What is an tunnel?
A tunnel is a way of forwarding many channels of information through a single channel. One analogy is the Channel Tunnel. In Calais, cars, vans and lorries are all destined for the UK. They all drive on to the train, although they do not know what route the train takes. At the other end of the tunnel in Folkestone, they disembark and continue on their journey. Applying it to network traffic, network data is collected at one point, transferred through the tunnel and then redistributed at another.
