Corsa Technology has been touting its programmable data-plane appliance as a way to implement SDN and OpenFlow. With the introduction of a smaller appliance today, the startup is talking more about a specific use case: virtualization for the metro and WAN networks.

Corsa is saying its hardware-based virtualization can slice the network into zones, separating traffic in order to preserve performance or maintain security. It can also be a first step toward automating on-demand services, says Carolyn Raab, Corsa's vice president of product management.

If that sounds familiar, it's because virtualization happens all day long in data centers. Corsa is hoping to apply the concept to the WAN and the metro edge.

A different approach is needed in those networks because their traffic is more varied than what you'd find in the data center, Raab says. The metro network faces a wider variety of protocols and bit rates, and video is a bigger factor there, especially in the age of content delivery networks (CDNs).

Corsa makes a data-plane appliance, the gimmick being that it uses FPGAs to apply any protocols you want. It's not quite the same thing as a white-box switch, but it has a similiar result: You can program the network, in this case using an OpenFlow interface.

The DP2000 family, announced today, gives Corsa a small, stackable alternative to the DP6400 line, which has been shipping for 18 months. The smaller format is meant to make it easier to migrate to SDN in small doses.

"Where, two years ago, everybody was: 'Yeah, we're gonna do SDN. We're gonna rip and replace' — that's not the case," says Raab.

Flexibility in the hardware helps the network adapt to different types of services, according to Corsa. That could be an advantage against the software-based virtualization offered by the likes of Arista and Cisco, where "the physical network is rigid, and it can't be changed for what the service wants," Raab says.

Corsa is saying it can provide pools of resources that can be assigned to services in the amounts needed. A service gets associated with, not only a software switch, but also with packet processing units (for traffic classification) and memory (TCAM for lookup tables and DDR for buffering). The end-user sees what appears to be a dedicated switch with those resources attached.

Conceptually, the idea resembles composable infrastructure, an emerging product category in which applications draw from pools of computing and storage resources at will. But composable infrastructure is meant for the data center, where traffic is traveling rack-to-rack. "Once you hit the metro, you're dealing with traffic that's coming from some distance away," meaning latency becomes a more pressing issue, Raab says. Corsa relies on its FPGA to help maintain a steady line rate.

In a sense, it's more fitting to compare Corsa to a microcosm of a metro router. It can perform the same functions but doesn't come packed with features the network operator doesn't necessarily want, Raab says.

Corsa has been shipping appliances for 18 months now, mostly into lab and test environments. Raab tells us customers are now tipping into the realm of production deployments.

Corsa's most recent funding was a $16.5 million Series B, announced a year ago.

Photo by Erin Geary on Flickr. CC2.0 license; photo has been cropped.