rfc1213-mib-ii.txt

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Network Working Group                                      K. McCloghrie
Request for Comments: 1213                      Hughes LAN Systems, Inc.
Obsoletes: RFC 1158                                              M. Rose
                                       Performance Systems International
                                                                 Editors
                                                              March 1991


           Management Information Base for Network Management
                       of TCP/IP-based internets:
                                 MIB-II

Status of this Memo

   This memo defines the second version of the Management Information
   Base (MIB-II) for use with network management protocols in TCP/IP-
   based internets.  This RFC specifies an IAB standards track protocol
   for the Internet community, and requests discussion and suggestions
   for improvements.  Please refer to the current edition of the "IAB
   Official Protocol Standards" for the standardization state and status
   of this protocol.  Distribution of this memo is unlimited.

Table of Contents

   1. Abstract...............................................    2
   2. Introduction ..........................................    2
   3. Changes from RFC 1156 .................................    3
   3.1 Deprecated Objects ...................................    3
   3.2 Display Strings ......................................    4
   3.3 Physical Addresses ...................................    4
   3.4 The System Group .....................................    5
   3.5 The Interfaces Group .................................    5
   3.6 The Address Translation Group ........................    6
   3.7 The IP Group .........................................    6
   3.8 The ICMP Group .......................................    7
   3.9 The TCP Group ........................................    7
   3.10 The UDP Group .......................................    7
   3.11 The EGP Group .......................................    7
   3.12 The Transmission Group ..............................    8
   3.13 The SNMP Group ......................................    8
   3.14 Changes from RFC 1158 ................. .............    9
   4. Objects ...............................................   10
   4.1 Format of Definitions ................................   10
   5. Overview ..............................................   10
   6. Definitions ...........................................   12
   6.1 Textual Conventions ..................................   12
   6.2 Groups in MIB-II .....................................   13
   6.3 The System Group .....................................   13



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   6.4 The Interfaces Group .................................   16
   6.5 The Address Translation Group ........................   23
   6.6 The IP Group .........................................   26
   6.7 The ICMP Group .......................................   41
   6.8 The TCP Group ........................................   46
   6.9 The UDP Group ........................................   52
   6.10 The EGP Group .......................................   54
   6.11 The Transmission Group ..............................   60
   6.12 The SNMP Group ......................................   60
   7. Acknowledgements ......................................   67
   8. References ............................................   69
   9. Security Considerations ...............................   70
   10. Authors' Addresses ...................................   70

1.  Abstract

   This memo defines the second version of the Management Information
   Base (MIB-II) for use with network management protocols in TCP/IP-
   based internets.  In particular, together with its companion memos
   which describe the structure of management information (RFC 1155)
   along with the network management protocol (RFC 1157) for TCP/IP-
   based internets, these documents provide a simple, workable
   architecture and system for managing TCP/IP-based internets and in
   particular the Internet community.

2.  Introduction

   As reported in RFC 1052, IAB Recommendations for the Development of
   Internet Network Management Standards [1], a two-prong strategy for
   network management of TCP/IP-based internets was undertaken.  In the
   short-term, the Simple Network Management Protocol (SNMP) was to be
   used to manage nodes in the Internet community.  In the long-term,
   the use of the OSI network management framework was to be examined.
   Two documents were produced to define the management information: RFC
   1065, which defined the Structure of Management Information (SMI)
   [2], and RFC 1066, which defined the Management Information Base
   (MIB) [3].  Both of these documents were designed so as to be
   compatible with both the SNMP and the OSI network management
   framework.

   This strategy was quite successful in the short-term: Internet-based
   network management technology was fielded, by both the research and
   commercial communities, within a few months.  As a result of this,
   portions of the Internet community became network manageable in a
   timely fashion.

   As reported in RFC 1109, Report of the Second Ad Hoc Network
   Management Review Group [4], the requirements of the SNMP and the OSI



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   network management frameworks were more different than anticipated.
   As such, the requirement for compatibility between the SMI/MIB and
   both frameworks was suspended.  This action permitted the operational
   network management framework, the SNMP, to respond to new operational
   needs in the Internet community by producing this document.

   As such, the current network management framework for TCP/IP- based
   internets consists of: Structure and Identification of Management
   Information for TCP/IP-based internets, RFC 1155 [12], which
   describes how managed objects contained in the MIB are defined;
   Management Information Base for Network Management of TCP/IP-based
   internets: MIB-II, this memo, which describes the managed objects
   contained in the MIB (and supercedes RFC 1156 [13]); and, the Simple
   Network Management Protocol, RFC 1098 [5], which defines the protocol
   used to manage these objects.

3.  Changes from RFC 1156

   Features of this MIB include:

   (1)  incremental additions to reflect new operational
        requirements;

   (2)  upwards compatibility with the SMI/MIB and the SNMP;

   (3)  improved support for multi-protocol entities; and,

   (4)  textual clean-up of the MIB to improve clarity and
        readability.

   The objects defined in MIB-II have the OBJECT IDENTIFIER prefix:

      mib-2      OBJECT IDENTIFIER ::= { mgmt 1 }

   which is identical to the prefix used in MIB-I.

3.1.  Deprecated Objects

   In order to better prepare implementors for future changes in the
   MIB, a new term "deprecated" may be used when describing an object.
   A deprecated object in the MIB is one which must be supported, but
   one which will most likely be removed from the next version of the
   MIB (e.g., MIB-III).

   MIB-II marks one object as being deprecated:

      atTable




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   As a result of deprecating the atTable object, the entire Address
   Translation group is deprecated.

   Note that no functionality is lost with the deprecation of these
   objects: new objects providing equivalent or superior functionality
   are defined in MIB-II.

3.2.  Display Strings

   In the past, there have been misinterpretations of the MIB as to when
   a string of octets should contain printable characters, meant to be
   displayed to a human.  As a textual convention in the MIB, the
   datatype

      DisplayString ::=
          OCTET STRING

   is introduced.  A DisplayString is restricted to the NVT ASCII
   character set, as defined in pages 10-11 of [6].

   The following objects are now defined in terms of DisplayString:

      sysDescr
      ifDescr

   It should be noted that this change has no effect on either the
   syntax nor semantics of these objects.  The use of the DisplayString
   notation is merely an artifact of the explanatory method used in
   MIB-II and future MIBs.

   Further it should be noted that any object defined in terms of OCTET
   STRING may contain arbitrary binary data, in which each octet may
   take any value from 0 to 255 (decimal).

3.3.  Physical Addresses

   As a further, textual convention in the MIB, the datatype

      PhysAddress ::=
          OCTET STRING

   is introduced to represent media- or physical-level addresses.

   The following objects are now defined in terms of PhysAddress:

      ifPhysAddress
      atPhysAddress
      ipNetToMediaPhysAddress



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   It should be noted that this change has no effect on either the
   syntax nor semantics of these objects.  The use of the PhysAddress
   notation is merely an artifact of the explanatory method used in
   MIB-II and future MIBs.

3.4.  The System Group

   Four new objects are added to this group:

      sysContact
      sysName
      sysLocation
      sysServices

   These provide contact, administrative, location, and service
   information regarding the managed node.

3.5.  The Interfaces Group

   The definition of the ifNumber object was incorrect, as it required
   all interfaces to support IP.  (For example, devices without IP, such
   as MAC-layer bridges, could not be managed if this definition was
   strictly followed.)  The description of the ifNumber object is
   changed accordingly.

   The ifTable object was mistaken marked as read-write, it has been
   (correctly) re-designated as not-accessible.  In addition, several
   new values have been added to the ifType column in the ifTable
   object:

      ppp(23)
      softwareLoopback(24)
      eon(25)
      ethernet-3Mbit(26)
      nsip(27)
      slip(28)
      ultra(29)
      ds3(30)
      sip(31)
      frame-relay(32)

   Finally, a new column has been added to the ifTable object:

      ifSpecific

   which provides information about information specific to the media
   being used to realize the interface.




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3.6.  The Address Translation Group

   In MIB-I this group contained a table which permitted mappings from
   network addresses (e.g., IP addresses) to physical addresses (e.g.,
   MAC addresses).  Experience has shown that efficient implementations
   of this table make two assumptions: a single network protocol
   environment, and mappings occur only from network address to physical
   address.

   The need to support multi-protocol nodes (e.g., those with both the
   IP and CLNP active), and the need to support the inverse mapping
   (e.g., for ES-IS), have invalidated both of these assumptions.  As
   such, the atTable object is declared deprecated.

   In order to meet both the multi-protocol and inverse mapping
   requirements, MIB-II and its successors will allocate up to two
   address translation tables inside each network protocol group.  That
   is, the IP group will contain one address translation table, for
   going from IP addresses to physical addresses.  Similarly, when a
   document defining MIB objects for the CLNP is produced (e.g., [7]),
   it will contain two tables, for mappings in both directions, as this
   is required for full functionality.

   It should be noted that the choice of two tables (one for each
   direction of mapping) provides for ease of implementation in many
   cases, and does not introduce undue burden on implementations which
   realize the address translation abstraction through a single internal
   table.

3.7.  The IP Group

   The access attribute of the variable ipForwarding has been changed
   from read-only to read-write.

   In addition, there is a new column to the ipAddrTable object,

      ipAdEntReasmMaxSize

   which keeps track of the largest IP datagram that can be re-assembled
   on a particular interface.

   The descriptor of the ipRoutingTable object has been changed to
   ipRouteTable for consistency with the other IP routing objects.
   There are also three new columns in the ipRouteTable object,

      ipRouteMask
      ipRouteMetric5
      ipRouteInfo



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   the first is used for IP routing subsystems that support arbitrary
   subnet masks, and the latter two are IP routing protocol-specific.

   Two new objects are added to the IP group:

      ipNetToMediaTable
      ipRoutingDiscards

   the first is the address translation table for the IP group
   (providing identical functionality to the now deprecated atTable in
   the address translation group), and the latter provides information
   when routes are lost due to a lack of buffer space.