My Lappy is running Ubuntu 12.04 LTS.
There is no best server found for IIT Kharagpur servers.
Error message: " Failed to download package files check your internet connection. " but it is connected to internet.
You have to try with some other server . you can set default server Nothing but main server . don't worry about server issues because they are temporary. they might be down for maintenance .
you can try again after some time .