rfc1155.txt

开发snmp的开发包有两个开放的SNMP开发库

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



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   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



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   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.


























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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



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   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.




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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.





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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



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   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).