Tests for Bufferbloat

Does the quality of your web conference, voice call, or gaming get bad from time to time? Do you ever tell others “Don’t use the internet!” because it might affect what you’re doing? If so, your router may have “bufferbloat” - unnecessary latency/lag created by your router buffering too much data.

The tests below check for the presence of bufferbloat. If any show high latency (say, above 50 msec, or a grade lower than “B”), read our recommendations at What can I do about Bufferbloat?

Easy: Web-based Tests

The web-based tests Waveform Bufferbloat Test and Fast.com (click the “Show more info” button) make accurate measurements of the latency during the download and upload parts of the test. This demonstrates the responsiveness of your network. Share the “letter grade” with your friends. Watch the Bloat / No Bloat videos at Youtube to see the test in action.

Quick: Test for Bufferbloat

If you want to observe latency under load (“bufferbloat”) for yourself, try this:

1. Start a ping to google.com. You’ll see a series of lines, one per ping, typically with times in the 20-100 msec range.
2. Start a speed test from one of the speed test services below while the pings continue:
   • http://fast.com
   • http://speedtest.net
3. Watch the ping times while the speed test is running. If the times jump up when uploading or downloading, then your router is probably bloated.

Best: Bufferbloat Tests

The suite of tests we developed to diagnose bufferbloat and other connectivity problems are good to 40GigE, but require the Flent RRUL test suite. Using the Flent tools, it is possible to get a good feel for how the connection behaves while you tune your settings.

Other network performance and latency tools

1. Apple’s RPM Tool measures responsiveness directly by fully loading the network and measuring the number of responses received in a fixed time. “Responsiveness” (measured in round-trips per minute - “RPM”) is a value ranging from around one hundred (poor) to a few thousand (good).
2. Flent is a tool designed to make consistent and repeatable network measurements. Its suite of tests log the data, and produce attractive graphs of the results. Flent’s RRUL test runs multiple netperf sessions simultaneously to heavily load the network in both directions.
3. netperf creates traffic through a network and measures its performance. Various tools, such as betterspeedtest.sh, netperfrunner.sh, and Flent, rely on netperf, which can be installed in the the OpenWrt firmware.
4. betterspeedtest.sh from OpenWrtScripts bundle is a script you can run on Linux/OSX or on OpenWrt to get concrete, repeatable tests of your network. It performs the same kind of download/upload test that is available from speedtest.net. It is better, though, because it continually measures your ping latency, and thus lets you know the performance and latency of each direction of data transfer.
5. The netperfrunner.sh script (part of the OpenWrtScripts bundle) simulates the RRUL Test by creating four simultaneous upload and download streams. This measures latency during heavy load in both directions.
6. The Quick Test (described above) does a rudimentary job of measuring performance. Although it may not run long enough to avoid the effects of Powerboost or other special cases implemented by ISPs, it can definitely point out situations where you’re “bufferbloated”.
7. iperf2 and iperf3 measure network performance. Despite the similar names, they are not compatible. Both are under active development: check each tool’s website for a comparison of their capabilities.
8. fast.com now tests for latency under load (cick the “Show more info” button.) Also see their press release.