rfc1271.txt

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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
   hostTimeTable.

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
   group.

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
   channelTable.

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
   logTable.

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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RFC 1271             Remote Network Monitoring MIB         November 1991


   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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RFC 1271             Remote Network Monitoring MIB         November 1991


   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.

6.  Definitions

          RFC1271-MIB DEFINITIONS ::= BEGIN

              IMPORTS
                  Counter                              FROM RFC1155-SMI
                  DisplayString                        FROM RFC1158-MIB
                  mib-2                                FROM RFC1213-MIB
                  OBJECT-TYPE                          FROM RFC-1212;

          --  This MIB module uses the extended OBJECT-TYPE macro as
          --  defined in [9].


          --  Remote Network Monitoring MIB

              rmon    OBJECT IDENTIFIER ::= { mib-2 16 }


              -- textual conventions

              OwnerString ::= DisplayString
              -- This data type is used to model an administratively
              -- assigned name of the owner of a resource. This
              -- information is taken from the NVT ASCII character set.
              -- 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.
              -- In some cases the agent itself will be the owner of
              -- an entry.  In these cases, this string shall be set
              -- to a string starting with 'monitor'.



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              --
              -- SNMP access control is articulated entirely in terms of
              -- the contents of MIB views; access to a particular SNMP
              -- object instance depends only upon its presence or
              -- absence in a particular MIB view and never upon its
              -- value or the value of related object instances. Thus,
              -- objects of this type afford resolution of resource
              -- contention only among cooperating managers; they
              -- realize no access control function with respect
              -- to uncooperative parties.
              --
              -- By convention, objects with this syntax are declared
              -- as having
              --
              --      SIZE (0..127)


              EntryStatus ::= INTEGER
                         { valid(1),
                           createRequest(2),
                           underCreation(3),
                           invalid(4)
                         }

              -- The status of a table entry.
              --
              -- Setting this object to the value invalid(4) has the
              -- effect of invalidating the corresponding entry.
              -- That is, it effectively disassociates the mapping
              -- identified with said entry.
              -- It is an implementation-specific matter as to whether
              -- the agent removes an invalidated entry from the table.
              -- Accordingly, management stations must be prepared to
              -- receive tabular information from agents that corresponds
              -- to entries currently not in use.  Proper
              -- interpretation of such entries requires examination
              -- of the relevant EntryStatus object.
              --
              -- An existing instance of this object cannot be set to
              -- createRequest(2).  This object may only be set to
              -- createRequest(2) when this instance is created.  When
              -- this object is created, the agent may wish to create
              -- supplemental object instances to complete a conceptual
              -- row in this table.  Immediately after completing the
              -- create operation, the agent must set this object to
              -- underCreation(3).
              --
              -- Entries shall exist in the underCreation(3) state until