[time-nuts] wifi with time sync

[Hal Murray]

> What standard protocol would you recommend I run from the command line on my
> computer  to get a quick estimate of the timing lag and variablilty  on my
> particular WiFi connection? 

I'd use ping.  But you said "quick estimate".

My wifi is crappy enough that its noise swamps everything else.  Out of 
habbit, I never ping a switch so I don't have to worry about the extra delay 
from its CPU.

-----

> To add to this I'd be curious in knowing about easy PC based ways to measure
> network latencies / delays with microsecond accuracy vs millisecond
> accuracy. 

I don't know of any "easy" way to do that.  If I wanted to work on that 
problem, I would investigate the PTP level time stamping that you can get 
from some Ethernet chips.

Most Unix like OSes now support getting a time stamp on received packets.  
That's interrupt level rather than hardware level.  I just poked around a 
bit.  I didn't find a simple way to get a transmit time stamp, but there was 
enough discussion that something might work.  Depends on your OS and hardware 
and ...

If the network is lightly loaded, you can probably assume that the packet has 
started when the call to send returns.

If you have a setup on a LAN with identical machines and can feed the same 
PPS pulse to both of them you can probably get the clocks in sync close to a 
microsecond.



-- 
These are my opinions.  I hate spam.