rfc3416.txt

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            binding's name in the request.

   If the processing of any variable binding fails for a reason other
   than listed above, then the Response-PDU is re-formatted with the
   same values in its request-id and variable-bindings fields as the
   received GetNextRequest-PDU, with the value of its error-status field
   set to "genErr", and the value of its error-index field is set to the
   index of the failed variable binding.

   Otherwise, the value of the Response-PDU's error-status field is set
   to "noError", and the value of its error-index field is zero.

   The generated Response-PDU is then encapsulated into a message.  If
   the size of the resultant message is less than or equal to both a
   local constraint and the maximum message size of the originator, it
   is transmitted to the originator of the GetNextRequest-PDU.

   Otherwise, an alternate Response-PDU is generated.  This alternate
   Response-PDU is formatted with the same values in its request-id
   field as the received GetNextRequest-PDU, with the value of its
   error-status field set to "tooBig", the value of its error-index
   field set to zero, and an empty variable-bindings field.  This
   alternate Response-PDU is then encapsulated into a message.  If the
   size of the resultant message is less than or equal to both a local
   constraint and the maximum message size of the originator, it is
   transmitted to the originator of the GetNextRequest-PDU.  Otherwise,
   the snmpSilentDrops [RFC3418] counter is incremented and the
   resultant message is discarded.

4.2.2.1.  Example of Table Traversal

   An important use of the GetNextRequest-PDU is the traversal of
   conceptual tables of information within a MIB.  The semantics of this
   type of request, together with the method of identifying individual
   instances of objects in the MIB, provides access to related objects
   in the MIB as if they enjoyed a tabular organization.



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   In the protocol exchange sketched below, an application retrieves the
   media-dependent physical address and the address-mapping type for
   each entry in the IP net-to-media Address Translation Table [RFC1213]
   of a particular network element.  It also retrieves the value of
   sysUpTime [RFC3418], at which the mappings existed.  Suppose that the
   command responder's IP net-to-media table has three entries:

   Interface-Number  Network-Address  Physical-Address  Type

      1            10.0.0.51     00:00:10:01:23:45  static
      1             9.2.3.4      00:00:10:54:32:10  dynamic
      2            10.0.0.15     00:00:10:98:76:54  dynamic

   The SNMP entity supporting a command generator application begins by
   sending a GetNextRequest-PDU containing the indicated OBJECT
   IDENTIFIER values as the requested variable names:

    GetNextRequest ( sysUpTime,
                   ipNetToMediaPhysAddress,
                   ipNetToMediaType )

   The SNMP entity supporting a command responder application responds
   with a Response-PDU:

    Response (( sysUpTime.0 =  "123456" ),
               ( ipNetToMediaPhysAddress.1.9.2.3.4 = "000010543210" ),
            ( ipNetToMediaType.1.9.2.3.4 =  "dynamic" ))

   The SNMP entity supporting the command generator application
   continues with:

    GetNextRequest ( sysUpTime,
                   ipNetToMediaPhysAddress.1.9.2.3.4,
                   ipNetToMediaType.1.9.2.3.4 )

   The SNMP entity supporting the command responder application responds
   with:

    Response (( sysUpTime.0 =  "123461" ),
               ( ipNetToMediaPhysAddress.1.10.0.0.51 = "000010012345" ),
            ( ipNetToMediaType.1.10.0.0.51 =  "static" ))

   The SNMP entity supporting the command generator application
   continues with:

    GetNextRequest ( sysUpTime,
                   ipNetToMediaPhysAddress.1.10.0.0.51,
                   ipNetToMediaType.1.10.0.0.51 )



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   The SNMP entity supporting the command responder application responds
   with:

    Response (( sysUpTime.0 =  "123466" ),
               ( ipNetToMediaPhysAddress.2.10.0.0.15 = "000010987654" ),
            ( ipNetToMediaType.2.10.0.0.15 =  "dynamic" ))

   The SNMP entity supporting the command generator application
   continues with:

    GetNextRequest ( sysUpTime,
                   ipNetToMediaPhysAddress.2.10.0.0.15,
                   ipNetToMediaType.2.10.0.0.15 )

   As there are no further entries in the table, the SNMP entity
   supporting the command responder application responds with the
   variables that are next in the lexicographical ordering of the
   accessible object names, for example:

    Response (( sysUpTime.0 =  "123471" ),
               ( ipNetToMediaNetAddress.1.9.2.3.4 = "9.2.3.4" ),
            ( ipRoutingDiscards.0 =  "2" ))

   Note how, having reached the end of the column for
   ipNetToMediaPhysAddress, the second variable binding from the command
   responder application has now "wrapped" to the first row in the next
   column.  Furthermore, note how, having reached the end of the
   ipNetToMediaTable for the third variable binding, the command
   responder application has responded with the next available object,
   which is outside that table.  This response signals the end of the
   table to the command generator application.

4.2.3.  The GetBulkRequest-PDU

   A GetBulkRequest-PDU is generated and transmitted at the request of
   an application.  The purpose of the GetBulkRequest-PDU is to request
   the transfer of a potentially large amount of data, including, but
   not limited to, the efficient and rapid retrieval of large tables.

   Upon receipt of a GetBulkRequest-PDU, the receiving SNMP entity
   processes each variable binding in the variable-binding list to
   produce a Response-PDU with its request-id field having the same
   value as in the request.

   For the GetBulkRequest-PDU type, the successful processing of each
   variable binding in the request generates zero or more variable
   bindings in the Response-PDU.  That is, the one-to-one mapping
   between the variable bindings of the GetRequest-PDU, GetNextRequest-



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   PDU, and SetRequest-PDU types and the resultant Response-PDUs does
   not apply for the mapping between the variable bindings of a
   GetBulkRequest-PDU and the resultant Response-PDU.

   The values of the non-repeaters and max-repetitions fields in the
   request specify the processing requested.  One variable binding in
   the Response-PDU is requested for the first N variable bindings in
   the request and M variable bindings are requested for each of the R
   remaining variable bindings in the request.  Consequently, the total
   number of requested variable bindings communicated by the request is
   given by N + (M * R), where N is the minimum of:  a) the value of the
   non-repeaters field in the request, and b) the number of variable
   bindings in the request; M is the value of the max-repetitions field
   in the request; and R is the maximum of:  a) number of variable
   bindings in the request - N, and b)  zero.

   The receiving SNMP entity produces a Response-PDU with up to the
   total number of requested variable bindings communicated by the
   request.  The request-id shall have the same value as the received
   GetBulkRequest-PDU.

   If N is greater than zero, the first through the (N)-th variable
   bindings of the Response-PDU are each produced as follows:

   (1)   The variable is located which is in the lexicographically
         ordered list of the names of all variables which are accessible
         by this request and whose name is the first lexicographic
         successor of the variable binding's name in the incoming
         GetBulkRequest-PDU.  The corresponding variable binding's name
         and value fields in the Response-PDU are set to the name and
         value of the located variable.

   (2)   If the requested variable binding's name does not
         lexicographically precede the name of any variable accessible
         by this request, i.e., there is no lexicographic successor,
         then the corresponding variable binding produced in the
         Response-PDU has its value field set to "endOfMibView", and its
         name field set to the variable binding's name in the request.

   If M and R are non-zero, the (N + 1)-th and subsequent variable
   bindings of the Response-PDU are each produced in a similar manner.
   For each iteration i, such that i is greater than zero and less than
   or equal to M, and for each repeated variable, r, such that r is
   greater than zero and less than or equal to R, the (N + ( (i-1) * R )
   + r)-th variable binding of the Response-PDU is produced as follows:






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   (1)   The variable which is in the lexicographically ordered list of
         the names of all variables which are accessible by this request
         and whose name is the (i)-th lexicographic successor of the (N
         + r)-th variable binding's name in the incoming
         GetBulkRequest-PDU is located and the variable binding's name
         and value fields are set to the name and value of the located
         variable.

   (2)   If there is no (i)-th lexicographic successor, then the
         corresponding variable binding produced in the Response-PDU has
         its value field set to "endOfMibView", and its name field set
         to either the last lexicographic successor, or if there are no
         lexicographic successors, to the (N + r)-th variable binding's
         name in the request.

   While the maximum number of variable bindings in the Response-PDU is
   bounded by N + (M * R), the response may be generated with a lesser
   number of variable bindings (possibly zero) for either of three
   reasons.

   (1)   If the size of the message encapsulating the Response-PDU
         containing the requested number of variable bindings would be
         greater than either a local constraint or the maximum message
         size of the originator, then the response is generated with a
         lesser number of variable bindings.  This lesser number is the
         ordered set of variable bindings with some of the variable
         bindings at the end of the set removed, such that the size of
         the message encapsulating the Response-PDU is approximately
         equal to but no greater than either a local constraint or the
         maximum message size of the originator.  Note that the number
         of variable bindings removed has no relationship to the values
         of N, M, or R.

   (2)   The response may also be generated with a lesser number of
         variable bindings if for some value of iteration i, such that i
         is greater than zero and less than or equal to M, that all of
         the generated variable bindings have the value field set to
         "endOfMibView".  In this case, the variable bindings may be
         truncated after the (N + (i * R))-th variable binding.

   (3)   In the event that the processing of a request with many
         repetitions requires a significantly greater amount of
         processing time than a normal request, then a command responder
         application may terminate the request with less than the full
         number of repetitions, providing at least one repetition is
         completed.





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   If the processing of any variable binding fails for a reason other
   than listed above, then the Response-PDU is re-formatted with the
   same values in its request-id and variable-bindings fields as the
   received GetBulkRequest-PDU, with the value of its error-status field
   set to "genErr", and the value of its error-index field is set to the
   index of the variable binding in the original request which
   corresponds to the failed variable binding.

   Otherwise, the value of the Response-PDU's error-status field is set
   to "noError", and the value of its error-index field to zero.

   The generated Response-PDU (possibly with an empty variable-bindings
   field) is then encapsulated into a message.  If the size of the
   resultant message is less than or equal to both a local constraint
   and the maximum message size of the originator, it is transmitted to
   the originator of the GetBulkRequest-PDU.  Otherwise, the
   snmpSilentDrops [RFC3418] counter is incremented and the resultant
   message is discarded.

4.2.3.1.  Another Example of Table Traversal

   This example demonstrates how the GetBulkRequest-PDU can be used as
   an alternative to the GetNextRequest-PDU.  The same traversal of the
   IP net-to-media table as shown in Section 4.2.2.1 is achieved with
   fewer exchanges.

   The SNMP entity supporting the command generator application begins
   by sending a GetBulkRequest-PDU with the modest max-repetitions value
   of 2, and containing the indicated OBJECT IDENTIFIER values as the
   requested variable names:

    GetBulkRequest [ non-repeaters = 1, max-repetitions = 2 ]
                  ( sysUpTime,
                    ipNetToMediaPhysAddress,
                    ipNetToMediaType )

   The SNMP entity supporting the command responder application responds
   with a Response-PDU:

    Response (( sysUpTime.0 =  "123456" ),
               ( ipNetToMediaPhysAddress.1.9.2.3.4 = "000010543210" ),
            ( ipNetToMediaType.1.9.2.3.4 =  "dynamic" ),
               ( ipNetToMediaPhysAddress.1.10.0.0.51 = "000010012345" ),
            ( ipNetToMediaType.1.10.0.0.51 =  "static" ))