Voting project architecture

Richard Tallent  answered to my previous blog about this project I have about a voting system:

The multi-dropdown approach seems reasonable, I've created my own code to do this in a way that is compatible with Mozilla and IE for internal projects at work (I hate postback). You could also try the Yahoo/DMOZ process of drilling down by links, which has the added advantages of better caching options and a way for them to back out.

On the problem of narrowing the search, here's a partial solution: store the IP address of each visitor who successfully chooses their school. When a new visitor arrives, check their IP. If previous visitors are in the same class C subnet, use that country / state / etc. as the default option ("Are you at Jefferson Elementary in Podunk, Texas?"). Since many votes will likely come from the same schools, you can avoid the selection process for all but the first visitor. Even if a class C is shared by several schools, selecting from a menu of a few options is easier than drilling down through thousands.

I like the idea, seem to be very interesting, but Richard or somebody else, do you know where I can find some articles on how I can read IP addresses and their subnet mask. What's about proxy servers ?

Thanks anyway Richard, because I think it help me a lot and this goes in the right direction !