[time-nuts] wifi with time sync

Bob Camp kb8tq at n1k.org
Fri Jan 13 13:48:27 EST 2017


I probably should have added that I already know that the switch will do sub 1 ms
LAN pings all day long with the near zero load that it’s running. Sorry about that.

Now, there certainly are OS level things on my laptop that will muck up pings. Unfortunately 
they also get into a number of timing things as well.


> On Jan 13, 2017, at 1:08 PM, Denny Page <denny at cococafe.com> wrote:
>> On Jan 13, 2017, at 09:40, Bob Camp <kb8tq at n1k.org> wrote:
>> Just for reference, I happen to be running a ping over my local WiFi to one of the switches
>> on the LAN. The ping response is anywhere from 2 ms out to 400 ms. Most of the time it’s 
>> in the 3 to 9 ms range. Simply taking that down to < 1 us would be a really big deal. 
> Ping, particularly to a switch, is not a good indication of actual latency in a local network. Hosts do not prioritize responding to icmp, and on a switch to icmp is the lowest “I’ll get around to it” priority the switch has. Pinging the switch that my host is directly attached to gives an average of 1.22ms. Pinging another host attached to the same switch gives an average of 100us. The actual port to port latency on the switch is 2.45us. Your mileage may vary.
> Denny
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