How to Distribute GPS-Time Over COTS-Based LANs

Ulrich Schmid, Martin Horauer, Nikolaus Kero

Abstract:	This paper shows how to distribute GPS-time with us-accuracy and below even in Ethernet-based distributed systems. Our SynUTC-approach is based upon a simple network controller-level hardware for timestamping data packets as they leave and arrive at a node, which comes in two flavors: The memory-based times-tamping method exploited by our Network Time Interface (NTI) M-Module timestamps data packets as the network controller accesses them in memory. This technique can be used for virtually any type of network and network controllers. For 10 Mb/s Ethernet, for example, our experimental evaluation revealed a time distribution accuracy down to the pus-range. Still, memory-based timestamping requires network controllers that cannot store entire packets on-chip, and the available configuration parameters must be carefully chosen in order to cope with the various hidden sources of timing uncertainty. To escape from those limitations, we recently developed a novel MII-based timestamping method that can be used in conjunction with almost any modern lo/100 Mb/s Ethernet chipset. The timestamping hardware sits at the standard MII-interface between network controller and transceiver here, and will allow a time distribution accuracy well below the ps-range.
Published in:	Proceedings of the 31th Annual Precise Time and Time Interval Systems and Applications Meeting December 7 - 9, 1999 Marriott's Laguna Cliffs Resort Dana Point, California
Pages:	545 - 560
Cite this article:	Schmid, Ulrich, Horauer, Martin, Kero, Nikolaus, "How to Distribute GPS-Time Over COTS-Based LANs," Proceedings of the 31th Annual Precise Time and Time Interval Systems and Applications Meeting, Dana Point, California, December 1999, pp. 545-560.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In