FQ_CoDel Optimizations for cable connections

[kaj]

I have a cable connection with Vodafone in Germany with a 1 Gbit/s download and 50 Mbit/s upload volume.
My cable router is switched to bridge mode and a pfsense is connected behind it.
I receive a WAN IPv4 and a WAN IPv6 address from the provider in dual-stack mode

With the standard settings of the FQ_CoDel Sceduler :

ECN: checked

• Firewall > Traffic Shaper > Limiters:
  * WANDownIPv4/WANDownIPv4Q
  * bandwidth: 600Mbps
  * Queue mgmt algo: Tail Drop
  * Scheduler: FQ_CODEL (5/100/1514/10240/4096)
  * Queue length: 3000
  * ECN: unchecked

Especially with the target parameter 5 ms and the interval value of 100 ms, I always have the problem that the latency in the download only improves when I limit the download bandwidth from 1 Gbit/s to around 600 Mbit/s

I have found a document at Cablelabs in relation to Docsis and AQM, under the website: https://www-res.cablelabs.com/wp-content/uploads/2019/02/28094021/DOCSIS-AQM_May2014.pdf

In chapter 4.2 the author has made tests with modified target and interval parameters, which are more suitable for use in cable environments. In his tests, he increased the Targer value from 5 ms to 20 ms and increased the Interval value from 100 ms to 150 ms.

I did the same and was very positively surprised by the result.

here my changes:

• Firewall > Traffic Shaper > Limiters:
  * WANDownIPv4/WANDownIPv4Q
  * bandwidth: 600Mbps
  * Queue mgmt algo: Tail Drop
  * Scheduler: FQ_CODEL (20/150/1514/10240/4096)
  * Queue length: 3000
  * ECN: unchecked

The result was so amazingly good that I upgraded my download limiter to 900 mbit/s and still achieved excellent results:

I have been testing for days and have further adjusted the target and the interval.

As we use both Docsis 3.0 and Docsis3.1 in Hibrid mode in Germany, I have set the target value to 10 ms for Docsis 3.0, as described in this document in section 3.2: https://www-res.cablelabs.com/wp-content/uploads/2019/02/28094118/Active_Queue_Management_Algorithms_DOCSIS_3_0.pdf

This is my final configuration at the moment:

• Firewall > Traffic Shaper > Limiters:
  * WANDownIPv4/WANDownIPv4Q
  * bandwidth: 960Mbps
  * Queue mgmt algo: Tail Drop
  * Scheduler: FQ_CODEL (10/150/1514/10240/4096)
  * Queue length: 4000
  * ECN: unchecked

The results speak for themselves:

Here are a few more results:
https://www.waveform.com/tools/bufferbloat?test-id=69bb2004-77cc-4d1d-867f-a17de3ac2a1d
https://www.waveform.com/tools/bufferbloat?test-id=4f70df70-2058-49b6-b900-b346d5e6ce3f
https://www.waveform.com/tools/bufferbloat?test-id=041d3bc3-64da-4145-920a-9b3cf51d5deb
https://www.waveform.com/tools/bufferbloat?test-id=56b7bfad-aa20-435d-9981-505cf77d747d

The amazing thing is that with FQ_Codel I always had problems with the download latency never going down, so I even thought that the FQ_Codel implementation was buggy. Since a few days I know that I have to adjust the parameters target and interval for a cable internet connection. The default values for target 5 ms and interval 100 ms, as you can read everywhere on the Internet, are not optimal for cable connections based on my findings.
It would be nice if other users could also test these values.

Best regards kaj