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RFC 1271

Remote Network Monitoring Management Information Base

Pages: 81
Obsoleted by:  1757
Updated by:  1513
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Network Working Group                                      S. Waldbusser
Request for Comments: 1271                    Carnegie Mellon University
                                                           November 1991

         Remote Network Monitoring Management Information Base

Status of this Memo

   This memo is an extension to the SNMP MIB.  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. The Network Management Framework.......................    2
   3. Objects ...............................................    2
   3.1 Format of Definitions ................................    3
   4. Overview ..............................................    3
   4.1 Remote Network Management Goals ......................    3
   4.2 Textual Conventions ..................................    5
   4.3 Structure of MIB .....................................    5
   4.3.1 The Statistics Group ...............................    6
   4.3.2 The History Group ..................................    6
   4.3.3 The Alarm Group ....................................    6
   4.3.4 The Host Group .....................................    6
   4.3.5 The HostTopN Group .................................    6
   4.3.6 The Matrix Group ...................................    7
   4.3.7 The Filter Group ...................................    7
   4.3.8 The Packet Capture Group ...........................    7
   4.3.9 The Event Group ....................................    7
   5. Control of Remote Network Monitoring Devices ..........    7
   5.1 Resource Sharing Among Multiple Management Stations ..    8
   5.2 Row Addition Among Multiple Management Stations ......    9
   6. Definitions ...........................................   10
   7. Acknowledgments .......................................   80
   8. References ............................................   80
   Security Considerations...................................   81
   Author's Address..........................................   81
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1.  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.

2.  The Network Management Framework

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

      RFC 1155 which defines the SMI, the mechanisms used for describing
      and naming objects for the purpose of management.  RFC 1212
      defines a more concise description mechanism, which is wholly
      consistent with the SMI.

      RFC 1156 which defines MIB-I, the core set of managed objects for
      the Internet suite of protocols.  RFC 1213, defines MIB-II, an
      evolution of MIB-I based on implementation experience and new
      operational requirements.

      RFC 1157 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.

3.  Objects

   Managed objects are accessed via a virtual information store, termed
   the Management Information Base or MIB.  Objects in the MIB are
   defined using the subset of Abstract Syntax Notation One (ASN.1) [7]
   defined in the SMI.  In particular, each object has a name, a syntax,
   and an encoding.  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 language is used for
   this purpose.  However, the SMI [3] purposely restricts the ASN.1
   constructs which may be used.  These restrictions are explicitly made
   for simplicity.

   The encoding of an object type is simply how that object type
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   is represented using the object type's syntax.  Implicitly
   tied to the notion of an object type's syntax and encoding is
   how the object type is represented when being transmitted on
   the network.

   The SMI specifies the use of the basic encoding rules of ASN.1 [8],
   subject to the additional requirements imposed by the SNMP.

3.1.  Format of Definitions

   Section 6 contains the specification of all object types
   contained in this MIB module.  The object types are defined
   using the conventions defined in the SMI, as amended by the
   extensions specified in [9,10].

4.  Overview

   Remote network monitoring devices 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.

   While many of the objects in this document are suitable for the
   management of any type of network, there are some which are specific
   to managing Ethernet networks.  The design of this MIB allows similar
   objects to be defined for other network types.  It is intended that
   future versions of this document will define extensions for other
   network types such as Token Ring and FDDI.

4.1.  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
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                  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.

              o Preemptive 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

              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
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                  deal with more than own management station,
                  potentially using its resources concurrently.

4.2.  Textual Conventions

   Two new data types are introduced as a textual convention in this MIB
   document.  These textual conventions enhance the readability of the
   specification and can ease comparison with other specifications if
   appropriate.  It should be noted that the introduction of the these
   textual conventions has no effect on either the syntax nor the
   semantics of any managed objects.  The use of these is merely an
   artifact of the explanatory method used.  Objects defined in terms of
   one of these methods are always encoded by means of the rules that
   define the primitive type.  Hence, no changes to the SMI or the SNMP
   are necessary to accommodate these textual conventions which are
   adopted merely for the convenience of readers and writers in pursuit
   of the elusive goal of clear, concise, and unambiguous MIB documents.

   The new data types are: OwnerString and EntryStatus.

4.3.  Structure of MIB

   The objects are arranged into the following groups:

                  - statistics

                  - history

                  - alarm

                  - host

                  - hostTopN

                  - matrix

                  - filter

                  - packet capture

                  - event

   These groups are the basic unit 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 host group must implement the hostControlTable, the hostTable and
   the hostTimeTable.
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   All groups in this MIB are optional.  Implementations of this MIB
   must also implement the system and interfaces group of MIB-II [6].
   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.

4.3.1.  The Statistics Group

   The statistics group contains statistics measured by the probe for
   each monitored interface on this device.  This group currently
   consists of the etherStatsTable but in the future will contain tables
   for other media types including Token Ring and FDDI.

4.3.2.  The History Group

   The history group records periodic statistical samples from a network
   and stores them for later retrieval.  This group currently consists
   of the historyControlTable and the etherHistoryTable.  In future
   versions of the MIB, this group may contain tables for other media
   types including Token Ring and FDDI.

4.3.3.  The Alarm Group

   The alarm group periodically takes statistical samples from variables
   in the probe and compares them to previously configured thresholds.
   If the monitored variable crosses a threshold, an event is generated.
   A hysteresis mechanism is implemented to limit the generation of
   alarms.  This group consists of the alarmTable and requires the
   implementation of the event group.

4.3.4.  The Host Group

   The host group contains statistics associated with each host
   discovered on the network.  This group discovers hosts on the network
   by keeping a list of source and destination MAC Addresses seen in
   good packets promiscuously received from the network.  This group
   consists of the hostControlTable, the hostTable, and the

4.3.5.  The HostTopN Group

   The hostTopN group is used to prepare reports that describe the hosts
   that top a list ordered by one of their statistics.  The available
   statistics are samples of one of their base statistics over an
   interval specified by the management station.  Thus, these statistics
   are rate based.  The management station also selects how many such
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   hosts are reported.  This group consists of the hostTopNControlTable
   and the hostTopNTable, and requires the implementation of the host

4.3.6.  The Matrix Group

   The matrix group stores statistics for conversations between sets of
   two addresses.  As the device detects a new conversation, it creates
   a new entry in its tables.  This group consists of the
   matrixControlTable, the matrixSDTable and the matrixDSTable.

4.3.7.  The Filter Group

   The filter group allows packets to be matched by a filter equation.
   These matched packets form a data stream that may be captured or may
   generate events.  This group consists of the filterTable and the

4.3.8.  The Packet Capture Group

   The Packet Capture group allows packets to be captured after they
   flow through a channel.  This group consists of the
   bufferControlTable and the captureBufferTable, and requires the
   implementation of the filter group.

4.3.9.  The Event Group

   The event group controls the generation and notification of events
   from this device.  This group consists of the eventTable and the

5.  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
   read-write in nature, while the data tables are typically read-only.
   Because the parameters in the control table often describe resulting
   data in the data table, many of the parameters can be modified only
   when the control entry is invalid.  Thus, the method for modifying
   these parameters is to invalidate the control entry, causing its
   deletion and the deletion of any associated data entries, and then
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   create a new control entry with the proper parameters.  Deleting the
   control entry also gives a convenient method for reclaiming the
   resources used by the associated data.

   Some objects in this MIB provide a mechanism to execute an action on
   the remote monitoring device.  These objects may execute an action as
   a result of a change in the state of the object.  For those objects
   in this MIB, a request to set an object to the same value as it
   currently holds would thus cause no action to occur.

   To facilitate control by multiple managers, resources have to be
   shared among the managers.  These resources are typically the memory
   and computation resources that a function requires.

5.1.  Resource Sharing Among Multiple Management Stations

   When multiple management stations wish to use functions that compete
   for a finite amount of resources on a device, a method to facilitate
   this sharing of resources is required.  Potential conflicts include:

              o Two management stations wish to simultaneously use
                resources that together would exceed the capability of
                the device.

              o A management station uses a significant amount of
                resources for a long period of time.

              o A management station uses resources and then crashes,
                forgetting to free the resources so others may
                use them.

   A mechanism is provided for each management station initiated
   function in this MIB to avoid these conflicts and to help resolve
   them when they occur.  Each function has a label identifying the
   initiator (owner) of the function.  This label is set by the
   initiator to provide for the following possibilities:

              o A management station may recognize resources it owns
                and no longer needs.

              o A network operator can find the management station that
                owns the resource and negotiate for it to be freed.

              o A network operator may decide to unilaterally free
                resources another network operator has reserved.

              o Upon initialization, a management station may recognize
                resources it had reserved in the past.  With this
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                information it may free the resources if it no longer
                needs them.

   Management stations and probes should support any format of the owner
   string dictated by the local policy of the organization.  It is
   suggested that this name contain one or more of the following: IP
   address, management station name, network manager's name, location,
   or phone number.  This information will help users to share the
   resources more effectively.

   There is often default functionality that the device wishes to set
   up.  The resources associated with this functionality are then owned
   by the device itself.  In this case, the device will set the relevant
   owner object to a string starting with 'monitor'.  Indiscriminate
   modification of the monitor-owned configuration by network management
   stations is discouraged.  In fact, a network management station
   should only modify these objects under the direction of the
   administrator of the probe, often the network administrator.

   When a network management station wishes to utilize a function in a
   monitor, it is encouraged to first scan the control table of that
   function to find an instance with similar parameters to share.  This
   is especially true for those instances owned by the monitor, which
   can be assumed to change infrequently.  If a management station
   decides to share an instance owned by another management station, it
   should understand that the management station that owns the instance
   may indiscriminately modify or delete it.

5.2.  Row Addition Among Multiple Management Stations

   The addition of new rows is achieved using the method described in
   [9].  In this MIB, rows are often added to a table in order to
   configure a function.  This configuration usually involves parameters
   that control the operation of the function.  The agent must check
   these parameters to make sure they are appropriate given restrictions
   defined in this MIB as well as any implementation specific
   restrictions such as lack of resources.  The agent implementor may be
   confused as to when to check these parameters and when to signal to
   the management station that the parameters are invalid.  There are
   two opportunities:

              o When the management station sets each parameter object.

              o When the management station sets the entry status object
                to valid.

   If the latter is chosen, it would be unclear to the management
   station which of the several parameters was invalid and caused the
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   badValue error to be emitted.  Thus, wherever possible, the
   implementor should choose the former as it will provide more
   information to the management station.

   A problem can arise when multiple management stations attempt to set
   configuration information simultaneously using SNMP.  When this
   involves the addition of a new conceptual row in the same control
   table, the managers may collide, attempting to create the same entry.
   To guard against these collisions, each such control entry contains a
   status object with special semantics that help to arbitrate among the
   managers.  If an attempt is made with the row addition mechanism to
   create such a status object and that object already exists, an error
   is returned.  When more than one manager simultaneously attempts to
   create the same conceptual row, only the first will succeed.  The
   others will receive an error.

(page 10 continued on part 2)

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