SDN vs. network virtualization: Q&A with VMware's Martin Casado

VMware's Martin Casado discusses the definition of SDN as it relates to network virtualization, and what to expect at this year's Interop conference.

There are many challenges associated with software-defined networking, but they start with the need to solidify a definition of the emerging technology. While vendors flood the market with so-called SDN technology, it can be difficult for end users to determine where to invest.

Martin Casado, OpenFlow creator and chief architect of networking at VMware, recently spoke with SearchSDN, offering up his definition of SDN and how it differs from network virtualization.

Casado is speaking at Interop in Las Vegas in a keynote panel on the transforming network. Here Casado gives us a sneak peek of what the panel will address -- including why software will play a central role at this networking event.

You're featured as a keynote speaker at this year's Interop on a panel called "Riding the ShockWave of Change in Networking," which will discuss the changing network. You're an original innovator of OpenFlow and SDN, but with the emergence of network virtualization, is there really such a thing as SDN? If so, what's your definition of it now?

Martin Casado: Network virtualization and SDN are two different things and somewhat incomparable. SDN is a mechanism and network virtualization is a … solution. SDN is relevant to system builders: I liken it to a way to build an engine. Someone building a car would use a new way of building an engine to build the car, but customers don't buy engines, they buy cars.

Another analogy for you: a programming language [that] would be the SDN with the program built out of it. You don't go to a customer and say, "I have Python, and I'm going to sell you Python." You say, "I built this program, and it uses Python."

So my definition of SDN is the original definition of SDN, which came out of research with a joint project at Stanford and Berkley. That definition is a network architecture where the control plane is decoupled from the data plane and the hardware from the data plane is generalized to allow more function.

SDN can be applied to many problems: graphic engineering, security, policy or network virtualization. Network virtualization, on the other hand, is a product category or solution set that customers use to change the paradigm of their network; so just as server virtualization changed the paradigm for server operations and management, network virtualization changed the paradigm for network operations and management. You can use SDN in network virtualization, but you don't have to, so it's difficult to compare the two.

The most important thing for the discourse at large is [to] make sure we're not conflating mechanisms that are useful to system builders and customer-basing solutions. I think that in order to make progress in a discussion, we need to define terms, clearly articulate terms, and use it as a basis of the discussion.

What are some of the challenges organizations and vendors alike are facing with the rapid innovation and changing definitions and expectations of SDN?

Casado: I think the primary difficulty as the customer is that SDN doesn't have a clear definition -- the customer doesn't know how to evaluate it. I don't think the vendors are having difficulties, because they're doing whatever they want and calling it SDN. But customers are confused, because they don't know what SDN means: it's a moving target. So to reign in the discourse, we have to be clear about what we're talking about.

This winter, VMware said it would roll out VMware NSX, a vendor-neutral, hypervisor-neutral and cloud management platform-neutral SDN controller that would integrate directly with the hypervisor to enable this capability. How will that play considering VMware's current approach to cloud and network virtualization management?

Casado: We were very clear in the announcement that it can be consumed by customers in one of two ways: one, part of a vertical integrated stack in which all pieces are simpler to use and operate, etc. The second model [is] it'll be available as an independent component that can integrate into any software stack. So whether [its] an ESX environment, a KVM environment, a vCloud environment or OpenStack environment, we support heterogeneous environments. We want to support both models, both the vertically integrated and the horizontally integrated, so you can use best-of-breed components in a horizontal supply model.

If VMware has a goal of creating SDN and network virtualization that stretches across any hardware, including commodity hardware, does the Cisco partnership still matter?

Casado: I would like to restate what's happening -- I don't think that's entirely accurate. Just like server virtualization is compatible with any server, network virtualization is compatible with any hardware. That doesn't mean the hardware can't be differentiated in a number of ways, whether manageability, etc.

So it's not accurate to say it's going to change the world of commodity hardware. It provides customers with choice: They can choose between hardware platforms; they can choose between using a solution that differentiates for customization or those that don't. We don't take part in that decision or supply advice. We work closely with Cisco, and we continue to work closely with Cisco, and there's no need to change that relationship as a result.

Is there anything else you'd like to add in regard to the discussions surrounding SDN?

Casado: The only thing I would add is: There's a lot of confusion around the term SDN, and confusion [around] how it dovetails with network virtualization. But independent of all that, there is a broader trend in networking, and this broader trend separate of SDN and network virtualization is we're seeing Web 2.0 data centers, big data centers, where there's general purpose hardware that provides the physical infrastructure.

So the software players are becoming important to the discourse in this dialogue. The panel at Interop is going to be Microsoft, VMware and Broadcom discussing this topic. It's going to be important to see these voices discuss this trend in networking.

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