What's new

Download rate limit bug in Cake?

  • SNBForums Code of Conduct

    SNBForums is a community for everyone, no matter what their level of experience.

    Please be tolerant and patient of others, especially newcomers. We are all here to share and learn!

    The rules are simple: Be patient, be nice, be helpful or be gone!


Occasional Visitor
Router is a DSL-AX82U via gnuton fork but it should be similar for all.

This is how the connection usually is when nothing is downloading and cake is configured: https://www.waveform.com/tools/bufferbloat?test-id=3c861818-d8ac-4f7f-9bae-dfb2dc889feb

When downloading the overwatch 2 season 3 update I decided to rate limit it in the battle net launcher to 20 Mbps and play something else. It became apparent this was a bad idea. Here is a waveform result as I downloaded: https://www.waveform.com/tools/bufferbloat?test-id=fec730b2-d28c-4be7-bd8c-127f9f672038

The jitter and download latency in particular is now much worse. I couldn't figure this out at all. I decided to take a break and then come back some hours later.

To see how bad it could get I downloaded Ubuntu with no limit in Chrome, this is when I got a nice surprise: https://www.waveform.com/tools/bufferbloat?test-id=5276cd72-fed1-413d-80ac-bc630a04784e

The jitter is now what I would consider fine. I thought to myself maybe the blizzard launcher is just wacky so I did the update again unthrottled in the battle net launcher and it now was much better in jitter and latency: https://www.waveform.com/tools/bufferbloat?test-id=365a5fff-e53e-46f2-b505-3deddb1f3e52

I thought to myself maybe it was just an ISP issue so again I throttled the blizzard launcher to ~20Mbps and the jitter/higher pings came back: https://www.waveform.com/tools/bufferbloat?test-id=7b47acc8-eede-4d03-9252-4dfb6ef4ed4d

Juts to see I throttled it to ~10Mbps and arguably the download latency and jitter is somehow worse than the 20Mbps limit: https://www.waveform.com/tools/bufferbloat?test-id=53f75547-42bc-4708-98a1-22cfeb304b79

It's almost like the lower the rate limit you set in software, the more sporadic the latency and jitter. I also had the exact same when running a torrent. With 0 limit my pings and jitter don't jump up by more than 2-3ms but as soon as you set a rate limit, in comes the sporadic latency and jitter is evident.

Don't get me wrong I sort of understand why this happens... well I think anyway. The limiters in battle net launcher/qbittorrent are probably not perfect and causing a weird congestion as it hits the wan and cake gets confused. However when no limit is set the software limiters don't have to do anything and cake expects the data as fast as possible and can properly allocate itself. It still doesn't seem like proper behavior but wanted to have this noted just incase.

Latest threads

Sign Up For SNBForums Daily Digest

Get an update of what's new every day delivered to your mailbox. Sign up here!