[Bloat] different speeds on different ports? (benchmarking fun)

[Aaron Wood <woody77@gmail.com>]

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I don't have a full writeup yet, but wanted to ask if people on here have
run into this.

I'm seeing a disparity between flent and the dslreports speed tests.  On my
connection at home (Comcast 150/12), I figured it was something related to
the test implementations, but minor.  But on a connect at a friend with
business-class Comcast (300/12), we're seeing a huge difference.  Flent
can't seem to achieve more than 120Mbps, often with an early, couple-second
hump at a much higher speed.  But dslreports' speed tests gets the full
300Mbps.

In looking closer at my connection, with sqm (cake) turned off, I'm seeing
~180Mbps download with 500ms of bufferbloat when I use the dslreports test (
http://www.dslreports.com/speedtest/20805152).

Yet flent can't come close to that, even with the tcp_12down test:

​
The current hypothesis that we have is that this is due to either traffic
class, or the ports that traffic are running on.  I've ruled out the ping
streams, as a parallel set of netperf tcp_maerts downloads has the same
120Mbps roof.

It would be interesting if we could run some netperf tests using port
80/443 for the listening socket for the data connection (although if doing
deep-packet inspection, we might need to use an actual HTTP transfer).

-Aaron

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