You could (maaaybe :-( establish the layering:

Coaxial - Ethernet - IP - TCP / Telnet - RFC822 email - PEM - DC-net - IP - TCP / Telnet - RFC822 email - PEM

Before somebody takes the above tooooo seriously, I'll add that it would take major work to modify TCP/IP to function as the second "TCP/IP" layer in the example above. This is because TCP/IP relies on dialogs between machines/nets instead of broadcasts (at least at the internetwork level), so messages should be traceable back to an inter-DC-net "table", but could not be traced back to a specific host. Pierre pierre@shell.portal.com