ReversePTP: A clock synchronization scheme for software-defined networks

We introduce REVERSEPTP, a clock synchronization scheme for software-defined networks (SDNs). REVERSEPTPis based on the Precision Time Protocol (PTP), but is conceptually reversed; in REVERSEPTP, all nodes (switches) in the network distribute timing information to a single software-based central node (the SDN controller), which tracks the state of all the clocks in the network. Hence, all computations and bookkeeping are performed by the central node, whereas the dumb' switches are only required to periodically send it their current time. In accordance with the SDN paradigm, the brain' is implemented in software, making REVERSEPTP flexible and programmable from an SDN programmer's perspective. We present the REVERSEPTParchitecture and discuss how it can be used in typical SDN architectures. Our experimental evaluation of a network with 34 REVERSEPTP-enabled nodes demonstrates the effectiveness and scalability of using REVERSEPTP. Copyright (c) 2016 John Wiley & Sons, Ltd.