Why performance monitor keeps current connections not zero even if all browser tabs have finished the page load?

I create a performance counter to monitor my website. It is Performance Monitor => Web Service => Currnet connections. And add my own website as instance.

One strange phenomenon bothers me a lot. When I type the url in chrome to visit the website, from the monitor view I can see the the current connection is 1.But the 1 lasts for a long time, around 2 minutes. I guess the connection from chrome to website jsut takes a few seconds, why the current connection in monitor is so long?

And when I close the chrom, the current connection in monitor go back to 0 immdediately.

Any connection exists between Chrome and website even if all the page have loaded? Thanks.

Finally, I got the answer by viewing TCP connections between browser and server site. Hopes this can help who is also curious about this.

Previously, I think that when the page content is completely loaded, the TCP connection will be closed. This is wrong.

I use the TCPViewer to view the connections. I type the URL in browser, and found when the page content is loaded, the TCP connection is not closed. It is still established. This is why the performance monitor keeps showing 1 connection when the page content is loaded.

After around 2 minutes, the TCP connection is closed. Then the performance monitor goes back to show 0 connection.