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

The loosey-goosey school
The other school of SDN tries to marry the SDN vision with traditional networks. The goal is to make the network more flexible, agile, and programmable, while making it easier for carriers and enterprises to preserve their network investment (and for vendors to keep selling what they've always been selling). This vision also has the advantage of making SDN purists turn red with anger and heat up until steam comes out of their ears, which is fun to watch.

Because it's embarrassing for grown people to say "loosey-goosey," people use "overlay networking" to refer to loosey-goosey SDN, because the SDN network is an overlay on top of the traditional network. Overlay networking is becoming mainstream now. It's embraced by companies including Cisco Systems Inc. (Nasdaq: CSCO), VMware Inc. (NYSE: VMW), and startups like PlumGrid Inc. and Midokura . (See Cisco & VMware Are Apple & Google of SDN and Midokura Does Net Virtualization at Web Scale .)

In the long run, overlay networks are doomed, as are the proprietary switches underlying them. But the long run is a long way away. The data can't wait for the long run -- the data has to flow now.

Both schools of SDN require enormous business transformations for carriers. Carriers will need new skills. They'll need to reorganize their networking departments around managing software, rather than hardware. How long will that transition take? Ask me again in 20 years or so. The data center transition to open systems is still sending shockwaves that show no signs of ending soon.

But wait, there's more
I discussed the competing visions of SDN with IDC analyst Brad Casemore, and he pointed out a third faction struggling for the networking market: The hyperscale cloud providers. These include Google (Nasdaq: GOOG) and Amazon.com Inc. (Nasdaq: AMZN) and service providers including CenturyLink Inc. (NYSE: CTL) and Verizon Communications Inc. (NYSE: VZ). Enterprise cloud providers are looking to eliminate enterprise networks entirely and run everything in the cloud. They're likely to achieve success in SMBs at first. For example, Pertino offers cloud VPN services for SMBs.

This model is potentially apocalyptic. If this model succeeds, the enterprise switch-and-router market would dry up, as enterprises basically outsource their networks entirely to cloud providers. These cloud providers are today major customers of networking vendors, but they are also competitive threats. Cisco is trying to play multiple sides in this game -- a loosey-goosey networking vendor and also a cloud provider with its Intercloud strategy. (See Cisco's Cloud Bet: What's in It for SPs? and Can Cisco Help SPs Offer Cloud-based Apps?)

It's like The Game of Thrones. This TV show, and the books on which it's based, tell the stories of warring noble houses in a mythical kingdom. Each one of these houses wants to be the one to put a king on the throne, and they are all-consumed with fighting each other.

But what none of these houses realize -- at least not yet -- is that there's a vast zombie army, called the White Walkers, assembling in the arctic far north of the kingdom, and the White Walkers threaten to descend on the kingdom and sweep all the noble houses aside.

In this metaphor, the houses of Westeros are the traditional networking vendors, and the White Walkers are the cloud providers.

— Mitch Wagner, , West Coast Bureau Chief, Light Reading. Got a tip about SDN or NFV? Send it to [email protected].

Want to learn more about SDN and the transport network? Check out the agenda for Light Reading's Big Telecom Event (BTE), which will take place on June 17 and 18 at the Sheraton Chicago Hotel and Towers. The event combines the educational power of interactive conference sessions devised and hosted by Heavy Reading's experienced industry analysts with multi-vendor interoperability and proof-of-concept networking and application showcases. For more on the event, the topics, and the stellar service provider speaker lineup, see Telecommunication Luminaries to Discuss the Hottest Industry Trends at Light Reading's Big Telecom Event in June.