It is supported in the Cisco Nexus product line of data center switches as well as those intended for the power industry and other IOS or IOS-XE based switches. PTP is a feature that can be configured on different vendor switches to act as either a boundary and/or transparent clock for the networks that they are attached to. The Members will evaluate the quality, stability, and logical distance to the clock source. When a network has multiple Master clock sources, a mechanism selects the best Master this mechanism is known as the Best Master Clock Algorithm. The Member will then adjust the received time based on the calculated path delay. Then, it uses that information to determine the delay between the devices by averaging the path delay. PTP measures the exact time messages are transmitted and received. PTP sends a message between the Master and Member device(s) to determine delay. The updates compensate for any switches in the path and give the event messages accuracy within one picosecond.
#Exact time clock update
There is also a role of transparent clock, which is to update the time interval field within the PTP event messages.
#Exact time clock Pc
These are not typically a PC or workstation but could be industrial devices, sensors, relays, monitoring and metering systems. That device will have only one network port to receive time.
The end client device, the Member to a Master, is known as an ordinary clock. One or more ports receive timing on while one or more to send time out. The Masters can also be known as a boundary clock, which is a clock source that has more than one network port.
The Grandmaster is the primary time source for the hierarchy and will typically get time from a GPS or atomic clock. From there, clocks on the individual segments (networks) would be Members and feed time from the Masters. A typical configuration would have a Grandmaster clock as the ultimate time source, and the Master clocks would feed from the Grandmaster thereby acting as Members. IEEE 1588 defines a hierarchical master-member architecture for clock distribution. Its intended use is over local area networks, such as Ethernet. PTP uses a lightweight packet structure that requires very little bandwidth to operate, and it’s important to note it uses a different structure for distributing time compared to NTP. Many of the changes done in the 2008 update were to accommodate the needs of the power industry but can useful with any application that requires precise timing. Timing precision improves network monitoring accuracy, supportability and troubleshooting of the grid. The primary use case for PTP that I’ve dealt with is in the power industry with smart grid power automation applications such as peak-hour billing, virtual power generators and outage monitoring and management these applications require extremely precise time. PTP was developed for packet based network for control and measurement systems. It is also known as PTPv2 and is not backward compatible with the older version. In 2008, the IEEE released a revised standard for PTP, known as 1588-2008, that improved the accuracy and precision of the protocol. PTP standard was first released in 2002 and known as 1588-2002. PTP is IEEE standard 1588 that can give local computing systems accuracy within the sub-microsecond range (such as microsecond, nanosecond or picoseconds) whereas NTP is within milliseconds or longer. Precision Time Protocol (PTP) is a protocol designed to go beyond what Network Time Protocol (NTP) can offer relative to accuracy.
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