On Thu, 16 Dec 1999 Alan Smithee wrote:
> With Dummynet configured for bake-off ISP environment, what kind
> of mean response time should I see? Should it still be around 1.50
> sec as it was with PolyMix-1?
The formula for PolyMix-2 and WAN simulation is no longer that
simple and obvious because
(a) there is packet loss on the network and
(b) packet delays affect the importance of persistent
connections (TCP handshake sequence is now appropriately
Without taking (a) and (b) into account the "ideal" response time is
miss: 75 + 0 + 55 + 2500 + 55 + 0 + 75 = 2760 msec
hit: 75 + 0 + 75 = 150 msec
average: 0.45*2760 + 0.55*150 = 1325 msec
Where "0" is an ideal proxy-introduced delay, and "2500" is mean server
side think time. Again, the first request on a connection will
experience an extra delay of at leat one packet round trip time (RTT).
You probably want to double check my calculations.
# ISP client
ipfw pipe 1 config delay 75ms plr 0.001
ipfw pipe 2 config delay 75ms plr 0.001
# ISP server
ipfw pipe 1 config delay 55ms plr 0.0005
ipfw pipe 2 config delay 55ms plr 0.0005
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