Airtime Fairness question

[Morac]

I've read some recommendations saying enabling Airtime Fairness helps devices maintain faster speeds. I've also read that it can cause stability problems so it should be disabled. I run Merlin's firmware on my RT-AC88U (always running latest one) and have always just left it on because it never seemed to cause problems, but tonight I noticed I was getting "poor" speeds on my iOS devices (100 to 150 mbps instead of the usual 230+ Mbps speeds).

I tried a bunch of things including rebooting the router before turning airtime fairness off and the speeds shot up to normal. I toggled airtime fairness off and on and could see it made a big difference all the sudden.

My question is why is this suddenly causing slowness on my iOS devices when nothing has changed on my devices, the router or my network?

Is this "expected" when the setting is enabled?

 

[thiggins]

Airtime fairness is supposed to keep slower devices from hogging air time (the time a device spends transmitting data). There is no standard way of doing this and some products are better at it than others.

If your devices have equal capability (2x2 AC for example), theoretically, enabling airtime fairness should not affect them.

How are you measuring device "speed"? What link rates are your devices reporting.

 

[Morac]

I'm running various internet speed tests. I also ran an app that measures LAN wifi speeds. The LAN speed seemed okay except for farther away from the router. Speed tests were all over the map though with fairness on. With it off they consistently maxed out my Internet download speeds.

 

[Adam Siemiginowski]

Airtime fairness is supposed to keep slower devices from hogging air time (the time a device spends transmitting data).

Does Airtime Fairness affect all devices connected via ethernet AND wireless?

Could Airtime Fairness potentially disconnect low-bandwidth hard-wired thermal printers that take a disproportionate amount of time to send a small message? Could it cause them to occasionally lose connection?

I have a thread related to my issue here: https://www.snbforums.com/threads/traffic-not-detected-in-adaptive-qos-bandwidth-monitor.41034/

 

[thiggins]

Does Airtime Fairness affect all devices connected via ethernet AND wireless?

No. WiFi traffic only

 

[netmik3]

I have to disable it or my printer won't connect

 

[Gt3911]

That's very interesting netmik3.

My printer keeps popping up "scan to print not available" as the printer seems to loose its connection. I disabled airtime fairness a few hours ago and haven't seen it complain yet! Looks hopeful. My old router never had an issue.

 

[0014]

I had to disable it to stop my Sonos system from randomly disconnecting/being unable to be found.

 

[Antec800]

I also found that I get much higher speeds on devices with it turned off

 

[PAPPL]

I had to disable "Airtime fairness" too, to stop my Chromecast Audio devices from randomly disconnecting/being unable to be found.
How can this bad setting be enabled by default.

 

[bachastain]

I just discovered the Asus Device Discovery couldn't find my 2 Asus routers (RT-AC66U B1 in Mesh) with Airtime Fairness enabled (by default). Oddly, Device Discovery worked from a wifi laptop, but not from a wifi Windows 10 PC on the same network. I disabled Airtime Fairness and now Device Discovery works everywhere. Bizarre.

 

[joe scian]

on flip side i have airtime fairness enabled on all wifi bands on an ac5300 and i dont have any issues with connectivity or device discovery

 

[Jeremy™]

I can confirm we have had Chromecast issues with the AC5300. Not all the time, but when it doesn't work, it's super annoying. Even a fresh Chromecast setup fails about 50% of the time after doing a hard reset.

Disabling airtime fairness seems to have resolved the issue.

 

[FadgewackeR]

I had to disable it to be able to connect to my Yamaha MusicCast equipment to my 2.4ghz wifi. I managed to somehow get 2 connected (through blind persistence) after a lot of messing about, but it would not manage the 3rd at all until I disabled airtime fairness.

 

[Sinner]

I realize im necroing a thread but its relevant. Has anyone determined what the issue is with airtime fairness? I have always had it disabled for similar reasons as well but its a feature that I would like to utilize if I could. Anyone know of any workarounds or other features that assist it to work as designed?

 

[netmik3]

I realize im necroing a thread but its relevant. Has anyone determined what the issue is with airtime fairness? I have always had it disabled for similar reasons as well but its a feature that I would like to utilize if I could. Anyone know of any workarounds or other features that assist it to work as designed?

Has to be bug in this protocol between broadcom and non broadcom chips, especially cheaper chips in printers, etc.

Crummy bug too, most people will never find this workaround or cause

 

[Sinner]

I notice it with more than just that.. infact it appears to have a huge impact not only on printers sonos devices etc but also dlna. I have a network server hardwired via 1gbs that shows up intermittent at best on wifi devices with airtime fairness enabled too.

 

[doczenith1]

I realize im necroing a thread but its relevant. Has anyone determined what the issue is with airtime fairness? I have always had it disabled for similar reasons as well but its a feature that I would like to utilize if I could. Anyone know of any workarounds or other features that assist it to work as designed?

I'm curious of your use case. From what I've read you need 20+ ac or n clients and a few old wireless G clients to reap any benefits of airtime fairness if I am understanding what airtime fairness does correctly.

 

[Sinner]

I have pretty much have all wireless clients and mostly mobile devices. With airtime fairness off I occasionally experience extreme drops in transfer rates on the high speed clients when one or more of the mobiles are in odd sleep modes or barely inrange. Its very noticeable transferring large files between pc's. Interference isnt the issue as its basically a farm and theyre connected at high rates. With airtime fairness on it limits the ranged,sleeping or poorly connected devices from hogging the airtime allowing the high sped clients to transfer at high speeds but I experience the connectivity and dlna detection issues etc. idealy id be able to have it on and access my online storage thru mobiles devices but almost all of us have to have it off because of the connectivity with sonos and home devices and dlna detection etc.

 

[Volt]

I noticed that in a situation where airtime fairness should help it actually makes things worse. With airtime fairness on, when I copy a large file from the USB drive attached to RT-AX56U to my laptop that has Wi-Fi 4 and 2 streams (we can consider this laptop a slow client) and, at the same time, play a video (via DLNA) from that drive on my TV (Wi-Fi 5, 2 streams), the video stutters every two seconds. At this time, the copy speed remains stable. When I run a speed test on my TV during the copy operation, I get about 20Mbits. My understanding is that with airtime fairness the file copy speed should be reduced to give more airtime to the TV, but it does not happen.

Turning airtime fairness off solves the problem: the video plays normally, and, during the playback, the file copy speed is reduced a bit. Moreover, the same speed test on the TV shows speeds that are on average 15 Mbits higher. I don't know whether it applies to other router models, but looks like Broadcom's driver copes with multiple clients better without the airtime fairness setting enabled.