how to measure delay

borgit borgit at
Sat Apr 22 13:12:41 EDT 2006

Hi guys,


We are trying to do some measurements with the hostAP driver code.
Specifically we are interested to measure the delay that it takes from the
time the frame is scheduled for transmission in the driver and to the time
that the ACK for it comes back.  Now, it is easy to start a timer at the
point when the packet is queued for transmission, but how can we know when
the ACK is received? Is there some kind of an interrupt generated when the
802.11 ACK is received?  Also, another problem is how to time this to a high
degree of precision.  We were thinking of using the jiffies value for this,
but that value only has precision of 10 to the power of -2.  We would be
interested in something that has precision in the microseconds, like in
tcpdump.  What could we use to get such a precision?


Thank for any information.




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