rfc2021.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

Network Working Group                                     S. Waldbusser
Request for Comments: 2021                                          INS
Category: Standards Track                                  January 1997


         Remote Network Monitoring Management Information Base
                               Version 2
                              using SMIv2

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   This memo defines a portion of the Management Information Base (MIB)
   for use with network management protocols in TCP/IP-based internets.
   In particular, it defines objects for managing remote network
   monitoring devices.

Table of Contents

1 The Network Management Framework ......................    2
2 Overview ..............................................    2
2.1 Remote Network Management Goals .....................    3
2.2 Structure of MIB ....................................    5
3 Control of Remote Network Monitoring Devices ..........    6
3.1 Resource Sharing Among  Multiple  Management  Sta-
     tions ..............................................    7
3.2 Row Addition Among Multiple Management Stations .....    9
4 Conventions ...........................................   10
5 RMON 2 Conventions ....................................   10
5.1 Usage of the term Application Level .................   10
5.2 Protocol Directory and Limited Extensibility ........   11
5.3 Errors in packets ...................................   11
6 Definitions ...........................................   12
7 Security Considerations ...............................  122
8 Appendix - TimeFilter Implementation Notes ...........   123
9 Acknowledgments ......................................   129
10 References ...........................................  129
11 Author's Address......................................  130






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RFC 2021             Remote Network Monitoring MIB          January 1997


1.  The Network Management Framework

   The Internet-standard Network Management Framework consists of three
   components.  They are:

   RFC 1902 [1] which defines the SMI, the mechanisms used for
   describing and naming objects for the purpose of management.

   RFC 1213, STD 17, [3] which defines MIB-II, the core set of
   managed objects for the Internet suite of protocols.

   RFC 1905 [4] which defines the SNMP, the protocol used for
   network access to managed objects.

   The Framework permits new objects to be defined for the purpose of
   experimentation and evaluation.

   Managed objects are accessed via a virtual information store, termed
   the Management Information Base or MIB.  Within a given MIB module,
   objects are defined using the SMI's OBJECT-TYPE macro.  At a minimum,
   each object has a name, a syntax, an access-level, and an
   implementation-status.

   The name is an object identifier, an administratively assigned name,
   which specifies an object type.  The object type together with an
   object instance serves to uniquely identify a specific instantiation
   of the object.  For human convenience, we often use a textual string,
   termed the object descriptor, to also refer to the object type.

   The syntax of an object type defines the abstract data structure
   corresponding to that object type.  The ASN.1 [6] language is used
   for this purpose.  However, RFC 1902 purposely restricts the ASN.1
   constructs which may be used.  These restrictions are explicitly made
   for simplicity.

   The access-level of an object type defines whether it makes "protocol
   sense" to read and/or write the value of an instance of the object
   type.  (This access-level is independent of any administrative
   authorization policy.)

   The implementation-status of an object type indicates whether the
   object is mandatory, optional, obsolete, or deprecated.

2.  Overview

   This document continues the architecture created in the RMON MIB [RFC
   1757] by providing a major feature upgrade, primarily by providing
   RMON analysis up to the application layer.



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RFC 2021             Remote Network Monitoring MIB          January 1997


   Remote network monitoring devices, often called monitors or probes,
   are instruments that exist for the purpose of managing a network.
   Often these remote probes are stand-alone devices and devote
   significant internal resources for the sole purpose of managing a
   network.  An organization may employ many of these devices, one per
   network segment, to manage its internet.  In addition, these devices
   may be used for a network management service provider to access a
   client network, often geographically remote.

   The objects defined in this document are intended as an interface
   between an RMON agent and an RMON management application and are not
   intended for direct manipulation by humans.  While some users may
   tolerate the direct display of some of these objects, few will
   tolerate the complexity of manually manipulating objects to
   accomplish row creation.  These functions should be handled by the
   management application.

2.1.  Remote Network Management Goals

    o Offline Operation
        There are sometimes conditions when a management
        station will not be in constant contact with its
        remote monitoring devices.  This is sometimes by
        design in an attempt to lower communications costs
        (especially when communicating over a WAN or
        dialup link), or by accident as network failures
        affect the communications between the management
        station and the probe.

        For this reason, this MIB allows a probe to be
        configured to perform diagnostics and to collect
        statistics continuously, even when communication with
        the management station may not be possible or
        efficient.  The probe may then attempt to notify
        the management station when an exceptional condition
        occurs.  Thus, even in circumstances where
        communication between management station and probe is
        not continuous, fault, performance, and configuration
        information may be continuously accumulated and
        communicated to the management station conveniently
        and efficiently.










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RFC 2021             Remote Network Monitoring MIB          January 1997


    o Proactive Monitoring
        Given the resources available on the monitor, it
        is potentially helpful for it continuously to run
        diagnostics and to log network performance.  The
        monitor is always available at the onset of any
        failure.  It can notify the management station of the
        failure and can store historical statistical
        information about the failure.  This historical
        information can be played back by the management
        station in an attempt to perform further diagnosis
        into the cause of the problem.

    o Problem Detection and Reporting
        The monitor can be configured to recognize
        conditions, most notably error conditions, and
        continuously to check for them.  When one of these
        conditions occurs, the event may be logged, and
        management stations may be notified in a number of
        ways.

    o Value Added Data
        Because a remote monitoring device represents a
        network resource dedicated exclusively to network
        management functions, and because it is located
        directly on the monitored portion of the network, the
        remote network monitoring device has the opportunity
        to add significant value to the data it collects.
        For instance, by highlighting those hosts on the
        network that generate the most traffic or errors, the
        probe can give the management station precisely the
        information it needs to solve a class of problems.

    o Multiple Managers
        An organization may have multiple management stations
        for different units of the organization, for different
        functions (e.g. engineering and operations), and in an
        attempt to provide disaster recovery.  Because
        environments with multiple management stations are
        common, the remote network monitoring device has to
        deal with more than own management station,
        potentially using its resources concurrently.










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RFC 2021             Remote Network Monitoring MIB          January 1997


2.2.  Structure of MIB

   The objects are arranged into the following groups:

        - protocol directory

        - protocol distribution

        - address mapping

        - network layer host

        - network layer matrix

        - application layer host

        - application layer matrix

        - user history

        - probe configuration

   These groups are the basic units of conformance.  If a remote
   monitoring device implements a group, then it must implement all
   objects in that group.  For example, a managed agent that implements
   the network layer matrix group must implement the nlMatrixSDTable and
   the nlMatrixDSTable.

   Implementations of this MIB must also implement the system and
   interfaces group of MIB-II [3].  MIB-II may also mandate the
   implementation of additional groups.

   These groups are defined to provide a means of assigning object
   identifiers, and to provide a method for managed agents to know which
   objects they must implement.

   This document also contains enhancements to tables defined in the
   RMON MIB [RFC 1757].  These enhancements include:

    1) Adding the DroppedFrames and LastCreateTime
       conventions to each table defined in the RMON MIB.

    2) Augmenting the RMON filter table with a mechanism
       that allows filtering based on an offset from the
       beginning of a particular protocol, even if the
       protocol headers are variable length.





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RFC 2021             Remote Network Monitoring MIB          January 1997


    3) Augmenting the RMON filter and capture status bits
       with additional bits for WAN media and generic media.
       These bits are defined here as:

        Bit     Definition
        6       For WAN media, this bit is set for packets
                coming from one direction and cleared for
                packets coming from the other direction.
                It is an implementation specific matter
                as to which bit is assigned to which
                direction, but it must be consistent for
                all packets received by the agent, and if
                the agent knows which end of the link is
                "local" and which end is "network", the bit
                should be set for packets from the "local"
                side and should be cleared for packets from
                the "network" side.

        7       For any media, this bit is set for any packet
                with a physical layer error. This bit may be
                set in addition to other media-specific bits
                that denote the same condition.

        8       For any media, this bit is set for any packet
                that is too short for the media. This bit may
                be set in addition to other media-specific
                bits that denote the same condition.
        9       For any media, this bit is set for any packet
                that is too long for the media. This bit may
                be set in addition to other media-specific bits
                that denote the same condition.

   These enhancements are implemented by RMON-2 probes that also
   implement RMON and do not add any requirements to probes that are
   compliant to just RMON.

3.  Control of Remote Network Monitoring Devices

   Due to the complex nature of the available functions in these
   devices, the functions often need user configuration.  In many cases,
   the function requires parameters to be set up for a data collection
   operation.  The operation can proceed only after these parameters are
   fully set up.

   Many functional groups in this MIB have one or more tables in which
   to set up control parameters, and one or more data tables in which to
   place the results of the operation.  The control tables are typically