NetFPGA based IEEE 1588 module for time-synchronized software-defined networking

Software Defined Networking (SDN) is an emerging technology to enhance flexible control on networks through abstraction of lower-level switch functionality. Recently using SDN to construct mobile backhaul networks has attracted a lot of attention. Although IEEE has defined IEEE 1588 Precision Time Protocol (PTP) for providing accurate time synchronization in Ethernet networks, how to distribute accurate time in SDN to facilitate synchronization among wireless base stations is still not clear. In this paper, we present an implementation of a NetFPGA based PTP module to support time-synchronized SDN. The PTP module can be embedded inside an SDN switch or can be placed as an external add-on module to an SDN switch. Both solutions can turn a PTP unaware switch into PTP aware. In our system, an SDN controller can configure the PTP module to determine the routing paths for clock distribution. We have developed a frequency compensation circuit to increase the accuracy. In addition, a moving average technique is applied to stabilize the clock output. Experimental results show that our NetFPGA based SDN switch can provide accurate clock distribution with maximum 50 nsec deviation along a three-hop path over 1 hour measurement. The performance of the proposed PTP switch can meet the microsecond-level requirement for time synchronization in cellular wireless networks.