IIS 6.0 seems slow behind BIG-IP

depends on scaling setting as well...tcp can be a beast to understand with several tweaks in the protocol assisting or countering effectiveness based on far too many attributes to cover in a forum post. I wrote an article series on the TCP protocol a while back that covers several of the settings. The one on windows and buffers is here:

 

 

http://devcentral.f5.com/Tutorials/TechTips/tabid/63/articleType/ArticleView/articleId/287/Investigating-the-LTM-TCP-Profile-Windows-amp-Buffers.aspx

 

 

The lan optimized profile is often (in my experience) the friendliest for wan and lan environments for standard http traffic. I'd give that one a try. Just to give you a real-word, I had an app that was "faster" without the BIG-IP by about 100%, until I put an optimized profile in place, and then the BIG-IP helped to trim the original avgl response time by about 12%.