NetFlow timers confusion.

I am having problems with understanding NetFlow timers and how they
impact when flows are sent to the collector.

1.
First, we have flow cache timers:
# ip flow-cache timeout active (default 30 minutes) and
# ip flow-cache timeout inactive seconds (default 15 seconds)
Cisco says that when those timers expire, flows are sent to the collector.

2.
Now in Version 9 we have additional template timers:
# ip flow-export template timeout-rate (default 30 minutes) and
# ip flow-export template refresh-rate (default 20 packets)
Cisco command reference says that timeout-rate :
"Specifies the interval (in minutes) that the router waits after
sending the templates (flow and options) before sending them again.
Range: 1 to 3600. Default: 30. "

My question are :
1. What is the relation between flow-cache timers and flow-export
template timers
2. Why flow-export cache timers were introduced ? It looks to me like
cache-flow timers are enough to decide when to send data to the
collector.

Can someone explain in simple words ?

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Received on Sun Jul 03 2011 - 18:06:39 ART