Kahn,

Fundamentally a WAN could be considered 2 or more geographically separated LAN's that are desired to be connected together. There are two principal types of WAN topologies, frame-relay and point-to-point. With the maturing of Internet products, VPN is now also a valid business option.

For frame-relay and point to point-to-point:

The hardware usually consists of routers and associated CSU/DSUs (modems) that connect to high-speed lines provided by the local Telco into your office.

Routers can be considered the gatekeepers of a local LAN to limit unwanted traffic on your slower speed WAN lines yet still provide connectivity to the home office. Common manufacturers are Cisco, 3Com, etc. There is typically one router located in each office.

The CSU/DSU's are matched to the line speed subscribed to. They are nothing more than a fancy mdoem. They take the serial (digital) output from the router and convert it to a format compatable with the telco line connected to. As with the router, there will be one CSU/DSU in each office. As line spped

The telco lines are ordered based on your desired speed and budget. The common breakdowns are as follows:

56kbps - Lowest speed/price. Telco's have several marketing names for
64k - ISDN -
128k - ISDN or Fractional T1
256k - Fractional T1
512k - Fractional T1
1.544mbps - Full T1
? - E1
45mbps - T3
OC-nn - Even faster/higher cost

Monthly line cost and line availability would require contacting you local Telco marketing rep.

Internet VPN Connection:

With today's proliferation of Internet products, the Internet is a viable alternative.
Most companies would either set up some type of secure access web page for lookup purposes or purchase hardware necessary for a VPN (Virtual Private Network) that would allow them to access resources as if they were on the LAN but limited to Internet Connection speed.

Sorry so long winded but I hope this helps.

Regards,

Tom