CakeQOS Problem with Zoom sent video quality (Cake QoS is a solution, but why?)

[Tom K.]

Hi SNB Gurus!

I have a strange (at least for me) problem with Zoom video calls and my home Asus router(s). I have 2 routers AX88U and GT-AX11000 Pro, both running the newest Merlin firmware. I'm not using them simultaneously, but I have tested this behaviour on both routers. My ISP nominal speeds are 700/50, in reality, I'm getting over 800 download and 45 upload speeds.

I have two Macbook Pros, one is M1 Pro 2021, the other is M2 Max 2023. They sit next to each other and don't have any anti-virus or anti-malware software that could block the network. Both are connected to the same home 5GHz wifi, with signal strength ~-40dBm.

When I join the same Zoom call from both laptops, the M1 machine sends video in very poor quality (320x180, 3-4fps), but the M2 machine sends HD quality with 30fps. When switch the M1 to my mobile phone wifi (5G) the quality improves and when the M1 laptop is used at my work, the sent video quality is HD.

Now, this is a bizarre observation: I can fix the M1 video by 1) installing and enabling the Cake QoS on the router AND 2) adding the predefined Zoom iptables rule with UDP port rang 8801:8810 in the Cake QoS settings tab. Just enabling Cake QoS without the iptables rule doesn't help at all.

What is this rule in the iptables doing in reality and would it be possible to enable it without the QoS? I don't think I need QoS with my Internet speeds.

Thanks!

Tom

 

[DJones]

Hi SNB Gurus!

I have a strange (at least for me) problem with Zoom video calls and my home Asus router(s). I have 2 routers AX88U and GT-AX11000 Pro, both running the newest Merlin firmware. I'm not using them simultaneously, but I have tested this behaviour on both routers. My ISP nominal speeds are 700/50, in reality, I'm getting over 800 download and 45 upload speeds.

I have two Macbook Pros, one is M1 Pro 2021, the other is M2 Max 2023. They sit next to each other and don't have any anti-virus or anti-malware software that could block the network. Both are connected to the same home 5GHz wifi, with signal strength ~-40dBm.

When I join the same Zoom call from both laptops, the M1 machine sends video in very poor quality (320x180, 3-4fps), but the M2 machine sends HD quality with 30fps. When switch the M1 to my mobile phone wifi (5G) the quality improves and when the M1 laptop is used at my work, the sent video quality is HD.

Now, this is a bizarre observation: I can fix the M1 video by 1) installing and enabling the Cake QoS on the router AND 2) adding the predefined Zoom iptables rule with UDP port rang 8801:8810 in the Cake QoS settings tab. Just enabling Cake QoS without the iptables rule doesn't help at all.

What is this rule in the iptables doing in reality and would it be possible to enable it without the QoS? I don't think I need QoS with my Internet speeds.

Thanks!

Tom

To answer your question as simply as I can. Cake SQM/CakeQoS-Merlin is a congestion control and traffic shaper. This allow packets to have priority based on binning. Binning occurs because dscp marking/wmm marking are identified as a certain type of media. ie. zoom, facetime,smtp,voip. What is happening when you set a table rule is your saying this port on this ip or any ip, locally or remotely, may set this priority for upload of data usually out to the WAN. Bulk, Streaming, Voice, Conferencing, Gaming. From lowest to highest priority. If you set this table set the corresponding device it belongs to as a static ip, and avoid mac address randomization on phones, or computers because if the mac address changes your static address could change. or set the static ip on your device locally or both.

Additionally Bandwidth Monitor on Asus routers can set general priority per device. Requires Trend Micro allowed.

Can you do this without router QoS. No/yes. On your lan devices you can use it's qos ie. if it's a computer; however it will only prioritize traffic on your system and not all your lan devices. Unless your computer is a server/router.

On windows you can set your congestion control type and optimize your tcp network connection using TCP Optimizer.
[URL unfurl="true"]https://www.speedguide.net/downloads.php[/URL]

On linux you can set your congestion control type and qdisc by using cli/terminal under nano /etc/sysctl.conf  ## Save then type sysctl -p to load configuration changes.


net.core.default_qdisc=fq    ## other options could be ie. "fq, fq_codel, htb, cake"  ##cake is available on kernel v4.19+, bbr is available on kernel 4.9+
net.ipv4.tcp_congestion_control=bbr ## other options could be ie. "bbr, cubic, reno"  You can google for more information.

On Mac OS you can set your congestion control type by typing in terminal

sysctl -w net.inet.tcp.INSERTCONGESTIONTYPEHERE=1    ## options could be cubic,reno,newreno  ##I am unaware if cake is supported.

CakeQoS also helps with bufferbloat. Bufferbloat is as it sounds your router buffering the packets to long creating latency. This causes spikes in your connection which can cause interruptions to video, or voip, or other real-time sensitive applications.

You can perform a bufferbloat test here:

Bufferbloat and Internet Speed Test - Waveform

Is bufferbloat causing issues with your internet connection? Run this test to find out.

www.waveform.com

If you have a connection that is over 300mbps you might notice some speed loss compared to QoS being off. This is due in part to QoS. ie. FlexQoS, or Cake, not supporting hardware acceleration. So it's a toss stability or full speed. Unfortunately these consumer routers are not able to support full speeds of up to 1gbps+ on no hardware acceleration as it would likely max out your cpu cores. By default with QoS off, "runner/archer/flow acceleration" & flow cache is enabled, but as soon as you use QoS on anything but adaptive QoS I believe it disables HW Acceleration.

 

[robinjoo1]

what QoS doesn't disable HW Acceleration

 

[DJones]

what QoS doesn't disable HW Acceleration

on cake it does, and flexqos flow cache should be disabled. Unsure about runner/archer on flexqos as I haven't used it in some time.

Quote @dave14305
ASUS Traditional QoS is usually not preferred because it cannot take advantage of hardware acceleration (referred to sometimes as CTF or Runner, depending on your router model). So your maximum connection speed may be limited by the router CPU capability. You have to define your own rules into High, Medium, Low buckets.

ASUS Adaptive QoS can use hardware acceleration and categorizes traffic using a DPI engine from Trend Micro. Other than prioritizing the major classes (gaming, VoIP, Web Surfing, etc.), there wasn't much control over how traffic was classified. And some people are wary of Trend Micro.

Merlin improved Asus QoS by implementing fq_codel.

FreshJR_QOS fixed a lot of the early flaws in Adaptive QoS and made it customizable in how traffic is categorized and how those categories are prioritized. It also improved the minimum/maximum rates per class. If you were going to use QoS on Merlin, you needed this script to absolve the sins of Asus. FreshJR himself has been absent for nearly a year, so the script is considered abandoned, but still functional.

FlexQoS is a fork and re-write of FreshJR_QOS, intended to make it more flexible with more rules possible and make it compatible with the latest Asus classes (e.g. Work-From-Home). It's currently available in beta for AC routers running 384.18 beta1. It's built on Merlin and FreshJR_QOS.

Cake is a newer queuing discipline (like fq_codel is an older one). It's available for AC86U and AX88U (HND) routers. Not my area of expertise, since my router isn't compatible.

 

[Tom K.]

Thanks, @DJones, I think I got the idea. The port range 8801:8810 is assigned to Conferencing traffic and Conferencing traffic has high priority, therefore the Zoom app was able to detect better network conditions and choose to stream video of better quality.

What I still don't get is:

- why on the second Mac (same OS version, same Wifi, same Zoom app version, same location, a bit newer hardware), the video was good without any QoS?
- there was nothing to prioritise the Zoom call against. I was doing those tests during the day when I was the only user of my wifi and there was plenty of bandwidth available. QoS shouldn't have any impact on the network.

 

[DJones]

Thanks, @DJones, I think I got the idea. The port range 8801:8810 is assigned to Conferencing traffic and Conferencing traffic has high priority, therefore the Zoom app was able to detect better network conditions and choose to stream video of better quality.

What I still don't get is:

- why on the second Mac (same OS version, same Wifi, same Zoom app version, same location, a bit newer hardware), the video was good without any QoS?
- there was nothing to prioritise the Zoom call against. I was also doing those tests during the day when I was the only user of my wifi and there was plenty of bandwidth available. QoS shouldn't have any impact on the network.

Sounds device specific. I would check and make sure your laptop or other devices were not updating or doing something in the background without your knowledge. If you watch bandwidth monitor you can see your wireless or wired devices live internet use. If multiple devices or that computer are using unrelated bandwidth it might be causing that issue. It could also be hardware, older wireless card, or general system lag from overheating, high cpu or disk usage. I would recommend trying the zoom call on wired and see if it improves. As to the exact reason I'm not sure.

You could try checking your mac os under disk utility to see if their are any issues with your boot disk. https://support.apple.com/en-ca/guide/disk-utility/dskutl1040/mac You might need to boot into Disk Utility in recovery mode to check your operating systems drive.

or try fsck in terminal of recovery mode. Disk Utility should be sufficient.

How to use fsck to check and repair macOS disks | AppleInsider

Apple's macOS, through UNIX, provides a variety of tools to keep your drives healthy, with one of them being the fsck Terminal command. Here's how to use it.

appleinsider.com

Use macOS Recovery on an Intel-based Mac

Learn how to use macOS Recovery on an Intel-based Mac.

support.apple.com

Use macOS Recovery on a Mac with Apple silicon

Learn how to use macOS Recovery on a Mac with Apple silicon.

support.apple.com

If you find it's only that mac os computer I would suggest contacting apple tech support or schedule a appointment at a genius bar. Disclaimer I used to work in apple support, but it's been a few years. Support may not be very helpful in this instance, until you can narrow down the cause and ensure it's that device only.

 

[Tom K.]

It is a combination of the M1 laptop and my home router (not a specific unit, as I replicated the same behaviour on AX88U and AX11000Pro). The M1 Mac streams good-quality video when connected to my work wifi or even to my mobile phone. It is not related to the intermittent background transfers, as I have tested this many times over a few days trying to investigate the issue.
Looks like it will remain a mystery.

 

[Tom K.]

Finally, I have a good theory of the underlying issue backed by evidence. In Australia, there's a single Internet infrastructure provider, government-owned NBN and several Retail Service Providers, that sell the NBN broadband to the end customers. The rumour is that those RSPs, huge ones, like Telstra or Optus, will add "something" on top of the plain NBN that makes 3rd party modems struggle sometimes. Maybe to optimise the traffic to NBN, and while their bundled routers compensate for this, 3rd party routers don't.
Zoom video upload seems to be impacted by those optimisations.

Some details that I don't fully understand here and here.

Luckily, changing a RSP is easy and takes 5 minutes. I did that yesterday and it solved my issue with Zoom and I don't have to have QoS enabled at all.

 

[DJones]

Finally, I have a good theory of the underlying issue backed by evidence. In Australia, there's a single Internet infrastructure provider, government-owned NBN and several Retail Service Providers, that sell the NBN broadband to the end customers. The rumour is that those RSPs, huge ones, like Telstra or Optus, will add "something" on top of the plain NBN that makes 3rd party modems struggle sometimes. Maybe to optimise the traffic to NBN, and while their bundled routers compensate for this, 3rd party routers don't.
Zoom video upload seems to be impacted by those optimisations.

Some details that I don't fully understand here and here.

Luckily, changing a RSP is easy and takes 5 minutes. I did that yesterday and it solved my issue with Zoom and I don't have to have QoS enabled at all.

Awesome find. Glad you managed to sort the issue out.