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rfc:std:std58

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))

  1. - format is YYMMDDHHMMZ or YYYYMMDDHHMMZ

McCloghrie, et al. Standards Track [Page 4]

RFC 2578 SMIv2 April 1999

  1. - where: YY - last two digits of year (only years
  2. - between 1900-1999)
  3. - YYYY - last four digits of the year (any year)
  4. - MM - month (01 through 12)
  5. - DD - day of month (01 through 31)
  6. - HH - hours (00 through 23)
  7. - MM - minutes (00 through 59)
  8. - Z - denotes GMT (the ASCII character Z)
  9. -
  10. - For example, "9502192015Z" and "199502192015Z" represent
  11. - 8:15pm GMT on 19 February 1995. Years after 1999 must use
  12. - the four digit year format. Years 1900-1999 may use the
  13. - 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
  1. - 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
  1. - 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,
  1. - note that SEQUENCEs for conceptual tables and
  2. - 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),
  1. - OCTET STRINGs with a more restrictive size
  2. - 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
  1. - 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
  1. - 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:
  1. any 7-bit displayable ASCII characters except quote ("),
  2. tab characters,
  3. spaces, and
  4. 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:
  1. named types defined by ASN.1 itself, specifically: INTEGER,

OCTET STRING, OBJECT IDENTIFIER, SEQUENCE, SEQUENCE OF type,

  1. 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.

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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

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         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: mrose@dbc.mtview.ca.us"
     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.

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 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.

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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.

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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.

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 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.)

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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

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 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,

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 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".)

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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);

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(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:

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(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

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 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.

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 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]

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     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.

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             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]

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(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: kzm@cisco.com

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

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
  1. - 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:
  1. the use of character codes 0-127 (decimal)
  1. the graphics characters (32-126) are interpreted as

US ASCII

  1. NUL, LF, CR, BEL, BS, HT, VT and FF have the special

meanings specified in RFC 854

  1. the other 25 codes have no standard interpretation
  1. the sequence 'CR LF' means newline
  1. the sequence 'CR NUL' means carriage-return
  1. an 'LF' not preceded by a 'CR' means moving to the

same column on the next line.

  1. 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]

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  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:
  1. `active', which indicates that the conceptual row is

available for use by the managed device;

  1. `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;
  1. `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);
  1. `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;
  1. `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,
  1. `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

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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:
  1. a value is returned, indicating that some other

management station has already created this conceptual

               row.  We return to interaction 1.
  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.

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RFC 2579 Textual Conventions for SMIv2 April 1999

  1. 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

  1. 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.
  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. 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.
  1. 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),
  1. - the following value is a state:
  2. - this value may be read, but not written

notReady(3),

  1. - the following three values are
  2. - actions: these values may be written,
  3. - 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:
  1. the value of year is in network-byte order
  2. 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: kzm@cisco.com
 David Perkins
 SNMPinfo
 3763 Benton Street
 Santa Clara, CA 95051
 USA
 Phone: +1 408 221-8702
 EMail: dperkins@snmpinfo.com
 Juergen Schoenwaelder
 TU Braunschweig
 Bueltenweg 74/75
 38106 Braunschweig
 Germany
 Phone: +49 531 391-3283
 EMail: schoenw@ibr.cs.tu-bs.de

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

SyntaxPart ::= "SYNTAX" Syntax

              | empty
  1. - 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"
  1. - 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

  1. - 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
  1. - 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

  1. - 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:

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 snmpBasicNotificationsGroup NOTIFICATION-GROUP
     NOTIFICATIONS { coldStart, authenticationFailure }
     STATUS        current
     DESCRIPTION
             "The two notifications which an agent is required to
             implement."
    ::= { snmpMIBGroups 7 }
 According to this invocation, the conformance group named
      { snmpMIBGroups 7 }
 contains 2 notifications.

5. Mapping of the MODULE-COMPLIANCE macro

 The MODULE-COMPLIANCE macro is used to convey a minimum set of
 requirements with respect to implementation of one or more MIB
 modules.  It should be noted that the expansion of the MODULE-
 COMPLIANCE macro is something which conceptually happens during
 implementation and not during run-time.
 A requirement on all "standard" MIB modules is that a corresponding
 MODULE-COMPLIANCE specification is also defined, either in the same
 information module or in a companion information module.

5.1. Mapping of the STATUS clause

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

5.2. Mapping of the DESCRIPTION clause

 The DESCRIPTION clause, which must be present, contains a textual
 definition of this compliance statement and should embody any
 information which would otherwise be communicated in any ASN.1
 commentary annotations associated with the statement.

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5.3. Mapping of the REFERENCE clause

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

5.4. Mapping of the MODULE clause

 The MODULE clause, which must be present, is repeatedly used to name
 each MIB module for which compliance requirements are being
 specified.  Each MIB module is named by its module name, and
 optionally, by its associated OBJECT IDENTIFIER as well.  The module
 name can be omitted when the MODULE-COMPLIANCE invocation occurs
 inside a MIB module, to refer to the encompassing MIB module.

5.4.1. Mapping of the MANDATORY-GROUPS clause

 The MANDATORY-GROUPS clause, which need not be present, names the one
 or more object or notification groups within the correspondent MIB
 module which are unconditionally mandatory for implementation.  If an
 agent claims compliance to the MIB module, then it must implement
 each and every object and notification within each conformance group
 listed.  That is, if an agent returns a noSuchObject exception in
 response to a management protocol get operation [4] for any object
 within any mandatory conformance group for every possible MIB view,
 or if the agent cannot generate each notification listed in any
 conformance group under the appropriate circumstances, then that
 agent is not a conformant implementation of the MIB module.

5.4.2. Mapping of the GROUP clause

 The GROUP clause, which need not be present, is repeatedly used to
 name each object and notification group which is conditionally
 mandatory for compliance to the MIB module.  The GROUP clause can
 also be used to name unconditionally optional groups.  A group named
 in a GROUP clause must be absent from the correspondent MANDATORY-
 GROUPS clause.
 Conditionally mandatory groups include those which are mandatory only
 if a particular protocol is implemented, or only if another group is
 implemented.  A GROUP clause's DESCRIPTION specifies the conditions
 under which the group is conditionally mandatory.
 A group which is named in neither a MANDATORY-GROUPS clause nor a
 GROUP clause, is unconditionally optional for compliance to the MIB
 module.

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5.4.3. Mapping of the OBJECT clause

 The OBJECT clause, which need not be present, is repeatedly used to
 specify each MIB object for which compliance has a refined
 requirement with respect to the MIB module definition.  The MIB
 object must be present in one of the conformance groups named in the
 correspondent MANDATORY-GROUPS clause or GROUP clauses.
 By definition, each object specified in an OBJECT clause follows a
 MODULE clause which names the information module in which that object
 is defined.  Therefore, the use of an IMPORTS statement, to specify
 from where such objects are imported, is redundant and is not
 required in an information module.

5.4.3.1. Mapping of the SYNTAX clause

 The SYNTAX clause, which need not be present, is used to provide a
 refined SYNTAX for the object named in the correspondent OBJECT
 clause.  Note that if this clause and a WRITE-SYNTAX clause are both
 present, then this clause only applies when instances of the object
 named in the correspondent OBJECT clause are read.
 Consult Section 9 of [2] for more information on refined syntax.

5.4.3.2. Mapping of the WRITE-SYNTAX clause

 The WRITE-SYNTAX clause, which need not be present, is used to
 provide a refined SYNTAX for the object named in the correspondent
 OBJECT clause when instances of that object are written.
 Consult Section 9 of [2] for more information on refined syntax.

5.4.3.3. Mapping of the MIN-ACCESS clause

 The MIN-ACCESS clause, which need not be present, is used to define
 the minimal level of access for the object named in the correspondent
 OBJECT clause.  If this clause is absent, the minimal level of access
 is the same as the maximal level specified in the correspondent
 invocation of the OBJECT-TYPE macro.  If present, this clause must
 not specify a greater level of access than is specified in the
 correspondent invocation of the OBJECT-TYPE macro.
 The level of access for certain types of objects is fixed according
 to their syntax definition.  These types include: conceptual tables
 and rows, auxiliary objects, and objects with the syntax of
 Counter32, Counter64 (and possibly, certain types of textual
 conventions).  A MIN-ACCESS clause should not be present for such

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

5.4.4. Mapping of the DESCRIPTION clause

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

5.5. Mapping of the MODULE-COMPLIANCE value

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

5.6. Usage Example

 The compliance statement contained in the (hypothetical) XYZv2-MIB
 might be:
 xyzMIBCompliance MODULE-COMPLIANCE
     STATUS  current
     DESCRIPTION
             "The compliance statement for XYZv2 entities which
             implement the XYZv2 MIB."
    MODULE  -- compliance to the containing MIB module
        MANDATORY-GROUPS { xyzSystemGroup,
                           xyzStatsGroup, xyzTrapGroup,
                           xyzSetGroup,
                           xyzBasicNotificationsGroup }
        GROUP   xyzV1Group
        DESCRIPTION
            "The xyzV1 group is mandatory only for those
             XYZv2 entities which also implement XYZv1."
::= { xyzMIBCompliances 1 }
 According to this invocation, to claim alignment with the compliance
 statement named
      { xyzMIBCompliances 1 }

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

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6. Mapping of the AGENT-CAPABILITIES macro

 The AGENT-CAPABILITIES macro is used to convey a set of capabilities
 present in an agent.  It should be noted that the expansion of the
 AGENT-CAPABILITIES macro is something which conceptually happens
 during implementation and not during run-time.
 When a MIB module is written, it is divided into units of conformance
 termed groups.  If an agent claims to implement a group, then it must
 implement each and every object, or each and every notification,
 within that group.  Of course, for whatever reason, an agent might
 implement only a subset of the groups within a MIB module.  In
 addition, the definition of some MIB objects/notifications leave some
 aspects of the definition to the discretion of an implementor.
 Practical experience has demonstrated a need for concisely describing
 the capabilities of an agent with respect to one or more MIB modules.
 The AGENT-CAPABILITIES macro allows an agent implementor to describe
 the precise level of support which an agent claims in regards to a
 MIB group, and to bind that description to the value of an instance
 of sysORID [3].  In particular, some objects may have restricted or
 augmented syntax or access-levels.
 If the AGENT-CAPABILITIES invocation is given to a management-station
 implementor, then that implementor can build management applications
 which optimize themselves when communicating with a particular agent.
 For example, the management-station can maintain a database of these
 invocations.  When a management-station interacts with an agent, it
 retrieves from the agent the values of all instances of sysORID [3].
 Based on this, it consults the database to locate each entry matching
 one of the retrieved values of sysORID.  Using the located entries,
 the management application can now optimize its behavior accordingly.
 Note that the AGENT-CAPABILITIES macro specifies refinements or
 variations with respect to OBJECT-TYPE and NOTIFICATION-TYPE macros
 in MIB modules, NOT with respect to MODULE-COMPLIANCE macros in
 compliance statements.

6.1. Mapping of the PRODUCT-RELEASE clause

 The PRODUCT-RELEASE clause, which must be present, contains a textual
 description of the product release which includes this set of
 capabilities.

6.2. Mapping of the STATUS clause

 The STATUS clause, which must be present, indicates whether this

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

6.3. Mapping of the DESCRIPTION clause

 The DESCRIPTION clause, which must be present, contains a textual
 description of this set of capabilities.

6.4. Mapping of the REFERENCE clause

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

6.5. Mapping of the SUPPORTS clause

 The SUPPORTS clause, which need not be present, is repeatedly used to
 name each MIB module for which the agent claims a complete or partial
 implementation.  Each MIB module is named by its module name, and
 optionally, by its associated OBJECT IDENTIFIER (as registered by the
 MODULE-IDENTITY macro, see [2]) as well.

6.5.1. Mapping of the INCLUDES clause

 The INCLUDES clause, which must follow each and every use of the
 SUPPORTS clause, is used to name each MIB group associated with the
 SUPPORTS clause, which the agent claims to implement.

6.5.2. Mapping of the VARIATION clause

 The VARIATION clause, which need not be present, is repeatedly used
 to name each object or notification which the agent implements in
 some variant or refined fashion with respect to the correspondent
 invocation of the OBJECT-TYPE or NOTIFICATION-TYPE macro.
 Note that the variation concept is meant for generic implementation
 restrictions, e.g., if the variation for an object depends on the
 values of other objects, then this should be noted in the appropriate
 DESCRIPTION clause.
 By definition, each object specified in a VARIATION clause follows a
 SUPPORTS clause which names the information module in which that
 object is defined.  Therefore, the use of an IMPORTS statement, to
 specify from where such objects are imported, is redundant and is not

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 required in an information module.

6.5.2.1. Mapping of the SYNTAX clause

 The SYNTAX clause, which need not be present, is used to provide a
 refined SYNTAX for the object named in the correspondent VARIATION
 clause.  Note that if this clause and a WRITE-SYNTAX clause are both
 present, then this clause only applies when instances of the object
 named in the correspondent VARIATION clause are read.
 Consult Section 9 of [2] for more information on refined syntax.
 Note that for enumerated INTEGERs and for the BITS construct, the
 changes allowed when updating a MIB module include the addition of
 enumerations and/or changing the labels of existing enumerations (see
 Section 10.2 of [2]).  This type of change can cause problems for an
 AGENT-CAPABILITIES macro written against the old revision of a MIB
 module.  One way to avoid such problems is to explicitly list all
 objects having an enumerated syntax in a VARIATION clause, even when
 all enumerations are currently supported.

6.5.2.2. Mapping of the WRITE-SYNTAX clause

 The WRITE-SYNTAX clause, which need not be present, is used to
 provide a refined SYNTAX for the object named in the correspondent
 VARIATION clause when instances of that object are written.
 Consult Section 9 of [2] for more information on refined syntax.

6.5.2.3. Mapping of the ACCESS clause

 The ACCESS clause, which need not be present, is used to indicate the
 agent provides less than the maximal level of access to the object or
 notification named in the correspondent VARIATION clause.
 The only value applicable to notifications is "not-implemented".
 The value "not-implemented" indicates the agent does not implement
 the object or notification, and in the ordering of possible values is
 equivalent to "not-accessible".
 The value "write-only" is provided solely for backward compatibility,
 and shall not be used for newly-defined object types.  In the
 ordering of possible values, "write-only" is less than "not-
 accessible".

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6.5.2.4. Mapping of the CREATION-REQUIRES clause

 The CREATION-REQUIRES clause, which need not be present, is used to
 name the columnar objects of a conceptual row to which values must be
 explicitly assigned, by a management protocol set operation, before
 the agent will allow the instance of the status column of that row to
 be set to `active'.  (Consult the definition of RowStatus [5].)
 If the conceptual row does not have a status column (i.e., the
 objects corresponding to the conceptual table were defined using the
 mechanisms in [6,7]), then the CREATION-REQUIRES clause, which need
 not be present, is used to name the columnar objects of a conceptual
 row to which values must be explicitly assigned, by a management
 protocol set operation, before the agent will create new instances of
 objects in that row.
 This clause must not be present unless the object named in the
 correspondent VARIATION clause is a conceptual row, i.e., has a
 syntax which resolves to a SEQUENCE containing columnar objects.  The
 objects named in the value of this clause usually will refer to
 columnar objects in that row.  However, objects unrelated to the
 conceptual row may also be specified.
 All objects which are named in the CREATION-REQUIRES clause for a
 conceptual row, and which are columnar objects of that row, must have
 an access level of "read-create".

6.5.2.5. Mapping of the DEFVAL clause

 The DEFVAL clause, which need not be present, is used to provide a
 alternate DEFVAL value for the object named in the correspondent
 VARIATION clause.  The semantics of this value are identical to those
 of the OBJECT-TYPE macro's DEFVAL clause.

6.5.2.6. Mapping of the DESCRIPTION clause

 The DESCRIPTION clause, which must be present for each use of the
 VARIATION clause, contains a textual description of the variant or
 refined implementation of the object or notification.

6.6. Mapping of the AGENT-CAPABILITIES value

 The value of an invocation of the AGENT-CAPABILITIES macro is an
 OBJECT IDENTIFIER, which names the value of sysORID [3] for which
 this capabilities statement is valid.

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6.7. Usage Example

 Consider how a capabilities statement for an agent might be
 described:
 exampleAgent AGENT-CAPABILITIES
     PRODUCT-RELEASE      "ACME Agent release 1.1 for 4BSD."
     STATUS               current
     DESCRIPTION          "ACME agent for 4BSD."
     SUPPORTS             SNMPv2-MIB
         INCLUDES         { systemGroup, snmpGroup, snmpSetGroup,
                            snmpBasicNotificationsGroup }
         VARIATION        coldStart
             DESCRIPTION  "A coldStart trap is generated on all
                          reboots."
     SUPPORTS             IF-MIB
         INCLUDES         { ifGeneralGroup, ifPacketGroup }
         VARIATION        ifAdminStatus
             SYNTAX       INTEGER { up(1), down(2) }
             DESCRIPTION  "Unable to set test mode on 4BSD."
         VARIATION        ifOperStatus
             SYNTAX       INTEGER { up(1), down(2) }
             DESCRIPTION  "Information limited on 4BSD."
     SUPPORTS             IP-MIB
         INCLUDES         { ipGroup, icmpGroup }
         VARIATION        ipDefaultTTL
             SYNTAX       INTEGER (255..255)
             DESCRIPTION  "Hard-wired on 4BSD."
         VARIATION        ipInAddrErrors
             ACCESS       not-implemented
             DESCRIPTION  "Information not available on 4BSD."
         VARIATION        ipNetToMediaEntry
             CREATION-REQUIRES { ipNetToMediaPhysAddress }
             DESCRIPTION  "Address mappings on 4BSD require
                          both protocol and media addresses."
     SUPPORTS             TCP-MIB
         INCLUDES         { tcpGroup }
         VARIATION        tcpConnState

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             ACCESS       read-only
             DESCRIPTION  "Unable to set this on 4BSD."
     SUPPORTS             UDP-MIB
         INCLUDES         { udpGroup }
     SUPPORTS             EVAL-MIB
         INCLUDES         { functionsGroup, expressionsGroup }
         VARIATION        exprEntry
             CREATION-REQUIRES { evalString, evalStatus }
             DESCRIPTION  "Conceptual row creation is supported."
     ::= { acmeAgents 1 }
 According to this invocation, an agent with a sysORID value of
      { acmeAgents 1 }
 supports objects defined in six MIB modules.
 From SNMPv2-MIB, five conformance groups are supported.
 From IF-MIB, the ifGeneralGroup and ifPacketGroup groups are
 supported.  However, the objects ifAdminStatus and ifOperStatus have
 a restricted syntax.
 From IP-MIB, all objects in the ipGroup and icmpGroup are supported
 except ipInAddrErrors, while ipDefaultTTL has a restricted range, and
 when creating a new instance in the ipNetToMediaTable, the set-
 request must create an instance of ipNetToMediaPhysAddress.
 From TCP-MIB, the tcpGroup is supported except that tcpConnState is
 available only for reading.
 From UDP-MIB, the udpGroup is fully supported.
 From the EVAL-MIB, all the objects contained in the functionsGroup
 and expressionsGroup conformance groups are supported, without
 variation.  In addition, creation of new instances in the expr table
 is supported, and requires both of the objects:  evalString and
 evalStatus, to be assigned a value.

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7. Extending an Information Module

 As experience is gained with a published information module, it may
 be desirable to revise that information module.
 Section 10 of [2] defines the rules for extending an information
 module.  The remainder of this section defines how conformance
 groups, compliance statements, and capabilities statements may be
 extended.

7.1. Conformance Groups

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

(1) A STATUS clause value of "current" may be revised as "deprecated"

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

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

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

   DESCRIPTION clause.

(4) Any editorial change.

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

7.2. Compliance Definitions

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

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 descriptor and a new OBJECT IDENTIFIER value.
 The following revisions are allowed:

(1) A STATUS clause value of "current" may be revised as "deprecated"

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

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

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

   DESCRIPTION clause(s).

(4) Any editorial change.

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

7.3. Capabilities Definitions

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

(1) A STATUS clause value of "current" may be revised as "obsolete".

   When making such a change, the DESCRIPTION clause should be updated
   to explain the rationale.

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

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

   DESCRIPTION clause(s).

(4) Any editorial change.

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

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8. Security Considerations

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

9. Editors' Addresses

 Keith McCloghrie
 Cisco Systems, Inc.
 170 West Tasman Drive
 San Jose, CA  95134-1706
 USA
 Phone: +1 408 526 5260
 EMail: kzm@cisco.com
 David Perkins
 SNMPinfo
 3763 Benton Street
 Santa Clara, CA 95051
 USA
 Phone: +1 408 221-8702
 Email: dperkins@snmpinfo.com
 Juergen Schoenwaelder
 TU Braunschweig
 Bueltenweg 74/75
 38106 Braunschweig
 Germany
 Phone: +49 531 391-3283
 EMail: schoenw@ibr.cs.tu-bs.de

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10. References

[1] Information processing systems - Open Systems Interconnection -

   Specification of Abstract Syntax Notation One (ASN.1),
   International Organization for Standardization.  International
   Standard 8824, (December, 1987).

[2] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M.

   and S. Waldbusser, "Structure of Management Information Version 2
   (SMIv2)", STD 58, RFC 2578, April 1999.

[3] The SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M. and

   S. Waldbusser, "Management Information Base for Version 2 of the
   Simple Network Management Protocol (SNMPv2)", RFC 1907, January
   1996.

[4] The SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M. and

   S. Waldbusser, "Protocol Operations for Version 2 of the Simple
   Network Management Protocol (SNMPv2)", RFC 1905, January 1996.

[5] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M.

   and S. Waldbusser, "Textual Conventions for SMIv2", STD 58,
   RFC 2579, April 1999.

[6] Rose, M. and K. McCloghrie, "Structure and Identification of

   Management Information for TCP/IP-based internets", STD 16, RFC
   1155, May 1990.

[7] Rose, M. and K. McCloghrie, "Concise MIB Definitions", STD 16, RFC

   1212, March 1991.

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11. Full Copyright Statement

 Copyright (C) The Internet Society (1999).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."

McCloghrie, et al. Standards Track [Page 29]

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