PTP Slave Time Correction

Each PTP network element maintains a PTP-free running time-of-day counter used as a basis for generating recovered clock signals and computing latencies, offsets and drift rates. The free-running counter runs on the local system clock, asynchronously to the clocks maintained by the other members of the PTP network. Correction factors are applied to the free-running clock in order to arrive at a local time value that is synchronized to the grand master clock. The PTP free-running time value consists of a 32-bit nanoseconds field, and a 48-bit seconds field. Every second the nanoseconds [31:0] field is rolled over and the 48-bit seconds [47:0] counter is incremented. The PTP network element uses the information calculated from the master clock's sync messages to perform local clock adjustments.