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different traffic shaping behaviour between version 2.15 and 2.18 agent
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different traffic shaping behaviour between version 2.15 and 2.18 agent
12-18-2015, 01:04 AM
Post: #1
different traffic shaping behaviour between version 2.15 and 2.18 agent
Hi Patrick,

I have a problem with the traffic shaping on our private desktop agents, I hope you can help with advice.

As you maybe know we use a patched webpagetest version for multistep measurements (see our fork/PR).
We used to measure with a multistep version based on your version 2.15 (2ddcdae2a0e1707a9a3dd2ce08f19057847c01c7 from January 2015). Some weeks ago we merged your version 2.18 (9c09213a2697a639c4bfbed643b172c114afd487 from September 2015).
We fixed our multistep functionality for the new version. With the PHP code it was quite a bit of work but now everything is fine and it works.
In the agent code we didn't have to do a lot to get it to work. The old multistep agent based on wpt version 2.15 also works with the new server code.

The problem: Version 2.18 agents measure slower load times with the same connectivity configured Sad
Here you can see graphs of the measurements. You can click on the data points to get to single webpagetest results.
The slower load times come from slower connectivity -> ttfb and download times of many resources are slower with version 2.18 agent.

If I measure with native connectivity I get same, very fast load times on both agents (about 300 to 400ms instead of about 1,000/1.,800ms with traffic shaping). Measurement on 2.15 agent runs with lower frequency.

So the problem seems to be related to dummynet / traffic shaping. I compared dummynet on both agents (2.15 and 2.18). Both agents run on root servers (no virtualization, 64bit, windows 7, actual browser versions) and use the same 64-bit dummynet version. I re-installed dummynet on both agents - no effect.

I now there have been maaaany commits between January and September this year and maybe this is question is not very fair, but:

If you have any idea about which changes between version 2.15 and 2.18 in agent / traffic shaping code could cause the changed load behaviour I would appreciate it very much.

Regards,
Nils Kuhn
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different traffic shaping behaviour between version 2.15 and 2.18 agent - nilskuhn - 12-18-2015 01:04 AM

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