[Netalyzr] netalyzr, java, bufferbloat and 50Mb/s links

Nicholas Weaver nweaver at ICSI.Berkeley.EDU
Mon Apr 16 08:21:36 PDT 2012

On Apr 16, 2012, at 8:10 AM, Maciej Soltysiak wrote:

> Hello!
> As part of my regular routing related to playing with home router firmware I noticed that recently netalyzr started showing low latency and buffering, even on stock router firmware.
> I've just read "Netalyzr: illuminating the edge network" and linked 2 facts together:
> a) I've been upgraded to 50Mb/s link (from 6Mb/s)
> b) the whitepaper says java puts a cap to 20Mb/s
> So I guess netalyzr tests are not able to fill my cable modem buffers.
> Is there a way to run the network latency/buffering test so that it is not hampered by java?

Not our test, but there is one that can work:

Do a background ping of www.google.com

During the ping, run Ookla's speedtest.net speedtester to load the network, and watch how the pings change.

The odds are, with a 50 Mb/s link, you don't have much of a buffer problem since most systems have the critical buffers sized in capacity, rather than delay, so by upping your bandwidth by 10x, you effectively make the buffer 10x shorter in time.

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