Here's why you really need SDN

Claims that software-defined networking can't scale in performance divert attention from SDN's huge benefit: flexibility

Last week, I wrote about the confused approach many of the largest network vendors are taking to software-defined networking (SDN). In most cases, the issue is that the shift to SDN from their current hardware-focused business would cause them real economic pain, not an aversion to the fundamental benefits for customers of freeing networks from specialty hardware.

Another reason to be wary of SDN is that it can't scale performance as well as hardware can, says Ali Kafel, director of product marketing at networking vendor Enterasys. He suggests that you simply can't switch and route data as well on a general-purpose processor as you can on the purpose-built ASICs used in today's specialty networking gear. For the most part, he's absolutely correct: A general-purpose x86 processor will never perform as well as an ASIC designed specifically for the task, especially if you throw a layer of virtualization in between.

However, focusing on performance alone misses the point of what SDN is all about. We saw that same misdirection in the early days of server virtualization, where hardware server vendors -- fearful of reduced server sales -- said the performance of general-purpose servers running multiple VMs wouldn't be able to adequately scale their performance versus running a single (nonvirtualized) instance. Yet today, server virtualization is extremely common, and you don't hear about scalability problems.

In any event, such complaints don't address SDN's rationale. Flexibility is the special sauce SDN and the virtualization that usually powers it can deliver -- especially when you consider the needs of the cloud. To see why, consider what kind of services a typical medium-size business might require if it were to make the jump to the cloud.

Let's say you're the infrastructure manager for a medium-size manufacturing company. You have a headquarters site, two satellite plants, and a few smaller sales offices scattered around the country. Over the last few years, you've shifted away from mainframe-based applications, and now almost all your infrastructure is virtualized on an x86 platform. As you're preparing the budget for your next major technology refresh, your CIO demands that you consider moving your infrastructure to the cloud.

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