SMI: Structure and identification of management information for TCP/IP-based internets

Network Working Group                                            M. Rose
Request for Comments:  1155            Performance Systems International
Obsoletes:  RFC 1065                                       K. McCloghrie
                                                      Hughes LAN Systems
                                                                May 1990



         Structure and Identification of Management Information
                       for TCP/IP-based Internets

                           Table of Contents

1. Status of this Memo .............................................  1
2. Introduction ....................................................  2
3. Structure and Identification of Management Information...........  4
3.1 Names ..........................................................  4
3.1.1 Directory ....................................................  5
3.1.2 Mgmt .........................................................  6
3.1.3 Experimental .................................................  6
3.1.4 Private ......................................................  7
3.2 Syntax .........................................................  7
3.2.1 Primitive Types ..............................................  7
3.2.1.1 Guidelines for Enumerated INTEGERs .........................  7
3.2.2 Constructor Types ............................................  8
3.2.3 Defined Types ................................................  8
3.2.3.1 NetworkAddress .............................................  8
3.2.3.2 IpAddress ..................................................  8
3.2.3.3 Counter ....................................................  8
3.2.3.4 Gauge ......................................................  9
3.2.3.5 TimeTicks ..................................................  9
3.2.3.6 Opaque .....................................................  9
3.3 Encodings ......................................................  9
4. Managed Objects ................................................. 10
4.1 Guidelines for Object Names .................................... 10
4.2 Object Types and Instances ..................................... 10
4.3 Macros for Managed Objects ..................................... 14
5. Extensions to the MIB ........................................... 16
6. Definitions ..................................................... 17
7. Acknowledgements ................................................ 20
8. References ...................................................... 21
9. Security Considerations.......................................... 21
10. Authors' Addresses.............................................. 22

1.  Status of this Memo

   This RFC is a re-release of RFC 1065, with a changed "Status of this
   Memo", plus a few minor typographical corrections.  The technical
   content of the document is unchanged from RFC 1065.

   This memo provides the common definitions for the structure and
   identification of management information for TCP/IP-based internets.
   In particular, together with its companion memos which describe the
   management information base along with the network management
   protocol, these documents provide a simple, workable architecture and
   system for managing TCP/IP-based internets and in particular, the
   Internet.

   This memo specifies a Standard Protocol for the Internet community.
   Its status is "Recommended".  TCP/IP implementations in the Internet
   which are network manageable are expected to adopt and implement this
   specification.

   The Internet Activities Board recommends that all IP and TCP
   implementations be network manageable.  This implies implementation
   of the Internet MIB (RFC-1156) and at least one of the two
   recommended management protocols SNMP (RFC-1157) or CMOT (RFC-1095).
   It should be noted that, at this time, SNMP is a full Internet
   standard and CMOT is a draft standard.  See also the Host and Gateway
   Requirements RFCs for more specific information on the applicability
   of this standard.

   Please refer to the latest edition of the "IAB Official Protocol
   Standards" RFC for current information on the state and status of
   standard Internet protocols.

   Distribution of this memo is unlimited.

2.  Introduction

   This memo describes the common structures and identification scheme
   for the definition of management information used in managing
   TCP/IP-based internets.  Included are descriptions of an object
   information model for network management along with a set of generic
   types used to describe management information.  Formal descriptions
   of the structure are given using Abstract Syntax Notation One (ASN.1)
   [1].

   This memo is largely concerned with organizational concerns and
   administrative policy:  it neither specifies the objects which are
   managed, nor the protocols used to manage those objects.  These
   concerns are addressed by two companion memos:  one describing the
   Management Information Base (MIB) [2], and the other describing the
   Simple Network Management Protocol (SNMP) [3].

   This memo is based in part on the work of the Internet Engineering
   Task Force, particularly the working note titled "Structure and
   Identification of Management Information for the Internet" [4].  This
   memo uses a skeletal structure derived from that note, but differs in
   one very significant way:  that note focuses entirely on the use of
   OSI-style network management.  As such, it is not suitable for use
   with SNMP.

   This memo attempts to achieve two goals:  simplicity and
   extensibility.  Both are motivated by a common concern:  although the
   management of TCP/IP-based internets has been a topic of study for
   some time, the authors do not feel that the depth and breadth of such
   understanding is complete.  More bluntly, we feel that previous
   experiences, while giving the community insight, are hardly
   conclusive.  By fostering a simple SMI, the minimal number of
   constraints are imposed on future potential approaches; further, by
   fostering an extensible SMI, the maximal number of potential
   approaches are available for experimentation.

   It is believed that this memo and its two companions comply with the
   guidelines set forth in RFC 1052, "IAB Recommendations for the
   Development of Internet Network Management Standards" [5] and RFC
   1109, "Report of the Second Ad Hoc Network Management Review Group"
   [6].  In particular, we feel that this memo, along with the memo
   describing the management information base, provide a solid basis for
   network management of the Internet.

3.  Structure and Identification of Management Information

   Managed objects are accessed via a virtual information store, termed
   the Management Information Base or MIB.  Objects in the MIB are
   defined using Abstract Syntax Notation One (ASN.1) [1].

   Each type of object (termed an object type) has a name, a syntax, and
   an encoding.  The name is represented uniquely as an OBJECT
   IDENTIFIER.  An OBJECT IDENTIFIER is an administratively assigned
   name.  The administrative policies used for assigning names are
   discussed later in this memo.

   The syntax for an object type defines the abstract data structure
   corresponding to that object type.  For example, the structure of a
   given object type might be an INTEGER or OCTET STRING.  Although in
   general, we should permit any ASN.1 construct to be available for use
   in defining the syntax of an object type, this memo purposely
   restricts the ASN.1 constructs which may be used.  These restrictions
   are made solely for the sake of simplicity.

   The encoding of an object type is simply how instances of that object
   type are represented using the object's type syntax.  Implicitly tied
   to the notion of an object's syntax and encoding is how the object is
   represented when being transmitted on the network.  This memo
   specifies the use of the basic encoding rules of ASN.1 [7].

   It is beyond the scope of this memo to define either the MIB used for
   network management or the network management protocol.  As mentioned
   earlier, these tasks are left to companion memos.  This memo attempts
   to minimize the restrictions placed upon its companions so as to
   maximize generality.  However, in some cases, restrictions have been
   made (e.g., the syntax which may be used when defining object types
   in the MIB) in order to encourage a particular style of management.
   Future editions of this memo may remove these restrictions.

3.1.  Names

   Names are used to identify managed objects.  This memo specifies
   names which are hierarchical in nature.  The OBJECT IDENTIFIER
   concept is used to model this notion.  An OBJECT IDENTIFIER can be
   used for purposes other than naming managed object types; for
   example, each international standard has an OBJECT IDENTIFIER
   assigned to it for the purposes of identification.  In short, OBJECT
   IDENTIFIERs are a means for identifying some object, regardless of
   the semantics associated with the object (e.g., a network object, a
   standards document, etc.)

   An OBJECT IDENTIFIER is a sequence of integers which traverse a
   global tree.  The tree consists of a root connected to a number of
   labeled nodes via edges.  Each node may, in turn, have children of
   its own which are labeled.  In this case, we may term the node a
   subtree.  This process may continue to an arbitrary level of depth.
   Central to the notion of the OBJECT IDENTIFIER is the understanding
   that administrative control of the meanings assigned to the nodes may
   be delegated as one traverses the tree.  A label is a pairing of a
   brief textual description and an integer.

   The root node itself is unlabeled, but has at least three children
   directly under it:  one node is administered by the International
   Organization for Standardization, with label iso(1); another is
   administrated by the International Telegraph and Telephone
   Consultative Committee, with label ccitt(0); and the third is jointly
   administered by the ISO and the CCITT, joint-iso-ccitt(2).

   Under the iso(1) node, the ISO has designated one subtree for use by
   other (inter)national organizations, org(3).  Of the children nodes
   present, two have been assigned to the U.S. National Institutes of
   Standards and Technology.  One of these subtrees has been transferred
   by the NIST to the U.S. Department of Defense, dod(6).

   As of this writing, the DoD has not indicated how it will manage its
   subtree of OBJECT IDENTIFIERs.  This memo assumes that DoD will
   allocate a node to the Internet community, to be administered by the
   Internet Activities Board (IAB) as follows:

      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.

   This memo, as a standard approved by the IAB, now specifies the
   policy under which this subtree of OBJECT IDENTIFIERs is
   administered.  Initially, four nodes are present:

      directory     OBJECT IDENTIFIER ::= { internet 1 }
      mgmt          OBJECT IDENTIFIER ::= { internet 2 }
      experimental  OBJECT IDENTIFIER ::= { internet 3 }
      private       OBJECT IDENTIFIER ::= { internet 4 }

3.1.1.  Directory

   The directory(1) subtree is reserved for use with a future memo that
   discusses how the OSI Directory may be used in the Internet.

3.1.2.  Mgmt

   The mgmt(2) subtree is used to identify objects which are defined in
   IAB-approved documents.  Administration of the mgmt(2) subtree is
   delegated by the IAB to the Internet Assigned Numbers Authority for
   the Internet.  As RFCs which define new versions of the Internet-
   standard Management Information Base are approved, they are assigned
   an OBJECT IDENTIFIER by the Internet Assigned Numbers Authority for
   identifying the objects defined by that memo.

   For example, the RFC which defines the initial Internet standard MIB
   would be assigned management document number 1.  This RFC would use
   the OBJECT IDENTIFIER

      { mgmt 1 }

   or

      1.3.6.1.2.1

   in defining the Internet-standard MIB.

   The generation of new versions of the Internet-standard MIB is a
   rigorous process.  Section 5 of this memo describes the rules used
   when a new version is defined.

3.1.3.  Experimental

   The experimental(3) subtree is used to identify objects used in
   Internet experiments.  Administration of the experimental(3) subtree
   is delegated by the IAB to the Internet Assigned Numbers Authority of
   the Internet.

   For example, an experimenter might received number 17, and would have
   available the OBJECT IDENTIFIER

      { experimental 17 }

   or

      1.3.6.1.3.17

   for use.

   As a part of the assignment process, the Internet Assigned Numbers
   Authority may make requirements as to how that subtree is used.

3.1.4.  Private

   The private(4) subtree is used to identify objects defined
   unilaterally.  Administration of the private(4) subtree is delegated
   by the IAB to the Internet Assigned Numbers Authority for the
   Internet.  Initially, this subtree has at least one child:

      enterprises   OBJECT IDENTIFIER ::= { private 1 }

   The enterprises(1) subtree is used, among other things, to permit
   parties providing networking subsystems to register models of their
   products.

   Upon receiving a subtree, the enterprise may, for example, define new
   MIB objects in this subtree.  In addition, it is strongly recommended
   that the enterprise will also register its networking subsystems
   under this subtree, in order to provide an unambiguous identification
   mechanism for use in management protocols.  For example, if the
   "Flintstones, Inc."  enterprise produced networking subsystems, then
   they could request a node under the enterprises subtree from the
   Internet Assigned Numbers Authority.  Such a node might be numbered:

      1.3.6.1.4.1.42

   The "Flintstones, Inc." enterprise might then register their "Fred
   Router" under the name of:

      1.3.6.1.4.1.42.1.1

3.2.  Syntax

   Syntax is used to define the structure corresponding to object types.
   ASN.1 constructs are used to define this structure, although the full
   generality of ASN.1 is not permitted.

   The ASN.1 type ObjectSyntax defines the different syntaxes which may
   be used in defining an object type.

3.2.1.  Primitive Types

   Only the ASN.1 primitive types INTEGER, OCTET STRING, OBJECT
   IDENTIFIER, and NULL are permitted.  These are sometimes referred to
   as non-aggregate types.

3.2.1.1.  Guidelines for Enumerated INTEGERs

   If an enumerated INTEGER is listed as an object type, then a named-
   number having the value 0 shall not be present in the list of
   enumerations.  Use of this value is prohibited.

3.2.2.  Constructor Types

   The ASN.1 constructor type SEQUENCE is permitted, providing that it
   is used to generate either lists or tables.

   For lists, the syntax takes the form:

      SEQUENCE { <type1>, ..., <typeN> }

   where each <type> resolves to one of the ASN.1 primitive types listed
   above.  Further, these ASN.1 types are always present (the DEFAULT
   and OPTIONAL clauses do not appear in the SEQUENCE definition).

   For tables, the syntax takes the form:

      SEQUENCE OF <entry>

   where <entry> resolves to a list constructor.

   Lists and tables are sometimes referred to as aggregate types.

3.2.3.  Defined Types

   In addition, new application-wide types may be defined, so long as
   they resolve into an IMPLICITly defined ASN.1 primitive type, list,
   table, or some other application-wide type.  Initially, few
   application-wide types are defined.  Future memos will no doubt
   define others once a consensus is reached.

3.2.3.1.  NetworkAddress

   This CHOICE represents an address from one of possibly several
   protocol families.  Currently, only one protocol family, the Internet
   family, is present in this CHOICE.

3.2.3.2.  IpAddress

   This application-wide type represents a 32-bit internet address.  It
   is represented as an OCTET STRING of length 4, in network byte-order.

   When this ASN.1 type is encoded using the ASN.1 basic encoding rules,
   only the primitive encoding form shall be used.

3.2.3.3.  Counter

   This application-wide type represents a non-negative integer which
   monotonically increases until it reaches a maximum value, when it
   wraps around and starts increasing again from zero.  This memo
   specifies a maximum value of 2^32-1 (4294967295 decimal) for
   counters.

3.2.3.4.  Gauge

   This application-wide type represents a non-negative integer, which
   may increase or decrease, but which latches at a maximum value.  This
   memo specifies a maximum value of 2^32-1 (4294967295 decimal) for
   gauges.

3.2.3.5.  TimeTicks

   This application-wide type represents a non-negative integer which
   counts the time in hundredths of a second since some epoch.  When
   object types are defined in the MIB which use this ASN.1 type, the
   description of the object type identifies the reference epoch.

3.2.3.6.  Opaque

   This application-wide type supports the capability to pass arbitrary
   ASN.1 syntax.  A value is encoded using the ASN.1 basic rules 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, encodings other
   than ASN.1 may be used in opaquely-encoded data.

3.3.  Encodings

   Once an instance of an object type has been identified, its value may
   be transmitted by applying the basic encoding rules of ASN.1 to the
   syntax for the object type.

4.  Managed Objects

   Although it is not the purpose of this memo to define objects in the
   MIB, this memo specifies a format to be used by other memos which
   define these objects.

   An object type definition consists of five fields:

   OBJECT:
   -------
      A textual name, termed the OBJECT DESCRIPTOR, for the object type,
      along with its corresponding OBJECT IDENTIFIER.

   Syntax:
      The abstract syntax for the object type.  This must resolve to an
      instance of the ASN.1 type ObjectSyntax (defined below).

   Definition:
      A textual description of the semantics of the object type.
      Implementations should ensure that their instance of the object
      fulfills this definition since this MIB is intended for use in
      multi-vendor environments.  As such it is vital that objects have
      consistent meaning across all machines.

   Access:
      One of read-only, read-write, write-only, or not-accessible.

   Status:
      One of mandatory, optional, or obsolete.

   Future memos may also specify other fields for the objects which they
   define.

4.1.  Guidelines for Object Names

   No object type in the Internet-Standard MIB shall use a sub-
   identifier of 0 in its name.  This value is reserved for use with
   future extensions.

   Each OBJECT DESCRIPTOR corresponding to an object type in the
   internet-standard MIB shall be a unique, but mnemonic, printable
   string.  This promotes a common language for humans to use when
   discussing the MIB and also facilitates simple table mappings for
   user interfaces.

4.2.  Object Types and Instances

   An object type is a definition of a kind of managed object; it is
   declarative in nature.  In contrast, an object instance is an
   instantiation of an object type which has been bound to a value.  For
   example, the notion of an entry in a routing table might be defined
   in the MIB.  Such a notion corresponds to an object type; individual
   entries in a particular routing table which exist at some time are
   object instances of that object type.

   A collection of object types is defined in the MIB.  Each such
   subject type is uniquely named by its OBJECT IDENTIFIER and also has
   a textual name, which is its OBJECT DESCRIPTOR.  The means whereby
   object instances are referenced is not defined in the MIB.  Reference
   to object instances is achieved by a protocol-specific mechanism:  it
   is the responsibility of each management protocol adhering to the SMI
   to define this mechanism.

   An object type may be defined in the MIB such that an instance of
   that object type represents an aggregation of information also
   represented by instances of some number of "subordinate" object
   types.  For example, suppose the following object types are defined
   in the MIB:


   OBJECT:
   -------
      atIndex { atEntry 1 }

   Syntax:
      INTEGER

   Definition:
      The interface number for the physical address.

   Access:
      read-write.

   Status:
      mandatory.


   OBJECT:
   -------
      atPhysAddress { atEntry 2 }

   Syntax:
      OCTET STRING

   Definition:
      The media-dependent physical address.

   Access:
      read-write.

   Status:
      mandatory.


   OBJECT:
   -------
      atNetAddress { atEntry 3 }

   Syntax:
      NetworkAddress

   Definition:
      The network address corresponding to the media-dependent physical
      address.

   Access:
      read-write.

   Status:
      mandatory.

   Then, a fourth object type might also be defined in the MIB:


   OBJECT:
   -------
      atEntry { atTable 1 }

   Syntax:

      AtEntry ::= SEQUENCE {
            atIndex
            INTEGER,
            atPhysAddress
            OCTET STRING,
            atNetAddress
            NetworkAddress
            }

   Definition:
      An entry in the address translation table.

   Access:
      read-write.

   Status:
      mandatory.

   Each instance of this object type comprises information represented
   by instances of the former three object types.  An object type
   defined in this way is called a list.

   Similarly, tables can be formed by aggregations of a list type.  For
   example, a fifth object type might also be defined in the MIB:


   OBJECT:
   ------
      atTable { at 1 }

   Syntax:
      SEQUENCE OF AtEntry

   Definition:
      The address translation table.

   Access:
      read-write.

   Status:
      mandatory.

   such that each instance of the atTable object comprises information
   represented by the set of atEntry object types that collectively
   constitute a given atTable object instance, that is, a given address
   translation table.

   Consider how one might refer to a simple object within a table.
   Continuing with the previous example, one might name the object type

      { atPhysAddress }

   and specify, using a protocol-specific mechanism, the object instance

      { atNetAddress } = { internet "10.0.0.52" }

   This pairing of object type and object instance would refer to all
   instances of atPhysAddress which are part of any entry in some
   address translation table for which the associated atNetAddress value
   is { internet "10.0.0.52" }.

   To continue with this example, consider how one might refer to an
   aggregate object (list) within a table.  Naming the object type
      { atEntry }

   and specifying, using a protocol-specific mechanism, the object
   instance

      { atNetAddress } = { internet "10.0.0.52" }

   refers to all instances of entries in the table for which the
   associated atNetAddress value is { internet "10.0.0.52" }.

   Each management protocol must provide a mechanism for accessing
   simple (non-aggregate) object types.  Each management protocol
   specifies whether or not it supports access to aggregate object
   types.  Further, the protocol must specify which instances are
   "returned" when an object type/instance pairing refers to more than
   one instance of a type.

   To afford support for a variety of management protocols, all
   information by which instances of a given object type may be usefully
   distinguished, one from another, is represented by instances of
   object types defined in the MIB.

4.3.  Macros for Managed Objects

   In order to facilitate the use of tools for processing the definition
   of the MIB, the OBJECT-TYPE macro may be used.  This macro permits
   the key aspects of an object type to be represented in a formal way.

      OBJECT-TYPE MACRO ::=
      BEGIN
          TYPE NOTATION ::= "SYNTAX" type (TYPE ObjectSyntax)
                            "ACCESS" Access
                            "STATUS" Status
          VALUE NOTATION ::= value (VALUE ObjectName)

          Access ::= "read-only"
                          | "read-write"
                          | "write-only"
                          | "not-accessible"
          Status ::= "mandatory"
                          | "optional"
                          | "obsolete"
          END

   Given the object types defined earlier, we might imagine the
   following definitions being present in the MIB:

                  atIndex OBJECT-TYPE

                          SYNTAX  INTEGER
                          ACCESS  read-write
                          STATUS  mandatory
                          ::= { atEntry 1 }

                  atPhysAddress OBJECT-TYPE
                          SYNTAX  OCTET STRING
                          ACCESS  read-write
                          STATUS  mandatory
                          ::= { atEntry 2 }

                  atNetAddress OBJECT-TYPE
                          SYNTAX  NetworkAddress
                          ACCESS  read-write
                          STATUS  mandatory
                          ::= { atEntry 3 }

                  atEntry OBJECT-TYPE
                          SYNTAX  AtEntry
                          ACCESS  read-write
                          STATUS  mandatory
                          ::= { atTable 1 }

                  atTable OBJECT-TYPE
                          SYNTAX  SEQUENCE OF AtEntry
                          ACCESS  read-write
                          STATUS  mandatory
                          ::= { at 1 }

                  AtEntry ::= SEQUENCE {
                      atIndex
                          INTEGER,
                      atPhysAddress
                          OCTET STRING,
                      atNetAddress
                          NetworkAddress
                  }

   The first five definitions describe object types, relating, for
   example, the OBJECT DESCRIPTOR atIndex to the OBJECT IDENTIFIER {
   atEntry 1 }.  In addition, the syntax of this object is defined
   (INTEGER) along with the access permitted (read-write) and status
   (mandatory).  The sixth definition describes an ASN.1 type called
   AtEntry.

5.  Extensions to the MIB

   Every Internet-standard MIB document obsoletes all previous such
   documents.  The portion of a name, termed the tail, following the
   OBJECT IDENTIFIER

      { mgmt version-number }

   used to name objects shall remain unchanged between versions.  New
   versions may:

      (1) declare old object types obsolete (if necessary), but not
      delete their names;

      (2) augment the definition of an object type corresponding to a
      list by appending non-aggregate object types to the object types
      in the list; or,

      (3) define entirely new object types.

   New versions may not:

      (1) change the semantics of any previously defined object without
      changing the name of that object.

   These rules are important because they admit easier support for
   multiple versions of the Internet-standard MIB.  In particular, the
   semantics associated with the tail of a name remain constant
   throughout different versions of the MIB.  Because multiple versions
   of the MIB may thus coincide in "tail-space," implementations
   supporting multiple versions of the MIB can be vastly simplified.

   However, as a consequence, a management agent might return an
   instance corresponding to a superset of the expected object type.
   Following the principle of robustness, in this exceptional case, a
   manager should ignore any additional information beyond the
   definition of the expected object type.  However, the robustness
   principle requires that one exercise care with respect to control
   actions:  if an instance does not have the same syntax as its
   expected object type, then those control actions must fail.  In both
   the monitoring and control cases, the name of an object returned by
   an operation must be identical to the name requested by an operation.

6.  Definitions

           RFC1155-SMI DEFINITIONS ::= BEGIN

           EXPORTS -- EVERYTHING
                   internet, directory, mgmt,
                   experimental, private, enterprises,
                   OBJECT-TYPE, ObjectName, ObjectSyntax, SimpleSyntax,
                   ApplicationSyntax, NetworkAddress, IpAddress,
                   Counter, Gauge, TimeTicks, Opaque;

            -- 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 }


            -- definition of object types

            OBJECT-TYPE MACRO ::=
            BEGIN
                TYPE NOTATION ::= "SYNTAX" type (TYPE ObjectSyntax)
                                  "ACCESS" Access
                                  "STATUS" Status
                VALUE NOTATION ::= value (VALUE ObjectName)

                Access ::= "read-only"
                                | "read-write"
                                | "write-only"
                                | "not-accessible"
                Status ::= "mandatory"
                                | "optional"
                                | "obsolete"
            END

               -- names of objects in the MIB

               ObjectName ::=
                   OBJECT IDENTIFIER

               -- syntax of objects in the MIB

               ObjectSyntax ::=
                   CHOICE {
                       simple
                           SimpleSyntax,

               -- note that simple SEQUENCEs are not directly
               -- mentioned here to keep things simple (i.e.,
               -- prevent mis-use).  However, application-wide
               -- types which are IMPLICITly encoded simple
               -- SEQUENCEs may appear in the following CHOICE

                       application-wide
                           ApplicationSyntax
                   }

                  SimpleSyntax ::=
                      CHOICE {
                          number
                              INTEGER,

                          string
                              OCTET STRING,

                          object
                              OBJECT IDENTIFIER,

                          empty
                              NULL
                      }

                  ApplicationSyntax ::=
                      CHOICE {
                          address
                              NetworkAddress,

                          counter
                              Counter,

                          gauge
                              Gauge,

                          ticks
                              TimeTicks,

                          arbitrary
                              Opaque

                  -- other application-wide types, as they are
                  -- defined, will be added here
                      }


                  -- application-wide types

                  NetworkAddress ::=
                      CHOICE {
                          internet
                              IpAddress
                      }

                  IpAddress ::=
                      [APPLICATION 0]          -- in network-byte order
                          IMPLICIT OCTET STRING (SIZE (4))

                  Counter ::=
                      [APPLICATION 1]
                          IMPLICIT INTEGER (0..4294967295)

                  Gauge ::=
                      [APPLICATION 2]
                          IMPLICIT INTEGER (0..4294967295)

                  TimeTicks ::=
                      [APPLICATION 3]
                          IMPLICIT INTEGER (0..4294967295)

                  Opaque ::=
                      [APPLICATION 4]          -- arbitrary ASN.1 value,
                          IMPLICIT OCTET STRING   --   "double-wrapped"

                  END

7.  Acknowledgements

   This memo was influenced by three sets of contributors to earlier
   drafts:

   First, Lee Labarre of the MITRE Corporation, who as author of the
   NETMAN SMI [4], presented the basic roadmap for the SMI.

   Second, several individuals who provided valuable comments on this
   memo prior to its initial distribution:

         James R. Davin, Proteon
         Mark S. Fedor, NYSERNet
         Craig Partridge, BBN Laboratories
         Martin Lee Schoffstall, Rensselaer Polytechnic Institute
         Wengyik Yeong, NYSERNet


   Third, the IETF MIB working group:

         Karl Auerbach, Epilogue Technology
         K. Ramesh Babu, Excelan
         Lawrence Besaw, Hewlett-Packard
         Jeffrey D. Case, University of Tennessee at Knoxville
         James R. Davin, Proteon
         Mark S. Fedor, NYSERNet
         Robb Foster, BBN
         Phill Gross, The MITRE Corporation
         Bent Torp Jensen, Convergent Technology
         Lee Labarre, The MITRE Corporation
         Dan Lynch, Advanced Computing Environments
         Keith McCloghrie, The Wollongong Group
         Dave Mackie, 3Com/Bridge
         Craig Partridge, BBN (chair)
         Jim Robertson, 3Com/Bridge
         Marshall T. Rose, The Wollongong Group
         Greg Satz, cisco
         Martin Lee Schoffstall, Rensselaer Polytechnic Institute
         Lou Steinberg, IBM
         Dean Throop, Data General
         Unni Warrier, Unisys

8.  References

   [1] Information processing systems - Open Systems Interconnection,
       "Specification of Abstract Syntax Notation One (ASN.1)",
       International Organization for Standardization, International
       Standard 8824, December 1987.

   [2] McCloghrie K., and M. Rose, "Management Information Base for
       Network Management of TCP/IP-based Internets", RFC 1156,
       Performance Systems International and Hughes LAN Systems, May
       1990.

   [3] Case, J., M. Fedor, M. Schoffstall, and J. Davin, The Simple
       Network Management Protocol", RFC 1157, University of Tennessee
       at Knoxville, Performance Systems International, Performance
       Systems International, and the MIT Laboratory for Computer
       Science, May 1990.

   [4] LaBarre, L., "Structure and Identification of Management
       Information for the Internet", Internet Engineering Task Force
       working note, Network Information Center, SRI International,
       Menlo Park, California, April 1988.

   [5] Cerf, V., "IAB Recommendations for the Development of Internet
       Network Management Standards", RFC 1052, IAB, April 1988.

   [6] Cerf, V., "Report of the Second Ad Hoc Network Management Review
       Group", RFC 1109, IAB, August 1989.

   [7] Information processing systems - Open Systems Interconnection,
       "Specification of Basic Encoding Rules for Abstract Notation One
       (ASN.1)", International Organization for Standardization,
       International Standard 8825, December 1987.

Security Considerations

   Security issues are not discussed in this memo.

Authors' Addresses

   Marshall T. Rose
   PSI, Inc.
   PSI California Office
   P.O. Box 391776
   Mountain View, CA 94039

   Phone: (415) 961-3380

   EMail: mrose@PSI.COM


   Keith McCloghrie
   The Wollongong Group
   1129 San Antonio Road
   Palo Alto, CA 04303

   Phone: (415) 962-7160

   EMail: sytek!kzm@HPLABS.HP.COM