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Versions: 02 RFC 1442

          Draft   Structure of Management Information for SNMPv2  Oct 92
          
          
                       Structure of Management Information
                               for version 2 of the
                   Simple Network Management Protocol (SNMPv2)
          
                             Thu Nov 12 08:51:15 1992                     |
          
          
                                 Jeffrey D. Case
                               SNMP Research, Inc.
                        University of Tennessee, Knoxville
                                 case@cs.utk.edu
          
          
                                 Keith McCloghrie
                                Hughes LAN Systems
                                   kzm@hls.com
          
          
                                 Marshall T. Rose
                           Dover Beach Consulting, Inc.
                              mrose@dbc.mtview.ca.us
          
          
                               Steven L. Waldbusser
                            Carnegie Mellon University
                            waldbusser@andrew.cmu.edu
          
          
          
          
          
          
          1.  Status of this Memo
          
          This document is an Internet Draft.  Internet Drafts are
          working documents of the Internet Engineering Task Force
          (IETF), its Areas, and its Working Groups.  Note that other
          groups may also distribute working documents as Internet
          Drafts.
          
          Internet Drafts are valid for a maximum of six months and may
          be updated, replaced, or obsoleted by other documents at any
          time.  It is inappropriate to use Internet Drafts as reference
          material or to cite them other than as a "work in progress".
          
          
          
          
          
          
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          Draft   Structure of Management Information for SNMPv2  Oct 92
          
          
          2.  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 management 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 four parts: object definitions, trap
          definitions, compliance definitions, and capabilities
          definitions.
          
          (1)  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.  Collections of related objects are grouped
               together to form a unit of conformance.  An ASN.1 macro,
               OBJECT-GROUP, is used to concisely convey the syntax and
               semantics of such a group.
          
          (2)  Notification definitions are used when describing an       |
               unsolicited transmission of management information.        |
               An ASN.1 macro, NOTIFICATION-TYPE, is used to concisely    |
               convey the syntax and semantics of a notification.         |
          
          (3)  Compliance definitions are used when describing
               requirements for agents with respect to object
               definitions.  An ASN.1 macro, MODULE-COMPLIANCE, is used
          
          
          
          
          
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               to concisely convey such requirements.
          
          (4)  Capability definitions are used when describing the
               capabilities of agents with respect to object
               definitions.  An ASN.1 macro, AGENT-CAPABILITIES, is used
               to concisely convey such capabilities.
          
          
          2.1.  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).                                                       +
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          3.  Definitions
          
          SNMPv2-SMI DEFINITIONS ::= BEGIN
          
          
          -- the path to the root
          
          internet      OBJECT IDENTIFIER ::= { iso org(3) dod(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 }
          
          
          snmpV2        OBJECT IDENTIFIER ::=
                              { joint-iso-ccitt mhs(6) group(6) mtr(200) 4 }
          snmpMappings  OBJECT IDENTIFIER ::= { snmpV2 1 }
          -- { snmpV2 2 } is obsolete
          
          -- these two values will go away
          -- when the SNMP Security working group reconvenes
          smpProtocols OBJECT IDENTIFIER ::= { snmpV2 3 }
          smpMD5AuthProtocol OBJECT IDENTIFIER ::= { smpProtocols 1 }
          
          snmpModules   OBJECT IDENTIFIER ::= { snmpV2 4 }
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          -- information about a module
          
          MODULE-IDENTITY MACRO ::=
          BEGIN
              TYPE NOTATION ::=
                            "LAST-UPDATED" value(update UTCTime)
                            "ORGANIZATION" value(organization Text)
                            "CONTACT-INFO" value(contact Text)
                            "DESCRIPTION" value(description Text)
                            RevisionPart
          
              VALUE NOTATION ::=
                            value(VALUE OBJECT IDENTIFIER)
          
              RevisionPart ::=
                            Revisions
                          | empty
              Revisions ::=
                            Revision
                          | Revisions Revision
              Revision ::=
                            "REVISION" value(update UTCTime)
                            "DESCRIPTION" value(description Text)
          
              -- uses the NVT ASCII character set
              Text ::= OCTET STRING
          END
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          -- definition for objects
          
          OBJECT-TYPE MACRO ::=
          BEGIN
              TYPE NOTATION ::=
                            "SYNTAX" type(ObjectSyntax)
                            UnitsPart
                            "MAX-ACCESS" Access
                            "STATUS" Status
                            "DESCRIPTION" value(description Text)
                            ReferPart
                            IndexPart
                            DefValPart
          
              VALUE NOTATION ::=
                            value(VALUE ObjectName)
          
              UnitsPart ::=
                            "UNITS" value(units Text)
                          | empty
          
              Access ::=
                            "not-accessible"
                          | "read-only"
                          | "read-write"
                          | "read-create"
          
              Status ::=
                            "current"
                          | "deprecated"
                          | "obsolete"
          
              ReferPart ::=
                            "REFERENCE" value(reference Text)
                          | empty
          
              IndexPart ::=
                            "INDEX"    "{" IndexTypes "}"
                          | "AUGMENTS" "{" Entry      "}"
                          | empty
              IndexTypes ::=
                            IndexType
                          | IndexTypes "," IndexType
          
          
          
          
          
          
          
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              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 ObjectSyntax) "}"
                          | empty
          
              -- uses the NVT ASCII character set
              Text ::= OCTET STRING
          END
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          -- names of objects
          
          ObjectName ::=
              OBJECT IDENTIFIER
          
          
          -- syntax of objects
          
          ObjectSyntax ::=
              CHOICE {
                  simple
                      SimpleSyntax,
          
                    -- note that SEQUENCEs for conceptual tables and
                    -- rows are not mentioned here...
          
                  application-wide
                      ApplicationSyntax
              }
          
          
          -- 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,
          
                  -- only the enumerated form is allowed
                  bit-value
                      BIT STRING
              }
          
          
          
          
          
          
          
          
          
          
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          -- indistinguishable from INTEGER, but never needs more than
          -- 32-bits for a two's complement representation
          Integer32 ::=
              [UNIVERSAL 2]
                  IMPLICIT INTEGER (-2147483648..2147483647)
          
          
          -- 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
              }
          
          -- in network-byte order
          IpAddress ::=
              [APPLICATION 0]
                  IMPLICIT OCTET STRING (SIZE (4))
          
          -- this wraps
          Counter32 ::=
              [APPLICATION 1]
                  IMPLICIT INTEGER (0..4294967295)
          
          
          
          
          
          
          
          
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          -- this doesn't wrap
          Gauge32 ::=
              [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 OSI NSAP addresses
          NsapAddress ::=
              [APPLICATION 5]
                  IMPLICIT OCTET STRING (SIZE (1 | 4..21))
          
          -- for counters that wrap in less than one hour with only 32 bits
          Counter64 ::=
              [APPLICATION 6]
                  IMPLICIT INTEGER (0..18446744073709551615)
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          -- definitions for object groups (a unit of conformance)
          
          OBJECT-GROUP MACRO ::=
          BEGIN
              TYPE NOTATION ::=
                            ObjectsPart
                            "STATUS" Status
                            "DESCRIPTION" value(description Text)
                            ReferPart
          
              VALUE NOTATION ::=
                            value(VALUE OBJECT IDENTIFIER)
          
              ObjectsPart ::=
                            "OBJECTS" "{" Objects "}"
              Objects ::=
                            Object
                          | Objects "," Object
              Object ::=
                            value(object ObjectName)
          
              Status ::=
                            "current"
                          | "deprecated"
                          | "obsolete"
          
              ReferPart ::=
                            "REFERENCE" value(reference Text)
                          | empty
          
              -- uses the NVT ASCII character set
              Text ::= OCTET STRING
          END
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          -- definitions for notifications                                |
          
          NOTIFICATION-TYPE MACRO ::=                                     |
          BEGIN
              TYPE NOTATION ::=
                            ObjectsPart
                            "STATUS" Status
                            "DESCRIPTION" value(description Text)
                            ReferPart
          
              VALUE NOTATION ::=
                            value (VALUE OBJECT IDENTIFIER)
          
              ObjectPart ::=
                            "OBJECTS" "{" Objects "}"
                          | empty
              Objects ::=
                            Object
                          | Objects "," Object
              Object ::=
                            value(object ObjectName)
          
              Status ::=
                            "current"
                          | "deprecated"
                          | "obsolete"
          
              ReferPart ::=
                          "REFERENCE" value (reference Text)
                        | empty
          
              -- uses the NVT ASCII character set
              Text ::= OCTET STRING
          END
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          -- definitions for compliance
          
          MODULE-COMPLIANCE MACRO ::=
          BEGIN
              TYPE NOTATION ::=
                            "STATUS" Status
                            "DESCRIPTION" value(description Text)
                            ReferPart
                            ModulePart
          
              VALUE NOTATION ::=
                            value(VALUE OBJECT IDENTIFIER)
          
              Status ::=
                            "current"
                          | "deprecated"
                          | "obsolete"
          
              ReferPart ::=
                          "REFERENCE" value (reference Text)
                        | empty
          
              ModulePart ::=
                            Modules
                          | empty
              Modules ::=
                            Module
                          | Modules Module
              Module ::=
                            -- name of module --
                            "MODULE" ModuleName
                            MandatoryPart
                            CompliancePart
          
              ModuleName ::=
                            identifier ModuleIdentifier
                          -- must not be empty unless contained
                          -- in MIB Module
                          | empty
              ModuleIdentifier ::=
                            value (moduleID OBJECT IDENTIFIER)
                          | empty
          
              MandatoryPart ::=
                            "MANDATORY-GROUPS" "{" Groups "}"
          
          
          
          
          
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                          | empty
          
              Groups ::=
                            Group
                          | Groups "," Group
              Group ::=
                            value(group OBJECT IDENTIFIER)
          
              CompliancePart ::=
                            Compliances
                          | empty
              Compliances ::=
                            Compliance
                          | Compliances Compliance
              Compliance ::=
                            Group
                          | Object
          
              Group ::=
                            "GROUP" value(object OBJECT IDENTIFIER)
                            "DESCRIPTION" value(description Text)
          
              Object ::=
                            "OBJECT" value(object ObjectName)
                            SyntaxPart
                            WriteSyntaxPart
                            AccessPart
                            "DESCRIPTION" value(description Text)
          
              -- must be a refinement for object's SYNTAX clause
              SyntaxPart ::=
                            "SYNTAX" type(SYNTAX)
                          | empty
          
              -- must be a refinement for object's SYNTAX clause
              WriteSyntaxPart ::=
                            "WRITE-SYNTAX" type(WriteSYNTAX)
                          | empty
          
              AccessPart ::=
                            "MIN-ACCESS" Access
                          | empty
              Access ::=
                            "not-accessible"
                          | "read-only"
          
          
          
          
          
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                          | "read-write"
                          | "read-create"
          
              -- uses the NVT ASCII character set
              Text ::= OCTET STRING
          END
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          -- definitions for agent capabilities
          
          AGENT-CAPABILITIES MACRO ::=
          BEGIN
              TYPE NOTATION ::=
                            "PRODUCT-RELEASE" value(release Text)
                            "STATUS" Status
                            "DESCRIPTION" value(description Text)
                            ReferPart
                            ModulePart
          
              VALUE NOTATION ::=
                            -- agent's sysObjectID [2] or snmpORID [3]
                            value(VALUE OBJECT IDENTIFIER)
          
              Status ::=
                            "current"
                          | "deprecated"
                          | "obsolete"
          
              ReferPart ::=
                          "REFERENCE" value (reference Text)
                        | empty
          
              ModulePart ::=
                            Modules
                          | empty
              Modules ::=
                            Module
                          | Modules Module
              Module ::=
                            -- name of module --
                            "SUPPORTS" ModuleName
                            "INCLUDES" "{" Groups "}"
                            VariationPart
          
              ModuleName ::=
                            identifier ModuleIdentifier
              ModuleIdentifier ::=
                            value (moduleID OBJECT IDENTIFIER)
                          | empty
          
              Groups ::=
                            Group
                          | Groups "," Group
          
          
          
          
          
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              Group ::=
                            value(group OBJECT IDENTIFIER)
          
              VariationPart ::=
                            Variations
                          | empty
              Variations ::=
                            Variation
                          | Variations Variation
          
              Variation ::=
                            "VARIATION" value(object ObjectName)
                            SyntaxPart
                            WriteSyntaxPart
                            AccessPart
                            CreationPart
                            DefValPart
                            "DESCRIPTION" value(description Text)
          
              -- must be a refinement for object's SYNTAX clause
              SyntaxPart ::=
                            "SYNTAX" type(SYNTAX)
                          | empty
          
              -- must be a refinement for object's SYNTAX clause
              WriteSyntaxPart ::=
                            "WRITE-SYNTAX" type(WriteSYNTAX)
                          | empty
          
              AccessPart ::=
                            "ACCESS" Access
                          | empty
          
              Access ::=
                            "not-implemented"
                          | "read-only"
                          | "read-write"
                          | "read-create"
                          -- following is for backward-compatibility only
                          | "write-only"
          
              CreationPart ::=
                            "CREATION-REQUIRES" "{" Cells "}"
                          | empty
          
          
          
          
          
          
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              Cells ::=
                            Cell
                          | Cells "," Cell
          
              Cell ::=
                            value(cell ObjectName)
          
              DefValPart ::=
                            "DEFVAL" "{" value (defval ObjectSyntax) "}"
                          | empty
          
              -- uses the NVT ASCII character set
              Text ::= OCTET STRING
          END
          
          
          END
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          4.  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 OBJECT-
               GROUP macros (if notification definitions are included,    |
               then the NOTIFICATION-TYPE macro is also used);            |
          
          (2)  compliance statements for MIB modules, which make use of
               the MODULE-COMPLIANCE macros; and,
          
          (3)  capability statements for agent implementations which
               make use of the AGENT-CAPABILITIES macros.
          
          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.
          
          
          4.1.  Macro Invocation
          
          Within an information module, each macro invocation appears
          as:
          
               <descriptor> <macro> <clauses> ::= <value>
          
          
          
          
          
          
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          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.
          
          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 each "standard"
          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.
          
          
          4.1.1.  Textual Clauses
          
          Some clauses in a macro invocation may take a textual value
          (e.g., the DESCRIPTION clause).
          
          
          4.2.  IMPORTing Symbols
          
          When symbols from "enterprise-specific" information modules
          are referenced  (e.g., a descriptor), there is the possibility
          of collision.
          
          To reference an external object, the IMPORTS statement must be  |
          used to identify both the descriptor and the module defining    |
          the descriptor.  If two different information modules define    |
          the same descriptor for different objects, then this ambiguity  |
          is resolved by prefixing the descriptor with the name of the    |
          information module and a dot                                    |
          ("."), i.e.,
          
          
          
          
          
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               "module.descriptor"                                        |
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          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.
          
          
          
          
          
          
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          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.
          
          
          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.
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          5.8.  Usage Example
          
          Consider how a skeletal MIB module might be constructed: e.g.,
          
               RFCxxxx-MIB DEFINITIONS ::= BEGIN
          
               IMPORTS
                   MODULE-IDENTITY, OBJECT-TYPE, OBJECT-GROUP, experimental
                       FROM SNMPv2-SMI;
          
          
               xxxx 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
          
          
          
          
          
          
          
          
          
          
          
          
          
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          6.  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.
          
          
          6.1.  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.  Any restriction on size, range,
          enumerations or repertoire specified in this clause represents
          the maximal level of support which makes "protocol sense".
          
          The semantics of ObjectSyntax are now described.
          
          
          6.1.1.  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 subtyped to be more constrained than the Integer32 type.
          In the former case, only those named-numbers so enumerated may
          be present as a value.  Further, the enumerated values must
          all be positive.
          
          A requirement on "standard" information modules is that the
          hyphen character is not allowed as a part of the label name
          for any named-number enumeration.
          
          
          6.1.2.  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
          
          
          
          
          
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          excess of 255 octets.
          
          
          6.1.3.  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).
          
          
          6.1.4.  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.
          
          
          6.1.5.  IpAddress
          
          The IpAddress type represents a 32-bit internet address.  It
          is represented as an OCTET STRING of length 4, in network
          byte-order.
          
          
          6.1.6.  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
          
          
          
          
          
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          defined with a SYNTAX clause value of TimeStamp (a textual      |
          convention defined in [4])                                      |
          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".
          
          
          6.1.7.  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.
          
          
          6.1.8.  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.
          
          
          6.1.9.  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 [5] 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.
          
          Further note that by use of the ASN.1 EXTERNAL type, non-ASN.1
          types may be used in opaquely-encoded data.
          
          
          
          
          
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          A requirement on "standard" MIB modules is that no object may
          have a SYNTAX clause value of Opaque.
          
          
          6.1.10.  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 a SYNTAX clause value of TimeStamp (a textual      |
          convention defined in [4])                                      |
          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.
          
          
          6.1.11.  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.
          
          
          
          
          
          
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          6.2.  Mapping of the UNITS clause
          
          This UNITS clause, which need not be present, contains a
          textual definition of the units associated with that object.
          
          
          6.3.  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".
          
          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".)
          
          
          6.4.  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 that object is obsolete,
          but that an implementor may wish to support that object to
          foster interoperability with older implementations.
          
          
          6.5.  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
          
          
          
          
          
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          any information which would otherwise be communicated in any
          ASN.1 commentary annotations associated with the object.
          
          
          6.6.  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.
          
          
          6.7.  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:
          
          
          
          
          
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               <descriptor> <syntax>
          
          where <descriptor> is the descriptor naming a subordinate
          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.
          
          
          
          
          
          
          
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          (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);
          
          Note that the IMPLIED keyword can only be present for string-
          valued objects, excluding IpAddress- and NsapAddress-valued
          objects.
          
          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.
          
          
          6.7.1.  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      |
          [4])                                                            |
          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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          6.8.  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.
          
          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.
          
          
          6.9.  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 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
          
          
          
          
          
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          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:
          
               ObjectSyntax        DEFVAL clause
               -----------------   ------------
               Integer32           1
                                   -- same for Gauge32, TimeTicks
               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.
          
          
          6.10.  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
          
          
          
          
          
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               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.
          
          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.
          
          
          6.10.1.  Naming Hierarchy
          
          The root of the subtree administered by the Internet Assigned
          Numbers Authority (IANA) for the Internet is:
          
               internet    OBJECT IDENTIFIER ::= { iso org(3) dod(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.
          
          
          
          
          
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          The mgmt(2) subtree is used to identify "standard" objects.
          
          The experimental(3) subtree is used to identify objects used
          in Internet experiments.  As a part of the assignment process,
          the IANA may make requirements as to how that subtree is used.
          
          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.
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          6.11.  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      OCTET STRING,
                  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      OCTET STRING
              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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          7.  Mapping of the OBJECT-GROUP macro
          
          When a MIB module is written, each collection of related
          managed objects defined within the MIB module is combined into
          a unit of conformance termed a MIB group.  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, a SNMPv2 entity acting in an agent
          role must return an reasonably accurate value for management
          protocol retrieval operations; similarly, if the object is
          writable, then in response to a management protocol set
          operation, a SNMPv2 entity must accordingly be able to
          reasonably influence the underlying managed entity.  If a
          SNMPv2 entity acting in an agent role can not implement an
          object, the management protocol provides for the SNMPv2 entity
          to return an exception or error, e.g, noSuchObject [6].  Under
          no circumstances shall a SNMPv2 entity 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 [6].
          
          
          7.1.  Mapping of the OBJECTS clause
          
          The OBJECTS clause which must be present, is used to name each
          object contained in the group.  Each of the named objects must
          be defined in the same information module as the OBJECT-GROUP
          macro appears, and must have a MAX-ACCESS clause value of
          "read-only", "read-write", or "read-create".
          
          
          7.2.  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 that object is obsolete,
          but that an implementor may wish to support that object to
          foster interoperability with older implementations.
          
          
          
          
          
          
          
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          7.3.  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.
          
          
          7.4.  Mapping of the REFERENCE clause
          
          The REFERENCE clause, which need not be present, contains a
          textual cross-reference to a group  defined in some other
          information module.  This is useful when de-osifying a MIB
          module produced by some other organization.
          
          
          7.5.  Mapping of the OBJECT-GROUP value
          
          The value of an invocation of the OBJECT-GROUP macro is the
          name of the group, which is an OBJECT IDENTIFIER, an
          administratively assigned name.
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          7.6.  Usage Example
          
          Consider how the system group from MIB-II [2] might be
          described:
          
          system OBJECT-GROUP
              OBJECTS     { sysDescr, sysObjectID, sysUpTime,
                            sysContact, sysName, sysLocation,
                            sysServices }
              STATUS  current
              DESCRIPTION
                      "The system group defines objects which are common
                      to all managed systems."
              ::= { mib-2 1 }
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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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 an 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 that object 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.                                     |
          
          
          
          
          
          
          
          
          
          
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          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 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.                                                           -
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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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.                             |
          The instance of ifIndex corresponding to this link will be
          present as the third variable in the variable-bindings field.
          
          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 [9] 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.  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.
          
          
          9.1.  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.
          The "deprecated" value indicates that that object is obsolete,
          but that an implementor may wish to support that object to
          foster interoperability with older implementations.
          
          
          9.2.  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.
          
          
          9.3.  Mapping of the REFERENCE clause
          
          The REFERENCE clause, which need not be present, contains a
          textual cross-reference to a compliance statement defined in
          some other information module.
          
          
          9.4.  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
          
          
          
          
          
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          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.
          
          
          9.4.1.  Mapping of the MANDATORY-GROUPS clause
          
          The MANDATORY-GROUPS clause, which need not be present, names
          the one or more groups within the correspondent MIB module
          which are unconditionally mandatory for implementation.  If a
          SNMPv2 entity acting in an agent role claims compliance to the
          MIB module, then it must implement each and every object
          within each group listed.  That is, if a SNMPv2 entity returns
          a noSuchObject exception in response to a management protocol
          get operation [6] for any object within any mandatory group
          for every MIB view, then that SNMPv2 entity is not a
          conformant implementation of the MIB module.
          
          
          9.4.2.  Mapping of the GROUP clause
          
          The GROUP clause which need not be present, is repeatedly used
          to name each MIB group which is conditionally mandatory or
          unconditionally optional for compliance to the MIB module.  A
          MIB 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 MIB group which is named in neither a MANDATORY-GROUPS
          clause nor a GROUP clause, is unconditionally optional for
          compliance to the MIB module.
          
          
          9.4.3.  Mapping of the OBJECT clause
          
          The OBJECT clause which need not be present, is repeatedly
          used to name each MIB object for which compliance has a
          refined requirement with respect to the MIB module definition.
          
          
          
          
          
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          The MIB object must be present in one of the groups named in
          the correspondent MANDATORY-GROUPS clause or GROUP clauses.
          
          
          9.4.3.1.  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 11 for more information on refined syntax.
          
          
          9.4.3.2.  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 11 for more information on refined syntax.
          
          
          9.4.3.3.  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 are:
          conceptual tables and rows, auxiliary objects, and objects
          with the syntax of Counter32, Counter64, or certain types of    |
          textual conventions (e.g., RowStatus [4]).                      |
          A MIN-ACCESS clause should not be present for such objects.
          
          
          
          
          
          
          
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          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.
          
          
          9.4.3.4.  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.
          
          
          9.5.  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
          requirements embodied by that invocation of the macro.
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          9.6.  Usage Example
          
          Consider how a compliance statement might be included at the
          end of the MIB-II document [2], assuming that objects groups
          were defined therein:
          
          rfc1213Compliance MODULE-COMPLIANCE
              STATUS  current
              DESCRIPTION
                      "The compliance statement for SNMPv2 entities
                      residing on systems which implement the Internet
                      suite of protocols."
              MODULE  -- compliance to the containing MIB module
                  MANDATORY-GROUPS   { system, snmp }
          
                  GROUP       interfaces
                  DESCRIPTION
                      "The interfaces group is mandatory for systems
                      with network interfaces."
          
                  GROUP       ip
                  DESCRIPTION
                      "The ip group is mandatory for systems which
                      implement IP."
          
                  GROUP       icmp
                  DESCRIPTION
                      "The icmp group is mandatory for systems which
                      implement ICMP."
          
                  GROUP       tcp
                  DESCRIPTION
                      "The tcp group is mandatory for systems which
                      implement TCP."
                      OBJECT      tcpConnState
                      MIN-ACCESS  read-only
                      DESCRIPTION
                          "A compliant system need not allow
                           write-access to this object."
          
                  GROUP       udp
                  DESCRIPTION
                      "The udp group is mandatory for systems which
                      implement UDP."
          
          
          
          
          
          
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                  GROUP       egp
                  DESCRIPTION
                      "The egp group is mandatory for systems which
                      implement EGP."
          
          ::= { mib2Compliance 1 }
          
          According to this invocation, to claim compliance with the
          specification named
          
               { mib2Compliance 1 }
          
          a system must implement RFC1213's system and snmp groups.  If
          the system implements any network interfaces, then RFC1213's
          interfaces group must be implemented.  Further, if the system
          implements any of the IP, ICMP, TCP, UDP, or EGP protocols,
          then the correspondent group in RFC1213 must be implemented,
          if compliance is to be claimed.  Finally, although RFC1213
          specifies that it makes "protocol sense" for the tcpConnState
          object to be writable, this specification allows the system to
          permit only read-only access and still claim compliance.
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          10.  Mapping of the AGENT-CAPABILITIES macro
          
          The AGENT-CAPABILITIES macro is used to convey the
          capabilities present in a SNMPv2
           entity acting in an agent role.  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 a SNMPv2 entity acting in an
          agent role claims to implement a group, then it must implement
          each and every object within that group.  Of course, for
          whatever reason, a SNMPv2 entity might implement only a subset
          of the groups within a MIB module.  In addition, the
          definition of some MIB objects 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 regards to the
          MIB groups that it implements.  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 sysObjectID [2]
          associated with the agent, or to the value of an instance of
          the snmpORID object in the snmpORTable [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 the agent's sysObjectID [2].  Based on
          this, it consults the database.  If an entry is found, then
          the management application can optimize its behavior
          accordingly.
          
          Note that this binding to sysObjectID may not always suffice
          to define all MIB objects to which an agent can provide
          access.  In particular, this situation occurs where the agent
          dynamically learns of the objects it supports.  In these
          cases, the snmpORID column of snmpORTable [3] contains
          
          
          
          
          
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          information which should be used in addition to sysObjectID.
          
          Note that the AGENT-CAPABILITIES macro specifies refinements
          or variations with respect to OBJECT-TYPE macros in MIB
          modules, NOT with respect to MODULE-COMPLIANCE macros in
          compliance statements.
          
          
          10.1.  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
          agent.
          
          
          10.2.  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 that object is obsolete,
          but that an implementor may wish to support that object to
          foster interoperability with older implementations.
          
          
          10.3.  Mapping of the DESCRIPTION clause
          
          The DESCRIPTION clause, which must be present, contains a
          textual description of this agent.
          
          
          10.4.  Mapping of the REFERENCE clause
          
          The REFERENCE clause, which need not be present, contains a
          textual cross-reference to a capability statement defined in
          some other information module.
          
          
          10.5.  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
          
          
          
          
          
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          IDENTIFIER as well.
          
          
          10.5.1.  Mapping of the INCLUDES clause
          
          The INCLUDES clause, which must be present for each use of the
          SUPPORTS clause, is used to name each MIB group associated
          with the SUPPORT clause, which the agent claims to implement.
          
          
          10.5.2.  Mapping of the VARIATION clause
          
          The VARIATION clause, which need not be present, is repeatedly
          used to name each MIB object which the agent implements in
          some variant or refined fashion with respect to the
          correspondent invocation of the OBJECT-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.
          
          
          10.5.2.1.  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 11 for more information on refined syntax.
          
          
          10.5.2.2.  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 11 for more information on refined syntax.
          
          
          
          
          
          
          
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          10.5.2.3.  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 named in the correspondent VARIATION
          clause.
          
          The value "not-implemented" indicates the agent does not
          implement the object, 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".
          
          
          10.5.2.4.  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(4)'.  (Consult   |
          the definition of RowStatus [4].)                               |
          
          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 [7,8]), 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 present unless the object named in the
          correspondent VARIATION clause is a conceptual row, i.e., has
          a syntax which resolves to a SEQUENCE containing columnar
          objects.  The objects named in the value of this clause
          usually will refer to columnar objects in that row.  However,
          objects unrelated to the conceptual row may also be specified.
          
          All objects which are named in the CREATION-REQUIRES clause
          for a conceptual row, and which are columnar objects of that
          row, must have an access level of "read-create".
          
          
          
          
          
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          10.5.2.5.  Mapping of the DEFVAL clause
          
          The DEFVAL clause, which need not be present, is used to
          provide a refined 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.
          
          
          10.5.2.6.  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.
          
          
          10.6.  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 sysObjectID [2]
          or snmpORID [3] for which this capabilities statement is
          valid.
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          10.7.  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             RFC1213-MIB
                  INCLUDES         { system, interfaces, at, ip, icmp,
                                     tcp, udp, snmp }
          
                  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"
          
                  VARIATION        atEntry
                      CREATION-REQUIRES { atPhysAddress }
                      DESCRIPTION  "Address mappings on 4BSD require
                                   both protocol and media addresses"
          
                  VARIATION        ipDefaultTTL
                      SYNTAX       INTEGER (255..255)
                      DESCRIPTION  "Hard-wired on 4BSD"
          
                  VARIATION        ipInAddrErrors
                      ACCESS       not-implemented
                      DESCRIPTION  "Information not available on 4BSD"
          
                  VARIATION        ipRouteType
                      SYNTAX       INTEGER { direct(3), indirect(4) }
                      WRITE-SYNTAX INTEGER { invalid(2), direct(3),
                                             indirect(4) }
                      DESCRIPTION  "Information limited on 4BSD"
          
                  VARIATION        tcpConnState
                      ACCESS       read-only
                      DESCRIPTION  "Unable to set this on 4BSD"
          
          
          
          
          
          
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              SUPPORTS             EVAL-MIB
                  INCLUDES         { functions, expressions }
                  VARIATION        exprEntry
                      CREATION-REQUIRES { evalString }
                      DESCRIPTION "Conceptual row creation supported"
          
              ::= { acmeAgents 1 }
          
          
          According to this invocation, an agent with a sysObjectID (or
          snmpORID) value of
          
               { acmeAgents 1 }
          
          supports two MIB modules.
          
          From MIB-II, all groups except the egp group are supported.
          However, the object ipInAddrErrors is not implemented, whilst
          the objects
          
               ifAdminStatus
               ifOperStatus
               ipDefaultTTL
               ipRouteType
          
          have a restricted syntax, and the object
          
               tcpConnState
          
          is available only for reading.  Note that in the case of the
          object ipRouteType the set of values which may be read is
          different than the set of values which may be written.
          Finally, when creating a new instance in the atTable, the
          set-request must create an instance of atPhysAddress.
          
          From the EVAL-MIB, all the objects contained in the functions
          and expressions groups are supported, without variation.  In
          addition, creation of new instances in the expr table is
          supported.
          
          
          
          
          
          
          
          
          
          
          
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          11.  Refined Syntax
          
          The SYNTAX and WRITE-SYNTAX clauses in the MODULE-COMPLIANCE
          and AGENT-CAPABILITIES macros allow an object's syntax to be
          refined.  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       -          -            -         -
                    Counter64       -          -            -         -
                  NsapAddress       -          -            -         -
          
          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, then the refined SYNTAX is expressed as an
          INTEGER and the restrictions of the table above are used.
          
          
          
          
          
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          12.  Extending an Information Module
          
          As experience is gained with a published information module,
          it may be desirable to revise that information module.
          
          
          12.1.  Object Definitions
          
          An object definition may be revised in any of the following
          ways:
          
          (1)  Existing objects with a status of "current" may be
               revised as "deprecated" or "obsolete".  Similarly,
               objects with a status of "deprecated" may be revised as
               "obsolete".
          
          (2)  A DEFVAL clause may be added or updated.
          
          (3)  A REFERENCE clause may be added or updated.
          
          (4)  A UNITS clause may be added.
          
          (5)  A conceptual row may be augmented by adding new columnar
               objects at the end of the row.
          
          (6)  Entirely new objects may be defined, named with
               previously unassigned OBJECT IDENTIFIER values.
          
          However, 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.
          
          Finally, note that changing the descriptor associated with an
          existing object, is not considered a semantic change, as these
          strings are used solely for local use, and are not passed via
          the management protocol.
          
          
          12.2.  Trap Definitions
          
          A trap definition may be revised in any of the following ways:
          
          
          
          
          
          
          
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          (1)  A REFERENCE clause may be added or updated.
          
          However, if the semantics of any previously defined trap 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 trap must also be
          changed.
          
          Finally, note that changing the descriptor associated with an
          existing trap, is not considered a semantic change, as these
          strings are used solely for local use, and are not passed via
          the management protocol.
          
          
          12.3.  Compliance Definitions
          
          If any non-editorial change is made to any clause of a
          compliance definition, then the OBJECT IDENTIFIER value
          associated with that compliance definition must also be
          changed, along with its associated descriptor.
          
          
          12.4.  Capabilities Definitions
          
          If any non-editorial change is made to any clause of a
          capabilities definition, then the OBJECT IDENTIFIER value
          associated with that capabilities definition must also be
          changed, along with its associated descriptor.
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          13.  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 optional group, 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.
          
          
          13.1.  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,
          
          
          
          
          
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          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.
          
          
          13.1.1.  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 [4].    |
          
          (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 [4],                   |
               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.
          
          
          
          
          
          
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          (7)  Tabular objects must be decomposed into rows of columnar
               objects.
          
          
          13.1.2.  Mapping to the UNITS clause
          
          If the description of this managed object defines a unit-
          basis, then mapping to this clause is straight-forward.
          
          
          13.1.3.  Mapping to the MAX-ACCESS clause
          
          This is straight-forward.
          
          
          13.1.4.  Mapping to the STATUS clause
          
          This is straight-forward.
          
          
          13.1.5.  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).
          
          
          13.1.6.  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.
          
          
          13.1.7.  Mapping to the INDEX clause
          
          If necessary, decide how instance-identifiers for columnar
          objects are to be formed and define this clause accordingly.
          
          
          13.1.8.  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.
          
          
          
          
          
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          13.2.  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.)
          
          
          13.2.1.  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.
          
          
          13.2.2.  Mapping to the MAX-ACCESS clause
          
          Always use read-write or read-create.
          
          
          13.2.3.  Mapping to the STATUS clause
          
          This is straight-forward.
          
          
          13.2.4.  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).
          
          
          13.2.5.  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.
          
          
          13.3.  Event Mapping
          
          Events are modeled as SNMPv2 traps using NOTIFICATION-TYPE      |
          macro.                                                          |
          However, recall that SNMPv2 emphasizes trap-directed polling.
          As such, few, and usually no, traps, need be defined for any
          
          
          
          
          
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          MIB module.
          
          
          13.3.1.  Mapping to the STATUS clause
          
          This is straight-forward.
          
          
          13.3.2.  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).
          
          
          13.3.3.  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.
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          14.  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.
          
          The section on compliance definitions is based, in part, on a
          conversation with James R. Davin in December, 1990.
          
          The section on capabilities definitions is based, in part, on
          RFC 1303.
          
          Finally, the comments of the SNMP Version 2 working group are
          gratefully acknowledged:
          
               Steve Alexander, Interactive Systems
               Uri Blumenthal, International Business Machines
               Jeffrey D. Case, SNMP Research, Inc.
               Tracy Cox, Bellcore
               James R. (Chuck) Davin, Bellcore
               Mike Davison, FiberCom
               Taso N. Devetzis, Bellcore
               Gary W. Haney, Martin Marietta Energy Systems
               Matt Hecht, SNMP Research, Inc.
               Susan E. Hicks, Martin Marietta Energy Systems
               Satish Joshi, SynOptics
               Mark Kepke, Hewlett-Packard
               Ken Key, SNMP Research, Inc.
               Michael Kornegay, Visisoft
               Deidre C. Kostick, Bellcore
               Cheryl Krupczak, Georgia Tech
               Robert C. Lushbaugh, Martin Marietta Energy Systems
               Keith McCloghrie, Hughes LAN Systems
               Dave Minnich, FiberCom
               Dave Perkins, SynOptics
               Marshall T. Rose, Dover Beach Consulting, Inc.
               Shawn A. Routhier, Epilogue Technology
               Jon Saperia, Digital Equipment Corporation
               Bob Stewart, Xyplex (chair)
               Robert Synder, Cisco Systems
               Maurice Turcotte, Racal Datacom
          
          
          
          
          
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               Steven L. Waldbusser, Carnegie Mellon University
               Bert Wijnen, International Business Machines
               Peter Wilson, 3Com
               Steven Wong, Digital Equipment Corporation
               Chris Young, Cabletron
               Kiho Yum, 3Com
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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          15.  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]  K. McCloghrie and M.T. Rose, Management Information Base
               for Network Management of TCP/IP-based internets: MIB-II.
               Request for Comments 1213, (March, 1991).
          
          [3]  J.D. Case, K. McCloghrie, M.T. Rose, S.L. Waldbusser,
               Management Information Base for version 2 of the Simple
               Network Management Protocol, Internet-Draft, (October 7,
               1992).
          
          [4]                                                             -
               J.D. Case, K. McCloghrie, M.T. Rose, S.L. Waldbusser,
               Textual Conventions for version 2 of the the Simple
               Network Management Protocol (SNMPv2), Internet-Draft,
               (October 7, 1992).
          
          [5]  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).                                    +
          
          [6]  J.D. Case, K. McCloghrie, M.T. Rose, S.L. Waldbusser,
               Protocol Operations for version 2 of the Simple Network
               Management Protocol (SNMPv2), Internet-Draft, (October 7,
               1992).
          
          [7]  M.T. Rose and K. McCloghrie, Structure and Identification
               of Management Information for TCP/IP-based internets.
               Request for Comments 1155, (May, 1990).
          
          [8]  M.T. Rose and K. McCloghrie, Concise MIB Definitions.
               Request for Comments 1212, (March, 1991).
          
          [9]  K. McCloghrie, J.R. Davin, J.M. Galvin, Definitions of
               Managed Objects for Administration of SNMP Parties.
               Request for Comments 1353, (July, 1992).
          
          
          
          
          
          
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          Table of Contents
          
          
          1 Status of this Memo ...................................    1
          2 Introduction ..........................................    2
          2.1 A Note on Terminology ...............................    3
          3 Definitions ...........................................    4
          3.1 The MODULE-IDENTITY macro ...........................    5
          3.2 The OBJECT-TYPE macro ...............................    6
          3.3 Object Names and Syntaxes ...........................    8
          3.4 The OBJECT-GROUP macro ..............................   11
          3.5 The NOTIFICATION-TYPE macro .........................   12
          3.6 The MODULE-COMPLIANCE macro .........................   13
          3.7 The AGENT-CAPABILITIES macro ........................   16
          4 Information Modules ...................................   19
          4.1 Macro Invocation ....................................   19
          4.1.1 Textual Clauses ...................................   20
          4.2 IMPORTing Symbols ...................................   20
          5 Mapping of the MODULE-IDENTITY macro ..................   22
          5.1 Mapping of the LAST-UPDATED clause ..................   22
          5.2 Mapping of the ORGANIZATION clause ..................   22
          5.3 Mapping of the CONTACT-INFO clause ..................   22
          5.4 Mapping of the DESCRIPTION clause ...................   22
          5.5 Mapping of the REVISION clause ......................   22
          5.6 Mapping of the DESCRIPTION clause ...................   23
          5.7 Mapping of the MODULE-IDENTITY value ................   23
          5.8 Usage Example .......................................   24
          6 Mapping of the OBJECT-TYPE macro ......................   25
          6.1 Mapping of the SYNTAX clause ........................   25
          6.1.1 Integer32 and INTEGER .............................   25
          6.1.2 OCTET STRING ......................................   25
          6.1.3 OBJECT IDENTIFIER .................................   26
          6.1.4 BIT STRING ........................................   26
          6.1.5 IpAddress .........................................   26
          6.1.6 Counter32 .........................................   26
          6.1.7 Gauge32 ...........................................   27
          6.1.8 TimeTicks .........................................   27
          6.1.9 Opaque ............................................   27
          6.1.10 Counter64 ........................................   28
          6.1.11 NsapAddress ......................................   28
          6.2 Mapping of the UNITS clause .........................   29
          6.3 Mapping of the MAX-ACCESS clause ....................   29
          6.4 Mapping of the STATUS clause ........................   29
          6.5 Mapping of the DESCRIPTION clause ...................   29
          6.6 Mapping of the REFERENCE clause .....................   30
          
          
          
          
          
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          6.7 Mapping of the INDEX clause .........................   30
          6.7.1 Creation and Deletion of Conceptual Rows ..........   32
          6.8 Mapping of the AUGMENTS clause ......................   33
          6.9 Mapping of the DEFVAL clause ........................   33
          6.10 Mapping of the OBJECT-TYPE value ...................   34
          6.10.1 Naming Hierarchy .................................   35
          6.11 Usage Example ......................................   37
          7 Mapping of the OBJECT-GROUP macro .....................   39
          7.1 Mapping of the OBJECTS clause .......................   39
          7.2 Mapping of the STATUS clause ........................   39
          7.3 Mapping of the DESCRIPTION clause ...................   40
          7.4 Mapping of the REFERENCE clause .....................   40
          7.5 Mapping of the OBJECT-GROUP value ...................   40
          7.6 Usage Example .......................................   41
          8 Mapping of the NOTIFICATION-TYPE macro ................   42
          8.1 Mapping of the OBJECTS clause .......................   42
          8.2 Mapping of the STATUS clause ........................   42
          8.3 Mapping of the DESCRIPTION clause ...................   42
          8.4 Mapping of the REFERENCE clause .....................   43
          8.5 Mapping of the NOTIFICATION-TYPE value ..............   43
          8.6 Usage Example .......................................   44
          9 Mapping of the MODULE-COMPLIANCE macro ................   45
          9.1 Mapping of the STATUS clause ........................   45
          9.2 Mapping of the DESCRIPTION clause ...................   45
          9.3 Mapping of the REFERENCE clause .....................   45
          9.4 Mapping of the MODULE clause ........................   45
          9.4.1 Mapping of the MANDATORY-GROUPS clause ............   46
          9.4.2 Mapping of the GROUP clause .......................   46
          9.4.3 Mapping of the OBJECT clause ......................   46
          9.4.3.1 Mapping of the SYNTAX clause ....................   47
          9.4.3.2 Mapping of the WRITE-SYNTAX clause ..............   47
          9.4.3.3 Mapping of the MIN-ACCESS clause ................   47
          9.4.3.4 Mapping of the DESCRIPTION clause ...............   48
          9.5 Mapping of the MODULE-COMPLIANCE value ..............   48
          9.6 Usage Example .......................................   49
          10 Mapping of the AGENT-CAPABILITIES macro ..............   51
          10.1 Mapping of the PRODUCT-RELEASE clause ..............   52
          10.2 Mapping of the STATUS clause .......................   52
          10.3 Mapping of the DESCRIPTION clause ..................   52
          10.4 Mapping of the REFERENCE clause ....................   52
          10.5 Mapping of the SUPPORTS clause .....................   52
          10.5.1 Mapping of the INCLUDES clause ...................   53
          10.5.2 Mapping of the VARIATION clause ..................   53
          10.5.2.1 Mapping of the SYNTAX clause ...................   53
          10.5.2.2 Mapping of the WRITE-SYNTAX clause .............   53
          
          
          
          
          
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          10.5.2.3 Mapping of the ACCESS clause ...................   54
          10.5.2.4 Mapping of the CREATION-REQUIRES clause ........   54
          10.5.2.5 Mapping of the DEFVAL clause ...................   55
          10.5.2.6 Mapping of the DESCRIPTION clause ..............   55
          10.6 Mapping of the AGENT-CAPABILITIES value ............   55
          10.7 Usage Example ......................................   56
          11 Refined Syntax .......................................   58
          12 Extending an Information Module ......................   59
          12.1 Object Definitions .................................   59
          12.2 Trap Definitions ...................................   59
          12.3 Compliance Definitions .............................   60
          12.4 Capabilities Definitions ...........................   60
          13 Appendix: de-OSIfying a MIB module ...................   61
          13.1 Managed Object Mapping .............................   61
          13.1.1 Mapping to the SYNTAX clause .....................   62
          13.1.2 Mapping to the UNITS clause ......................   63
          13.1.3 Mapping to the MAX-ACCESS clause .................   63
          13.1.4 Mapping to the STATUS clause .....................   63
          13.1.5 Mapping to the DESCRIPTION clause ................   63
          13.1.6 Mapping to the REFERENCE clause ..................   63
          13.1.7 Mapping to the INDEX clause ......................   63
          13.1.8 Mapping to the DEFVAL clause .....................   63
          13.2 Action Mapping .....................................   64
          13.2.1 Mapping to the SYNTAX clause .....................   64
          13.2.2 Mapping to the MAX-ACCESS clause .................   64
          13.2.3 Mapping to the STATUS clause .....................   64
          13.2.4 Mapping to the DESCRIPTION clause ................   64
          13.2.5 Mapping to the REFERENCE clause ..................   64
          13.3 Event Mapping ......................................   64
          13.3.1 Mapping to the STATUS clause .....................   65
          13.3.2 Mapping to the DESCRIPTION clause ................   65
          13.3.3 Mapping to the REFERENCE clause ..................   65
          14 Acknowledgements .....................................   66
          15 References ...........................................   68
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
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