PTP versus NTP accuracy expectations

Accuracy depends on the installation

PTP can offer higher accuracy than NTP in suitable environments. A protocol name alone does not establish the accuracy of an installed system. Reference quality, network conditions, and device configuration still need to be considered.

Reference accuracy and client accuracy

GNSS receiver timing accuracy, the server’s local timing output, and synchronization measured at a remote NTP or PTP client are different measurements. The accuracy of the internal GNSS reference must not be treated as the accuracy delivered over the network.

NTP client accuracy depends strongly on network delay, changes in delay, and path asymmetry. If the forward and return delays differ, the client’s estimate of its clock offset can be biased. A stable GNSS reference does not remove this network error.

PTP can provide substantially tighter synchronization on networks with suitable timestamping hardware, compatible clients and appropriate timing infrastructure. Protocol choice alone does not establish an end-to-end guarantee. Compare the measured client result with the specification for the installed equipment and the requirements of the application.

Compare the same time basis

Before interpreting a time difference as an accuracy problem, confirm that the displays use the same time basis. A consistent PTP offset can be a timescale interpretation issue; see PTP time appears 37 seconds offset from UTC.

GMR6000 profile support

The GMR6000 Rev D datasheet lists PTP as an optional feature and identifies default, media, power, and telecom profiles. See GMR6000 profile list when comparing the time source with a client. This list applies to the GMR6000; it does not establish the capabilities of other GMR models or PCIe cards.

Profile compatibility is one part of a working PTP installation. Select the profile required by the receiving equipment, then assess timing performance in the installed network. The profile list alone is not a numerical client-accuracy guarantee.

Source: GMR6000 datasheet, Rev D, pages 2–3.

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