Can AJAX slow down because of virus scanners or active network filtering?

Question

I just heard one of the clients having really bad performance on IE6 despite modern hardware and decent network connection. So we are suspecting either one or both to be the reason for the bad performance. Unfortunately no exact details of firewalls or such known at the moment...

What kind of issues you have had with web applications using AJAX heavily because of virus scanners or strange corporate network filters? And what kind of approach you have used to tackle them?

edit: Application on IE6 has been tested elsewhere and it performed well enough.

Answer 1

When I see AJAX and IE6 in the same sentence, I think "bad performance".

Answer 2

if contemporary browsers at the site work ok, then it's very likely slow javascript execution in ie6.

that said, performance problems are usually found and solved by measurements, not speculation.

Answer 3

It could be related to version of the jscript dll on the machine. Check out this KB entry. Note that this dll version does not seem to correlate with the version of IE6; i.e. 2 machines with the same IE6 version could have different jscript dll versions.

Have you checked on other machines with IE6? Same version / different version?

Answer 4

The reason turned out to be gzip compression on the server.