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rfc:rfc1442
        Network Working Group                                  J. Case
        Request for Comments: 1442                 SNMP Research, Inc.
                                                         K. McCloghrie
                                                    Hughes LAN Systems
                                                               M. Rose
                                          Dover Beach Consulting, Inc.
                                                         S. Waldbusser
                                            Carnegie Mellon University
                                                            April 1993
                     Structure of Management Information
                             for version 2 of the
                 Simple Network Management Protocol (SNMPv2)
        Status of this Memo
        This RFC specifes an IAB standards track protocol for the
        Internet community, and requests discussion and suggestions
        for improvements.  Please refer to the current edition of the
        "IAB Official Protocol Standards" for the standardization
        state and status of this protocol.  Distribution of this memo
        is unlimited.
        Table of Contents
        1 Introduction ..........................................    2
        1.1 A Note on Terminology ...............................    3
        2 Definitions ...........................................    4
        3.1 The MODULE-IDENTITY macro ...........................    5
        3.2 Object Names and Syntaxes ...........................    7
        3.3 The OBJECT-TYPE macro ...............................   10
        3.5 The NOTIFICATION-TYPE macro .........................   12
        3 Information Modules ...................................   13
        3.1 Macro Invocation ....................................   13
        3.1.1 Textual Clauses ...................................   14
        3.2 IMPORTing Symbols ...................................   14
        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 ..................   17
        5.4 Mapping of the DESCRIPTION clause ...................   17
        5.5 Mapping of the REVISION clause ......................   17
        5.6 Mapping of the DESCRIPTION clause ...................   18
        5.7 Mapping of the MODULE-IDENTITY value ................   18
        5.8 Usage Example .......................................   19
        Case, McCloghrie, Rose & Waldbusser                  [Page  i]
        RFC 1442                SMI for SNMPv2              April 1993
        6 Mapping of the OBJECT-IDENTITY macro ..................   20
        6.1 Mapping of the STATUS clause ........................   20
        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 .......................................   21
        7 Mapping of the OBJECT-TYPE macro ......................   22
        7.1 Mapping of the SYNTAX clause ........................   22
        7.1.1 Integer32 and INTEGER .............................   22
        7.1.2 OCTET STRING ......................................   23
        7.1.3 OBJECT IDENTIFIER .................................   23
        7.1.4 BIT STRING ........................................   23
        7.1.5 IpAddress .........................................   23
        7.1.6 Counter32 .........................................   24
        7.1.7 Gauge32 ...........................................   24
        7.1.8 TimeTicks .........................................   24
        7.1.9 Opaque ............................................   25
        7.1.10 NsapAddress ......................................   25
        7.1.11 Counter64 ........................................   26
        7.1.12 UInteger32 .......................................   26
        7.2 Mapping of the UNITS clause .........................   26
        7.3 Mapping of the MAX-ACCESS clause ....................   27
        7.4 Mapping of the STATUS clause ........................   27
        7.5 Mapping of the DESCRIPTION clause ...................   27
        7.6 Mapping of the REFERENCE clause .....................   28
        7.7 Mapping of the INDEX clause .........................   28
        7.7.1 Creation and Deletion of Conceptual Rows ..........   30
        7.8 Mapping of the AUGMENTS clause ......................   31
        7.8.1 Relation between INDEX and AUGMENTS clauses .......   31
        7.9 Mapping of the DEFVAL clause ........................   32
        7.10 Mapping of the OBJECT-TYPE value ...................   33
        7.11 Usage Example ......................................   35
        8 Mapping of the NOTIFICATION-TYPE macro ................   37
        8.1 Mapping of the OBJECTS clause .......................   37
        8.2 Mapping of the STATUS clause ........................   37
        8.3 Mapping of the DESCRIPTION clause ...................   37
        8.4 Mapping of the REFERENCE clause .....................   37
        8.5 Mapping of the NOTIFICATION-TYPE value ..............   38
        8.6 Usage Example .......................................   39
        9 Refined Syntax ........................................   40
        10 Extending an Information Module ......................   41
        10.1 Object Assignments .................................   41
        10.2 Object Definitions .................................   41
        10.3 Notification Definitions ...........................   42
        Case, McCloghrie, Rose & Waldbusser                  [Page ii]
        RFC 1442                SMI for SNMPv2              April 1993
        11 Appendix: de-OSIfying a MIB module ...................   43
        11.1 Managed Object Mapping .............................   43
        11.1.1 Mapping to the SYNTAX clause .....................   44
        11.1.2 Mapping to the UNITS clause ......................   45
        11.1.3 Mapping to the MAX-ACCESS clause .................   45
        11.1.4 Mapping to the STATUS clause .....................   45
        11.1.5 Mapping to the DESCRIPTION clause ................   45
        11.1.6 Mapping to the REFERENCE clause ..................   45
        11.1.7 Mapping to the INDEX clause ......................   45
        11.1.8 Mapping to the DEFVAL clause .....................   45
        11.2 Action Mapping .....................................   46
        11.2.1 Mapping to the SYNTAX clause .....................   46
        11.2.2 Mapping to the MAX-ACCESS clause .................   46
        11.2.3 Mapping to the STATUS clause .....................   46
        11.2.4 Mapping to the DESCRIPTION clause ................   46
        11.2.5 Mapping to the REFERENCE clause ..................   46
        11.3 Event Mapping ......................................   46
        11.3.1 Mapping to the STATUS clause .....................   47
        11.3.2 Mapping to the DESCRIPTION clause ................   47
        11.3.3 Mapping to the REFERENCE clause ..................   47
        12 Acknowledgements .....................................   48
        13 References ...........................................   52
        14 Security Considerations ..............................   54
        15 Authors' Addresses ...................................   54
        Case, McCloghrie, Rose & Waldbusser                   [Page 1]
        RFC 1442                SMI for SNMPv2              April 1993
        1.  Introduction
        A network management system contains: several (potentially
        many) nodes, each with a processing entity, termed an agent,
        which has access to management instrumentation; at least one
        management station; and, a management protocol, used to convey
        management information between the agents and management
        stations.  Operations of the protocol are carried out under an
        administrative framework which defines both authentication and
        authorization policies.
        Network management stations execute management applications
        which monitor and control network elements.  Network elements
        are devices such as hosts, routers, terminal servers, etc.,
        which are monitored and controlled through access to their
        management information.
        Management information is viewed as a collection of managed
        objects, residing in a virtual information store, termed the
        Management Information Base (MIB).  Collections of related
        objects are defined in MIB modules.  These modules are written
        using a subset of OSI's Abstract Syntax Notation One (ASN.1)
        [1].  It is the purpose of this document, the Structure of
        Management Information (SMI), to define that subset.
        The SMI is divided into three parts: module definitions,
        object definitions, and, trap 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.
        Case, McCloghrie, Rose & Waldbusser                   [Page 2]
        RFC 1442                SMI for SNMPv2              April 1993
        1.1.  A Note on Terminology
        For the purpose of exposition, the original Internet-standard
        Network Management Framework, as described in RFCs 1155, 1157,
        and 1212, is termed the SNMP version 1 framework (SNMPv1).
        The current framework is termed the SNMP version 2 framework
        (SNMPv2).
        Case, McCloghrie, Rose & Waldbusser                   [Page 3]
        RFC 1442                SMI for SNMPv2              April 1993
        2.  Definitions
        SNMPv2-SMI DEFINITIONS ::= BEGIN
  1. - the path to the root
        internet       OBJECT IDENTIFIER ::= { iso 3 6 1 }
        directory      OBJECT IDENTIFIER ::= { internet 1 }
        mgmt           OBJECT IDENTIFIER ::= { internet 2 }
        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 }
  1. - transport domains

snmpDomains OBJECT IDENTIFIER ::= { snmpV2 1 }

  1. - transport proxies

snmpProxys OBJECT IDENTIFIER ::= { snmpV2 2 }

  1. - module identities

snmpModules OBJECT IDENTIFIER ::= { snmpV2 3 }

        Case, McCloghrie, Rose & Waldbusser                   [Page 4]
        RFC 1442                SMI for SNMPv2              April 1993
  1. - definitions for information modules
        MODULE-IDENTITY MACRO ::=
        BEGIN
            TYPE NOTATION ::=
                          "LAST-UPDATED" value(Update UTCTime)
                          "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 UTCTime)
                          "DESCRIPTION" Text
  1. - uses the NVT ASCII character set

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

        END
        Case, McCloghrie, Rose & Waldbusser                   [Page 5]
        RFC 1442                SMI for SNMPv2              April 1993
        OBJECT-IDENTITY MACRO ::=
        BEGIN
            TYPE NOTATION ::=
                          "STATUS" Status
                          "DESCRIPTION" Text
                          ReferPart
            VALUE NOTATION ::=
                          value(VALUE OBJECT IDENTIFIER)
            Status ::=
                          "current"
                        | "obsolete"
            ReferPart ::=
                        "REFERENCE" Text
                      | empty
            Text ::= """" string """"
        END
        Case, McCloghrie, Rose & Waldbusser                   [Page 6]
        RFC 1442                SMI for SNMPv2              April 1993
  1. - names of objects
        ObjectName ::=
            OBJECT IDENTIFIER
  1. - syntax of objects
        ObjectSyntax ::=
            CHOICE {
                simple
                    SimpleSyntax,
  1. - note that SEQUENCEs for conceptual tables and
  2. - rows are not mentioned here…
                application-wide
                    ApplicationSyntax
            }
  1. - built-in ASN.1 types
        SimpleSyntax ::=
            CHOICE {
                -- INTEGERs with a more restrictive range
                -- may also be used
                integer-value
                    INTEGER (-2147483648..2147483647),
                string-value
                    OCTET STRING,
                objectID-value
                    OBJECT IDENTIFIER,
  1. - only the enumerated form is allowed

bit-value

                    BIT STRING
            }
        Case, McCloghrie, Rose & Waldbusser                   [Page 7]
        RFC 1442                SMI for SNMPv2              April 1993
  1. - indistinguishable from INTEGER, but never needs more than
  2. - 32-bits for a two's complement representation

Integer32 ::=

            [UNIVERSAL 2]
                IMPLICIT INTEGER (-2147483648..2147483647)
  1. - application-wide types
        ApplicationSyntax ::=
            CHOICE {
                ipAddress-value
                    IpAddress,
                counter-value
                    Counter32,
                gauge-value
                    Gauge32,
                timeticks-value
                    TimeTicks,
                arbitrary-value
                    Opaque,
                nsapAddress-value
                    NsapAddress,
                big-counter-value
                    Counter64,
                unsigned-integer-value
                    UInteger32
            }
  1. - in network-byte order
  2. - (this is a tagged type for historical reasons)

IpAddress ::=

            [APPLICATION 0]
                IMPLICIT OCTET STRING (SIZE (4))
        Case, McCloghrie, Rose & Waldbusser                   [Page 8]
        RFC 1442                SMI for SNMPv2              April 1993
  1. - this wraps

Counter32 ::=

            [APPLICATION 1]
                IMPLICIT INTEGER (0..4294967295)
  1. - this doesn't wrap

Gauge32 ::=

            [APPLICATION 2]
                IMPLICIT INTEGER (0..4294967295)
  1. - hundredths of seconds since an epoch

TimeTicks ::=

            [APPLICATION 3]
                IMPLICIT INTEGER (0..4294967295)
  1. - for backward-compatibility only

Opaque ::=

            [APPLICATION 4]
                IMPLICIT OCTET STRING
  1. - for OSI NSAP addresses
  2. - (this is a tagged type for historical reasons)

NsapAddress ::=

            [APPLICATION 5]
                IMPLICIT OCTET STRING (SIZE (1 | 4..21))
  1. - for counters that wrap in less than one hour with only 32 bits

Counter64 ::=

            [APPLICATION 6]
                IMPLICIT INTEGER (0..18446744073709551615)
  1. - an unsigned 32-bit quantity

UInteger32 ::=

            [APPLICATION 7]
                IMPLICIT INTEGER (0..4294967295)
        Case, McCloghrie, Rose & Waldbusser                   [Page 9]
        RFC 1442                SMI for SNMPv2              April 1993
  1. - definition for objects
        OBJECT-TYPE MACRO ::=
        BEGIN
            TYPE NOTATION ::=
                          "SYNTAX" type(Syntax)
                          UnitsPart
                          "MAX-ACCESS" Access
                          "STATUS" Status
                          "DESCRIPTION" Text
                          ReferPart
                          IndexPart
                          DefValPart
            VALUE NOTATION ::=
                          value(VALUE ObjectName)
            UnitsPart ::=
                          "UNITS" Text
                        | empty
            Access ::=
                          "not-accessible"
                        | "read-only"
                        | "read-write"
                        | "read-create"
            Status ::=
                          "current"
                        | "deprecated"
                        | "obsolete"
            ReferPart ::=
                          "REFERENCE" Text
                        | empty
            IndexPart ::=
                          "INDEX"    "{" IndexTypes "}"
                        | "AUGMENTS" "{" Entry      "}"
                        | empty
            IndexTypes ::=
                          IndexType
                        | IndexTypes "," IndexType
        Case, McCloghrie, Rose & Waldbusser                  [Page 10]
        RFC 1442                SMI for SNMPv2              April 1993
            IndexType ::=
                          "IMPLIED" Index
                        | Index
            Index ::=
                            -- use the SYNTAX value of the
                            -- correspondent OBJECT-TYPE invocation
                          value(Indexobject ObjectName)
            Entry ::=
                            -- use the INDEX value of the
                            -- correspondent OBJECT-TYPE invocation
                          value(Entryobject ObjectName)
            DefValPart ::=
                          "DEFVAL" "{" value(Defval Syntax) "}"
                        | empty
  1. - uses the NVT ASCII character set

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

        END
        Case, McCloghrie, Rose & Waldbusser                  [Page 11]
        RFC 1442                SMI for SNMPv2              April 1993
  1. - definitions for notifications
        NOTIFICATION-TYPE MACRO ::=
        BEGIN
            TYPE NOTATION ::=
                          ObjectsPart
                          "STATUS" Status
                          "DESCRIPTION" Text
                          ReferPart
            VALUE NOTATION ::=
                          value(VALUE OBJECT IDENTIFIER)
            ObjectsPart ::=
                          "OBJECTS" "{" Objects "}"
                        | empty
            Objects ::=
                          Object
                        | Objects "," Object
            Object ::=
                          value(Name ObjectName)
            Status ::=
                          "current"
                        | "deprecated"
                        | "obsolete"
            ReferPart ::=
                        "REFERENCE" Text
                      | empty
  1. - uses the NVT ASCII character set

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

        END
        END
        Case, McCloghrie, Rose & Waldbusser                  [Page 12]
        RFC 1442                SMI for SNMPv2              April 1993
        3.  Information Modules
        An "information module" is an ASN.1 module defining
        information relating to network management.
        The SMI describes how to use a subset of ASN.1 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].
        This classification scheme does not imply a rigid taxonomy.
        For example, a "standard" information module might 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.
        All information modules start with exactly one invocation of
        the MODULE-IDENTITY macro, which provides contact and revision
        history.  This invocation must appear immediately after any
        IMPORTs or EXPORTs 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>
        Case, McCloghrie, Rose & Waldbusser                  [Page 13]
        RFC 1442                SMI for SNMPv2              April 1993
        names the macro being invoked, and <clauses> and <value>
        depend on the definition of the macro.
        An ASN.1 identifier consists of one or more letters, digits,
        or hyphens.  The initial character must be a lower-case
        letter, and the final character may not be a hyphen.  Further,
        a hyphen may not be immediatedly followed by another hyphen.
        For all descriptors appearing in an information module, the
        descriptor shall be unique and mnemonic, and shall not exceed
        64 characters in length.  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.  Further, within any information
        module, the hyphen is not allowed as a character in any
        descriptor.
        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 Clauses
        Some clauses in a macro invocation may take a textual value
        (e.g., the DESCRIPTION clause).  Note that, in order to
        conform to the ASN.1 syntax, the entire value of these clauses
        must be enclosed in double quotation marks, and therefore
        cannot itself contain double quotation marks, although the
        value may be multi-line.
        3.2.  IMPORTing Symbols
        To reference an external object, the IMPORTS statement must be
        used to identify both the descriptor and the module defining
        the descriptor.
        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
        Case, McCloghrie, Rose & Waldbusser                  [Page 14]
        RFC 1442                SMI for SNMPv2              April 1993
        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 even when there is no
        collision when IMPORTing symbols.
        Finally, the IMPORTS statement may not be used to import an
        ASN.1 named type which corresponds to either the SEQUENCE or
        SEQUENCE OF type.
        Case, McCloghrie, Rose & Waldbusser                  [Page 15]
        RFC 1442                SMI for SNMPv2              April 1993
        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:
             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.
        Case, McCloghrie, Rose & Waldbusser                  [Page 16]
        RFC 1442                SMI for SNMPv2              April 1993
        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.
        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.
        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 made to this information
        module, in reverse chronological order.  Each instance of this
        clause contains the date and time of the revision.
        Case, McCloghrie, Rose & Waldbusser                  [Page 17]
        RFC 1442                SMI for SNMPv2              April 1993
        5.6.  Mapping of the DESCRIPTION clause
        The DESCRIPTION clause, which must be present for each
        REVISION clause, contains a high-level textual description of
        the revision identified in that REVISION clause.
        5.7.  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 referring to the information module containing the
        invocation.
        Case, McCloghrie, Rose & Waldbusser                  [Page 18]
        RFC 1442                SMI for SNMPv2              April 1993
        5.8.  Usage Example
        Consider how a skeletal MIB module might be constructed: e.g.,
        FIZBIN-MIB DEFINITIONS ::= BEGIN
        IMPORTS
            MODULE-IDENTITY, OBJECT-TYPE, experimental
                FROM SNMPv2-SMI;
        fizbin MODULE-IDENTITY
            LAST-UPDATED "9210070433Z"
            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      "9210070433Z"
            DESCRIPTION
                    "Initial version of this MIB module."
        -- contact IANA for actual number
            ::= { experimental xx }
        END
        Case, McCloghrie, Rose & Waldbusser                  [Page 19]
        RFC 1442                SMI for SNMPv2              April 1993
        6.  Mapping of the OBJECT-IDENTITY macro
        The OBJECT-IDENTITY macro is used to define information about
        an OBJECT IDENTIFIER assignment.  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.
        The values "current", and "obsolete" are self-explanatory.
        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 an object assignment defined in
        some other information module.
        6.4.  Mapping of the OBJECT-IDENTITY value
        The value of an invocation of the OBJECT-IDENTITY macro is an
        OBJECT IDENTIFIER.
        Case, McCloghrie, Rose & Waldbusser                  [Page 20]
        RFC 1442                SMI for SNMPv2              April 1993
        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 }
        Case, McCloghrie, Rose & Waldbusser                  [Page 21]
        RFC 1442                SMI for SNMPv2              April 1993
        7.  Mapping of the OBJECT-TYPE macro
        The OBJECT-TYPE macro is used to define a 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.
        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 alternatives defined in the
        ObjectSyntax CHOICE.
        Full ASN.1 sub-typing is allowed, as appropriate to the
        underingly ASN.1 type, primarily as an aid to implementors in
        understanding the meaning of the object.  Any such restriction
        on size, range, enumerations or repertoire specified in this
        clause represents the maximal level of support which makes
        "protocol sense".  Of course, sub-typing is not allowed for
        the Counter32 or Counter64 types, but is allowed for the
        Gauge32 type.
        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.
        The INTEGER type may also be used to represent integer-valued
        information, if it contains named-number enumerations, or if
        it is sub-typed to be more constrained than the Integer32
        type.  In the former 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.
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        Finally, the hyphen character is not allowed as a part of the
        label name for any named-number enumeration.
        7.1.2.  OCTET STRING
        The OCTET STRING type represents arbitrary binary or textual
        data.  Although there is no SMI-specified size limitation for
        this type, MIB designers should realize that there may be
        implementation and interoperability limitations for sizes in
        excess of 255 octets.
        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.  BIT STRING
        The BIT STRING type represents an enumeration of named bits.
        This collection is assigned non-negative, contiguous values,
        starting at zero.  Only those named-bits so enumerated may be
        present in a value.
        A requirement on "standard" MIB modules is that the hyphen
        character is not allowed as a part of the label name for any
        named-bit enumeration.
        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.
        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].
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        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 a SYNTAX clause value of TimeStamp (a textual
        convention defined in [3]) indicating the time of the last
        discontinuity.
        The value of the MAX-ACCESS clause for objects with a SYNTAX
        clause value of Counter32 is always "read-only".
        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.
        The maximum value can not be greater than 2^32-1 (4294967295
        decimal).  The value of a Gauge has its maximum value whenever
        the information being modeled is greater or equal to that
        maximum value; if the information being modeled subsequently
        decreases below the maximum value, the Gauge also decreases.
        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.
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        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 when MIB-II's sysUpTime
        [7] was zero, and the second reference epoch is defined as the
        current value of sysUpTime.
        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.  NsapAddress
        The NsapAddress type represents an OSI address as a variable-
        length OCTET STRING.  The first octet of the string contains a
        binary value in the range of 0..20, and indicates the length
        in octets of the NSAP.  Following the first octet, is the
        NSAP, expressed in concrete binary notation, starting with the
        most significant octet.  A zero-length NSAP is used as a
        "special" address meaning "the default NSAP" (analogous to the
        IP address of 0.0.0.0).  Such an NSAP is encoded as a single
        octet, containing the value 0.  All other NSAPs are encoded in
        at least 4 octets.
        Note that the NsapAddress type is a tagged type for historical
        reasons.  Network addresses should be represented using an
        invocation of the TEXTUAL-CONVENTION macro [3].
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        7.1.11.  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 a SYNTAX clause value of TimeStamp (a textual
        convention defined in [3]) indicating the time of the last
        discontinuity.
        The value of the MAX-ACCESS clause for objects with a SYNTAX
        clause value of Counter64 is always "read-only".
        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.
        7.1.12.  UInteger32
        The UInteger32 type represents integer-valued information
        between 0 and 2^32-1 inclusive (0 to 4294967295 decimal).
        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.
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        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.  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 either
        an auxiliary object (see Section 7.7) or an object which is
        accessible only via a notificationn (e.g., snmpTrapOID [5]).
        These values are ordered, from least to greatest: "not-
        accessible", "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".)
        7.4.  Mapping of the STATUS clause
        The STATUS clause, which must be present, indicates whether
        this definition is current or historic.
        The values "current", and "obsolete" are self-explanatory.
        The "deprecated" value indicates that the object is obsolete,
        but that an implementor may wish to support that object to
        foster interoperability with older 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.
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        7.6.  Mapping of the REFERENCE clause
        The REFERENCE clause, which need not be present, contains a
        textual cross-reference to an object defined in some other
        information module.  This is useful when de-osifying a MIB
        module produced by some other organization.
        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.
        Management operations apply exclusively to scalar objects.
        However, it is convenient for developers of management
        applications to impose imaginary, tabular structures on the
        ordered collection of objects that constitute 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
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        object, and <syntax> has the value of that subordinate
        object's SYNTAX clause, optionally omitting the sub-typing
        information.  Further, these ASN.1 types are always present
        (the DEFAULT and OPTIONAL clauses are disallowed in the
        SEQUENCE definition).  The MAX-ACCESS clause for conceptual
        tables and rows is "not-accessible".
        For leaf objects which are not columnar objects, 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.
        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 syntax
        of those objects indicate how to form the instance-identifier:
        (1)  integer-valued: a single sub-identifier taking the
             integer value (this works only for non-negative
             integers);
        (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: `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);
        (5)  IpAddress-valued: 4 sub-identifiers, in the familiar
             a.b.c.d notation.
        (6)  NsapAddress-valued: `n' sub-identifiers, where `n' is the
             length of the value (each octet of the value is encoded
             in a separate sub-identifier);
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        Note that the IMPLIED keyword can only be present for objects
        having a variable-length syntax (e.g., variable-length strings
        or object identifier-valued objects).  Further, the IMPLIED
        keyword may appear at most once within the INDEX clause, and
        if so, is associated with the right-most object having a
        variable-length syntax.  Finally, the IMPLIED keyword may not
        be used on a variable-length string object if that string
        might have a value of zero-length.
        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 newly-defined auxiliary objects is "not-
        accessible".  However, a conceptual row must contain at least
        one columnar object which is not an auxiliary object (i.e.,
        the value of the MAX-ACCESS clause for such an object is
        either "read-only" or "read-create").
        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.
        7.7.1.  Creation and Deletion of Conceptual Rows
        For newly-defined conceptual rows which allow the creation of
        new object instances and 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.
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        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
        extension.  Instances of subordinate columnar objects of a
        conceptual row extension 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 extension
        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.
        Note that a base conceptual row may be augmented by multiple
        conceptual row extensions.
        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.
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        (2)  Otherwise, if there is a sparse relationship between the
             conceptuals rows of this table and an existing table,
             then an INDEX clause should be used which is identical to
             that in the existing table.
        (3)  Otherwise, 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 a SNMPv2 entity acting in an agent role when an object
        instance is created.
        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 a SNMPv2 entity acting in an
        agent role might use.
        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
        a SNMPv2 entity acting in an agent role might use.
        By way of example, consider the following possible DEFVAL
        clauses:
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       ObjectSyntax        DEFVAL clause
       -----------------   ------------
       Integer32           1
                           -- same for Gauge32, TimeTicks, UInteger32
       INTEGER             valid -- enumerated value
       OCTET STRING        'ffffffffffff'H
       OBJECT IDENTIFIER   sysDescr
       BIT STRING          { primary, secondary } -- enumerated values
             IpAddress           'c0210415'H -- 192.33.4.21
        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 "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.
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        Further note that although conceptual tables and rows are
        given administratively assigned names, these conceptual
        objects may not be manipulated in aggregate form by the
        management protocol.
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        7.11.  Usage Example
        Consider how one might define a conceptual table and its
        subordinates.
        evalSlot OBJECT-TYPE
            SYNTAX      INTEGER
            MAX-ACCESS  read-only
            STATUS      current
            DESCRIPTION
                    "The index number of the first unassigned entry in
                    the evaluation table.
                    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 underCreation(1).  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
                    "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 }
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        EvalEntry ::=
            SEQUENCE {
                evalIndex       Integer32,
                evalString      DisplayString,
                evalValue       Integer32,
                evalStatus      RowStatus
            }
        evalIndex OBJECT-TYPE
            SYNTAX      Integer32
            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 executed."
            DEFVAL  { 0 }
                ::= { evalEntry 3 }
        evalStatus OBJECT-TYPE
            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 }
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        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 the
        ordered sequence of MIB objects which are contained within
        every instance of the notification.
        8.2.  Mapping of the STATUS clause
        The STATUS clause, which must be present, indicates whether
        this definition is current or historic.
        The values "current", and "obsolete" are self-explanatory.
        The "deprecated" value indicates that the notification is
        obsolete, but that an implementor may wish to support that
        object to foster interoperability with older 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
        object.  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 a notification defined in some
        other information module.  This is useful when de-osifying a
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        MIB module produced by some other organization.
        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.
        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.
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        8.6.  Usage Example
        Consider how a linkUp trap might be described:
        linkUp NOTIFICATION-TYPE
            OBJECTS { ifIndex }
            STATUS  current
            DESCRIPTION
                    "A linkUp trap signifies that the SNMPv2 entity,
                    acting in an agent role, recognizes that one of
                    the communication links represented in its
                    configuration has come up."
            ::= { snmpTraps 4 }
        According to this invocation, the trap authoritatively
        identified as
             { snmpTraps 4 }
        is used to report a link coming up.
        Note that a SNMPv2 entity acting in an agent role can be
        configured to send this trap to zero or more SNMPv2 entities
        acting in a manager role, depending on the contents of the
        aclTable and viewTable [8] tables.  For example, by judicious
        use of the viewTable, a SNMPv2 entity acting in an agent role
        might be configured to send all linkUp traps to one particular
        SNMPv2 entity, and linkUp traps for only certain interfaces to
        other SNMPv2 entities.
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        9.  Refined Syntax
        Some macros allow an object's syntax to be refined (e.g., the
        SYNTAX clause in the MODULE-COMPLIANCE macro [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 on
    object syntax         range   enumeration     size    repertoire
    -----------------     -----   -----------     ----    ----------
              INTEGER      (1)        (2)           -         -
         OCTET STRING       -          -           (3)       (4)
    OBJECT IDENTIFIER       -          -            -         -
           BIT STRING       -         (2)           -         -
            IpAddress       -          -            -         -
            Counter32       -          -            -         -
              Gauge32      (1)         -            -         -
            TimeTicks       -          -            -         -
          NsapAddress       -          -            -         -
            Counter64       -          -            -         -
        where:
        (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;
        (3)  the size in characters of the value may be refined by
             raising the lower-bounds, by reducing the upper-bounds,
             and/or by reducing the alternative size choices; or,
        (4)  the repertoire of characters in the value may be reduced
             by further sub-typing.
        Otherwise no refinements are possible.
        Note that when refining an object with a SYNTAX clause value
        of Integer32 or UInteger32, the refined SYNTAX is expressed as
        an INTEGER and the restrictions of the table above are used.
        Case, McCloghrie, Rose & Waldbusser                  [Page 40]
        RFC 1442                SMI for SNMPv2              April 1993
        10.  Extending an Information Module
        As experience is gained with a published information module,
        it may be desirable to revise that information module.
        To begin, the invocation of the MODULE-IDENTITY macro should
        be updated to include information about the revision.
        Usually, this consists of updating the LAST-UPDATED clause and
        adding a pair of REVISION and DESCRIPTION clauses.  However,
        other existing clauses in the invocation may be updated.
        Note that the module's label (e.g., "FIZBIN-MIB" from the
        example in Section 5.8), is not changed when the information
        module is revised.
        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.
        (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".
        (3)  A DEFVAL clause may be added or updated.
        (4)  A REFERENCE clause may be added or updated.
        (5)  A UNITS clause may be added.
        (6)  A conceptual row may be augmented by adding new columnar
             objects at the end of the row.
        Case, McCloghrie, Rose & Waldbusser                  [Page 41]
        RFC 1442                SMI for SNMPv2              April 1993
        (7)  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 those specifically allowed above), then the
        OBJECT IDENTIFIER value associated with that object must also
        be changed.
        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.
        Finally, note that if an object has the value of its STATUS
        clause changed, then the value of its DESCRIPTION clause
        should be updated accordingly.
        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.
        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.
        Finally, note that if an object has the value of its STATUS
        clause changed, then the value of its DESCRIPTION clause
        should be updated accordingly.
        Case, McCloghrie, Rose & Waldbusser                  [Page 42]
        RFC 1442                SMI for SNMPv2              April 1993
        11.  Appendix: de-OSIfying a MIB module
        There has been an increasing amount of work recently on taking
        MIBs defined by other organizations (e.g., the IEEE) and de-
        osifying them for use with the Internet-standard network
        management framework.  The steps to achieve this are
        straight-forward, though tedious.  Of course, it is helpful to
        already be experienced in writing MIB modules for use with the
        Internet-standard network management framework.
        The first step is to construct a skeletal MIB module, as shown
        earlier in Section 5.8.  The next step is to categorize the
        objects into groups.  Optional objects are not permitted.
        Thus, when a MIB module is created, optional objects must be
        placed in a additional groups, which, if implemented, all
        objects in the group must be implemented.  For the first pass,
        it is wisest to simply ignore any optional objects in the
        original MIB: experience shows it is better to define a core
        MIB module first, containing only essential objects; later, if
        experience demands, other objects can be added.
        11.1.  Managed Object Mapping
        Next for each managed object class, determine whether there
        can exist multiple instances of that managed object class.  If
        not, then for each of its attributes, use the OBJECT-TYPE
        macro to make an equivalent definition.
        Otherwise, if multiple instances of the managed object class
        can exist, then define a conceptual table having conceptual
        rows each containing a columnar object for each of the managed
        object class's attributes.  If the managed object class is
        contained within the containment tree of another managed
        object class, then the assignment of an object is normally
        required for each of the "distinguished attributes" of the
        containing managed object class.  If they do not already exist
        within the MIB module, then they can be added via the
        definition of additional columnar objects in the conceptual
        row corresponding to the contained managed object class.
        In defining a conceptual row, it is useful to consider the
        optimization of network management operations which will act
        upon its columnar objects.  In particular, it is wisest to
        avoid defining more columnar objects within a conceptual row,
        Case, McCloghrie, Rose & Waldbusser                  [Page 43]
        RFC 1442                SMI for SNMPv2              April 1993
        than can fit in a single PDU.  As a rule of thumb, a
        conceptual row should contain no more than approximately 20
        objects.  Similarly, or as a way to abide by the "20 object
        guideline", columnar objects should be grouped into tables
        according to the expected grouping of network management
        operations upon them.  As such, the content of conceptual rows
        should reflect typical access scenarios, e.g., they should be
        organized along functional lines such as one row for
        statistics and another row for parameters, or along usage
        lines such as commonly-needed objects versus rarely-needed
        objects.
        On the other hand, the definition of conceptual rows where the
        number of columnar objects used as indexes outnumbers the
        number used to hold information, should also be avoided.  In
        particular, the splitting of a managed object class's
        attributes into many conceptual tables should not be used as a
        way to obtain the same degree of flexibility/complexity as is
        often found in MIBs with a myriad of optionals.
        11.1.1.  Mapping to the SYNTAX clause
        When mapping to the SYNTAX clause of the OBJECT-type macro:
        (1)  An object with BOOLEAN syntax becomes a TruthValue [3].
        (2)  An object with INTEGER syntax becomes an Integer32.
        (3)  An object with ENUMERATED syntax becomes an INTEGER with
             enumerations, taking any of the values given which can be
             represented with an Integer32.
        (4)  An object with BIT STRING syntax but no enumerations
             becomes an OCTET STRING.
        (5)  An object with a character string syntax becomes either
             an OCTET STRING, or a DisplayString [3], depending on the
             repertoire of the character string.
        (6)  A non-tabular object with a complex syntax, such as REAL
             or EXTERNAL, must be decomposed, usually into an OCTET
             STRING (if sensible).  As a rule, any object with a
             complicated syntax should be avoided.
        Case, McCloghrie, Rose & Waldbusser                  [Page 44]
        RFC 1442                SMI for SNMPv2              April 1993
        (7)  Tabular objects must be decomposed into rows of columnar
             objects.
        11.1.2.  Mapping to the UNITS clause
        If the description of this managed object defines a unit-
        basis, then mapping to this clause is straight-forward.
        11.1.3.  Mapping to the MAX-ACCESS clause
        This is straight-forward.
        11.1.4.  Mapping to the STATUS clause
        This is straight-forward.
        11.1.5.  Mapping to the DESCRIPTION clause
        This is straight-forward: simply copy the text, making sure
        that any embedded double quotation marks are sanitized (i.e.,
        replaced with single-quotes or removed).
        11.1.6.  Mapping to the REFERENCE clause
        This is straight-forward: simply include a textual reference
        to the object being mapped, the document which defines the
        object, and perhaps a page number in the document.
        11.1.7.  Mapping to the INDEX clause
        If necessary, decide how instance-identifiers for columnar
        objects are to be formed and define this clause accordingly.
        11.1.8.  Mapping to the DEFVAL clause
        Decide if a meaningful default value can be assigned to the
        object being mapped, and if so, define the DEFVAL clause
        accordingly.
        Case, McCloghrie, Rose & Waldbusser                  [Page 45]
        RFC 1442                SMI for SNMPv2              April 1993
        11.2.  Action Mapping
        Actions are modeled as read-write objects, in which writing a
        particular value results in a state change.  (Usually, as a
        part of this state change, some action might take place.)
        11.2.1.  Mapping to the SYNTAX clause
        Usually the Integer32 syntax is used with a distinguished
        value provided for each action that the object provides access
        to.  In addition, there is usually one other distinguished
        value, which is the one returned when the object is read.
        11.2.2.  Mapping to the MAX-ACCESS clause
        Always use read-write or read-create.
        11.2.3.  Mapping to the STATUS clause
        This is straight-forward.
        11.2.4.  Mapping to the DESCRIPTION clause
        This is straight-forward: simply copy the text, making sure
        that any embedded double quotation marks are sanitized (i.e.,
        replaced with single-quotes or removed).
        11.2.5.  Mapping to the REFERENCE clause
        This is straight-forward: simply include a textual reference
        to the action being mapped, the document which defines the
        action, and perhaps a page number in the document.
        11.3.  Event Mapping
        Events are modeled as SNMPv2 notifications using
        NOTIFICATION-TYPE macro.  However, recall that SNMPv2
        emphasizes trap-directed polling.  As such, few, and usually
        no, notifications, need be defined for any MIB module.
        Case, McCloghrie, Rose & Waldbusser                  [Page 46]
        RFC 1442                SMI for SNMPv2              April 1993
        11.3.1.  Mapping to the STATUS clause
        This is straight-forward.
        11.3.2.  Mapping to the DESCRIPTION clause
        This is straight-forward: simply copy the text, making sure
        that any embedded double quotation marks are sanitized (i.e.,
        replaced with single-quotes or removed).
        11.3.3.  Mapping to the REFERENCE clause
        This is straight-forward: simply include a textual reference
        to the notification being mapped, the document which defines
        the notification, and perhaps a page number in the document.
        Case, McCloghrie, Rose & Waldbusser                  [Page 47]
        RFC 1442                SMI for SNMPv2              April 1993
        12.  Acknowledgements
        The section on object definitions (and MIB de-osification) is
        based, in part, on RFCs 1155 and 1212.  The IMPLIED keyword is
        based on a conversation with David T. Perkins in December,
        1991.
        The section on trap definitions is based, in part, on RFC
        1215.
        Finally, the comments of the SNMP version 2 working group are
        gratefully acknowledged:
             Beth Adams, Network Management Forum
             Steve Alexander, INTERACTIVE Systems Corporation
             David Arneson, Cabletron Systems
             Toshiya Asaba
             Fred Baker, ACC
             Jim Barnes, Xylogics, Inc.
             Brian Bataille
             Andy Bierman, SynOptics Communications, Inc.
             Uri Blumenthal, IBM Corporation
             Fred Bohle, Interlink
             Jack Brown
             Theodore Brunner, Bellcore
             Stephen F. Bush, GE Information Services
             Jeffrey D. Case, University of Tennessee, Knoxville
             John Chang, IBM Corporation
             Szusin Chen, Sun Microsystems
             Robert Ching
             Chris Chiotasso, Ungermann-Bass
             Bobby A. Clay, NASA/Boeing
             John Cooke, Chipcom
             Tracy Cox, Bellcore
             Juan Cruz, Datability, Inc.
             David Cullerot, Cabletron Systems
             Cathy Cunningham, Microcom
             James R. (Chuck) Davin, Bellcore
             Michael Davis, Clearpoint
             Mike Davison, FiberCom
             Cynthia DellaTorre, MITRE
             Taso N. Devetzis, Bellcore
             Manual Diaz, DAVID Systems, Inc.
             Jon Dreyer, Sun Microsystems
             David Engel, Optical Data Systems
        Case, McCloghrie, Rose & Waldbusser                  [Page 48]
        RFC 1442                SMI for SNMPv2              April 1993
             Mike Erlinger, Lexcel
             Roger Fajman, NIH
             Daniel Fauvarque, Sun Microsystems
             Karen Frisa, CMU
             Shari Galitzer, MITRE
             Shawn Gallagher, Digital Equipment Corporation
             Richard Graveman, Bellcore
             Maria Greene, Xyplex, Inc.
             Michel Guittet, Apple
             Robert Gutierrez, NASA
             Bill Hagerty, Cabletron Systems
             Gary W. Haney, Martin Marietta Energy Systems
             Patrick Hanil, Nokia Telecommunications
             Matt Hecht, SNMP Research, Inc.
             Edward A. Heiner, Jr., Synernetics Inc.
             Susan E. Hicks, Martin Marietta Energy Systems
             Geral Holzhauer, Apple
             John Hopprich, DAVID Systems, Inc.
             Jeff Hughes, Hewlett-Packard
             Robin Iddon, Axon Networks, Inc.
             David Itusak
             Kevin M. Jackson, Concord Communications, Inc.
             Ole J. Jacobsen, Interop Company
             Ronald Jacoby, Silicon Graphics, Inc.
             Satish Joshi, SynOptics Communications, Inc.
             Frank Kastenholz, FTP Software
             Mark Kepke, Hewlett-Packard
             Ken Key, SNMP Research, Inc.
             Zbiginew Kielczewski, Eicon
             Jongyeoi Kim
             Andrew Knutsen, The Santa Cruz Operation
             Michael L. Kornegay, VisiSoft
             Deirdre C. Kostik, Bellcore
             Cheryl Krupczak, Georgia Tech
             Mark S. Lewis, Telebit
             David Lin
             David Lindemulder, AT&T/NCR
             Ben Lisowski, Sprint
             David Liu, Bell-Northern Research
             John Lunny, The Wollongong Group
             Robert C. Lushbaugh Martin, Marietta Energy Systems
             Michael Luufer, BBN
             Carl Madison, Star-Tek, Inc.
             Keith McCloghrie, Hughes LAN Systems
             Evan McGinnis, 3Com Corporation
        Case, McCloghrie, Rose & Waldbusser                  [Page 49]
        RFC 1442                SMI for SNMPv2              April 1993
             Bill McKenzie, IBM Corporation
             Donna McMaster, SynOptics Communications, Inc.
             John Medicke, IBM Corporation
             Doug Miller, Telebit
             Dave Minnich, FiberCom
             Mohammad Mirhakkak, MITRE
             Rohit Mital, Protools
             George Mouradian, AT&T Bell Labs
             Patrick Mullaney, Cabletron Systems
             Dan Myers, 3Com Corporation
             Rina Nathaniel, Rad Network Devices Ltd.
             Hien V. Nguyen, Sprint
             Mo Nikain
             Tom Nisbet
             William B. Norton, MERIT
             Steve Onishi, Wellfleet Communications, Inc.
             David T. Perkins, SynOptics Communications, Inc.
             Carl Powell, BBN
             Ilan Raab, SynOptics Communications, Inc.
             Richard Ramons, AT&T
             Venkat D. Rangan, Metric Network Systems, Inc.
             Louise Reingold, Sprint
             Sam Roberts, Farallon Computing, Inc.
             Kary Robertson, Concord Communications, Inc.
             Dan Romascanu, Lannet Data Communications Ltd.
             Marshall T. Rose, Dover Beach Consulting, Inc.
             Shawn A. Routhier, Epilogue Technology Corporation
             Chris Rozman
             Asaf Rubissa, Fibronics
             Jon Saperia, Digital Equipment Corporation
             Michael Sapich
             Mike Scanlon, Interlan
             Sam Schaen, MITRE
             John Seligson, Ultra Network Technologies
             Paul A. Serice, Corporation for Open Systems
             Chris Shaw, Banyan Systems
             Timon Sloane
             Robert Snyder, Cisco Systems
             Joo Young Song
             Roy Spitier, Sprint
             Einar Stefferud, Network Management Associates
             John Stephens, Cayman Systems, Inc.
             Robert L. Stewart, Xyplex, Inc. (chair)
             Kaj Tesink, Bellcore
             Dean Throop, Data General
        Case, McCloghrie, Rose & Waldbusser                  [Page 50]
        RFC 1442                SMI for SNMPv2              April 1993
             Ahmet Tuncay, France Telecom-CNET
             Maurice Turcotte, Racal Datacom
             Warren Vik, INTERACTIVE Systems Corporation
             Yannis Viniotis
             Steven L. Waldbusser, Carnegie Mellon Universitty
             Timothy M. Walden, ACC
             Alice Wang, Sun Microsystems
             James Watt, Newbridge
             Luanne Waul, Timeplex
             Donald E. Westlake III, Digital Equipment Corporation
             Gerry White
             Bert Wijnen, IBM Corporation
             Peter Wilson, 3Com Corporation
             Steven Wong, Digital Equipment Corporation
             Randy Worzella, IBM Corporation
             Daniel Woycke, MITRE
             Honda Wu
             Jeff Yarnell, Protools
             Chris Young, Cabletron
             Kiho Yum, 3Com Corporation
        Case, McCloghrie, Rose & Waldbusser                  [Page 51]
        RFC 1442                SMI for SNMPv2              April 1993
        13.  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]  Case, J., McCloghrie, K., Rose, M., and Waldbusser, S.,
             "Conformance Statements for version 2 of the the Simple
             Network Management Protocol (SNMPv2)", RFC 1444, SNMP
             Research, Inc., Hughes LAN Systems, Dover Beach
             Consulting, Inc., Carnegie Mellon University, April 1993.
        [3]  Case, J., McCloghrie, K., Rose, M., and Waldbusser, S.,
             "Textual Conventions for version 2 of the the Simple
             Network Management Protocol (SNMPv2)", RFC 1443, SNMP
             Research, Inc., Hughes LAN Systems, Dover Beach
             Consulting, Inc., Carnegie Mellon University, April 1993.
        [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]  Case, J., McCloghrie, K., Rose, M., and Waldbusser, S.,
             "Management Information Base for version 2 of the Simple
             Network Management Protocol (SNMPv2)", RFC 1450, SNMP
             Research, Inc., Hughes LAN Systems, Dover Beach
             Consulting, Inc., Carnegie Mellon University, April 1993.
        [6]  Case, J., McCloghrie, K., Rose, M., and Waldbusser, S.,
             "Protocol Operations for version 2 of the Simple Network
             Management Protocol (SNMPv2)", RFC 1448, SNMP Research,
             Inc., Hughes LAN Systems, Dover Beach Consulting, Inc.,
             Carnegie Mellon University, April 1993.
        [7]  McCloghrie, K., and Rose, M., "Management Information
             Base for Network Management of TCP/IP-based internets:
             MIB-II", STD 17, RFC 1213, March 1991.
        [8]  McCloghrie, K., and Galvin, J., "Party MIB for version 2
             of the Simple Network Management Protocol (SNMPv2)", RFC
             1447, Hughes LAN Systems, Trusted Information Systems,
        Case, McCloghrie, Rose & Waldbusser                  [Page 52]
        RFC 1442                SMI for SNMPv2              April 1993
             April 1993.
        Case, McCloghrie, Rose & Waldbusser                  [Page 53]
        RFC 1442                SMI for SNMPv2              April 1993
        14.  Security Considerations
        Security issues are not discussed in this memo.
        15.  Authors' Addresses
             Jeffrey D. Case
             SNMP Research, Inc.
             3001 Kimberlin Heights Rd.
             Knoxville, TN  37920-9716
             US
             Phone: +1 615 573 1434
             Email: case@snmp.com
             Keith McCloghrie
             Hughes LAN Systems
             1225 Charleston Road
             Mountain View, CA  94043
             US
             Phone: +1 415 966 7934
             Email: kzm@hls.com
             Marshall T. Rose
             Dover Beach Consulting, Inc.
             420 Whisman Court
             Mountain View, CA  94043-2186
             US
             Phone: +1 415 968 1052
             Email: mrose@dbc.mtview.ca.us
             Steven Waldbusser
             Carnegie Mellon University
             4910 Forbes Ave
             Pittsburgh, PA  15213
             US
             Phone: +1 412 268 6628
             Email: waldbusser@cmu.edu
        Case, McCloghrie, Rose & Waldbusser                  [Page 54]
/data/webs/external/dokuwiki/data/pages/rfc/rfc1442.txt · Last modified: 1993/04/30 22:08 (external edit)