Optical networking vendors are banding together to bring OpenFlow down to their layer.

There's no formal standards effort yet, but Ping Pan, an architect at Infinera Corp., hopes to change that soon. With help from several other companies, he's been circulating a proposal for the Optical Transport Switch (OTS), an optical box that can receive commands from a software-defined networking (SDN) controller.

"Our goal is to create a common interface from the Open Networking Foundation (ONF), so every single transport switch can talk to every single controller," Pan says. Multiple companies are contributing to the OTS effort, discussing it within a newly formed transport group in the ONF.

The OTS takes a cue from Nicira (now part of VMware Inc.), in that it creates a network overlay to connect one virtual machine to another. But Nicira focused on Layer 2 for the data center. Service providers would like to see the same overlay applied arbitrarily across network layers, Pan says.

One possible application could be to turn up bandwidth for transfers between data centers. This could be done using bandwidth-on-demand, which has become the feature to mention when discussing SDN and service-provider networks. (See Carrier Ethernet Has a Job for SDN.)

The OTS isn't a new type of box. What Pan and others are suggesting is to install a small piece of software onto transport gear, giving an SDN controller the ability to do provisioning, monitoring and service discovery from afar. (The group is using OpenFlow as a starting point, just because of the protocol's ubiquity, but the stated goal is to target SDN controllers in general.)

Of course, the network owner would also be able to control access to those functions -- for instance, hiding the network topology, which a lot of providers prefer to keep secret.

"It is a similar concept to OVS (Open vSwitch) where a virtual switch is running in a physical hardware (in this case transport switch) and provides programmability to upper layer applications," writes Toshal Dudhwala, a product manager at Ixia, in an email to Light Reading.

Like a lot of ideas, OTS is easy to describe but more complicated to actually implement.

For one thing, OpenFlow would have to change. The protocol was created for a packet world; it relies on recognizing the first packet of any given flow, for instance. It doesn't know what to do with a wavelength. "In order to make this work, we need to make sure OpenFlow can be extended to set up optical cross-connects and to aggregate packet flows into optical flows," Pan says.

The group would also have to pick a protocol to handle configuration between the OpenFlow controller and the OTS, the difficulty being that they have to find an option that scales, Pan says.

Interest clearly exists in getting OpenFlow to command the optical layer. Calient Technologies Inc. announced last week that it's added an OpenFlow API to its S320 all-optical switch. The move isn't related to OTS, and Calient hasn't participated in OTS discussions yet. That could change as the company's focus expands beyond the data center and into metro networks, Calient officials said in a statement emailed to Light Reading

The other companies that have contributed to the OTS discussion include (in the order listed on Pan's presentation) ADVA Optical Networking, Ciena Corp., Juniper Networks Inc., Ericsson AB, Huawei Technologies Co. Ltd., Vello Systems and Big Switch Networks.

For more

• Cyan Spins 'Blue Planet' for SDN
• OpenFlow's Optical Connection

— Craig Matsumoto, Managing Editor, Light Reading