rfc2263.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

   request for management information to an SNMP engine which is
   "closer" or "downstream in the path" to the SNMP engine which has
   access to that information, and to deliver the response containing
   the information back to the SNMP engine from which the request was
   received.  The context information in a request is used to determine
   which SNMP engine has access to the requested information, and this
   is used to determine where and how to forward the request.






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   For the second type, the proxy forwarder's role is to determine which
   SNMP engines should receive notifications about management
   information from a particular location.  The context information in a
   notification message determines the location to which the information
   contained in the notification applies.  This is used to determine
   which SNMP engines should receive notification about this
   information.

   For the third type, the proxy forwarder's role is to determine which
   previously forwarded request or notification (if any) the response
   matches, and to forward the response back to the initiator of the
   request or notification.

   For the fourth type, the proxy forwarder's role is to determine which
   previously forwarded request or notification (if any) the report
   indication matches, and to forward the report indication back to the
   initiator of the request or notification.

   When forwarding messages, a proxy forwarder application must perform
   a translation of incoming management target information into outgoing
   management target information.  How this translation is performed is
   implementation specific.  In many cases, this will be driven by a
   preconfigured translation table.  If a proxy forwarder application
   makes the contents of this table SNMP manageable, it MUST use the
   SNMP-PROXY-MIB module defined in this document.

3.5.1.  Request Forwarding

   There are two phases for request forwarding.  First, the incoming
   request needs to be passed through the proxy application.  Then, the
   resulting response needs to be passed back.  These phases are
   described in the following two sections.

3.5.1.1.  Processing an Incoming Request

   A proxy forwarder application that wishes to forward request messages
   must first register with the Dispatcher using the
   registerContextEngineID abstract service interface.  The proxy
   forwarder must register each contextEngineID for which it wishes to
   forward messages, as well as for each pduType.  Note that as the
   configuration of a proxy forwarder is changed, the particular
   contextEngineID values for which it is forwarding may change.  The
   proxy forwarder should call the registerContextEngineID and
   unregisterContextEngineID abstract service interfaces as needed to
   reflect its current configuration.






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   A proxy forwarder application should never attempt to register a
   value of contextEngineID which is equal to the snmpEngineID of the
   SNMP engine to which the proxy forwarder is associated.

   Once the proxy forwarder has registered for the appropriate
   contextEngineId values, it can start processing messages.  The
   following procedure is used:

(1)  A message is received using the processPdu abstract service
     interface.  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 should result in a single management target.

(2)  If appropriate outgoing management target information cannot be
     found, the proxy forwarder increments the snmpProxyDrops counter
     [RFC1907], and then calls the Dispatcher using the
     returnResponsePdu abstract service interface.  Parameters are:

       -  The messageProcessingModel is the value from the processPdu
          call.

       -  The securityModel is the value from the processPdu call.

       -  The securityName is the value from the processPdu call.

       -  The securityLevel is the value from the processPdu call.

       -  The contextEngineID is the value from the processPdu call.

       -  The contextName is the value from the processPdu call.

       -  The pduVersion is the value from the processPdu call.

       -  The PDU is an undefined value.

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

       -  The stateReference is the value from the processPdu call.

       -  The statusInformation indicates that an error occurred and
          includes the OID and value of the snmpProxyDrops object.

     Processing of the message stops at this point.  Otherwise,





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(3)  A new PDU is constructed.  A unique value of request-id should be
     used in the new PDU (this value will enable a subsequent response
     message to be correlated with this request).  The remainder of the
     new PDU is identical to the received PDU, unless the incoming SNMP
     version is SNMPv2 or SNMPv3 and the outgoing SNMP version is
     SNMPv1, in which case the proxy forwarder must apply the
     translation rules as documented in [RFC1908].

(4)  The proxy forwarder calls the Dispatcher to generate the forwarded
     message, using the sendPdu abstract service interface.  The
     parameters are:

       -  The transportDomain is that of the outgoing management target.

       -  The transportAddress is that of the outgoing management
          target.

       -  The messageProcessingModel is that of the outgoing management
          target.

       -  The securityModel is that of the outgoing management target.

       -  The securityName is that of the outgoing management target.

       -  The securityLevel is that of the outgoing management target.

       -  The contextEngineID is the value originally received.

       -  The contextName is the value originally received.

       -  The pduVersion is the version of the PDU to be sent.

       -  The PDU is the value constructed in step (3) above.

       -  The expectResponse argument indicates that a response is
          expected.  If the sendPdu call is unsuccessful, the proxy
          forwarder performs the steps described in (2) above.
          Otherwise:

(5)  The proxy forwarder caches the following information in order to
     match an incoming response to the forwarded request:

       -  The sendPduHandle returned from the call to sendPdu,

       -  The request-id from the received PDU.

       -  the contextEngineID,




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       -  the contextName,

       -  the stateReference,

       -  the incoming management target information,

       -  the outgoing management information,

       -  any other information needed to match an incoming response to
          the forwarded request.

     If this information cannot be cached (possibly due to a lack of
     resources), the proxy forwarder performs the steps described in (2)
     above.  Otherwise:

(6)  Processing of the request stops until a response to the forwarded
     request is received, or until an appropriate time interval has
     expired.  If this time interval expires before a response has been
     received, the cached information about this request is removed.

3.5.1.2.  Processing an Incoming Response

   A proxy forwarder follows the following procedure when an incoming
   response is received:

(1)  The incoming response 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, contextEngineID, contextName, outgoing management
     target information, and the request-id contained in the received
     PDU (the proxy forwarder must extract the request-id for this
     purpose).  If an appropriate cache entry cannot be found,
     processing of the response is halted.  Otherwise:

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

(3)  A new Response PDU is constructed, using the request-id value from
     the original forwarded request (as extracted from the cache).  All
     other values are identical to those in the received Response PDU.

(4)  If the incoming SNMP version is SNMPv1 and the outgoing SNMP
     version is SNMPv2 or SNMPv3, the proxy forwarder must apply the
     translation rules documented in [RFC1908].

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




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       -  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 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 Report Indication

   A proxy forwarder follows the following procedure when an incoming
   report indication is received:

(1)  The incoming report indication 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 report
     indication is halted.  Otherwise:

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

(3)  If the original incoming management target information indicates
     SNMPv1, processing of the report indication 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 contain the contextEngineID,
          contextName, counter OID, and counter value received in the
          report indication.

3.5.2.  Notification Forwarding