I wanted to improve client side performance of the WebSphere Portal site, so i did YSlow analysis of the login page and one of the recommendations that i got from YSlow was to "Compress components with GZIP"
So i wanted to see effects of GZIP on the WebSphere Portal performance, so what i did is i did delete everything from my browser cache and then tried accessing the portal login page, and used firefox to see how much data is being downloaded
When i access the portal login page with empty cache, the browser is trying to download 16 resources, close to 1 MB of data for downloading all the 16 resources.
Then i configured my HttpServer, which is seating infront of WebSphere Portal to gzip all the text resources and i tried accessing the same page after clearing browser cache, it made 16 requests to download all the resources as before, but the amount of data being downloaded came down to 240.9KB from 1 MB (without gzip) before and the time it took to download and execute the resources came down from 2.9 seconds to 1.8 second.
The GZIP compression reduces size of Http Response by close to 70 %. The actual performance improvement would depend on the network speed for the client. For the clients who have slow network this could be a big boost