Re: Apple Catalina Appears to Introduce Massive Jitter

[colin johnston <colinj () gt86car org uk>]

This does seem to be solved with the checksum disable below, or at least pings down to sub 10ms on Mac book air with 
Catalina beta 10.15.6, why aim performs far better I don’t know. I tried to introduce load after cksum disable and it 
did not see ping spikes as before

How do we now explain to Apple to fix ?

Col


> On 29 Oct 2020, at 14:08, J. Hellenthal via NANOG <nanog () nanog org> wrote:
>
> 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.