Intel PRO 2200 power save acting wierdly
I am needed some help to understand if my Intel pro 2200 card (on FC4,kernel > 2.6.10) has the power save mode working.
From what I read,
#iwpriv eth1 set_power 5
should set the card to have a timeout of 25ms and a sleep time of 1000ms. I verified it from the driver by checking using
#iwpriv eth1 get_power
Next, I wanted to make sure that it is actually going to sleep for 1000ms. So I decide to ping (ICMP echo request)a host whose actual round trip time is about 120ms. With the power save mode on, I expected that the ICMP echo reply will not reach my machine back for about 1000ms since the AP should buffer it until my card wakes up. Each ping was sent at an interval of 1 second.
However, I found that I got back ICMP replies at an average of 180ms. So there is some delay in getting the ICMP replies back, but not even close to what I expected.
What is happening? Is my card not using the power save mode properly or is the AP not implementing the power save mode properly? If my card was indeed sleeping and the AP not buffering as it should, packets should have been dropped, which it was not. So it seems both are not implementing the mode, and the small delay is due to the confusion of the card setting. Does this make any sense? As far as I know intel pro 2200 should be able to set power save mode properly with linux. I tried two APs, one a belkin wireless router and another on a public hotspot and had the same perplexing small delay, but not the delay I expected.