rfc2573.txt

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     -  The securityModel is that of the original incoming management
        target extracted from the cache.

     -  The securityName is that of the original incoming management
        target extracted from the cache.

     -  The securityLevel is that of the original incoming management
        target extracted from the cache.

     -  The contextEngineID is the value extracted from the cache.

     -  The contextName is the value extracted from the cache.

     -  The pduVersion indicates the version of the PDU to be returned.

     -  The PDU is the (possibly translated) Response PDU.

     -  The maxSizeResponseScopedPDU is a local value indicating the
        maximum size of a ScopedPDU that the application can accept.

     -  The stateReference is the value extracted from the cache.

     -  The statusInformation indicates that no error occurred and that
        a Response PDU message should be generated.

3.5.1.3.  Processing an Incoming Internal-Class PDU

   A proxy forwarder follows the following procedure when an incoming
   Internal-Class PDU is received:

   (1)  The incoming Internal-Class PDU is received using the
        processResponsePdu interface.  The proxy forwarder uses the
        received parameters to locate an entry in its cache of pending
        forwarded requests.  This is done by matching the received
        parameters with the cached values of sendPduHandle.  If an
        appropriate cache entry cannot be found, processing of the
        Internal-Class PDU is halted.  Otherwise:

   (2)  The cache information is extracted, and removed from the cache.

   (3)  If the original incoming management target information indicates
        an SNMP version which does not support Report PDUs, processing
        of the Internal-Class PDU is halted.





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   (4)  The proxy forwarder calls the Dispatcher using the
        returnResponsePdu abstract service interface.  Parameters are:

     -  The messageProcessingModel indicates the Message Processing
        Model by which the original incoming message was processed.

     -  The securityModel is that of the original incoming management
        target extracted from the cache.

     -  The securityName is that of the original incoming management
        target extracted from the cache.

     -  The securityLevel is that of the original incoming management
        target extracted from the cache.

     -  The contextEngineID is the value extracted from the cache.

     -  The contextName is the value extracted from the cache.

     -  The pduVersion indicates the version of the PDU to be returned.

     -  The PDU is unused.

     -  The maxSizeResponseScopedPDU is a local value indicating the
        maximum size of a ScopedPDU that the application can accept.

     -  The stateReference is the value extracted from the cache.

     -  The statusInformation contains values specific to the Internal-
        Class PDU type (for example, for a Report PDU, the
        statusInformation contains the contextEngineID, contextName,
        counter OID, and counter value received in the incoming Report
        PDU).

3.5.2.  Notification Forwarding

   A proxy forwarder receives notifications in the same manner as a
   notification receiver application, using the processPdu abstract
   service interface.  The following procedure is used when a
   notification is received:

   (1)  The incoming management target information received from the
        processPdu interface is translated into outgoing management
        target information.  Note that this translation may vary for
        different values of contextEngineID and/or contextName.  The
        translation may result in multiple management targets.





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   (2)  If appropriate outgoing management target information cannot be
        found and the notification was an Unconfirmed-Class PDU,
        processing of the notification is halted.  If appropriate
        outgoing management target information cannot be found and the
        notification was a Confirmed-Class PDU, the proxy forwarder
        increments the snmpProxyDrops object, and calls the Dispatcher
        using the returnResponsePdu abstract service interface.  The
        parameters are:

     -  The messageProcessingModel is the received value.

     -  The securityModel is the received value.

     -  The securityName is the received value.

     -  The securityLevel is the received value.

     -  The contextEngineID is the received value.

     -  The contextName is the received value.

     -  The pduVersion is the received value.

     -  The PDU is an undefined and unused value.

     -  The maxSizeResponseScopedPDU is a local value indicating the
        maximum size of a ScopedPDU that the application can accept.

     -  The stateReference is the received value.

     -  The statusInformation indicates that an error occurred and that
        a Report message should be generated.

   Processing of the message stops at this point.  Otherwise,

   (3)  The proxy forwarder generates a notification using the
        procedures described in the preceding section on Notification
        Originators, with the following exceptions:

     -  The contextEngineID and contextName values from the original
        received notification are used.

     -  The outgoing management targets previously determined are used.

     -  No filtering mechanisms are applied.






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     -  The variable-bindings from the original received notification
        are used, rather than retrieving variable-bindings from local
        MIB instrumentation.  In particular, no access-control is
        applied to these variable-bindings.

     -  If the original notification contains a Confirmed-Class PDU,
        then any outgoing management targets, for which the outgoing
        SNMP version does not support and PDU types which are both
        Notification-Class and Confirmed-Class PDUs, will not be used
        when generating the forwarded notifications.

     -  If, for any of the outgoing management targets, the incoming
        SNMP version and the outgoing SNMP version support different PDU
        versions, the proxy forwarder may need to perform a translation
        on the PDU.  (A method for performing such a translation is
        described in [COEX].)

   (4)  If the original received notification contains an Unconfirmed-
        Class PDU, processing of the notification is now completed.
        Otherwise, the original received notification must contain a
        Confirmed-Class PDU, and processing continues.

   (5)  If the forwarded notifications included any Confirmed-Class
        PDUs, processing continues when the procedures described in the
        section for Notification Originators determine that either:

     -  None of the generated notifications containing Confirmed-Class
        PDUs have been successfully acknowledged within the longest of
        the time intervals, in which case processing of the original
        notification is halted, or,

     -  At least one of the generated notifications containing
        Confirmed-Class PDUs is successfully acknowledged, in which case
        a response to the original received notification containing an
        Confirmed-Class PDU is generated as described in the following
        steps.

   (6)  A Response-Class PDU is constructed, using the values of
        request-id and variable-bindings from the original received
        Notification-Class PDU, and error-status and error-index values
        of 0.

   (7)  The Dispatcher is called using the returnResponsePdu abstract
        service interface.  Parameters are:

     -  The messageProcessingModel is the originally received value.

     -  The securityModel is the originally received value.



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     -  The securityName is the originally received value.

     -  The securityLevel is the originally received value.

     -  The contextEngineID is the originally received value.

     -  The contextName is the originally received value.

     -  The pduVersion indicates the version of the PDU constructed in
        step (6) above.

     -  The PDU is the value constructed in step (6) above.

     -  The maxSizeResponseScopedPDU is a local value indicating the
        maximum size of a ScopedPDU that the application can accept.

     -  The stateReference is the originally received value.

     -  The statusInformation indicates that no error occurred and that
        a Response-Class PDU message should be generated.

4.  The Structure of the MIB Modules

   There are three separate MIB modules described in this document, the
   management target MIB, the notification MIB, and the proxy MIB.  The
   following sections describe the structure of these three MIB modules.

   The use of these MIBs by particular types of applications is
   described later in this document:

     -  The use of the management target MIB and the notification MIB in
        notification originator applications is described in section 6.

     -  The use of the notification MIB for filtering notifications in
        notification originator applications is described in section 7.

     -  The use of the management target MIB and the proxy MIB in proxy
        forwarding applications is described in section 8.

4.1.  The Management Target MIB Module

   The SNMP-TARGET-MIB module contains objects for defining management
   targets.  It consists of two tables and conformance/compliance
   statements.







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   The first table, the snmpTargetAddrTable, contains information about
   transport domains and addresses.  It also contains an object,
   snmpTargetAddrTagList, which provides a mechanism for grouping
   entries.

   The second table, the snmpTargetParamsTable, contains information
   about SNMP version and security information to be used when sending
   messages to particular transport domains and addresses.

   The Management Target MIB is intended to provide a general-purpose
   mechanism for specifying transport address, and for specifying
   parameters of SNMP messages generated by an SNMP entity.  It is used
   within this document for generation of notifications and for proxy
   forwarding.  However, it may be used for other purposes.  If another
   document makes use of this MIB, that document is responsible for
   specifying how it is used.  For example, [COEX] uses this MIB for
   source address validation of SNMPv1 messages.

4.1.1.  Tag Lists

   The snmpTargetAddrTagList object is used for grouping entries in the
   snmpTargetAddrTable.  The value of this object contains a list of tag
   values which are used to select target addresses to be used for a
   particular operation.

   A tag value, which may also be used in MIB objects other than
   snmpTargetAddrTagList, is an arbitrary string of octets, but may not
   contain a delimiter character.  Delimiter characters are defined to
   be one of the following characters:

     -  An ASCII space character (0x20).

     -  An ASCII TAB character (0x09).

     -  An ASCII carriage return (CR) character (0x0D).

     -  An ASCII line feed (LF) character (0x0B).

   In addition, a tag value may not have a zero length.  Generally, a
   particular MIB object may contain either

     -  a single tag value, in which case the value of the MIB object
        may not contain a delimiter character, or:

     -  a MIB object may contain a list of tag values, separated by
        single