Software-defined networking (SDN) is coming on strong, thanks to a glut of startups and the emerging popularity of organizations like the Open Networking Foundation (ONF) and its participating members. VMware's $1.2 billion acquisition of Nicira, which was up until that point the best-known SDN startup, seemed to validate the idea that SDN, at least at a discussion level, is creeping into the technology mainstream, fueled by virtualization's move into the network.

Here's a look at 10 more SDN startups bandied about as potential acquisition targets, all part of a market that researcher IDC predicts to be at about $2 billion by 2016.

CEO: Eric Johnson

Why should solution providers, in particular, be watching what happens to ADARA Networks? Because of the emerging SDN players, ADARA is about the only one to have fully articulated a channel strategy, opened up sales to solution providers and even added two-tier distribution, in the form of Tech Data, which now features ADARA's Full Stack Engine and SDN Solutions in its Solutions Center. The Full Stack Engine is a full-service platform that integrates all seven layers of the OSI-model network to virtualize various computing and network resources, applications, content, data and client systems used in the infrastructure. It brings together the capabilities of four ADARA products, such as the Gemini Series multicast routers and Mercury Series Layer 7 routers, into an integrated system. Though the company is planning to be independent for now, ADARA CEO Eric Johnson told CRN in an August interview that ADARA is most certainly "in play." "We've been approached about acquisition," he said. "We may become part of a larger organization."

CEO: Guido Appenzeller

Other than Nicira, Big Switch Networks is probably the best known and best marketed of the emerging class of SDN startups, having thrown its support with the OpenFlow protocol and attracted some big name executives to its ranks as it prepares for a commercial version of Floodlight, its controller software.

Most industry pundits agree that Big Switch will find a home with one of the industry's tier-one players, and speculation seems to have settled on IBM as a potential acquirer, given IBM's stepped up focus on data center convergence and the work it's done with Big Switch already around projects like IBM's Open Data Center Interoperable Network (ODIN).

CEO: Yaron Simler

Palo Alto, Calif.-based ConteXtream bills itself as a provider of "cloud-scale network virtualization for cloud, managed hosting and broadband service providers." In December 2011, the two-year-old company unleashed ConteXtream Grid for Cloud and Managed Hosting Providers, a distributed virtual Layer 4-7 switch that, when deployed as an overlay to existing network infrastructure, connects an unlimited number of network endpoints to what the company describes as a flat network, easy to manage and free of the headaches that come with network administration.

CEO: Dante Malagrino

Embrane prides itself as having already looked beyond the SDN trend, which according to President and CEO Dante Malagrino, "tends to be focused very narrowly on Layer 2 and Layer 3" networking. Embrane has won good notices for Heleos, the nearly year-old distributed software platform it offers for driving the programmable networking trend into Layer 4-7 functions such as load balancers, firewalls, VPN and WAN optimization. A good fit for a larger data center player?

CEO: John Chambers (via Cisco)

OK, so it's a pretty obvious choice: Insiemi's status as a potential Cisco "spin-in" -- Cisco supplied the $100 million seed round and has the rights to finish the job on the company for up to $750 million more -- means it already has an acquirer in the wings. That doesn't make Insiemi any less interesting compared to the current crop of SDN start-ups, though if Cisco was in the mix to acquire Nicira, as several sources hold, what does that say about Cisco's faith in this project?

CEO: Steve Georgis

Founded in Colorado in 2008, LineRate emerged from stealth during this past April's Open Networking Summit with software that delivers services on top of virtualized networks. LineRate's appeal is that it works on platforms running commodity x86-based servers, meaning customers can theoretically set up and deploy network services without the hassle of configuring physical networking and infrastructure products. Among LineRate's offerings thus far is LineRate Proxy, which offers full proxy Layer 4-7 network services, from content filtering to load balancing. Its early customers included Photobucket, and it sells LineRate Proxy -- and presumably will do so for future products -- using pay-for-capacity subscription licensing.

CEO: Tatsuya Kato

Proof that SDN innovators aren't grown exclusively in North America, Midokura is a Japanese company with plenty of early good notices. The company's emerging strategy seems to center on Layer 2-7 distributed virtual networking for OpenStack-based environments, and it has pulled in about $6 million from various investors, including Japan-based VCs. The product most of Midokura's observers have focused on thus far is called MidoNet, a software platform capable of creating virtual switches, firewalls and other pieces of software-based network infrastructure without the need to change or adjust the physical network.

CEO: David Husak

Plexxi is among SDN startups that have copped some pretty decent VC investments thus far, having confirmed a $20.1 million round as recently as June and brought its total VC take to just shy of $50 million. More from Plexxi is expected soon; the company earlier in the summer launched a private beta program with select customers to test out what it describes as an "integrated hardware/software offering that allows data center operators to build and manage a network from the perspective of the needs of the application or workloads." The phrase Plexxi uses to describe its approach is "affinity-driven networking."

CEO: Awais Nemat

The SDN space's latest buzz company -- the network virtualization space's, really -- is PlumGrid, which sewed up a $10.7 million funding round in August from U.S. Venture Partners and Hummer Winblad Venture Partners to follow a $2 million round in 2011. Its engineering and executive teams come from Cisco, Marvell, Sun Microsystems, VMware, Nicira and other places, and while not much is yet known about its products and services, PlumGrid not so modestly describes itself as "the future of networking."

Securing virtualized environments is a hot market these days, and demand for startups that can allay the security concerns of software-defined networks (SDN) is sure to be pretty decent, if acquisitions by Cisco and Juniper into VM security thus far are any indication. That's why we're curious about vArmour, a new company founded by veterans from the former NetScreen, including seven-year Juniper executive Michael Shieh. Little is yet known about what vArmour is up to, but it's already building a buzz, and it was spotted at the Open Networking Summit in April demonstrating its tech with Big Switch.