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

These web-based tests demonstrate the responsiveness of your network by making accurate measurements of the latency during the download and upload parts of the test.

• Waveform Bufferbloat Test Gives a letter grade for your performance
• speedtest.net Test Web, iOS, and Android apps that measure latency
• Cloudflare Speed Test Provides very detailed statistics of data rates and latency

Quick: Test for Bufferbloat

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

1. In a terminal window, 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 the list above. They all send/receive traffic to add load to your network.
3. Watch the ping times. If the times jump up when uploading or downloading, then your router is probably bloated.

Best: Bufferbloat Tests

Flent is a suite of tests we developed to diagnose bufferbloat and other connectivity problems. Because Flent has been tested to 40GigE, you can get a good feel for how the connection behaves while you tune your settings. In particular, Flent’s RRUL test shows download and upload speeds and latency in one set of charts.

Other network performance and latency tools

1. Apple’s RPM Test 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 is “better” because it continually measures your ping latency, and thus lets you know the performance and latency for 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.