Many IT executives consider the WAN to be a monolithic entity: a giant network that connects all the organization's sites across a common infrastructure.

They couldn't be more wrong. Broadly speaking, in the typical organization there are three main categories of connectivity. Really big sites (such as data centers) that generate tons of traffic require fat pipes, low latency and multiple layers of redundancy, as I discussed in a previous column.

Often, companies use optical circuits or point-to-point Ethernet to interconnect data centers, because of these requirements. Headquarters sites may also qualify as "really big", depending on how much traffic they generate. But they may not: less traffic is sourced from headquarters as servers are moved away to data centers. Similarly, contact center sites require high reliability and moderate bandwidth (those thousands of calls need to get through, but they don't consume as much bandwidth as you might think). So again, contact centers may or may not qualify as really big. Either way, though, these sites are special cases.

There also are the ordinary sites: headquarters facilities and branch and distributed offices of various flavors. These are the sites that IT folks generally think of as comprising the WAN. Depending on the type of organization, there may be a half-dozen of these sites, or thousands, and they could be geographically dispersed or close by. And their bandwidth requirements vary radically. Retail companies, for example, are famous for having thousands of sites around the country (or world), with middling requirements for connectivity at each. Universities may have only a half-dozen buildings scattered around a campus, but with high bandwidth requirements.

But the real challenge that trips up IT execs, more often than not, is the "everything else" category: full- or part-time telecommuters, branch offices in remote locations that can't connect to the main WAN, and mobile services. Not only are these edge sites the trickiest to manage, they can also generate as much as 40% of the overall WAN cost. Worse, branch-office support can consume as much as 35% of all IT support costs.

Some good tips for managing the WAN edges:

* Confront the issue. Don't try to handle, say, telecommuters on a case-by-case basis. Have a standard supported configuration, train staff in common issues, and work with human resources to understand users' requirements for support (even when the organization isn't paying for the services).