I need to determine the average U/L and D/L data during 1 days operation of a particular IPSec VPN tunnel that is terminating on a PIX 515 (other end is Draytek Vigor). When I look at the tunnel stats using the PDM, I see the number of packets encypted/decrypted but I am assuming these packets would be of variable length, so I cant get an accurate U/L D/L figure, is this correct ?
If there is no other way to see this information, can I assume a "worst case" packet size in order to calculate this figure.
What I want to be able to achieve is to monitor the throughput and make a statement such as "500MB up 650MB down reuired in a 24 hour period (average)" etc.
The reason for this is that this tunnel is being moved to a provider that charges on total throughput (as in 1GB per week) rather than speed.
I dont have the ability to measure data requirement of individual apps and dont know the overhead that the VPN encryption adds.