I want to understand how to determine whether my internet connection is a bottleneck or not during a jmeter stress test.

Here is a bit of background for my problem:

I made a stress test with a 2 hours duration, with 2000 threads ramped up over the whole 2 hours duration hoping to find the upper limit of the server, but I am thinking that maybe I hit some other limit and not the server's, as it's not shutting down, aka not responding with 4xx or 5xx error codes. I can only see in the report that the transactions per second go fairly quickly to 580, but they then will not go above.

When I run the stress test against one server endpoint and the load keeps increasing, I need to be connected to a VPN to have access to that endpoint.

Most of the stress test runs I tried, behave like this:

Although, the number of threads increases, like this:

And I only have Non-HTTP error response codes which are not reflected in the server logs, aka the server reports no 4xx or 5xx error codes:

The server will not go over 580 TPS, but it will not throw errors either:

As per