It's well known that Plexxi is advocating fiber transport around the data center. What's quirky is that this transport is happening on fiber rings, mimicking the add/drop traffic patterns of the telecom world.

Yes, a hip software-defined networking (SDN) startup wants to talk about DWDM optical rings. They're going old-school Light Reading on us.

But Cambridge, Mass.-based Plexxi, which sells a top-of-rack switch, isn't just about optical, or just about Layer 2 switching. In a sense, it's grabbing at every layer of the networking stack and every piece of cloud computing.

Its software sorts resources -- storage, bandwidth, computing power -- into groups that Plexxi calls "affinities." Then it connects those virtual machines via a DWDM wavelength on the optical ring, with Plexxi software keeping track of the changes in network topology.

"People are doing things like workload placement based on where resources are available, where there's memory available -- that's workload placement today. We can't make the network another thing we have to solve for. We'll make the network match the workload placement," says Mat Mathews, vice president of product management.

"What we've done is hire a bunch of MIT PhDs who do algorithms. And this is a more efficient way to control network topologies than running distributed protocols that are nondeterministic, because we can say, 'Make it fit exactly.'"

The setup implies that Plexxi has developed the kind of multilayer management system being championed by companies such as Cyan Inc.

Plexxi uses off-the-shelf optics, taking advantage of inexpensive components that can reach spans of 2km. Some customization might have been involved; Plexxi didn't develop any photonics itself, but Mathews describes the company as having specified certain things about the optics to tailor to its particular market.

One thing Plexxi doesn't do is move virtual machines. In VMware Inc. (NYSE: VMW) verbiage, Plexxi doesn't initiate vSphere vMotions. What it will do is react to a vMotion action by making sure the application keeps getting what it needs from the network.

The eerie part is that Plexxi can do this without any knowledge of the applications themselves. Its software can look at traffic flows and draw its own conclusions -- dishing unused bandwidth to an application that looks like it needs it, for instance. But apps that explicitly request things from the software -- apps that explain the affinities they want -- would get first dibs on altering the DWDM network, Mathews says.

Plexxi's switches communicate with each other through an agent that's similar to OpenFlow but includes control of the physical layer. Plexxi doesn't have plans to offer OpenFlow in place of that agent, but the company could work with OpenFlow networks by opening up an API to an OpenFlow controller, Mathews says. In that way, Plexxi could interoperate with the non-Plexxi majority of the data center.

Plexxi exists in that annoying pre-dawn space that's now called "beta," meaning it's shipping to a few customers and is still tweaking the product. The company didn't even want Light Reading publishing the name of its software, because the name might be altered depending on what goes on in beta (or in trademark due-diligence checking).

But Plexxi does have customers, and it's got some devoted investors that have supplied $48 million in three funding rounds in 18 months. Only the first round was really necessary; the others were initiated by the investors to prevent Plexxi from seeking other investors, Mathews says.

— Craig Matsumoto, Managing Editor, Light Reading