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Network Virtualization vs. Software-Defined Networks: What the Heck is the Difference?

Most of the time I love new technology. At the risk of using an old metaphor, it’s like a new car. It has cool features that old cars don’t have.

But one of the things I hate about new technology is when companies try to differentiate themselves by twisting terminology. Everyone wants to be the leading vendor of X, but they know they’re not, so their marketing department comes up with a variant of X that makes the executives happy, but ends up confusing everybody else.

The latest version of this semantic fiasco is software-defined networks vs. network virtualization. Even though I’ve been writing about it for a while – as long as it’s been around, actually – I’m still not sure I would pass a quiz on the difference. And now there’s this supposedly new variant called “network functions virtualization.” Excuse me, what exactly are you virtualizing if not the functions? What defines network virtualization if not the decoupling of network hardware from the software running on top of it (hence, software-defined)?

Here’s the problem with this wordplay: vendors are trying to educate prospects about new technology in order to sell it, and they’re having the exact opposite effect.

The effects of this obfuscation are clear. According to Amy-jo Crowley’s recent article in CBR Online, aptly entitled UK Firms Struggle to Grasp Software-Defined Networking, “a survey of 200 IT decision makers found that 40% of businesses are planning to deploy SDN” within the next five years, while another 34% said “they are planning to deploy Network Functions Virtualisation (NFV) during the same period.”

No surprise there. The surprise comes from the fact that whoever compiled the survey was able to tease these salient results: 37% of survey respondents admitted they didn’t fully understand how SDN worked, while 45% admitted the same thing about NFV. Now I don’t feel so bad. Even though I’m one of those people who tends to equate the verbiage of SDN and network virtualization, I still want to remain open to understanding how other people either conflate or separate the concepts. In my search, I discovered a piece written last year by Overture Networks CTO Prayson Pate, who contributes to SDN Central, entitled NFV and SDN: What’s the Difference?

Pate noted that while SDN’s “reason for being” was the “separation of control and data [and] centralization of control and programmability,” NFV’s purpose was the “relocation of network functions from dedicated appliances to generic servers.” Uh … how is that relocation done? Through programmability. Still what software-defined means, folks.

Pate offers further clarification by noting that SDN is more likely to be found running in data centers and the cloud, while NFV is more likely to be found in a service provider’s network. Uh … like a cloud service provider?

I was all ready to run with that particular bifurcation – carriers for NFV, data centers for SDN – when I stumbled across this enlightening Information Age article from early October, Paving The Way for Enterprise Mobility with SDN. It quoted analysts at the UK research firm Micromarketmonitor, who estimate that the SDN market will grow from £9.8 million in 2013 to £190 million by 2018, and further say, “The belief is that the market will be driven by the rollout of 4G LTE networks, as SDN is expected to provide telecom operators with the opportunity to change network infrastructure within a short span of time in order to support their high bandwidth requirements.”

The closest anyone actually came to clearing up the confusion was consultant Jim Metzler writing in early October at SearchSDN, in an article entitled SDN and Network Virtualization: How Do They Work Together? Metzler said that “network virtualization can be implemented in a software-defined network … when a controller implements [both] Layer 2 and Layer 3 constructs.” He also suggests that SDN can handle network virtualization using overlay networks, but “the market is still spending time thinking about them.”

The upshot is pretty simple: even people in the industry aren’t clear on the differentiation. And the more vendors try and tongue-twist their way into a leadership position, the less likely they’re going to be successful. Sell yourself on what you do, not what you call it.

And even if there was a clear distinction between virtualization on a carrier-grade network and virtualization on a data center network – which there isn’t – before long chances are the boundaries would blur. Carriers want simplicity and flexibility in network management the same way CIOs do. CIOs want the same kind of reliability and agility that carriers have.

So there’s really no reason to introduce fear, uncertainty, and doubt about a supposed difference between SDN, NFV, and network virtualization. Because there isn’t one.

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