
For many systems administrators, choosing and managing a VPN system is often quite a headache. Inflexible clients, servers, and protocols often prevent VPN's from being smoothly integrated into an already functioning network. The fact that many VPN clients are installed on users' home computers, well out of the reach of the systems administration team, often means that troubleshooting and upgrading VPN systems is time consuming and a struggle for both admins and users.
AFAIK ssh only tunnels *ports*, that is, it can tunnel your local port 80 (http), 6000 (X11), ..., but you need to specify each of them.
Here we want to tunnel the whole path from one box to another.