The Packet Forwarding Engine technology are Cisco developed 
Network Processors, which accelerates certain features in 
order to provide better network performance.
        
An agent uses this MIB to monitor the performance history 
on any active PFE pipeline listed in the ENTITY-MIB (RFC 2737)
entPhysicalTable. This monitoring is via measurement periods
of actual, 1-minute, 5-minutes and 15-minutes.
        
For the 1-minute and 5-minute measurement periods, perfor-
mance statistics are calculated and displayed based on pre-
vious 1 minute and 5 minute respectively.
        
For the 15-minute period, the performance statistics are
accumulated in fifteen minute intervals.  At any one time, 
an agent maintains one current (incomplete) interval and up 
to 96 completed intervals (24 hours worth).  Fewer than 96 
intervals of data will be available if the agent has been 
restarted within the last 24 hours. In addition, there is a 
rolling 24-hour total of each performance statistic.
        
There is no requirement for an agent to ensure fixed rela-
tionship between the start of a fifteen minute interval and 
any wall clock; however some agents may align the fifteen 
minute intervals with quarter hours.