On a local area networkit achieves clock accuracy in the sub-microsecond range, making it suitable for measurement and control systems. IEEE was published in November and includes backward-compatible improvements to the publication. Several profiles have been defined for applications including telecommunicationselectric power distribution and audiovisual.
IEEE It is also designed for applications that cannot bear the cost of a GPS receiver at each node, or for which GPS signals are inaccessible. InIEEE was released as a revised standard; also known as PTP version 2 PTPv2it improves accuracy, precision and robustness but is not backward compatible with the original version.
The IEEE standards describe a hierarchical master—slave architecture for clock distribution. Under this architecture, a time distribution system consists of one or more communication media network segmentsand one or more clocks. An ordinary clock is a device with a single network connection and is either the source of master or leader or destination for slave or follower a synchronization reference.
A boundary clock has multiple network connections and can accurately synchronize one network segment to another. A synchronization master is selected for each of the network segments in the system. The root timing reference is called the grandmaster.
The boundary clocks with a presence on that segment then relay accurate time to the other segments to which they are also connected. A simplified PTP system frequently consists of ordinary clocks connected to a single network, and no boundary clocks are used.
A grandmaster is elected and all other clocks synchronize directly to it. The transparent clock modifies PTP messages as they pass through the device. This scheme improves distribution accuracy by compensating for delivery variability across the network.
PTP typically uses the same epoch as Unix time start of 1 January Synchronization and management of a PTP system is achieved through the exchange of messages across the communications medium. To this end, PTP uses the following message types. Messages are categorized as event and general messages.
Event messages are time-critical in that accuracy in transmission and receipt timestamp accuracy directly affects clock distribution accuracy. General messages are more conventional protocol data units in that the data in these messages Sökfrågor of importance to PTP, but their transmission and receipt timestamps are not.
A domain [i] is an interacting set of clocks that synchronize to one another using PTP. Domains allow multiple clock distribution systems to share the same communications medium. The best master clock BMC algorithm performs a distributed selection of the best candidate clock based on the following clock properties:.
The current clock master transmits this information at regular interval.