IE performance problem (long send request time)

Subject: ASP.NET web application

Action: from client(IE web browser) sent sync http request(using javascript) to server (to ASP.NET web app)

Problem: from time to time request takes too long (20 - 50 seconds)

With IE 9 developers tools I performed testing (results on screenshot)

http://oi51.tinypic.com/mav6fb.jpg

You can see 16 seconds d开发者_如何学Curation - for period between request was initialy created to when the request is sent. Why is soo long? How I can control this?

Thanks for answers ( Sorry for my English =)