SDN architectures

The Three Faces of SDN

As software-defined networking (SDN) becomes more popular, vendors wrestle to promote visions of the technology that put their own products in the best light. That's natural for the lifecycle of any emerging technology -- every vendor needs to be able to say, "We do that."

I separate the vendors into three different buckets. This is not rigorous at all, just a handy mental guide to help think about SDN. The three buckets are the Pure Players, the loosey-goosey school, and the zombie army of the White Walkers. (For a more rigorous definition of SDN, see Defining SDN & NFV.)

Pure players
The pure vision of SDN is built on dumb commodity switches, with all the intelligence running in central controllers, as described by OpenFlow and the Open Networking Foundation. The vendors in this bucket either sell commodity switches, like Big Switch Networks and Pica8 Inc. , or they sell software, as in the case of Cumulus Networks. (See Murray Leads Big Switch Into Bare Metal Battle, Pica8 Adds Muscle to ABC – 'Anybody But Cisco', and Cumulus Intros Network OS.)

The goal for the vendors in this bucket is to make the network more flexible. Carrier networks lag far behind data centers in flexibility and virtualization. Data centers began switching from proprietary to commodity hardware in the 90s, and that technology became standard in the 2000s. Networks are just now beginning that transition. The result is that you have incredibly sophisticated virtual data centers that can be configured on the fly entirely in software. When you configure the network underlying those virtual servers, that requires hardware changes. You need to send out a guy wearing a Game of Thrones T-shirt to move around hardware and plug things in manually.

Changes take weeks. This contributes to a perception that carriers are hard to work with and slow. That's not a good way for a business to be perceived.

The pure vision of SDN puts all those changes in software, which saves on opex. And the hardware is inexpensive and interchangeable, so carriers and enterprises save a lot of money on capex.

More importantly, carriers suddenly become as flexible as cloud providers. They can provision networks in minutes or hours. Combine SDN with NFV, and suddenly carriers can replace CPE with software, and do neat business things like offer 30-day trials of new services. Indeed, SDN (and its cousin NFV) are vital tools to help carriers make the transition to cloud providers. (See Why Verizon Needed a Cloud Reboot, NTT Taps SDN to Enhance Cloud Flexibility, and A Peek Inside CenturyLink's Cloud Expansion.)

The problem is that this kind of transition is a huge task. Data centers took decades to make the transition to open systems. Linux Torvalds released the first version of Linux in 1991. The technology required 20 years to mature, until finally Sun Microsystems, the queen of dotcom servers, fell to competitive pressure and was acquired by Oracle in 2010.

Will the transition to SDN be faster now that open systems in the data center have paved the way? Perhaps, but we're still talking about the better part of a decade at least. Service providers, particularly Tier 1s, have billions of dollars of sunk costs in traditional networking. Only a fool would burn all that down to make a greenfield start. The transition will be gradual and cautious.

However, even in the short term, we'll start seeing niches where SDN is valuable. SDN provides competitive pressure on traditional switch vendors like Cisco Systems Inc. (Nasdaq: CSCO), Juniper Networks Inc. (NYSE: JNPR), and Brocade Communications Systems Inc. (Nasdaq: BRCD).

Next page: The loosey-goosey school

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