Packet Pacing [LWN.net]

Packet Pacing

Posted Apr 26, 2022 1:04 UTC (Tue) by mtaht (guest, #11087)
In reply to: Täht: The state of fq_codel and sch_cake worldwide by Sesse
Parent article: Täht: The state of fq_codel and sch_cake worldwide

Sess, so far as I remember you were the originator of the need for packet pacing, am I right in that? I'm planning pieces on each subsystem in play...

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Packet Pacing

Posted Apr 26, 2022 7:26 UTC (Tue) by Sesse (subscriber, #53779) [Link] (3 responses)

Well, yes and no. I made a series of blog posts in 2012 where I demonstrated (empirically, qualitatively) that packet pacing for video streaming helped reduce loss (and thus rebuffering) significantly. This was in preparation for the video streaming at The Gathering, which I led at the time—now they use Twitch, unfortunately. The idea of paced TCP was not new, however. It had come up a number of times in academia, and there were supposedly Linux patches lying around somewhere, but I never found them and believe they would be outdated anyway. My implementation at the time was using HTB, putting each stream manually in its own bucket. For a hack, it worked beautifully.

You could argue that my postings on this brought the benefits of packet pacing to the attention of others, probably including you and Eric Dumazet, which in turn wrote sch_fq (and I believe implemented fq_codel in Linux?). I cannot say for sure what impact it actually had, though, as it's entirely possible this was just something "everybody" knew about and waited for its time.

Packet Pacing

Posted Apr 26, 2022 15:23 UTC (Tue) by mtaht (guest, #11087) [Link] (2 responses)

Can you point me back to those blogs?

Yes, you convinced me that the relevant 2004 paper (which I can't remember), was wrong. But everyone, including me, thought it was impossible to do, until eric burned a weekend or two (I think he was on a plane flight?) doing it. And then it changed the world. It's still changing it. I'm seeing people doing IW256 w/pacing...

I can't remember when other concepts for packet pacing arrived, like TIMELY and so on, but IMHO packet pacing was the single most important innovation we've had for servers in the last 5+ years, one that keeps giving and giving... the BBR attempt at netflix failed, in part, (I think) because BSD didn't have the infrastructure for highres time....

Packet Pacing

Posted Apr 26, 2022 15:45 UTC (Tue) by Sesse (subscriber, #53779) [Link]

They've expired, like nearly everything else on my blog. I can send you an offline copy if you send me an email.

Packet Pacing

Posted Apr 26, 2022 16:11 UTC (Tue) by mtaht (guest, #11087) [Link]

Ah, the relevant lwn is this: https://lwn.net/Articles/564978/

But to me, it's more of the human story that I'm trying to recall.