Dell PowerSwitch S5212F-ON EMC SmartFabric OS10 User Guide Release 10.5.1 - Page 167

End-to-end Calculates the residence time of the PTP event message and updates the correction field (CF) of the transparent clock event message before forwarding the message. The ports are not in any specific state. Best master clock algorithm PTP uses the best master clock algorithm (BMCA) to compare clocks in a network. BMCA determines the status of ports in the network: ● Master-A clock that provides time to other clocks in the network. ● Slave-A clock that receives time from other clocks in the network. ● Passive-A port that is not a master or slave. This algorithm determines if the newly discovered foreign clock is better than the local clock. The grandmaster field in the Announce message contains information about the foreign master clock. Information about the local clock is present in the default data set of the clock. The foreign and local clocks are compared based on the following attributes: 1. Priority1-(Applicable only for the system-default profile) Configurable attribute that determines the master from an ordered set of clocks. Priority1 is the most significant of the six attributes that devices use to select a master clock. The lower the value of priority1, the higher its priority. 2. ClockClass-Defines the traceability of a clock. 3. ClockAccuracy-Defines the accuracy of a clock. 4. OffsetScaledLogVariance-Defines the stability of a clock. 5. Priority2-Configurable attribute that determines a master among equivalent clocks. Priority2 is the fifth-most significant attribute out of the six attributes that devices use to select a master clock. The lower the value of priority2, the higher its priority. 6. ClockIdentity-Unique identifier that determines a master when two clocks are exactly the same. The clock with the lower clock identity has the highest preference. When a PTP node receives two Announce messages from the same foreign master, PTP selects the best master based on the StepsRemoved field of the Announce message. This field indicates the number of boundary clocks between the local clock and the grandmaster clock. Message types ● Event messages: Timed messages with an accurate timestamp that is generated at both the transmit time and receive time. System management 167