AWDL on Macs can interfere with your WiFi connections

3 points by llm_nerd ↗ HN
This is a PSA for Mac users on wireless, as it surely quietly affects many others. Please don't upvote this but let it roll off new, hopefully having helped someone along the way.

For years I've endured the fact that my Macs see periodic latency spikes when connected to WiFi. My Windows box on the same band / router would see solid 1ms pings to the router all day long, but my Macs would jump to 100ms+ for several seconds every 11 seconds or so. It compromised any streaming type activity, such as video conferencing or cloud gaming.

Today it irritated me enough that I actually dug into it, learning that there is a feature on Apple devices called Apple Wireless Direct Link (AWDL) which forcefully changes the channel of your wifi chipset periodically if necessary to (speculatively?) connect with other Apple devices. In the case given I'm seeing these spikes while simply using my Mac and not actively or intentionally using AWDL functionality -- I'm not pasting files across devices, screen casting, etc -- but still the jumps to 100ms or worse (sometimes 300ms+).

AWDL has a fixed set of channels that it uses, and by setting my home wifi router to the same channel AWDL uses (149 for 5Ghz in NA), it no longer performs the channel hopping and my ping is a constant sub-4ms, averaging about 2ms. Huge improvement.

Logically this means that there would be interference, and indeed some vendors recommend avoiding the AWDL channels preemptively, but using the AWDL functions like pasting across devices and I see no negative impact on my other wifi consumers.

https://www.threads.net/@dwforbes/post/C3saGR6Ok3t

1 comment

[ 3.5 ms ] story [ 10.7 ms ] thread
Yeah I was testing out my new home internet service provider and seeing ping from my Macbook to the internet that was all over the place. I got worried and tried from my router - totally normal, so phew.

Later on I remembered this experience and realised something must be up with my wifi. Very long story short, nothing is wrong with my wifi but everything is wrong with my household of Apple devices.

Ping from my router to anything non-Apple on wifi is rock solid. Ping from router to any Apple device (computers, phones, Apple TV) is a mess with periods of stable low latency mixed with random stretches fluctuating between 70 and 250ms.

This is really, really bad isn’t it? Like it would render Apple a complete no go for latency sensitive gaming. It would also explain why despite the fact that I have what I think is a good home network (an ISP with great routing, MikroTik + bridged Eeros, cake running on my WAN link tested with flent rrul), the internet just feels slow sometimes. Pages load slowly one second and not the next, Airplay to my Sonos speakers drops out under specific conditions etc.

Unfortunately I can’t pick channels with Eero so now I am considering changing my access points just to see if it fixes this issue. I feel a bit crazy doing this, but when looking back I’ve rationalised a lot of weird slow internet behaviour to my own error, eg not knowing exactly how to configure cake properly perhaps.