Optical circuit switch maker Calient Technologies is pushing further into the SDN realm, having announced this week an OpenDaylight-based controller that allows data center operators to reconfigure extremely large data transfers -- so-called 'elephant' flows -- from packet to optical circuit switching.

Such elephant flows constitute more than 60% of traffic in large cloud data centers, according to Calient, and can overload packet switching facilities, adversely affecting other smaller data flows, called "mouse" flows. (Yes, folklore suggest elephants are afraid of mice, but in the modern data center, it just ain't so.)

Calient's Optical Topology Management Controller aims to ease that situation by moving big transfers off the packet switches. Daniel Tardent, vice president of marketing at Calient Technologies Inc. , speaking from the SuperComputing 14 conference in New Orleans this week, said: "When an application wants to send a whole bunch of data, the controller can configure optical topology on-demand for the data center so the application can take advantage of greater reliability." (See Calient Unveils Optical SDN Controller.)

By the first quarter next year, Calient will add the capability to actively monitor data center traffic flows in hybrid packet-optical environments. The controller currently works with Calient's S-Series optical circuit switches, but because it is built on the OpenDaylight framework, it could control circuit switches or packet switches from another vendor.

Still, Tardent claims Calient's ability to control optical circuit switches differentiates its controller from a bevy of other SDN controllers. "As the data center market moves to 100G, there are compelling cost advantages to using optical circuit switching in that venue," he says.

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Calient is not a novice at the SDN game, and arguably was at the forefront of applying SDN technology to the optical layer. The vendor added OpenFlow support for its S320 optical circuit switch way back in November 2012. Calient also developed an SDN partnership with Plexxi early the following year, and more recently announced an OpenDaylight plugin for its switches. (See Calient Adds OpenFlow Support and Calient & Plexxi Launch SDN Data Center System.)

— Dan O'Shea, Managing Editor, Light Reading