Google Analytics use some query parameters to identify campaigns and to do cookie control. This is all handled by javascript code. Take a look at the following example:

http://www.example.com/?utm_source=newsletter&utm_medium=email&utm_ter m=October%2B2008&utm_campaign=promotion

This will set cookies via JavaScript with the right campaign origin. This query parameters can have multiple and sometimes random values. Since they are used as cache hash keys the cache performance is heavily degraded in some scenarios.

I suppose there's a not so hard configuration on cache servers to just ignore all query parameters or specific query parameters. Am I right?

Does anyone know how hard is it in popular web cache solutions, to create ?

I'm not interested in a specific web cache solution. It would be great to hear about the one you use.