Abstract
This paper presents the complete design and implementation of a low-cost, low-footprint, network time protocol server core for field programmable gate arrays. The core uses a carefully designed modular architecture, which is fully implemented in hardware using digital circuits and systems. Most remarkable novelties introduced are a hardware-optimized timekeeping algorithm implementation, and a full-hardware protocol stack and automatic network configuration. As a result, the core is able to achieve similar accuracy and performance to typical high-performance network time protocol server equipment. The core uses a standard global positioning system receiver as time reference, has a small footprint and can easily fit in a low-range field-programmable chip, greatly scaling down from previous system-on-chip time synchronization systems. Accuracy and performance results show that the core can serve hundreds of thousands of network time clients with negligible accuracy degradation, in contrast to state-of-the-art high-performance time server equipment. Therefore, this core provides a valuable time server solution for a wide range of emerging embedded and distributed network applications such as the Internet of Things and the smart grid, at a fraction of the cost and footprint of current discrete and embedded solutions.
Highlights
Network time synchronization allows the nodes in a distributed system to share a common time through exchanging time synchronization packets with one or more reference nodes
To validate the proposed design and to estimate its performance, different aspects of the system have been evaluated: (i) Resources used by the implementation; (ii) Accuracy of the network time protocol (NTP) core’s local clock with respect to time reference; (iii) Client-side precision measured by a standard NTP client; And (iv) performance of the server core operating under different load conditions
The NTP server core has been implemented on a XC3S500E chip: a low-range, obsoleted, Xilinx field programmable gate array (FPGA) device, with a master clock working at 50 MHz
Summary
Network time synchronization allows the nodes in a distributed system to share a common time through exchanging time synchronization packets with one or more reference nodes (the time servers). The two main network synchronization protocols are network time protocol (NTP) [5], and IEEE 1588 precision time protocol (PTP) [6] Both define various accuracy categories among their servers, with stratum-1 servers (NTP) or master clocks (PTP) being the most accurate references in the network. These top-level time sources are usually high-performance discrete synchronization servers from several manufacturers [7,8,9,10] that use an external time reference, such as global positioning system (GPS) [11], as a time source.
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