An index that uniquely identifies an entry in
the nlMatrixTopNTable among those in the same report.
This index is between 1 and N, where N is the
number of entries in this report.
If the value of nlMatrixTopNControlRateBase is equal to
nlMatrixTopNPkts, increasing values of nlMatrixTopNIndex shall
be assigned to entries with decreasing values of
nlMatrixTopNPktRate until index N is assigned or there are no
more nlMatrixTopNEntries.
If the value of nlMatrixTopNControlRateBase is equal to
nlMatrixTopNOctets, increasing values of nlMatrixTopNIndex
shall be assigned to entries with decreasing values of
nlMatrixTopNOctetRate until index N is assigned or there are
no more nlMatrixTopNEntries.