Timeout error during web browser load test.

Timeout error during web browser load test.

I run multiple web browsers (Google Chrome) at the same time in my site's load test to measure how many seconds it takes to get a response.

I have multiple web browsers running on a single PC, but there is a high probability of a timeout error (about 37% of all requests) and overall response is slow (usually less than 1 second, but average 5 seconds).

■Question
I would like to isolate and identify the cause of the timeout error and slowness, but is there any good way or tool?
Also, could you please let me know if you can predict the cause from the following information?
Please let me know if any small information can be solved.

■ Configuration
PC → Router (cheap on the market) → Hub (cheap on the market) → Optical Modem → Apartment VDSL Collective Equipment → Internet (Provider) → Self-Site Server

■ Points
I would like to isolate the cause of bottlenecks and timeouts in the above configuration.

■Operation information
[10 browsers x 20 access per PC] This is a set
Once one set is complete, the next set is automatically operated.

■ Numerical information
Also, the resources being accessed are as follows:
CPU: 30-50% Network reception: 10 Mbps to 45 Mbps
*Is the network line speed simply insufficient because it is a MAX 100 Mbps line?

In addition, the number of timeouts and slowness tend to be particularly noticeable during the night.
Is it because of the apartment VDSL collection device → around the Internet (provider)?

Or is the CUP spec of the PC simply not enough because I use a lot of CPU?

■ Tool information
I use a test tool called Selenium WebDriver to automatically operate a web browser (Google Chrome).

■Environment
Win 8.1 Pro Google Chrome Selenium WebDriver

http google-chrome selenium-webdriver

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