[Bloat] Win10 Updates vs cake

Ryan Mounce ryan at mounce.com.au
Thu Dec 21 22:57:32 EST 2017

Some further reading on the issue


Ryan Mounce

On 22 December 2017 at 13:25, Ryan Mounce <ryan at mounce.com.au> wrote:
> I've experienced this recently myself. In my case I have a 100Mbps
> link from my ISP and their shaper will queue up to about 120ms worth
> of packets (on top of the ~10ms baseline latency). I run cake in
> ingress mode at 99.2Mbps, which has normally been enough to keep
> everything in check and keep my ISP's queue empty at least in the
> steady state.
> Boot up a Windows 10 PC that's been unused for a few months, let it
> update and bam! 100-130ms RTT, family member's Netflix stream in the
> next room stalls completely, and running a quick speedtest on a
> different machine (that should get ~50% share of the link under normal
> circumstances with dual-dsthost) yields about 1.2Mbps on a 100Mbps
> link! I performed a quick pcap while this was happening and determined
> that Windows Update had started on the order of 120 parallel HTTP
> downloads from 2 different Akamai cache IPs (within my ISP's network
> 20ms away).
> The 20ms jump in latency in your case just indicates that there is a
> small buffer in your DSLAM, however it is still being flooded by the
> parallel transfers from the CDN.
> Windows 10 probably deserves most of the blame for opening so many
> parallel connections, however I think there is also some concern here
> with Akamai's FastTCP not responding to congestion signals.
> Regards,
> Ryan Mounce
> On 22 December 2017 at 12:31, Rich Brown <richb.hanover at gmail.com> wrote:
>> I'm using LEDE 17.01.4 on my Archer C7v2. I have a 7mbps/768kbps ADSL2+ connection through Fairpoint. The modem stats page shows its "attainable rates" (kbps): 13330/1272 and Rates: 8271/1181. My SQM settings are:
>> Download: 7000 (kbps)
>> Upload: 925
>> Queue Disc: Cake/piece_of_cake.qos
>> Link Layer: ATM/44 bytes overhead
>> Advanced Options: default
>> I have noticed that Win10 updates cause the network connection to become unusable for other services/people, as if I had bufferbloat. But ping times remain stable - they jump from ~20-22 msec unloaded to 40-50 msec.
>> Experiments I have tried:
>> - Setting download speed to 5000 makes the connection usable for other people, although the ping times remain about the same (40-50 msec)
>> - Setting the download speed to 8600 still keeps ping times down, but that really harms other people's performance.
>> - The link rates (download and upload) seem to track the SQM setting, measured with both YAMon and the built-in real-time graphs.  I get ~6,000 kbps with a 7000 download setting, I got ~3,000kbps at the 5000 setting. I get ~8500 kbps after setting download to 8600.
>> - This doesn't seem to happen when I'm downloading other kinds of files (I haven't tried torrenting files...) Downloading non-Win10 update files seems to leave the connection in a fairly responsive state.
>> Any thoughts? What other experiments should I make? Thanks!
>> Rich
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