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+
+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
+
+
+
+Rose & McCloghrie [Page 1]
+
+RFC 1155 SMI May 1990
+
+
+ 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
+
+
+
+Rose & McCloghrie [Page 2]
+
+RFC 1155 SMI May 1990
+
+
+ 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.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Rose & McCloghrie [Page 3]
+
+RFC 1155 SMI May 1990
+
+
+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
+
+
+
+Rose & McCloghrie [Page 4]
+
+RFC 1155 SMI May 1990
+
+
+ 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.
+
+
+
+
+Rose & McCloghrie [Page 5]
+
+RFC 1155 SMI May 1990
+
+
+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.
+
+
+
+
+
+Rose & McCloghrie [Page 6]
+
+RFC 1155 SMI May 1990
+
+
+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
+
+
+
+Rose & McCloghrie [Page 7]
+
+RFC 1155 SMI May 1990
+
+
+ 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
+
+
+
+Rose & McCloghrie [Page 8]
+
+RFC 1155 SMI May 1990
+
+
+ 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.
+
+
+
+
+
+
+
+
+
+
+
+
+
+Rose & McCloghrie [Page 9]
+
+RFC 1155 SMI May 1990
+
+
+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
+
+
+
+Rose & McCloghrie [Page 10]
+
+RFC 1155 SMI May 1990
+
+
+ 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.
+
+
+
+Rose & McCloghrie [Page 11]
+
+RFC 1155 SMI May 1990
+
+
+ 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.
+
+
+
+
+Rose & McCloghrie [Page 12]
+
+RFC 1155 SMI May 1990
+
+
+ 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
+
+
+
+Rose & McCloghrie [Page 13]
+
+RFC 1155 SMI May 1990
+
+
+ { 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
+
+
+
+Rose & McCloghrie [Page 14]
+
+RFC 1155 SMI May 1990
+
+
+ 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.
+
+
+
+
+
+
+
+Rose & McCloghrie [Page 15]
+
+RFC 1155 SMI May 1990
+
+
+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.
+
+
+
+
+
+
+
+
+
+Rose & McCloghrie [Page 16]
+
+RFC 1155 SMI May 1990
+
+
+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
+
+
+
+
+Rose & McCloghrie [Page 17]
+
+RFC 1155 SMI May 1990
+
+
+ -- 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
+
+
+
+Rose & McCloghrie [Page 18]
+
+RFC 1155 SMI May 1990
+
+
+ -- 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
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Rose & McCloghrie [Page 19]
+
+RFC 1155 SMI May 1990
+
+
+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
+
+
+
+
+
+
+
+
+
+
+Rose & McCloghrie [Page 20]
+
+RFC 1155 SMI May 1990
+
+
+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.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Rose & McCloghrie [Page 21]
+
+RFC 1155 SMI May 1990
+
+
+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
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Rose & McCloghrie [Page 22]
+ \ No newline at end of file