IEEE1588 (PTP: Precise Time Protocol), which aims for the sub-microsecond range of clock synchronization in a minimal network, is currently focused on highly precise clock synchronization. Boundary Clock (BC) and VLAN Priority are considered to be features that improve PTP accuracy. Although some papers addressed the accuracy, these evaluations were realized using different evaluation metrics and environments. We make them comparable to analyse the contribution of BC and VLAN Priority to precise clock synchronization. Our accuracy evaluation used PTP nodes available on the market and shows the results following the test cases defined in the ITU-T G.8261 Recommendation and IEEE1588 standard. The measurement results show that the accuracy was better than 200 nanoseconds with BC enabled, while it was about one microsecond with BC disabled. We observed that the accuracy was improved to approximately 850 nanoseconds when VLAN Priority was enabled.