3 ms·

I've been running BBR on both my web server and my own laptop for quite some time now with good results. It's included in the mainline Linux kernel - if you hav

by ejrv 8y ago

I've been running BBR on both my web server and my own laptop for quite some time now with good results. It's included in the mainline Linux kernel - if you have kernel 4.9 or newer you can probably trial BBR yourself with these sysctls: net.ipv4.tcp_congestion_control=bbr net.core.default_qdisc=fq Most vaguely recent distributions (Debian stable, Ubuntu, etc) now support it, and a few (like Solus) even default to using BBR.

nieksand 8y ago
I've been interested in BBR since the ACM Queue article and finally turned it on yesterday on my home workstation. But slide 27 in the slide deck is incredibly troubling, where it shows BBR completely destroying the throughput of a neighboring host using Cubic. (Cubic being the default on modern Linux). Even if everyone upgrades to BBR, slide 30 shows more trouble in paradise with BBR not getting to a stable bandwidth allocation. I have a hard time reconciling this with the ACM Queue article, since supposedly Google saw great results rolling it out at Youtube. ACM Queue article: https://queue.acm.org/detail.cfm?id=3022184 https://queue.acm.org/detail.cfm?id=3022184
- Arnt 8y ago
  Youtube doesn't have neighbouring senders using Cubic, and doesn't try to fill the path's narrowest hop. It tries to send the video at exact playback speed and if possible at high quality, and its notions of success will reflect that. IIRC (I read the paper too) the Youtube numbers assumed that the bandwidth available and needed are both largely stable, and that their success was in using that better. Ie. they assumed that if 4mbps appeared available most of the time, then it really was available all of the time. If the capacity of the narrowest point is 10Mbps and 4mbps youtube streaming briefly competes against a bulk download from a Cubic sender, then BPR would hold the Cubic-using download to 60%, which Youtube might count as success and you might or might not.

by ejrv 8y ago

nieksand 8y ago

I've been interested in BBR since the ACM Queue article and finally turned it on yesterday on my home workstation. But slide 27 in the slide deck is incredibly troubling, where it shows BBR completely destroying the throughput of a neighboring host using Cubic. (Cubic being the default on modern Linux). Even if everyone upgrades to BBR, slide 30 shows more trouble in paradise with BBR not getting to a stable bandwidth allocation. I have a hard time reconciling this with the ACM Queue article, since supposedly Google saw great results rolling it out at Youtube. ACM Queue article: https://queue.acm.org/detail.cfm?id=3022184 https://queue.acm.org/detail.cfm?id=3022184

Arnt 8y ago
Youtube doesn't have neighbouring senders using Cubic, and doesn't try to fill the path's narrowest hop. It tries to send the video at exact playback speed and if possible at high quality, and its notions of success will reflect that. IIRC (I read the paper too) the Youtube numbers assumed that the bandwidth available and needed are both largely stable, and that their success was in using that better. Ie. they assumed that if 4mbps appeared available most of the time, then it really was available all of the time. If the capacity of the narrowest point is 10Mbps and 4mbps youtube streaming briefly competes against a bulk download from a Cubic sender, then BPR would hold the Cubic-using download to 60%, which Youtube might count as success and you might or might not.