How does network emulation work?

WebPageTest General Discussion
1

Hi,

I am currently analyzing webpages with webpagetest (private instance) through mobile emulation. I have tried to emulate network connectivity - bandwidth, latency and packet loss rate - and got result a bit different from my expectation.

Here is my question. How exactly do network connectivity values emulate actual request? Are those numbers just added to current network status of agent? Or does WPT set the agent’s actual network status as closely as the values of network connectivity? My experiment showed me that they are doing something, but I am wondering how exactly those numbers affect on actual network status.

2

Could anybody pls give me any kind of answer?

The answer to the question, don’t know the answer, question itself is wrong, or inappropriate forum, anything would helps me.

3

The network is shaped using DummyNet - http://info.iet.unipi.it/~luigi/dummynet/
(Network Link Conditioner of iOS / MacOS uses the same technology)

Each device has it’s own set of DummyNet queues configured to the settings in the test.

The latencies are additional, so depending of where you are in the work you might want to use an agent that’s closer to you - if you change the latency the simplest place to see it’s affect is in the TCP connect time

4

Andy, I appreciate you answer. It helps me a lot to figure out how the network emulation work. Thank you again and stay warm!