The highest OSI layer at which flows are processed. This is
used to give an indication of how much detail is contained in
the flows created on the interface. An interface reporting
that flows being processed at L4 will create flows that
have information from L2, L3, and L4. In general, interfaces
reporting processing at L4 would be expected to have a higher
number of flows than interfaces reporting processing at L2
assuming all else equal.