Idea for ftp (apt yum) mirrors

[Jaap A. Haitsma]

For popular ftp sites there usually exist quite a number of mirrors. The 
link on the webpage of the original developer/owner to his own ftp site.
Furthermore there is usually a page containing all the mirror sites.

Consquence of this is that ftp site of the original developer/owner gets 
most of the traffic and quite some users experience a download which is 
slower then would be needed (a mirror close by would probably be faster).

For Windooz there exist programs which you run on your machine which 
automatically find the best mirror or download from multiple mirrors
E.g. Download Accelelator http://www.speedbit.com/DAP7/DefaultT.asp?

Disadvantage of this is that you need this extra program.

Isn't it possible to solve this just on the server side, so that for a 
user it is just transparent where the file comes from.

I'll try to explain it further with an example.

Let's say redhat publishes a new file and put a link on their webpage
If a user now clicks on the link a javascript will run in the browser of 
  the user which checks which of the mirrors is geographically close by 
and has still spare capacity and starts downloading from that file.
This has 3 advantages. The user receives the file earlier, Redhat saves 
some bandwidth and its completely transparent

I don't know if javascript can do this but I just use for explaining the 
idea.

You could also enhance apt or yum with this.

Does this exist? Is it possible? If it possible/exists why does nobody 
use it.

Jaap