"Tunnels have been the refuge of many a smuggler!"
In the good old days (and even now), smugglers would need to ship foreign contraband (unauthorized products) across the borders without the border security forces or coast guard finding out. To do this, tunnels were commonly used.
The network world has startling similarities when it comes to shipping unsupported and unauthorized protocols across the network borders. This is done by the means of tunneling. In a nutshell, what a tunnel involves is encapsulating the unsupported (or unauthorized) protocol in the data portion of the IP datagram and then using the IP protocol to send it. Tunneling protocols work mostly at the ...