Thursday, July 16, 2020

Bufferbloat on TPLink Archer C7 v3

This is an interesting (and very technical) subject, so skip it if you don't care 😇. Simply put, your router / Wifi access point is a little dumb, and is so busy with downloads that it can't do concurrent uploads fast enough.

It's fixable (somewhat) by using QoS, as I tried on my Archer C7 v3.


Bufferbloat

Some modems / routers have issues with 'bufferbloat'. You can find more about 'bufferbloat' here.

This might happen when one user is gaming, and other users are downloading or streaming.

To quickly test use this link, or watch the 'temporary'  latency numbers in fast.com go up and reach 500+ when downloading.

There's no easy solution, besides buying a better router... But, unfortunately, there are little to no specs regarding bufferbloat, so your only options might be to play with QoS settings, or select a new router based on the speed of its CPU (not easy either).


Archer C7 v3

The TP Link Archer C7 v3 has an option in its firmware called QoS, which appears to fix (part of) the problem.

You'll find the option in your router settings under Advanced / QoS. I was operating with QoS enabled to make sure my PS4 downloads wouldn't eat up all bandwidth.


Test setup

Ziggo (NL), 50 mbps cable modem, 1 gbps home network, Dell M2800, ethernet, outside peak hours


Results

1. QoS disabled

  • down: 40 mbps
  • up: 2.6 mbps
  • unloaded: 11 ms
  • loaded: 29 ms
  • down: 51 mbps
  • up: 4.7 mpbs
  • overall: C
  • bufferbloat: F
  • quality: A+
  • speed: -

2. QoS enabled, max speed 1000 mbps up, 1000 mbps down

Note that real speeds are around 4 mbps up and 50 mbps down.

  • down: 48 mbps
  • up: 4.1 mbps
  • unloaded: 11 ms
  • loaded: 21 ms
  • down: 50 mbps
  • up: 4.6 mpbs
  • overall: C
  • bufferbloat: F
  • quality: A+
  • speed: -

3. QoS enabled, max speed 4.5 mbps up, 50 mbps down

Note that real speeds are around 4 mbps up and 50 mbps down.

  • down: 44 mbps
  • up: 3.2 mbps
  • unloaded: 13 ms
  • loaded: 27 ms
  • down: 44 mbps
  • up: 4.0 mpbs
  • overall: A
  • bufferbloat: A
  • quality: A
  • speed: -
It's obvious that these settings decrease the impact of bufferbloat and may help somewhat, but it isn't a real solution, as it starts wasting a little bandwidth. However, I don't have any other options in my el-cheapo router...


Conclusions

1. It appears setting QoS on this ol' cheap Archer C7 v3 fixes the issue somewhat, at the cost of a little upload speed. Note that I have a relative slow cable connection, so my router doesn't have to work too hard shuffling all those packets 😉

2. I don't know what level of priority is assigned to unlisted devices in the priority table, i.e. if something is NOT assigned to any of the high / middle / low categories, then how is it treated? This isn't documented. My suspicion is it is treated below low level, but that requires some more testing. Some better documentation would have been nice, TPLink! 😕

3. I had some bandwidth issues with my daughter's iPad when the PS4 tried to update / download, and would eat up all bandwidth whilst doing so. By adding her iPad to the 'high priority' group everything worked smoothly. Thus far I did not have to add any other devices to the table. We're fine for now 😅

4. If you use these settings, then don't forget to check the available upload / download speed now and again. Some ISP's, in spite of their money grabbing nature, may offer free, gradual speed increases, and you would miss out on those if you have incorrectly set your maximal bandwidth. So, now and again, disable QoS and do a speed test and check if your settings are still right.

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