Software-defined networks in large-scale radio telescopes

Traditional networks are relatively static and rely on a complex stack of interoperating protocols for proper operation. Modern large-scale science instruments, such as radio telescopes, consist of an interconnected collection of sensors generating large quantities of data, transported over high-bandwidth IP over Ethernet networks. The concept of a software-defined network (SDN) has recently gained popularity, moving control over the data flow to a programmable software component, the network controller. In this paper we explore the viability of such an SDN in sensor networks typical of future large-scale radio telescopes, such as the Square Kilometre Array (SKA). Based on experience with the LOw Frequency ARray (LOFAR), a recent radio telescope, we show that the addition of such software control adds to the reliability and flexibility of the instrument. We identify some essential technical SDN requirements for this application, and investigate the level of functional support on three current switches and a virtual software switch. A proof of concept application validates the viability of this concept. While we identify limitations in the SDN implementations and performance of two of our hardware switches, excellent performance is shown on a third.