less than the second value.
- when multiple ranges are specified, the ranges may
not overlap but may touch. For example, (1..4 | 4..9)
is invalid, and (1..4 | 5..9) is valid.
- the ranges must be a subset of the maximum range of the
base type.
McCloghrie, et al. Standards Track [Page 40]
RFC 2578 SMIv2 April 1999
11.2. Examples
Some examples of legal sub-typing:
Integer32 (-20..100)
Integer32 (0..100 | 300..500)
Integer32 (300..500 | 0..100)
Integer32 (0 | 2 | 4 | 6 | 8 | 10)
OCTET STRING (SIZE(0..100))
OCTET STRING (SIZE(0..100 | 300..500))
OCTET STRING (SIZE(0 | 2 | 4 | 6 | 8 | 10))
SYNTAX TimeInterval (0..100)
SYNTAX DisplayString (SIZE(0..32))
(Note the last two examples above are not valid in a TEXTUAL
CONVENTION, see [3].)
Some examples of illegal sub-typing:
Integer32 (150..100) -- first greater than second
Integer32 (0..100 | 50..500) -- ranges overlap
Integer32 (0 | 2 | 0 ) -- value duplicated
Integer32 (MIN..-1 | 1..MAX) -- MIN and MAX not allowed
Integer32 (SIZE (0..34)) -- must not use SIZE
OCTET STRING (0..100) -- must use SIZE
OCTET STRING (SIZE(-10..100)) -- negative SIZE
12. Security Considerations
This document defines a language with which to write and read
descriptions of management information. The language itself has no
security impact on the Internet.
13. Editors' Addresses
Keith McCloghrie
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
USA
Phone: +1 408 526 5260
EMail:
[email protected]
McCloghrie, et al. Standards Track [Page 41]
RFC 2578 SMIv2 April 1999
David Perkins
SNMPinfo
3763 Benton Street
Santa Clara, CA 95051
USA
Phone: +1 408 221-8702
EMail:
[email protected]
Juergen Schoenwaelder
TU Braunschweig
Bueltenweg 74/75
38106 Braunschweig
Germany
Phone: +49 531 391-3283
EMail:
[email protected]
14. 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, "Conformance Statements for SMIv2", STD 58,
RFC 2580, April 1999.
[3] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M.
and S. Waldbusser, "Textual Conventions for SMIv2", STD 58,
RFC 2579, April 1999.
[4] Information processing systems - Open Systems Interconnection -
Specification of Basic Encoding Rules for Abstract Syntax Notation
One (ASN.1), International Organization for Standardization.
International Standard 8825, (December, 1987).
[5] 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.
[6] 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.
McCloghrie, et al. Standards Track [Page 42]
RFC 2578 SMIv2 April 1999
15. 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."
McCloghrie, et al. Standards Track [Page 43]
Network Working Group Editors of this version:
Request for Comments: 2579 K. McCloghrie
STD: 58 Cisco Systems
Obsoletes: 1903 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
Textual Conventions 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 ..................................................2
1.1 A Note on Terminology .......................................2
2 Definitions ...................................................2
3 Mapping of the TEXTUAL-CONVENTION macro ......................20
3.1 Mapping of the DISPLAY-HINT clause .........................21
3.2 Mapping of the STATUS clause ...............................22
3.3 Mapping of the DESCRIPTION clause ..........................23
3.4 Mapping of the REFERENCE clause ............................23
3.5 Mapping of the SYNTAX clause ...............................23
4 Sub-typing of Textual Conventions ............................23
5 Revising a Textual Convention Definition .....................23
McCloghrie, et al. Standards Track [Page 1]
RFC 2579 Textual Conventions for SMIv2 April 1999
6 Security Considerations ......................................24
7 Editors' Addresses ...........................................25
8 References ...................................................25
9 Full Copyright Statement .....................................26
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].
When designing a MIB module, it is often useful to define new types
similar to those defined in the SMI. In comparison to a type defined
in the SMI, each of these new types has a different name, a similar
syntax, but a more precise semantics. These newly defined types are
termed textual conventions, and are used for the convenience of
humans reading the MIB module. It is the purpose of this document to
define the initial set of textual conventions available to all MIB
modules.
Objects defined using a textual convention are always encoded by
means of the rules that define their primitive type. However,
textual conventions often have special semantics associated with
them. As such, an ASN.1 macro, TEXTUAL-CONVENTION, is used to
concisely convey the syntax and semantics of a textual convention.
1.1. A Note on Terminology
For the purpose of exposition, the original Structure of Management
Information, as described in RFCs 1155 (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-TC DEFINITIONS ::= BEGIN
IMPORTS
TimeTicks FROM SNMPv2-SMI;
-- definition of textual conventions
TEXTUAL-CONVENTION MACRO ::=
McCloghrie, et al. Standards Track [Page 2]
RFC 2579 Textual Conventions for SMIv2 April 1999
BEGIN
TYPE NOTATION ::=
DisplayPart
"STATUS" Status
"DESCRIPTION" Text
ReferPart
"SYNTAX" Syntax
VALUE NOTATION ::=
value(VALUE Syntax) -- adapted ASN.1
DisplayPart ::=
"DISPLAY-HINT" Text
| empty
Status ::=
"current"
| "deprecated"
| "obsolete"
ReferPart ::=
"REFERENCE" Text
| empty
-- a character string as defined in [2]
Text ::= value(IA5String)
Syntax ::= -- Must be one of the following:
-- a base type (or its refinement), or
-- a BITS pseudo-type
type
| "BITS" "{" NamedBits "}"
NamedBits ::= NamedBit
| NamedBits "," NamedBit
NamedBit ::= identifier "(" number ")" -- number is nonnegative
END
DisplayString ::= TEXTUAL-CONVENTION
DISPLAY-HINT "255a"
STATUS current
DESCRIPTION
"Represents textual information taken from the NVT ASCII
McCloghrie, et al. Standards Track [Page 3]
RFC 2579 Textual Conventions for SMIv2 April 1999
character set, as defined in pages 4, 10-11 of RFC 854.
To summarize RFC 854, the NVT ASCII repertoire specifies:
- the use of character codes 0-127 (decimal)
- the graphics characters (32-126) are interpreted as
US ASCII
- NUL, LF, CR, BEL, BS, HT, VT and FF have the special
meanings specified in RFC 854
- the other 25 codes have no standard interpretation
- the sequence 'CR LF' means newline
- the sequence 'CR NUL' means carriage-return
- an 'LF' not preceded by a 'CR' means moving to the
same column on the next line.
- the sequence 'CR x' for any x other than LF or NUL is
illegal. (Note that this also means that a string may
end with either 'CR LF' or 'CR NUL', but not with CR.)
Any object defined using this syntax may not exceed 255
characters in length."
SYNTAX OCTET STRING (SIZE (0..255))
PhysAddress ::= TEXTUAL-CONVENTION
DISPLAY-HINT "1x:"
STATUS current
DESCRIPTION
"Represents media- or physical-level addresses."
SYNTAX OCTET STRING
MacAddress ::= TEXTUAL-CONVENTION
DISPLAY-HINT "1x:"
STATUS current
DESCRIPTION
"Represents an 802 MAC address represented in the
`canonical' order defined by IEEE 802.1a, i.e., as if it
were transmitted least significant bit first, even though
802.5 (in contrast to other 802.x protocols) requires MAC
addresses to be transmitted most significant bit first."
SYNTAX OCTET STRING (SIZE (6))
McCloghrie, et al. Standards Track [Page 4]
RFC 2579 Textual Conventions for SMIv2 April 1999
TruthValue ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"Represents a boolean value."
SYNTAX INTEGER { true(1), false(2) }
TestAndIncr ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"Represents integer-valued information used for atomic
operations. When the management protocol is used to specify
that an object instance having this syntax is to be
modified, the new value supplied via the management protocol
must precisely match the value presently held by the
instance. If not, the management protocol set operation
fails with an error of `inconsistentValue'. Otherwise, if
the current value is the maximum value of 2^31-1 (2147483647
decimal), then the value held by the instance is wrapped to
zero; otherwise, the value held by the instance is
incremented by one. (Note that regardless of whether the
management protocol set operation succeeds, the variable-
binding in the request and response PDUs are identical.)
The value of the ACCESS clause for objects having this
syntax is either `read-write' or `read-create'. When an
instance of a columnar object having this syntax is created,
any value may be supplied via the management protocol.
When the network management portion of the system is re-
initialized, the value of every object instance having this
syntax must either be incremented from its value prior to
the re-initialization, or (if the value prior to the re-
initialization is unknown) be set to a pseudo-randomly
generated value."
SYNTAX INTEGER (0..2147483647)
AutonomousType ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"Represents an independently extensible type identification
value. It may, for example, indicate a particular sub-tree
with further MIB definitions, or define a particular type of
protocol or hardware."
SYNTAX OBJECT IDENTIFIER
InstancePointer ::= TEXTUAL-CONVENTION
STATUS obsolete
McCloghrie, et al. Standards Track [Page 5]
RFC 2579 Textual Conventions for SMIv2 April 1999
DESCRIPTION
"A pointer to either a specific instance of a MIB object or
a conceptual row of a MIB table in the managed device. In
the latter case, by convention, it is the name of the
particular instance of the first accessible columnar object
in the conceptual row.
The two uses of this textual convention are replaced by
VariablePointer and RowPointer, respectively."
SYNTAX OBJECT IDENTIFIER
VariablePointer ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"A pointer to a specific object instance. For example,
sysContact.0 or ifInOctets.3."
SYNTAX OBJECT IDENTIFIER
RowPointer ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"Represents a pointer to a conceptual row. The value is the
name of the instance of the first accessible columnar object
in the conceptual row.
For example, ifIndex.3 would point to the 3rd row in the
ifTable (note that if ifIndex were not-accessible, then
ifDescr.3 would be used instead)."
SYNTAX OBJECT IDENTIFIER
RowStatus ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"The RowStatus textual convention is used to manage the
creation and deletion of conceptual rows, and is used as the
value of the SYNTAX clause for the status column of a
conceptual row (as described in Section 7.7.1 of [2].)
McCloghrie, et al. Standards Track [Page 6]
RFC 2579 Textual Conventions for SMIv2 April 1999
The status column has six defined values:
- `active', which indicates that the conceptual row is
available for use by the managed device;
- `notInService', which indicates that the conceptual
row exists in the agent, but is unavailable for use by
the managed device (see NOTE below); 'notInService' has
no implication regarding the internal consistency of
the row, availability of resources, or consistency with
the current state of the managed device;
- `notReady', which indicates that the conceptual row
exists in the agent, but is missing information
necessary in order to be available for use by the
managed device (i.e., one or more required columns in
the conceptual row have not been instanciated);
- `createAndGo', which is supplied by a management
station wishing to create a new instance of a
conceptual row and to have its status automatically set
to active, making it available for use by the managed
device;
- `createAndWait', which is supplied by a management
station wishing to create a new instance of a
conceptual row (but not make it available for use by
the managed device); and,
- `destroy', which is supplied by a management station
wishing to delete all of the instances associated with
an existing conceptual row.
Whereas five of the six values (all except `notReady') may
be specified in a management protocol set operation, only
three values will be returned in response to a management
protocol retrieval operation: `notReady', `notInService' or
`active'. That is, when queried, an existing conceptual row
has only three states: it is either available for use by
the managed device (the status column has value `active');
it is not available for use by the managed device, though
the agent has sufficient information to attempt to make it
so (the status column has value `notInService'); or, it is
not available for use by the managed device, and an attempt
to make it so would fail because the agent has insufficient
information (the state column has value `notReady').
McCloghrie, et al. Standards Track [Page 7]
RFC 2579 Textual Conventions for SMIv2 April 1999
NOTE WELL
This textual convention may be used for a MIB table,
irrespective of whether the values of that table's
conceptual rows are able to be modified while it is
active, or whether its conceptual rows must be taken
out of service in order to be modified. That is, it is
the responsibility of the DESCRIPTION clause of the
status column to specify whether the status column must
not be `active' in order for the value of some other
column of the same conceptual row to be modified. If
such a specification is made, affected columns may be
changed by an SNMP set PDU if the RowStatus would not
be equal to `active' either immediately before or after
processing the PDU. In other words, if the PDU also
contained a varbind that would change the RowStatus
value, the column in question may be changed if the
RowStatus was not equal to `active' as the PDU was
received, or if the varbind sets the status to a value
other than 'active'.
Also note that whenever any elements of a row exist, the
RowStatus column must also exist.
McCloghrie, et al. Standards Track [Page 8]
RFC 2579 Textual Conventions for SMIv2 April 1999
To summarize the effect of having a conceptual row with a
status column having a SYNTAX clause value of RowStatus,
consider the following state diagram:
STATE
+--------------+-----------+-------------+-------------
| A | B | C | D
| |status col.|status column|
|status column | is | is |status column
ACTION |does not exist| notReady | notInService| is active
--------------+--------------+-----------+-------------+-------------
set status |noError ->D|inconsist- |inconsistent-|inconsistent-
column to | or | entValue| Value| Value
createAndGo |inconsistent- | | |
| Value| | |
--------------+--------------+-----------+-------------+-------------
set status |noError see 1|inconsist- |inconsistent-|inconsistent-
column to | or | entValue| Value| Value
createAndWait |wrongValue | | |
--------------+--------------+-----------+-------------+-------------
set status |inconsistent- |inconsist- |noError |noError
column to | Value| entValue| |
active | | | |
| | or | |
| | | |
| |see 2 ->D|see 8 ->D| ->D
--------------+--------------+-----------+-------------+-------------
set status |inconsistent- |inconsist- |noError |noError ->C
column to | Value| entValue| |
notInService | | | |
| | or | | or
| | | |
| |see 3 ->C| ->C|see 6
--------------+--------------+-----------+-------------+-------------
set status |noError |noError |noError |noError ->A
column to | | | | or
destroy | ->A| ->A| ->A|see 7
--------------+--------------+-----------+-------------+-------------
set any other |see 4 |noError |noError |see 5
column to some| | | |
value | | see 1| ->C| ->D
--------------+--------------+-----------+-------------+-------------
(1) goto B or C, depending on information available to the
agent.
(2) if other variable bindings included in the same PDU,
McCloghrie, et al. Standards Track [Page 9]
RFC 2579 Textual Conventions for SMIv2 April 1999
provide values for all columns which are missing but
required, and all columns have acceptable values, then
return noError and goto D.
(3) if other variable bindings included in the same PDU,
provide legal values for all columns which are missing but
required, then return noError and goto C.
(4) at the discretion of the agent, the return value may be
either:
inconsistentName: because the agent does not choose to
create such an instance when the corresponding
RowStatus instance does not exist, or
inconsistentValue: if the supplied value is
inconsistent with the state of some other MIB object's
value, or
noError: because the agent chooses to create the
instance.
If noError is returned, then the instance of the status
column must also be created, and the new state is B or C,
depending on the information available to the agent. If
inconsistentName or inconsistentValue is returned, the row
remains in state A.
(5) depending on the MIB definition for the column/table,
either noError or inconsistentValue may be returned.
(6) the return value can indicate one of the following
errors:
wrongValue: because the agent does not support
notInService (e.g., an agent which does not support
createAndWait), or
inconsistentValue: because the agent is unable to take
the row out of service at this time, perhaps because it
is in use and cannot be de-activated.
(7) the return value can indicate the following error:
inconsistentValue: because the agent is unable to
remove the row at this time, perhaps because it is in
use and cannot be de-activated.
McCloghrie, et al. Standards Track [Page 10]
RFC 2579 Textual Conventions for SMIv2 April 1999
(8) the transition to D can fail, e.g., if the values of the
conceptual row are inconsistent, then the error code would
be inconsistentValue.
NOTE: Other processing of (this and other varbinds of) the
set request may result in a response other than noError
being returned, e.g., wrongValue, noCreation, etc.
Conceptual Row Creation
There are four potential interactions when creating a
conceptual row: selecting an instance-identifier which is
not in use; creating the conceptual row; initializing any
objects for which the agent does not supply a default; and,
making the conceptual row available for use by the managed
device.
Interaction 1: Selecting an Instance-Identifier
The algorithm used to select an instance-identifier varies
for each conceptual row. In some cases, the instance-
identifier is semantically significant, e.g., the
destination address of a route, and a management station
selects the instance-identifier according to the semantics.
In other cases, the instance-identifier is used solely to
distinguish conceptual rows, and a management station
without specific knowledge of the conceptual row might
examine the instances present in order to determine an
unused instance-identifier. (This approach may be used, but
it is often highly sub-optimal; however, it is also a
questionable practice for a naive management station to
attempt conceptual row creation.)
Alternately, the MIB module which defines the conceptual row
might provide one or more objects which provide assistance
in determining an unused instance-identifier. For example,
if the conceptual row is indexed by an integer-value, then
an object having an integer-valued SYNTAX clause might be
defined for such a purpose, allowing a management station to
issue a management protocol retrieval operation. In order
to avoid unnecessary collisions between competing management
stations, `adjacent' retrievals of this object should be
different.
Finally, the management station could select a pseudo-random
number to use as the index. In the event that this index
McCloghrie, et al. Standards Track [Page 11]
RFC 2579 Textual Conventions for SMIv2 April 1999
was already in use and an inconsistentValue was returned in
response to the management protocol set operation, the
management station should simply select a new pseudo-random
number and retry the operation.
A MIB designer should choose between the two latter
algorithms based on the size of the table (and therefore the
efficiency of each algorithm). For tables in which a large
number of entries are expected, it is recommended that a MIB
object be defined that returns an acceptable index for
creation. For tables with small numbers of entries, it is
recommended that the latter pseudo-random index mechanism be
used.
Interaction 2: Creating the Conceptual Row
Once an unused instance-identifier has been selected, the
management station determines if it wishes to create and
activate the conceptual row in one transaction or in a
negotiated set of interactions.
Interaction 2a: Creating and Activating the Conceptual Row
The management station must first determine the column
requirements, i.e., it must determine those columns for
which it must or must not provide values. Depending on the
complexity of the table and the management station's
knowledge of the agent's capabilities, this determination
can be made locally by the management station. Alternately,
the management station issues a management protocol get
operation to examine all columns in the conceptual row that
it wishes to create. In response, for each column, there
are three possible outcomes:
- a value is returned, indicating that some other
management station has already created this conceptual
row. We return to interaction 1.
- the exception `noSuchInstance' is returned,
indicating that the agent implements the object-type
associated with this column, and that this column in at
least one conceptual row would be accessible in the MIB
view used by the retrieval were it to exist. For those
columns to which the agent provides read-create access,
the `noSuchInstance' exception tells the management
station that it should supply a value for this column
when the conceptual row is to be created.
McCloghrie, et al. Standards Track [Page 12]
RFC 2579 Textual Conventions for SMIv2 April 1999
- the exception `noSuchObject' is returned, indicating
that the agent does not implement the object-type
associated with this column or that there is no
conceptual row for which this column would be
accessible in the MIB view used by the retrieval. As
such, the management station can not issue any
management protocol set operations to create an
instance of this column.
Once the column requirements have been determined, a
management protocol set operation is accordingly issued.
This operation also sets the new instance of the status
column to `createAndGo'.
When the agent processes the set operation, it verifies that
it has sufficient information to make the conceptual row
available for use by the managed device. The information
available to the agent is provided by two sources: the
management protocol set operation which creates the
conceptual row, and, implementation-specific defaults
supplied by the agent (note that an agent must provide
implementation-specific defaults for at least those objects
which it implements as read-only). If there is sufficient
information available, then the conceptual row is created, a
`noError' response is returned, the status column is set to
`active', and no further interactions are necessary (i.e.,
interactions 3 and 4 are skipped). If there is insufficient
information, then the conceptual row is not created, and the
set operation fails with an error of `inconsistentValue'.
On this error, the management station can issue a management
protocol retrieval operation to determine if this was
because it failed to specify a value for a required column,
or, because the selected instance of the status column
already existed. In the latter case, we return to
interaction 1. In the former case, the management station
can re-issue the set operation with the additional
information, or begin interaction 2 again using
`createAndWait' in order to negotiate creation of the
conceptual row.
McCloghrie, et al. Standards Track [Page 13]
RFC 2579 Textual Conventions for SMIv2 April 1999
NOTE WELL
Regardless of the method used to determine the column
requirements, it is possible that the management
station might deem a column necessary when, in fact,
the agent will not allow that particular columnar
instance to be created or written. In this case, the
management protocol set operation will fail with an
error such as `noCreation' or `notWritable'. In this
case, the management station decides whether it needs
to be able to set a value for that particular columnar
instance. If not, the management station re-issues the
management protocol set operation, but without setting
a value for that particular columnar instance;
otherwise, the management station aborts the row
creation algorithm.
Interaction 2b: Negotiating the Creation of the Conceptual
Row
The management station issues a management protocol set
operation which sets the desired instance of the status
column to `createAndWait'. If the agent is unwilling to
process a request of this sort, the set operation fails with
an error of `wrongValue'. (As a consequence, such an agent
must be prepared to accept a single management protocol set
operation, i.e., interaction 2a above, containing all of the
columns indicated by its column requirements.) Otherwise,
the conceptual row is created, a `noError' response is
returned, and the status column is immediately set to either
`notInService' or `notReady', depending on whether it has
sufficient information to (attempt to) make the conceptual
row available for use by the managed device. If there is
sufficient information available, then the status column is
set to `notInService'; otherwise, if there is insufficient
information, then the status column is set to `notReady'.
Regardless, we proceed to interaction 3.
Interaction 3: Initializing non-defaulted Objects
The management station must now determine the column
requirements. It issues a management protocol get operation
to examine all columns in the created conceptual row. In
the response, for each column, there are three possible
outcomes:
McCloghrie, et al. Standards Track [Page 14]
RFC 2579 Textual Conventions for SMIv2 April 1999
- a value is returned, indicating that the agent
implements the object-type associated with this column
and had sufficient information to provide a value. For
those columns to which the agent provides read-create
access (and for which the agent allows their values to
be changed after their creation), a value return tells
the management station that it may issue additional
management protocol set operations, if it desires, in
order to change the value associated with this column.
- the exception `noSuchInstance' is returned,
indicating that the agent implements the object-type
associated with this column, and that this column in at
least one conceptual row would be accessible in the MIB
view used by the retrieval were it to exist. However,
the agent does not have sufficient information to
provide a value, and until a value is provided, the
conceptual row may not be made available for use by the
managed device. For those columns to which the agent
provides read-create access, the `noSuchInstance'
exception tells the management station that it must
issue additional management protocol set operations, in
order to provide a value associated with this column.
- the exception `noSuchObject' is returned, indicating
that the agent does not implement the object-type
associated with this column or that there is no
conceptual row for which this column would be
accessible in the MIB view used by the retrieval. As
such, the management station can not issue any
management protocol set operations to create an
instance of this column.
If the value associated with the status column is
`notReady', then the management station must first deal with
all `noSuchInstance' columns, if any. Having done so, the
value of the status column becomes `notInService', and we
proceed to interaction 4.
McCloghrie, et al. Standards Track [Page 15]
RFC 2579 Textual Conventions for SMIv2 April 1999
Interaction 4: Making the Conceptual Row Available
Once the management station is satisfied with the values
associated with the columns of the conceptual row, it issues
a management protocol set operation to set the status column
to `active'. If the agent has sufficient information to
make the conceptual row available for use by the managed
device, the management protocol set operation succeeds (a
`noError' response is returned). Otherwise, the management
protocol set operation fails with an error of
`inconsistentValue'.
NOTE WELL
A conceptual row having a status column with value
`notInService' or `notReady' is unavailable to the
managed device. As such, it is possible for the
managed device to create its own instances during the
time between the management protocol set operation
which sets the status column to `createAndWait' and the
management protocol set operation which sets the status
column to `active'. In this case, when the management
protocol set operation is issued to set the status
column to `active', the values held in the agent
supersede those used by the managed device.
If the management station is prevented from setting the
status column to `active' (e.g., due to management station
or network failure) the conceptual row will be left in the
`notInService' or `notReady' state, consuming resources
indefinitely. The agent must detect conceptual rows that
have been in either state for an abnormally long period of
time and remove them. It is the responsibility of the
DESCRIPTION clause of the status column to indicate what an
abnormally long period of time would be. This period of
time should be long enough to allow for human response time
(including `think time') between the creation of the
conceptual row and the setting of the status to `active'.
In the absence of such information in the DESCRIPTION
clause, it is suggested that this period be approximately 5
minutes in length. This removal action applies not only to
newly-created rows, but also to previously active rows which
are set to, and left in, the notInService state for a
prolonged period exceeding that which is considered normal
for such a conceptual row.
McCloghrie, et al. Standards Track [Page 16]
RFC 2579 Textual Conventions for SMIv2 April 1999
Conceptual Row Suspension
When a conceptual row is `active', the management station
may issue a management protocol set operation which sets the
instance of the status column to `notInService'. If the
agent is unwilling to do so, the set operation fails with an
error of `wrongValue' or `inconsistentValue'. Otherwise,
the conceptual row is taken out of service, and a `noError'
response is returned. It is the responsibility of the
DESCRIPTION clause of the status column to indicate under
what circumstances the status column should be taken out of
service (e.g., in order for the value of some other column
of the same conceptual row to be modified).
Conceptual Row Deletion
For deletion of conceptual rows, a management protocol set
operation is issued which sets the instance of the status
column to `destroy'. This request may be made regardless of
the current value of the status column (e.g., it is possible
to delete conceptual rows which are either `notReady',
`notInService' or `active'.) If the operation succeeds,
then all instances associated with the conceptual row are
immediately removed."
SYNTAX INTEGER {
-- the following two values are states:
-- these values may be read or written
active(1),
notInService(2),
-- the following value is a state:
-- this value may be read, but not written
notReady(3),
-- the following three values are
-- actions: these values may be written,
-- but are never read
createAndGo(4),
createAndWait(5),
destroy(6)
}
TimeStamp ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"The value of the sysUpTime object at which a specific
occurrence happened. The specific occurrence must be
McCloghrie, et al. Standards Track [Page 17]
RFC 2579 Textual Conventions for SMIv2 April 1999
defined in the description of any object defined using this
type.
If sysUpTime is reset to zero as a result of a re-
initialization of the network management (sub)system, then
the values of all TimeStamp objects are also reset.
However, after approximately 497 days without a re-
initialization, the sysUpTime object will reach 2^^32-1 and
then increment around to zero; in this case, existing values
of TimeStamp objects do not change. This can lead to
ambiguities in the value of TimeStamp objects."
SYNTAX TimeTicks
TimeInterval ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"A period of time, measured in units of 0.01 seconds."
SYNTAX INTEGER (0..2147483647)
DateAndTime ::= TEXTUAL-CONVENTION
DISPLAY-HINT "2d-1d-1d,1d:1d:1d.1d,1a1d:1d"
STATUS current
DESCRIPTION
"A date-time specification.
field octets contents range
----- ------ -------- -----
1 1-2 year* 0..65536
2 3 month 1..12
3 4 day 1..31
4 5 hour 0..23
5 6 minutes 0..59
6 7 seconds 0..60
(use 60 for leap-second)
7 8 deci-seconds 0..9
8 9 direction from UTC '+' / '-'
9 10 hours from UTC* 0..13
10 11 minutes from UTC 0..59
* Notes:
- the value of year is in network-byte order
- daylight saving time in New Zealand is +13
For example, Tuesday May 26, 1992 at 1:30:15 PM EDT would be
displayed as:
1992-5-26,13:30:15.0,-4:0
McCloghrie, et al. Standards Track [Page 18]
RFC 2579 Textual Conventions for SMIv2 April 1999
Note that if only local time is known, then timezone
information (fields 8-10) is not present."
SYNTAX OCTET STRING (SIZE (8 | 11))
StorageType ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"Describes the memory realization of a conceptual row. A
row which is volatile(2) is lost upon reboot. A row which
is either nonVolatile(3), permanent(4) or readOnly(5), is
backed up by stable storage. A row which is permanent(4)
can be changed but not deleted. A row which is readOnly(5)
cannot be changed nor deleted.
If the value of an object with this syntax is either
permanent(4) or readOnly(5), it cannot be written.
Conversely, if the value is either other(1), volatile(2) or
nonVolatile(3), it cannot be modified to be permanent(4) or
readOnly(5). (All illegal modifications result in a
'wrongValue' error.)
Every usage of this textual convention is required to
specify the columnar objects which a permanent(4) row must
at a minimum allow to be writable."
SYNTAX INTEGER {
other(1), -- eh?
volatile(2), -- e.g., in RAM
nonVolatile(3), -- e.g., in NVRAM
permanent(4), -- e.g., partially in ROM
readOnly(5) -- e.g., completely in ROM
}
McCloghrie, et al. Standards Track [Page 19]
RFC 2579 Textual Conventions for SMIv2 April 1999
TDomain ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"Denotes a kind of transport service.
Some possible values, such as snmpUDPDomain, are defined in
the SNMPv2-TM MIB module. Other possible values are defined
in other MIB modules."
REFERENCE "The SNMPv2-TM MIB module is defined in RFC 1906."
SYNTAX OBJECT IDENTIFIER
TAddress ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"Denotes a transport service address.
A TAddress value is always interpreted within the context of a
TDomain value. Thus, each definition of a TDomain value must
be accompanied by a definition of a textual convention for use
with that TDomain. Some possible textual conventions, such as
SnmpUDPAddress for snmpUDPDomain, are defined in the SNMPv2-TM
MIB module. Other possible textual conventions are defined in
other MIB modules."
REFERENCE "The SNMPv2-TM MIB module is defined in RFC 1906."
SYNTAX OCTET STRING (SIZE (1..255))
END
3. Mapping of the TEXTUAL-CONVENTION macro
The TEXTUAL-CONVENTION macro is used to convey the syntax and
semantics associated with a textual convention. It should be noted
that the expansion of the TEXTUAL-CONVENTION macro is something which
conceptually happens during implementation and not during run-time.
The name of a textual convention must consist of one or more letters
or digits, with the initial character being an upper case letter.
The name must not conflict with any of the reserved words listed in
section 3.7 of [2], should not consist of all upper case letters, and
shall not exceed 64 characters in length. (However, names longer
than 32 characters are not recommended.) The hyphen is not allowed
in the name of a textual convention (except for use in information
modules converted from SMIv1 which allowed hyphens in ASN.1 type
assignments). Further, all names used for the textual conventions
defined in all "standard" information modules shall be unique.
McCloghrie, et al. Standards Track [Page 20]
RFC 2579 Textual Conventions for SMIv2 April 1999
3.1. Mapping of the DISPLAY-HINT clause
The DISPLAY-HINT clause, which need not be present, gives a hint as
to how the value of an instance of an object with the syntax defined
using this textual convention might be displayed. The DISPLAY-HINT
clause must not be present if the Textual Convention is defined with
a syntax of: OBJECT IDENTIFIER, IpAddress, Counter32, Counter64, or
any enumerated syntax (BITS or INTEGER). The determination of
whether it makes sense for other syntax types is dependent on the
specific definition of the Textual Convention.
When the syntax has an underlying primitive type of INTEGER, the hint
consists of an integer-format specification, containing two parts.
The first part is a single character suggesting a display format,
either: `x' for hexadecimal, or `d' for decimal, or `o' for octal, or
`b' for binary. For all types, when rendering the value, leading
zeros are omitted, and for negative values, a minus sign is rendered
immediately before the digits. The second part is always omitted for
`x', `o' and `b', and need not be present for `d'. If present, the
second part starts with a hyphen and is followed by a decimal number,
which defines the implied decimal point when rendering the value.
For example:
Hundredths ::= TEXTUAL-CONVENTION
DISPLAY-HINT "d-2"
...
SYNTAX INTEGER (0..10000)
suggests that a Hundredths value of 1234 be rendered as "12.34"
When the syntax has an underlying primitive type of OCTET STRING, the
hint consists of one or more octet-format specifications. Each
specification consists of five parts, with each part using and
removing zero or more of the next octets from the value and producing
the next zero or more characters to be displayed. The octets within
the value are processed in order of significance, most significant
first.
The five parts of a octet-format specification are:
(1) the (optional) repeat indicator; if present, this part is a `*',
and indicates that the current octet of the value is to be used as
the repeat count. The repeat count is an unsigned integer (which
may be zero) which specifies how many times the remainder of this
octet-format specification should be successively applied. If the
repeat indicator is not present, the repeat count is one.
McCloghrie, et al. Standards Track [Page 21]
RFC 2579 Textual Conventions for SMIv2 April 1999
(2) the octet length: one or more decimal digits specifying the number
of octets of the value to be used and formatted by this octet-
specification. Note that the octet length can be zero. If less
than this number of octets remain in the value, then the lesser
number of octets are used.
(3) the display format, either: `x' for hexadecimal, `d' for decimal,
`o' for octal, `a' for ascii, or `t' for UTF-8. If the octet
length part is greater than one, and the display format part refers
to a numeric format, then network-byte ordering (big-endian
encoding) is used interpreting the octets in the value. The octets
processed by the `t' display format do not necessarily form an
integral number of UTF-8 characters. Trailing octets which do not
form a valid UTF-8 encoded character are discarded.
(4) the (optional) display separator character; if present, this part
is a single character which is produced for display after each
application of this octet-specification; however, this character is
not produced for display if it would be immediately followed by the
display of the repeat terminator character for this octet-
specification. This character can be any character other than a
decimal digit and a `*'.
(5) the (optional) repeat terminator character, which can be present
only if the display separator character is present and this octet-
specification begins with a repeat indicator; if present, this part
is a single character which is produced after all the zero or more
repeated applications (as given by the repeat count) of this
octet-specification. This character can be any character other
than a decimal digit and a `*'.
Output of a display separator character or a repeat terminator
character is suppressed if it would occur as the last character of
the display.
If the octets of the value are exhausted before all the octet-format
specification have been used, then the excess specifications are
ignored. If additional octets remain in the value after interpreting
all the octet-format specifications, then the last octet-format
specification is re-interpreted to process the additional octets,
until no octets remain in the value.
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.
McCloghrie, et al. Standards Track [Page 22]
RFC 2579 Textual Conventions for SMIv2 April 1999
The value "obsolete" means the definition is obsolete and should not
be implemented and/or can be removed if previously implemented.
While the value "deprecated" also indicates an obsolete definition,
it permits new/continued implementation in order to foster
interoperability with older/existing implementations.
3.3. Mapping of the DESCRIPTION clause
The DESCRIPTION clause, which must be present, contains a textual
definition of the textual convention, which provides all semantic
definitions necessary for implementation, and should embody any
information which would otherwise be communicated in any ASN.1
commentary annotations associated with the object.
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 SYNTAX clause
The SYNTAX clause, which must be present, defines abstract data
structure corresponding to the textual convention. The data
structure must be one of the alternatives defined in the ObjectSyntax
CHOICE or the BITS construct (see section 7.1 in [2]). Note that
this means that the SYNTAX clause of a Textual Convention can not
refer to a previously defined Textual Convention.
An extended subset of the full capabilities of ASN.1 (1988) sub-
typing is allowed, as appropriate to the underlying ASN.1 type. Any
such restriction on size, range or enumerations specified in this
clause represents the maximal level of support which makes "protocol
sense". Restrictions on sub-typing are specified in detail in
Section 9 and Appendix A of [2].
4. Sub-typing of Textual Conventions
The SYNTAX clause of a TEXTUAL CONVENTION macro may be sub-typed in
the same way as the SYNTAX clause of an OBJECT-TYPE macro (see
section 11 of [2]).
5. Revising a Textual Convention Definition
It may be desirable to revise the definition of a textual convention
after experience is gained with it. However, changes are not allowed
if they have any potential to cause interoperability problems "over
McCloghrie, et al. Standards Track [Page 23]
RFC 2579 Textual Conventions for SMIv2 April 1999
the wire" between an implementation using an original specification
and an implementation using an updated specification(s). Such
changes can only be accommodated by defining a new textual convention
(i.e., a new name).
The following revisions are allowed:
(1) A SYNTAX clause containing an enumerated INTEGER may have new
enumerations added or existing labels changed. Similarly, named
bits may be added or existing labels changed for the BITS
construct.
(2) 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.
(3) A REFERENCE clause may be added or updated.
(4) A DISPLAY-HINTS clause may be added or updated.
(5) Clarifications and additional information may be included in the
DESCRIPTION clause.
(6) Any editorial change.
Note that with the introduction of the TEXTUAL-CONVENTION macro,
there is no longer any need to define types in the following manner:
DisplayString ::= OCTET STRING (SIZE (0..255))
When revising an information module containing a definition such as
this, that definition should be replaced by a TEXTUAL-CONVENTION
macro.
6. Security Considerations
This document defines the means to define new data types for the
language used to write and read descriptions of management
information. These data types have no security impact on the
Internet.
McCloghrie, et al. Standards Track [Page 24]
RFC 2579 Textual Conventions for SMIv2 April 1999
7. Editors' Addresses
Keith McCloghrie
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
USA
Phone: +1 408 526 5260
EMail:
[email protected]
David Perkins
SNMPinfo
3763 Benton Street
Santa Clara, CA 95051
USA
Phone: +1 408 221-8702
EMail:
[email protected]
Juergen Schoenwaelder
TU Braunschweig
Bueltenweg 74/75
38106 Braunschweig
Germany
Phone: +49 531 391-3283
EMail:
[email protected]
8. 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
Waldbusser, S., "Transport Mappings for Version 2 of the" Simple
Network Management Protocol (SNMPv2)", RFC 1906, January 1996.
McCloghrie, et al. Standards Track [Page 25]
RFC 2579 Textual Conventions for SMIv2 April 1999
9. 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."
McCloghrie, et al. Standards Track [Page 26]
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
McCloghrie, et al. Standards Track [Page 2]
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 ::=
McCloghrie, et al. Standards Track [Page 3]
RFC 2580 Conformance Statements for SMIv2 April 1999
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
McCloghrie, et al. Standards Track [Page 4]
RFC 2580 Conformance Statements for SMIv2 April 1999
-- 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 ::=
McCloghrie, et al. Standards Track [Page 5]
RFC 2580 Conformance Statements for SMIv2 April 1999
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 ::=
McCloghrie, et al. Standards Track [Page 6]
RFC 2580 Conformance Statements for SMIv2 April 1999
"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 ::=
McCloghrie, et al. Standards Track [Page 7]
RFC 2580 Conformance Statements for SMIv2 April 1999
-- 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
McCloghrie, et al. Standards Track [Page 8]
RFC 2580 Conformance Statements for SMIv2 April 1999
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
McCloghrie, et al. Standards Track [Page 9]
RFC 2580 Conformance Statements for SMIv2 April 1999
-- 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.
McCloghrie, et al. Standards Track [Page 10]
RFC 2580 Conformance Statements for SMIv2 April 1999
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.
McCloghrie, et al. Standards Track [Page 11]
RFC 2580 Conformance Statements for SMIv2 April 1999
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.
McCloghrie, et al. Standards Track [Page 12]
RFC 2580 Conformance Statements for SMIv2 April 1999
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:
McCloghrie, et al. Standards Track [Page 13]
RFC 2580 Conformance Statements for SMIv2 April 1999
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.
McCloghrie, et al. Standards Track [Page 14]
RFC 2580 Conformance Statements for SMIv2 April 1999
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.
McCloghrie, et al. Standards Track [Page 15]
RFC 2580 Conformance Statements for SMIv2 April 1999
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
McCloghrie, et al. Standards Track [Page 16]
RFC 2580 Conformance Statements for SMIv2 April 1999
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 }
McCloghrie, et al. Standards Track [Page 17]
RFC 2580 Conformance Statements for SMIv2 April 1999
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.
McCloghrie, et al. Standards Track [Page 18]
RFC 2580 Conformance Statements for SMIv2 April 1999
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
McCloghrie, et al. Standards Track [Page 19]
RFC 2580 Conformance Statements for SMIv2 April 1999
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
McCloghrie, et al. Standards Track [Page 20]
RFC 2580 Conformance Statements for SMIv2 April 1999
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".
McCloghrie, et al. Standards Track [Page 21]
RFC 2580 Conformance Statements for SMIv2 April 1999
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.
McCloghrie, et al. Standards Track [Page 22]
RFC 2580 Conformance Statements for SMIv2 April 1999
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
McCloghrie, et al. Standards Track [Page 23]
RFC 2580 Conformance Statements for SMIv2 April 1999
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.
McCloghrie, et al. Standards Track [Page 24]
RFC 2580 Conformance Statements for SMIv2 April 1999
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
McCloghrie, et al. Standards Track [Page 25]
RFC 2580 Conformance Statements for SMIv2 April 1999
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.
McCloghrie, et al. Standards Track [Page 26]
RFC 2580 Conformance Statements for SMIv2 April 1999
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:
[email protected]
David Perkins
SNMPinfo
3763 Benton Street
Santa Clara, CA 95051
USA
Phone: +1 408 221-8702
Email:
[email protected]
Juergen Schoenwaelder
TU Braunschweig
Bueltenweg 74/75
38106 Braunschweig
Germany
Phone: +49 531 391-3283
EMail:
[email protected]
McCloghrie, et al. Standards Track [Page 27]
RFC 2580 Conformance Statements for SMIv2 April 1999
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.
McCloghrie, et al. Standards Track [Page 28]
RFC 2580 Conformance Statements for SMIv2 April 1999
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."
McCloghrie, et al. Standards Track [Page 29]
