Beta kits for Big Switch Networks' "P+V" architecture — the combined physical-/virtual-network control plane that's an alternative to network overlays — are on their way to customers in a couple of weeks, says Kyle Forster, Big Switch's president.

That's a key step in Big Switch's next phase of life, and it also emphasizes the thickening division in software-defined networking (SDN) approaches: overlays vs. what Big Switch calls a unified P+V approach. (Bob McCouch, on his Herding Packets blog, calls it "flow programmability.")

VMware is among the biggest champions of overlays, offering the NSX platform derived from Nicira's work. On the unified side, Big Switch will have company when Cisco launches the Insieme platform (or switch or whatever) on Nov. 6.

One obvious difference between the Big Switch and Cisco approaches is that Big Switch is advocating generic, bare-metal switches for the physical half of P+V, whereas it's a pretty fair bet that Cisco isn't.

Big Switch was one of a few vendors giving demos at this week's Open Networking User Group (ONUG) meeting. The company's Unified Physical+Virtual (P+V) SDN switching fabric was the centerpiece of five demos: two related to cloud fabrics, two for the company's Big Tap monitoring fabric, and a demo of automated provisioning on the Switch Light operating system, Big Switch's software that runs bare-metal switches.

Big Switch chose this approach earlier in the year after deciding overlay networks would add more complexity to the network than they would subtract. For example, a lot of engineering goes into the gateway that moves packets into and out of the overlay network, says Kyle Forster, Big Switch's president.

What's difficult, though, is that the overlay model sounds easier: In oversimplified terms, you just drop it on top of your current network. The alternative "is a really hard sell for somebody who's never tried either," Forster says. Big Switch is hoping for some good testimonials from those beta customers that have already tried overlays.

It could take a while. As Forster told SDxCentral in September, the company prefers beta cycles to be long, even longer than one year.

(Photo: The back wall at Big Switch headquarters. It might look familiar.)