TimeFilter edits

--------------------

TimeFilter TC Definition:

OLD:

        "To be used for the index to a table.  Allows an application
        to download only those rows changed since a particular time.
        A row is considered changed if the value of any object in the
        row changes or if the row is created or deleted.

NEW:
        "To be used for the index to a table.  Allows an application
        to download only those rows changed since a particular time.
        A row is considered changed if the value of any object in the
        row changes or if the row is created.

---------------


11.  Appendix - TimeFilter Implementation Notes

Sec 11, num 1, para 1:

OLD:

The TimeFilter mechanism allows an NMS to reduce the number of
SNMP transactions required for a 'table-update' operation.
Polling of tables that incorporate a 'TimeFilter' INDEX can be
reduced to a theoretical minimum (if used correctly). It can
be easily implemented by an agent in a way independent of the
number of NMS applications using the same time-filtered table.

NEW:

The TimeFilter mechanism allows an NMS to reduce the number of
SNMP transactions required for a 'table-update' operation,
by retrieving only the rows that have changed since a specified
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
time (usually the last poll time).  Polling of tables that 
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
incorporate a 'TimeFilter' INDEX can be reduced to a theoretical 
minimum (if used correctly). It can be easily implemented by an 
agent in a way independent of the number of NMS applications using 
the same time-filtered table.


Sec 11, num 1, para 3:

OLD:

The TimeFilter is a boolean filtering function applied in
internal Get* PDU processing. If the 'last-change-time' of the
specified instance is less than the particular TimeFilter
INDEX value, then the instance is considered 'not-present'
(skipped for GetNext and GetBulk PDUs; 'noSuchInstance' or
returned to the requester.

NEW:

The TimeFilter is a boolean filtering function applied in
internal Get* PDU processing. If the 'last-change-time' of the
specified instance is less than the particular TimeFilter
INDEX value, then the instance is considered 'not-present',
and it is skipped for GetNext and GetBulk PDUs, or a 'noSuchInstance' 
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
exception is returned for Get PDUs.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

--------

OLD:
When an agent receives a Get, GetNext, or GetBulk PDU
requesting a time-filtered instance, the following agent has
determined that the instance is within the MIB view indicated
by the community string in the PDU.

NEW:
When an agent receives a Get, GetNext, or GetBulk PDU
requesting a time-filtered instance, after the agent has
                                     ^^^^^^^^^
determined that the instance is within the MIB view indicated
by the community string in the PDU, the following conceptual
                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^
test is applied to determine if the object is returned or 
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
filtered:
^^^^^^^^^

------------------------------------------

sec 1.1:

OLD:

   In implementation, the time-filtered rows (one for each tick of
   sysUpTime) are only conceptual. The agent simply filters a real table
   based on:
       * the current value of sysUpTime
       * the TimeFilter value passed in the varbind
       * the last-update timestamp of each requested counter
 
NEW:

   In implementation, the time-filtered rows (one for each tick of
   sysUpTime) are only conceptual. The agent simply filters a real table
   based on:
       * the current value of sysUpTime
       * the TimeFilter value passed in the varbind
       * the last-update timestamp of each requested row
                                                     ^^^

---------------------------------------------


Proposed New text for sec 8, sec. 1.1, after last para:


After some deployment experience, it has been determined that a
time-filtered table is more efficient to use if the agent
stops a "MIB walk" operation after one time-filtered entry.  
That is, a GetNext or GetBulk operation will provide one pass through a given
table, i.e., the agent will continue to the next object or table,
instead of incrementing a TimeMark INDEX value, even if
there exists higher TimeMark values which are valid for
the same conceptual row.

It is acceptable for an agent to implement a time-filtered table
in this manner, or in the traditional manner, in which every
conceptual time-filtered instance will be returned in GetNext
and GetBulk PDU responses.

-------------------------------------------------------

sec 2.2:

OLD:
          fooCounts.0.2 == 0  # visible since created at time
0

NEW:
          fooCounts.0.2 == 0  # visible; created at time 0


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