What Can I Do About Bufferbloat?

Bufferbloat is high latency (or lag) that occurs when there’s other traffic on your network. Use the DSLReports Speed Test or run one of the Tests for Bufferbloat to see if it’s present.

TL;DR - if tests show bufferbloat, your router is letting bulk traffic (uploads/downloads) interfere with (and slow down) your time-sensitive traffic (gaming, Skype, Facetime, etc.) Twiddling with QoS might help, but a faster internet connection probably won’t help at all. You will need to find a way to fix the router.

How Can I Tell if My Router Has Bufferbloat?

  • Use DSL Reports Speed Test or any of the other tests on Tests for Bufferbloat
  • A good router that protects against bufferbloat will hold the induced latency (extra latency above the no-traffic levels) below 30 msec.
  • Above 100 msec, people will notice that the network feels slow: voice calls begin to sound bad, web browsing feels sticky, and you start to lag out when gaming.
  • If ping times/latency gets high while the speed test is running and drop back down when the speed test completes, it means your router is bloated. You have probably noticed that the network feels draggy or slow when other people use the network.

To Eliminate Bufferbloat in your Network…

You will need a router whose manufacturer understands the principles of bufferbloat, and has updated the firmware to use one of the Smart Queue Management algorithms such as cake, fq_codel, PIE, or others.

  1. If your router has SQM settings, you can measure latency under load without SQM, then turn on SQM and iterate: adjust the router settings and measure latency until the latency gets as low as possible while retaining good speeds. See, for example, this tuning session.
  2. We continue to be hopeful that commercial router vendors will offer SQM in their stock firmware. Here is a list of those that do:
  3. Install the LEDE 17.01 or OpenWrt Chaos Calmer firmware on your current router. These builds are now stable and include the luci-app-sqm package. There’s a guide at the LEDE web site: https://lede-project.org/docs/howto/sqm
  4. Or install suitable DD-WRT (www.dd-wrt.com) or Gargoyle (www.gargoyle-router.com) firmware. We understand that current builds of both products support fq_codel.
  5. Finally, if none of these seem to be options, call your router vendor’s support line. With the information from the DSLReports Speed Test or the Quick Test for Bufferbloat in hand, you can mention that the ping times get really high when up/downloading files, and that it really hurts your network performance. Ask if they’re working on the problem, and when they’re going to release a firmware update that solves it.

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Bufferbloat Related Projects

Congestion Control Blog
Lede Project (OpenWrt)
Flent Network Test Suite
Sqm-Scripts
The Cake shaper
AQMs in BSD
IETF AQM WG

Network Performance Related Resources


Jim Gettys' Blog - The chairman of the Fjord
Toke's Blog - Karlstad University's work on bloat
Voip Users Conference - Weekly Videoconference mostly about voip
Candelatech - A wifi testing company that "gets it".