Building a resilient, high-capacity WAN has never been what I'd call simple. In the old days (you know, 10 years ago), it was typically a mishmash of frame-relay and point-to-point leased line circuits mixed with ATM in higher-end, converged applications. Today, those technologies and their successors are being displaced by a variety of IP-based Ethernet circuits. Although I think this shift to Ethernet-based WAN implementations is hugely liberating when it comes to WAN design, it has its drawbacks. Chief among those drawbacks: It becomes a lot more difficult to know exactly what you're buying. When I buy a point-to-point T1, I know with some certainty that I'll have a 1.5Mbps channel from site A to site B. The data I push into the pipe from the router at site A will end up at the site B side in exactly the same order and typically with a very predictable and consistent latency. Ethernet-based systems, while far more flexible and feature-rich, have a much higher degree of variability due in large part to the same flexibility they offer customers. As a result, you need to have a much better understanding of the technologies that modern Ethernet-based carriers use and what might differentiate the options you have available. Without that understanding, you might end up paying too much for a service that won't meet your needs in the long run.
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This story, "What you need to know to build a solid Ethernet WAN" was originally published by InfoWorld.