Researchers integrate Openflow with path computation to improve network navigation

What do software defined networking (SDN) and services like Google Maps have in common? Ramon Casellas, a research associate at the Catalonia Technological Center of Telecommunications (CTTC) near Barcelona, will answer this question when he describes the system developed by his team and colleagues at KDDI R&D Labs in Japan at the Optical Fiber Communication Conference and Exposition/National Fiber Optic Engineers Conference (OFC/NFOEC) March 17-21 in Anaheim, CA.

The research represents one of many OFC/NFOEC talks on future network capabilities made possible by SDN, expected to be a popular topic at this year’s event. The use of SDN concepts for controlling optical networks is under study within the Open Networking Foundation and in the labs of optical communications technology vendors (see, for example, "Infinera, ESnet demo Transport SDN via Open Transport Switch").

Services like Google maps use algorithms to determine the fastest route from point A to point B, even factoring in real-time traffic information to redirect you if, for example, a parade is blocking part of your route. Now, researchers from Spain and Japan have achieved this kind of traffic control for the connections in fiber-optic networks. The flexible-grid system can even redirect the traffic-congesting parade to another street (by re-arranging one or more existing connections), so you (a single new connection) wouldn’t have to go out of your way to avoid gridlock.

The system designed by Casellas and colleagues combines two elements: an OpenFlow controller and a so-called stateful path computation element (PCE). An OpenFlow controller uses a protocol that allows the behavior of a network device to be remotely configured. This enables packets of data to navigate the path through the network more efficiently, as if there were multiple, but coordinated remote traffic controllers helping to guide the network traffic. A PCE, in simple terms, is a dedicated computer that finds network routes between endpoints. The functions of a PCE are conceptually similar to Google Maps or GPS navigation systems, according to Casellas.

A stateful PCE keeps track of current connections, enabling it to dynamically correct the path computations for all of the connections in the network. Because the existing connections are stored in an internal database, advanced algorithms can use information about them to enhance network speed and efficiency. They do this by improving the optimization of the active connections over the network as a whole instead of individually.

The underlying idea is that having extra information is helpful to improve the performance of the path computation, and thus the network. Essentially, the system knows every connection on a network and what it is doing at any given time, with the ability to reroute those connections midstream based on new connections coming in to the network.

“Combining a stateful PCE with OpenFlow provides an efficient solution for operating transport networks,” said Casellas. “An OpenFlow controller and a stateful PCE have several functions in common but also complement each other, and it makes sense to integrate them. This allows a return on investment and reduces operational expenses and time-to-market.”

Casellas and his colleagues successfully tested their system by using it to dynamically control the optical spectrum in the fibers in a flexible-grid optical network. In such networks, he says, the intrinsic constraints of the optical technology—for example, caused by physical defects in the network—justify the deployment of PCEs.

Casellas’ presentation at OFC/NFOEC, titled “An integrated stateful PCE/OpenFlow controller for the control and management of flexi-grid optical networks,” will take place Wednesday, March 20, at 3:45 PM in the Anaheim Convention Center.

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