What would happen in your example, if 20 Users wanted to download big files?
Would then the small slots be still free, so that small downloads can pass by unhindered?
What would happen if teh slots for small files and large files are filled and a downloader of small files would get into the queue?
Would he/she then have to wait, till the downloaders in the Queue before him/her have begun downloading, that means till a slot in Big-Files is free?
If not, you'd either have no Queue for small files (your client simply answers "busy"), or a seperate one (to be able to get the download at once, when a slot is free for small files, feels a lot like a second queue).
For a page containing teh summary of a a discussion (and the discussion itself) about Queues generally (so we don't repeat everything here again), you can look here:
http://draketo.de/inhalt/krude-ideen...sscussion.html