Is this paper's description of ATC services over the internet actually practical? I read this paper recently; it's titled ATC over the World Wide Web,
a case study and prototypical implementation. The paper says:


  "In the context of radar surveillance for regional airports DFS
  (Deutsche Flugsicherung Air Navigation Service) must provide a
  possibility for the controller to monitor and control the dedicated
  airspace in a safe manner without the need for a complex and locally
  installed radar surveillance system. In other words: The aim is to
  provide the controller in the tower with a PHOENIX Controller Working
  Position (CWP) over the World Wide Web (WWW). The CWP receives the
  surveillance data over the Internet. This approach allows the usage of
  a standard PC connected to the internet in a standardized manner (e.g.
  DSL)."


The PHOENIX is a Radar Data Processing System (RDPS) for air traffic control that's been developed at the Deutsche Flugsicherung (DFS).

My question is: why does a client need to send their ATC over the Internet for this? DFS still has to set up the hardware in the client tower. So, why doesn't the client use the conventional method to transmit/receive ATC and then, if needed, send the ATC through the Internet (on the ground) to the vendor (DFS) for real-time processing?
For the scope of the article you should read Internet as IP VPN.In practice you would have at least dual links with some kind of SLA attached. All this is much cheaper than having and maintaining your own radar on site.  At my employer we have a system which gets information from various radars over an IP VPN ( been there , done that ).