Tag: Latency

  • BBR Congestion Talk is Online

    A talk describing Google’s new TCP congestion control algorithm, BBR, is now online. Such a beautiful and simple solution to a long standing problem. This one of those situations when you have to wonder why this wasn’t done before. On a related note, it’s interesting how BBR separates the retransmission and congestion control (rate) logic.…

  • P4 Workshop Presentations

    If you into networking or specifically P4 you should take a look at the recent P4 workshop presentations. http://p4.org/p4-workshop-2016/

  • Latency in large systems

    Improve small job completion times by 47% by running full clones. http://highscalability.com/blog/2014/11/3/improve-small-job-completion-times-by-47-by-running-full-clo.html There was a good article in Communications of the ACM about how to deal with large latency variations a few months ago if you are interested in reading more.

  • TSO sizing and the FQ scheduler [LWN.net]


  • My Linux Journal article is now available

    My article on Packet Queueing in the Linux Kernel appeared in the July 2013 issue of Linux Journal. Now that a month has past, Linux Journal’s great copyright policy allows me to post the content. You can find the full article at the URL below. Queueing in the Linux Network Stack

  • Packet Queueing Article Published in Linux Journal

    Some time ago I started writing a blog post to help myself better understand where packets can be queued within the Linux kernel. This relates to my long time interest in optimizing for latency and experimenting with the kernel’s QoS features. By the time I was ready to hit the publish button, the blog post…

  • Improving my home Internet performance

    For a long time I’ve experimented with shaping my upstream traffic via Linux’s traffic management functionality (tc command) with the goal of improving my Internet connection’s performance. The latest incarnation of this configuration can be found in this script. Anecdotally this configuration greatly improves interactive performance. Use cases such as Skype calls work without a…

  • Per packet overhead on VDSL2 – part 3

    Previous instalments: Per packet overhead on VDSL Per packet overhead on VDSL2 – part 2 Related Bufferbloat list thread For tonight’s edition I have increased the number of small packet sizes in the experiment and dropped the larger sizes. For each of the following data sizes (iperf -l) there are five seconds of traffic: 0,…

  • Per packet overhead on VDSL2 – part 2

    A few days ago I wrote about some interesting latency results I observed on my home Internet connection with small packets. This post adds a bit more data. In this experiment I disabled all upstream traffic shaping and then used iperf to blast UDP packets of various sizes to a destination host I control. The…

  • Per packet overhead on VDSL2

    My home router (Linux box) is configured to shape upstream traffic to just below the link rate to avoid Bufferbloat – this greatly improves interactive performance under load. Recently I’ve experimented with various packet sizes. The charts below show the effect of small packets. Between 0-6 seconds the link is idle. From 6-14 seconds the…