I am happy to share that I have been successful in making a 20Mbps DSL link improve from a “D” Bufferbloat grade to an “A” grade on Speed test - how fast is your internet? | DSLReports, ISP Information on my Balance One Core running 8.0.2 build 4407:
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Enable “DSL/Cable Optimization”. By itself, this didn’t affect the “D” grade. On a Balance, it is under “Network->QoS->Application->DSL/Cable Optimization”. On a Surf Soho, it is under “Advanced->QoS->Application->DSL/Cable Optimization”.
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Configure the Upload Bandwidth to 500 kbps and the Download Bandwidth to 15Mbps. A good starting point is 10-15% below your ISP’s provisioned speeds. I ended up being more aggressive than 10% since my 20Mb DSL link is slowing down a great deal more these days.
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Enable “Mitigate bufferbloat” on the Support page. This is the option which turns on fq_codel for Upload, but not currently for Download. On my Balance, this was “http://192.168.xxx.1/cgi-bin/MANGA/support.cgi”. On the home page, I just change “index.cgi” to “support.cgi” in the url to reach this special option.
Caveat: Given that Peplink’s fq_codel is only working for Uploads, not Downloads, your mileage may vary.
For the record, here is my starting DSL test, followed by enabling DSL/Cable Optimization, and finally after Mitigate bufferbloat. Yes, my DSL download speeds are all over the map these days. And yes, the final run at 20.9Mbps exceeded the WAN Download Bandwidth configuration of 15Mbps (currently fq_codel is not currently working for download).
http://www.dslreports.com/speedtest/61510917
http://www.dslreports.com/speedtest/61512191
http://www.dslreports.com/speedtest/61512767
(My Balance One Core replaced my Surf Soho dual WAN setup when Comcast/Xfinity doubled my speed.)