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42 lines
2.4 KiB
Plaintext
42 lines
2.4 KiB
Plaintext
// Module included in the following assemblies:
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//
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// * networking/ptp/about-ptp.adoc
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:_mod-docs-content-type: CONCEPT
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[id="ptp-overview-of-gnss-grandmaster-clock_{context}"]
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= Overview of GNSS timing for PTP grandmaster clocks
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{product-title} supports receiving precision PTP timing from Global Navigation Satellite System (GNSS) sources and grandmaster clocks (T-GM) in the cluster.
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[IMPORTANT]
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====
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{product-title} supports PTP timing from GNSS sources with Intel E810 Westport Channel NICs only.
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====
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.Overview of Synchronization with GNSS and T-GM
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image::319_OpenShift_PTP_bare-metal_OCP_nodes_1023_PTP.png[GNSS and T-GM system architecture]
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Global Navigation Satellite System (GNSS)::
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GNSS is a satellite-based system used to provide positioning, navigation, and timing information to receivers around the globe.
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In PTP, GNSS receivers are often used as a highly accurate and stable reference clock source.
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These receivers receive signals from multiple GNSS satellites, allowing them to calculate precise time information.
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The timing information obtained from GNSS is used as a reference by the PTP grandmaster clock.
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+
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By using GNSS as a reference, the grandmaster clock in the PTP network can provide highly accurate timestamps to other devices, enabling precise synchronization across the entire network.
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Digital Phase-Locked Loop (DPLL)::
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DPLL provides clock synchronization between different PTP nodes in the network.
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DPLL compares the phase of the local system clock signal with the phase of the incoming synchronization signal, for example, PTP messages from the PTP grandmaster clock.
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The DPLL continuously adjusts the local clock frequency and phase to minimize the phase difference between the local clock and the reference clock.
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[id="handling-leap-second-events-in-gnss_{context}"]
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== Handling leap second events in GNSS-synced PTP grandmaster clocks
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A leap second is a one-second adjustment that is occasionally applied to Coordinated Universal Time (UTC) to keep it synchronized with International Atomic Time (TAI).
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UTC leap seconds are unpredictable.
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Internationally agreed leap seconds are listed in link:https://hpiers.obspm.fr/iers/bul/bulc/ntp/leap-seconds.list[leap-seconds.list].
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This file is regularly updated by the International Earth Rotation and Reference Systems Service (IERS).
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An unhandled leap second can have a significant impact on far edge RAN networks.
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It can cause the far edge RAN application to immediately disconnect voice calls and data sessions.
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