Apple Catalina Appears to Introduce Massive Jitter

Thu Oct 29 12:07:50 UTC 2020

Hi all.

I've been on High Sierra for several years now due to a limitation with 
an app that couldn't deal with Apple's latest rounds of system 
permissions since Mojave. Eventually, I gave up on waiting for them to 
fix it and upgraded my older Butterfly keyboard laptop to Catalina 4 
weeks ago.

At the same time, I picked up the new Magic keyboard laptop 2 weeks ago 
which came with Catalina.

Over the past week, I've been troubleshooting a massive jitter issue on 
Catalina, just between itself and my home router. For control, I have a 
Windows PC (tower-top) using a wireless adapter to connect to my home 
network. That has no jitter at all.

I have noticed as much as 300ms+ jitter on Catalina.

I then asked a few friends around the world to run tests for me on their 
own Catalina installations to their local router over wi-fi, and the 
results are the same. Jitter so high that what should be a 1ms - 5ms 
latency can (for a short period) jump to 200ms+, 300ms+, 400ms+.

On the off-chance that it is an issue with the new wireless chips on the 
later MacBook models, one of my friends tested the same on a 2013 
MacBook Pro running a beta version of Big Sur. Same story!

Another friend in South East Asia, testing on a 2018 13-inch MacBook Pro 
running Catalina, also had the same issue.

A Google search suggests that this is some known issue since Mojave, to 
do with Location Services, and some other apps, in a non-deterministic way:

https://apple.stackexchange.com/questions/263638/macbook-pro-experiencing-ping-spikes-to-local-router

For me, even after disabling all or some Location Services features, the 
problem remains.

Is anyone else seeing this on their Catalina Mac's while on wi-fi? If 
so, does anyone know what's going on here?

Ideally, this wouldn't matter if it was just a cosmetic issue - but I do 
actually see physical impact to performance of network access to/from 
the laptop, which has all the hallmarks of high jitter and/or packet loss.

An app like Zoom, which can display network performance data for a 
session in real-time, does indicate nominal packet loss for audio and 
video on this device, while other devices on the same WLAN are happy.

Thoughts?

Mark.
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