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Bufferbloat is a flaw found in many routers. Bufferbloat causes considerably increased latency and network slowdown when there is other traffic on your network that uses the router.

Third-party router firmware such as the latest version of OpenWrt LEDE (vers 17.01.5) is supposed to fix the bufferbloat issue.

However, using OpenWrt LEDE 17.01.5 on a BT Home Hub 5 type A router, I find that I am still suffering from some bufferbloat, as measured by the DSL Reports Speed Test, which gives me low score on the bufferbloat measurement (a D to F score typically).

Interestingly my bufferbloat is much worse on upload compared to download: my normal ping time is around 8 ms, and this goes up to about 50 mg during the download phase on the DSL Reports test, but goes up to around 600 ms during the upload phase.

In terms of the quality score, DSL Reports gives me an A or B typically. But my bufferbloat score is low, so clearly the bufferbloat issue is still present.

Does anyone have any suggestions as to why I am still getting some bufferbloat, when the OpenWrt LEDE firmware is designed to fix the bufferbloat problem?

When I was using the BT Home Hub 5 with standard firmware, the bufferbloat problem was even worse, with latency going up to 2000 ms during upload. So installing OpenWrt LEDE has made an improvement, but has not entirely fixed the problem.

I am connected to my ISP by ASDL2+, using PPPoA with LLC encapsulation. I have a fast (by ASDL standards) download speed of around 18.5 Mbps, due to being very close to my telephone exchange, and upload speed of around 1 Mbps. I use the Plusnet ISP in the UK.

Ash90
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1 Answers1

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It's probably one of two things, maybe both:

  1. Although OpenWrt/LEDE contain the fq_codel network scheduler that combats bufferbloat, it's possible you didn't enable it. Go verify that you're using fq_codel as your network scheduler.
  2. Even if you're using fq_codel so your OpenWrt/LEDE router doesn't experience bloat, bloat may be building up on other devices on your network, such as your broadband modem or other routers, gateways, or Wi-Fi APs. The good news is, if you enable HTB traffic shaping to make your OpenWrt router a slight bottleneck for all traffic going into or out of your network, it can use fq_codel to fight bufferbloat before bloat can build up on any other devices on your network. So enable that as well.

Also, look into cake/sqm-scripts; it's included in recent versions of OpenWrt/LEDE, and it's the latest way to make sure you're set up to battle bufferbloat in the most efficient manner.

Spiff
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