Re: Apple Catalina Appears to Introduce Massive Jitter

["J. Hellenthal via NANOG" <nanog () nanog org>]

I believe I have seen the same thing with a Mid 2015 11,4 running catalina. Not diagnosing further because I could not 
find a reason for it fast enough and not sure if it really had an impact at the moment…. but could you try the 
following 


sudo sysctl net.link.generic.system.hwcksum_tx=0
sudo sysctl net.link.generic.system.hwcksum_rx=0
sudo ifconfig en0 -rxcsum


in reverse … to restore the settings 

sudo sysctl net.link.generic.system.hwcksum_tx=1
sudo sysctl net.link.generic.system.hwcksum_rx=1
sudo ifconfig en0 rxcsum


If you have some specific tests to run I would be willing to run them here on Big Sur with the same laptop but I have 
nothing now that runs Catalina


Wireshark used to in Catalina rack up cksum errors a lot while these were all at their defaults.



> On Oct 29, 2020, at 08:23, Mark Tinka <mark.tinka () seacom com> wrote:
>
>
>
> On 10/29/20 15:04, Cory Sell wrote:
>
> > Might be worth disabling each AP to see if there's one out there having an issue playing nice with the MacBook. Also 
> > try different combinations of two APs working together. It's possible the MacBook is flip flopping because the power 
> > levels are fighting each other.
>
> Tested all that, as well as dropping Tx power levels on each of the AP's to Low so that there isn't any power coming 
> from any other AP (despite being quite far, already).
>
> And to confirm, when the laptop locks into an AP, it doesn't try to join another one. When in range, power is very 
> good (between -37dB and -52dB). When I walk away, that AP becomes too far (as bad as -80dB), but the next one close 
> by is far better (same good values as before) and laptop connects and sticks to that.
>
> Again, only impacts Catalina. No other Apple device, or the Windows PC that is on the same WLAN.
>
>
> > Does the Mac have this issue at your local coffee shop or another establishment with Wi-Fi? You can try to rule out 
> > the AirPort card in the Mac itself.
>
> Never tried, I generally work from home. If I'm out, it's faster to tether to my 4G service rather than any public 
> wi-fi.
>
> Mark.


-- 

J. Hellenthal

The fact that there's a highway to Hell but only a stairway to Heaven says a lot about anticipated traffic volume.