When you do this, what you have isn't the internet any more.
The beauty and the failing of the net is that everyone is equal and every device is treated like every other device. Unfortunately this is not a good thing to carry realtime data.
There have been attempts to do what you describe with QoS management, where some kinds of traffic gets treated differently than other kinds of traffic. In general, these things don't work very well, because the underlying protocol isn't designed for it.
If you want a largescale nationwide network to handle realtime data like VOIP, video traffic, and high resolution X-rays at the same time, it ought to be built very differently than the Internet. Because the Internet just isn't built for that. Sorry.
--scott
"C'est un Nagra. C'est suisse, et tres, tres precis."