A Novel Enhancement for the Best Master Clock Algorithm Associated with the Precision Time Protocol for the Fractional Gaussian Noise Case

The IEEE1588v2, also known as the precision time protocol (PTP), is a Master–Slave packet exchange protocol, where the Slave’s clock skew accuracy depends on the Master’s clock skew accuracy. Since there might be several optional Masters for one Slave in the Ethernet network, the best Master Clock Algorithm (BMCA) selects for that Slave the best Master clock based on the comparison from the data given by each optional Master via its Announcement message. It is well known that the packet delay variation (PDV) has a significant impact on the Slave’s clock skew accuracy. A higher PDV will lead to a lower Slave clock skew performance from the mean square error (MSE) perspective. Up to now, the information on the PDV’s variances from the Master-to-Slave and Slave-to-Master paths is not supplied in the Announcement message associated with each Master. Thus, the BMCA is blind to that information and does not consider it when selecting the best Master clock for the Slave. As a result, clock skew degradation might be obtained in the Slave. In this work, some information on the PDV’s variances from the Master-to-Slave and Slave-to-Master paths is derived for the fractional Gaussian noise (fGn) case for the Hurst exponent H in the range of 0.5H1, which depends neither on the constant time offset between the Master and Slave clocks nor on the clock skew between them. In addition, it does not depend on the constant delays between the Master and Slave. Thus, the BMCA may now use this new information to better select the optional Master in the Ethernet network based also on the PDV, which has not been done up to now.