When your network traffic passes through a carrier’s lines, it is no longer a LAN, it is a WAN.
A WAN (Wide Area Network) is a network (usually connecting two or more LANs (Local Area Networks)) using carrier lines (telephone company, etc.), satellite links, or tin cans and string not belonging to your company. The Internet is the largest WAN on this planet. A WAN carries real (packetized) network traffic, not “direct connect” terminal sessions as with “Remote Control” programs (or traditional terminals) (although these sessions can be “encapsulated” within network packets and carried over a WAN).
Setting up a WAN is not for the faint of heart. Just negotiating with the carrier for the kind of service you need is daunting enough. Then there’s all that exotic (and expensive) communications equipment to deal with. But, if you have to have it, then you have to have it.
At each end of a WAN link you will have a router attached to your network on one side and a carrier service on the other side. The router may feed into an ISDN terminal device, a DSU/CSU, a DSL interface, a T1 multiplexor, a fractional T1 multiplexor, or whatever have you. If the carrier service you use is Frame Relay, the routers themselves will be called FRADs (Frame Relay Access Devices.
Until recently, WAN meant leased lines but today a growing amount of WAN traffic is being handled through the Internet using Virtual Private Networks. While Internet connections may not have as predictable a performance as a leased line network, it sure is a lot cheaper. DSL access to the Internet is making it possible to push fairly high data rates over the Internet at very reasonable cost.
Before you do anything at all with a WAN, you must understand your traffic and how it relates to WAN performance. The WAN will not achieve data rates anywhere near those of your LAN. If you (or your software) expect high data rates, you may have a problem, or need to spend a whole lot of money you didn’t expect to need to spend.
Automation Access put in an Internet WAN link between Burbank and Hawaii for a client (with appropriate warnings about performance). Unfortunately, his accounting software proved to be a single user program at heart with LAN features tacked on (as so many small business packages are). The WAN traffic it generated was awesome, and performance didn’t even begin to approach unacceptable. Citrix MetaFrame had to be installed to keep most of the traffic confined to the server. Expensive, but cheaper than changing accounting software.