Richard Hoptroff, Hoptroff London

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This paper describes Hoptroff's development of direct terrestrial IP connections to national standards institute timescales for downstream distribution of traceable time to several industries including financial services and media. The objective was to provide resilience and scalability through diversity in time delivery, avoiding reliance on GNSS navigational satellite technology. as required by US Executive Order 13905 and FAA Order 1770.68. In terms of methodology, Hoptroff originally developed techniques for long distance terrestrial PTP time distribution to provide low-cost, environmentally friendly traceable time as a utility for financial services. This is made possible in part by working closely with telecoms companies to reduce jitter, and in part adaptive signal processing at the receiving end. Together, they provide accurate time transmission of the order of a microsecond over 1000km, which can provide a stable base to establish a chain of comparisons on devices and applications at scale. As the business has grown, concerns about dependencies on GNSS highlighted a new merit of this approach – the need for independence from satellite sources, which is now required for US Critical National Infrastructure. Hence our decision to build terrestrial upstream connections direct to scientific institutions that did not rely on satellite connectivity. To this end, Hoptroff has installed layer 2 dark fiber connections from NIST at Boulder, CO, RISE at Borås, Sweden and NPL, Teddington, UK to its timing hubs in New York, London and Tokyo to provide a fully terrestrial time distribution mechanism. Time handover mechanism varies with institution. With RISE and NPL, handover is via a PTP feed, which is very hands-off in that no equipment needs to be installed on-premises. With NIST, on the other hand, handover is an analog 1PPS / 10MHz connection to our on-premises equipment, allowing us to get physically closer to the UTC(NIST) timescale – in the same building! Time delivery from the point of handover is over private IP network connectivity. The long-distance nature of distribution of time over PTP on IP networks means that the timing is somewhat degraded at the point of reception when we compare it to GNSS sources, of the order of a microsecond. In addition, there are brief, rare, but easily detectable deviations in asymmetry over the network. The paper presents typical results from NIST, NPL and RISE, though it must be emphasized that deviations from UTC are by far the result of the network connectivity rather than any deviation from UTC of the institutions’ timescales. We conclude that direct terrestrial connectivity to standards institutes using PTP over IP is an important contribution to establishing a system of systems to ensure stable distribution of UTC timescales at massive scale and low cost The microsecond accuracies achieved may not quite match GNSS, but in terms of accuracy, security, diversity and reliability, they are fit-for purpose for industries' needs, and provide the resilience they rely upon, and address the requirements of US Executive Order 13905 and FAA Order 1770.68.