SDN architectures

SDN Startup Does Optical Rings

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

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Pete Baldwin 12/5/2012 | 5:21:36 PM
re: SDN Startup Does Optical Rings

Didn't think of this earlier, but -- if you built with Plexxi, would that lead to less usage of vmotion, and less of a need for VXLANs?

I haven't really thought it through; it just occurred to me now. Would you be able to get by with less moving-around of virtual machines in the network, or is that an unrelated factor? (Or totally irrelevant?)

Mat Mathews 12/5/2012 | 5:21:35 PM
re: SDN Startup Does Optical Rings

Hi Craig - thanks for the great writeup!

Re: VM mobility - our solution would not alter the need/usage of VM mobility (like vMotion), yet our fabric solution will make sure to understand and reorganize itself appropriately as this moves occur. This is more than just managing port profile moves, but also making sure any network attributes needed by associated workloads are preserved.

WRT the need for VxLAN - the use of edge network overlays such as VxLAN are meant to solve a number of issue such as extending L2 domains across L3 routed boundaries, VLAN expansion, and others. These edge network overlays look to us like just another type of Affinity Group and we would ensure that the physical fabric is best matched to the needs of those overlay tunnels, thereby creating a very efficient fabric "underlay". This helps ensure customers don't have to overbuild or overprovision a fabric to accomodate the dynamic and unpredictable network effects that overlays could have, and also makes the network "co-orchestrated" with this new overlay network, rather than a separately managed entity.

More details are coming soon!

rainbowarrior 12/5/2012 | 5:21:35 PM
re: SDN Startup Does Optical Rings

Good to see someone is putting "Networking" back into SDN with real networking gear. Interesting concept but I guess it will have to compare cost-wise to Ethernet. What's the price point going to look like?

Pete Baldwin 12/5/2012 | 5:21:34 PM
re: SDN Startup Does Optical Rings

Thanks for the explanation, Mat.  Sorry we gave away everything in that photo.  :)

Mat Mathews 12/5/2012 | 5:21:34 PM
re: SDN Startup Does Optical Rings

Thanks!  We'll announce price points soon (this fall), but it is fundamentally an Ethernet-based solution and will be *very* cost effective compared to traditional leaf-spine, multi-tier, or clos/fat-tree fabrics.

victorblake 12/5/2012 | 5:21:30 PM
re: SDN Startup Does Optical Rings

ADC Etherloop

NetInsight Ether(something forgot the name)



All similar concepts of integrating optical transport w/ Ethernet. I think there have all been strong technologies and products. They problem all of these face is that they all verticially integrate Ethernet and optical which is fine if you have fiber to burn for one application. For operations that need to share the fiber between two different applications (SONET and Ethernet for example) that won't work. Of course that is diminisihing problem, explaing the success of Infinera and perhaps some new SDN startups.

I do not see any reason Infinera could put an SDN API in front of their platform to do the same. Unfortunately for them doing so would also make their product a commodity. But isn't that the challenge for an open standard for all of the incumbent vendors ?



martent1999 12/5/2012 | 5:21:28 PM
re: SDN Startup Does Optical Rings


with due respect, the types of products you mention are in a different class from where the Plexxi solution fits. The Plexxi solution is focused on the datacenter ToR, Aggregation and Core layers using an optical fabric...


Pete Baldwin 12/5/2012 | 5:21:26 PM
re: SDN Startup Does Optical Rings

I don't think you'll see much demand for Sonet in the data center, which is the place Plexxi is targeting. Likewise, i don't think Plexxi has any ambitions on being part of the telecom market.

So, while I see your point about optical+Ethernet integration, the networks Plexxi is targeting would be just Ethernet.

But to your point -- yes, this kind of integration has been done before.

About putting an API in front of an Infinera box -- that does sound like it would work. Infinera does think its optical transport could benefit SDN networks, and I think they envision an approach not too different from what you're talking about -- they don't think it would commoditize their gear.

patentchoi 12/5/2012 | 5:21:24 PM
re: SDN Startup Does Optical Rings

The lurking fear in trying to do it all, is that no single component of the solution will stand out, and then it becomes an easy picking for the big boyz. Hopefully DC will be a well constrained problem long enough for the solution to gain acceptance.

victorblake 12/5/2012 | 5:21:24 PM
re: SDN Startup Does Optical Rings

Craig and martinet1999 --

I understand and agree with both of you. I wasn't trying to suggest anything other than to make the technology analogy.

As for SONET in the data center. I can't help but to say that of course, as a transport for 10G Ethernet, it's already there in any locations requiring longer distances than typical baseband Ethernet transports. But that's not my point.

Will be interesting to see what Infinera, and for that matter the POTS folks do with SDN.


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