<< I am wondering what does it take to build up a WAN. I take it that a WAN is not VPN, but rather a private network that spans remote locations. So the solution is really hardware based rather than software based like VPN?
In short:
What do companies have to do if they need a WAN, and what do WAN providers have to do to build one? >>
You just about answer your own question...but I'll clarify a few things:
WAN = Wide Area Network, and as you correctly state, it is a network that spans geographically separate locations. Most WANs are also private networks, in that their services, nodes, etc. are not just openly advertised on any public network (like the Internet).
A basic WAN link (vastly simplified) looks like this:
LAN #1->Router->CSU/DSU->Circuit->CSU/DSU->Router->LAN #2
The key difference between this and a VPN is the circuit. Basically, this stands for the type of connection you pay a telco provider to furnish. It can be anything from a leased 9.6K line all the way up to an OC-whatever. The difference in cost is usually based on two things: distance of circuit, and committed bandwidth.
VPN = Virtual Private Network, which means that it too is a "private" network. Since it is "virtual," however, instead of using a privately commissioned circuit, it uses a public network (the Internet, normally) to send encrypted traffic between sites.
However, a VPN is not necessarily software-based. Site-to-site VPNs usually use hardware to setup VPN links. Remote users connecting to VPNs might be more likely to use sofwtware clients for authentication, etc. Just depends.
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