rfc1158.txt

<VC++网络游戏建摸与实现>源代码

Network Working Group                                   M. Rose, Editor
Request for Comments: 1158            Performance Systems International
                                                               May 1990


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

1.  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.  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.

   This document on MIB-II incorporates all of the technical content of
   RFC 1156 on MIB-I and extends it, without loss of compatibilty.
   However, MIB-I as described in RFC 1156 is full Standard Protocol of
   the Internet, while the MIB-II described here is Proposed Standard
   Protocol of the Internet.

   This memo defines a mandatory extension to the base MIB (RFC 1156)
   and is a Proposed Standard for the Internet community.  The
   extensions described here are currently Elective, but when they
   become a standard, they will have the same status as RFC 1156, that
   is, Recommended.  The Internet Activities Board recommends that all
   IP and TCP implementations be network manageable.  This implies
   implementation of the Internet MIB (RFC 1156 and the extensions in
   RFC 1158) and at least one of the two recommended management
   protocols SNMP (RFC 1157) or CMOT (RFC 1095).

   This version of the MIB specification, MIB-II, is an incremental
   refinement of MIB-I.  As such, it has been designed according to two
   criteria: first, changes have been made in response to new
   operational requirements in the Internet; and, second, the changes
   are entirely upwards compatible in order to minimize impact on the
   network as the managed nodes in the Internet transition from MIB-I to
   MIB-II.

   It is expected that additional MIB groups and variables will be
   defined over time to accommodate the monitoring and control needs of
   new or changing components of the Internet.




IETF SNMP Working Group                                         [Page 1]

RFC 1158                         MIB II                         May 1990


   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.

                             Table of Contents


   1. Status of this Memo ..................................    1
   2. Introduction .........................................    3
   3. Changes from MIB-I ...................................    4
   3.1 Deprecated Objects ..................................    4
   3.2 Display Strings .....................................    5
   3.3 The System Group ....................................    5
   3.4 The Interfaces Group ................................    5
   3.5 The Address Translation Group .......................    6
   3.6 The IP Group ........................................    7
   3.7 The ICMP Group ......................................    7
   3.8 The TCP Group .......................................    7
   3.9 The UDP Group .......................................    7
   3.10 The EGP Group ......................................    8
   3.11 The Transmission Group .............................    8
   3.12 The SNMP Group .....................................    8
   4. Objects ..............................................    8
   4.1 Object Groups .......................................    9
   4.2 Format of Definitions ...............................   10
   5. Object Definitions ...................................   10
   5.1 The System Group ....................................   11
   5.2 The Interfaces Group ................................   14
   5.2.1 The Interfaces table ..............................   15
   5.3 The Address Translation Group .......................   27
   5.4 The IP Group ........................................   30
   5.4.1 The IP Address table ..............................   38
   5.4.2 The IP Routing table ..............................   41
   5.4.3 The IP Address Translation table ..................   48
   5.5 The ICMP Group ......................................   51
   5.6 The TCP Group .......................................   61
   5.6.1 The TCP Connection table ..........................   66
   5.6.2 Additional TCP Objects ............................   69
   5.7 The UDP Group .......................................   70
   5.7.1 The UDP Listener table ............................   72
   5.8 The EGP Group .......................................   73
   5.8.1 The EGP Neighbor table ............................   75
   5.8.2 Additional EGP variables ..........................   83
   5.9 The Transmission Group ..............................   83
   5.10 The SNMP Group .....................................   83
   6. Definitions ..........................................   95



IETF SNMP Working Group                                         [Page 2]

RFC 1158                         MIB II                         May 1990


   7. Identification of OBJECT instances for use with  the
      SNMP .................................................  126
   7.1 ifTable Object Type Names ...........................  127
   7.2 atTable Object Type Names ...........................  127
   7.3 ipAddrTable Object Type Names .......................  128
   7.4 ipRoutingTable Object Type Names ....................  128
   7.5 ipNetToMediaTable Object Type Names .................  129
   7.6 tcpConnTable Object Type Names ......................  129
   7.7 udpTable Object Type Names ..........................  130
   7.8 egpNeighTable Object Type Names .....................  130
   8.  Acknowledgements ....................................  130
   9.  References ..........................................  131
   10. Security Considerations..............................  133
   11. Author's Address.....................................  133

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 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



IETF SNMP Working Group                                         [Page 3]

RFC 1158                         MIB II                         May 1990


   Management Information for TCP/IP-based internets, RFC 1155 [13],
   which describes how managed objects contained in the MIB are
   defined; Management Information Base for Network Management of
   TCP/IP-based internets (version 2), this memo, which describes
   the managed objects contained in the MIB; and, the Simple
   Network Management Protocol, RFC 1157 [14], which defines the
   protocol used to manage these objects.

   Consistent with the IAB directive to produce simple, workable
   systems in the short-term, the list ofc objects (e.g., for BSD UNIX)
      were excluded.

   7) It was agreed to avoid heavily instrumenting critical
      sections of code.  The general guideline was one counter
      per critical section per layer.

3.  Changes from MIB-I

   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 }

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

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



IETF SNMP Working Group                                         [Page 4]

RFC 1158                         MIB II                         May 1990


   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 [7].

   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.  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.

3.4.  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



IETF SNMP Working Group                                         [Page 5]

RFC 1158                         MIB II                         May 1990


   accordingly.

   The ifTable object was mistaken marked as read-write, it has been
   (correctly) re-designated as read-only.  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)

   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.

3.5.  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., [8]),
   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.



IETF SNMP Working Group                                         [Page 6]

RFC 1158                         MIB II                         May 1990


3.6.  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.  There is also a new column in
   the ipRoutingTable object,

                  ipRouteMask

   which is used for IP routing subsystems that support arbitrary subnet
   masks.

   One new object is added to the IP group:

                  ipNetToMediaTable

   which is the address translation table for the IP group (providing
   identical functionality to the now deprecated atTable in the address
   translation group).

3.7.  The ICMP Group

   There are no changes to this group.

3.8.  The TCP Group

   Two new variables are added:

                  tcpInErrs
                  tcpOutRsts

   which keep track of the number of incoming TCP segments in error and
   the number of resets generated by a TCP.

3.9.  The UDP Group

   A new table:

                  udpTable

   is added.




IETF SNMP Working Group                                         [Page 7]

RFC 1158                         MIB II                         May 1990


3.10.  The EGP Group

   Experience has indicated a need for additional objects that are
   useful in EGP monitoring.  In addition to making several additions to
   the egpNeighborTable object, a new variable is added:

                  egpAs

   which gives the autonomous system associated with this EGP entity.

3.11.  The Transmission Group

   MIB-I was lacking in that it did not distinguish between different
   types of transmission media.  A new group, the Transmission group, is
   allocated for this purpose:

                  transmission OBJECT IDENTIFIER ::= { mib-2 10 }

   When Internet-standard definitions for managing transmission media
   are defined, the transmission group is used to provide a prefix for
   the names of those objects.

   Typically, such definitions reside in the experimental portion of the
   MIB until they are "proven", then as a part of the Internet
   standardization process, the definitions are accordingly elevated and
   a new object identifier, under the transmission group is defined.  By
   convention, the name assigned is:

                  type OBJECT IDENTIFIER    ::= { transmission number }

   where "type" is the symbolic value used for the media in the ifType
   column of the ifTable object, and "number" is the actual integer
   value corresponding to the symbol.

3.12.  The SNMP Group

   The application-oriented working groups of the IETF have been tasked
   to be receptive towards defining MIB variables specific to their
   respective applications.

   For the SNMP, it is useful to have statistical information.  A new
   group, the SNMP group, is allocated for this purpose:

                  snmp   OBJECT IDENTIFIER ::= { mib-2 11 }

4.  Objects

   Managed objects are accessed via a virtual information store, termed



IETF SNMP Working Group                                         [Page 8]

RFC 1158                         MIB II                         May 1990


   the Management Information Base or MIB.  Objects in the MIB are
   defined using Abstract Syntax Notation One (ASN.1) [9].

   The mechanisms used for describing these objects are specified the
   companion memo, the SMI.  In particular, each object has a name, a