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This document contains a list of Frequently Asked Questions (FAQ). Entries are not listed in any particular order or priority.

  1. What are the benefit of using OnTime’s 1588 impementation

    IEEE1588 enables high-accuracy synchronization of clocks over the Ethernet. With it’s close to wire implementation, OnTime can achieve better than 50 ns synchronization between a Grand Master clock and a slave clock.

  2. What is the difference between PTPv1 and PTPv2?

    PTPv2 introduces many features to IEEE1588 that add flexibility and accuracy to the standard. PTPv2 offers higher effective resolution when communicating time stamps and additional flexibility in communication, by introducing unicast messaging and more flexible sync message rates. Version 2 also adds transparent clock functionality, which enables two devices to synchronize accurately when separated by intermediate network devices.

  3. Can PTPV1 and PTPv2 exist in the same network?

    The second version is not back compatible with the first version of the standard. A PTP V1 device cannot be synchronized with a PTP V2 device due to the diffirence generated by the new message format of the PTP V2. In order to permit the retro compatibility, OnTime has implemented a specific feature that allows PTP version configuration per port. And thus make possible network with both PTP implementation.

  4. Does IEEE1588 work without special hardware?

    The concept of PTP is to be able to achieve sub microsecond accuracy through an Ethernet network. Using equipment that has no support for hardware timestampling will deteriorate this precision and the main aspect of the protocol and its purpose will be lost. In order to support the best capability of the PTP the whole network from the masterclock down to the slave clock must have a 1588 implementation, preferably with a close to wire implementation.

  5. How accurate is PTP?

    The accuracy is directly link to the implementation of the protocol. The closest to the wire the time stamping is done, the better is the accuracy.

  6. What is the difference between one-step and two-step clocks?

    The number of steps associated with a clock denotes the steps required for the clock to exchange its time-stamp data. One-step clocks are capable of inserting the time-stamp data of outgoing packets into the packet itself, whereas two-step clocks send the time-stamps of packets separately. This is easily seen in sync packet transmission – one-step clocks insert the egress time stamp of sync packets into the sync packet itself, whereas two-step clocks send the egress time stamp of a sync packet in a separate “follow-up” packet.

  7. What is the difference between a Transparent Clock and a Slave Clock?

    The Transparent clock is the mechanism that compensates for the residual latency and corrects the time stamp in the synchronization message whereas the Slave clock is the regulation algorithm that compensate for the clock drift of the network element. Both must coexist to reach the best accuracy.

  8. What is a Grand Master Clock?

    A grand Master Clock, commonly named GMC, is the network element that is linked to a GPS receiver and gives the time in forms of UDP messages according to the 1588 standard.

  9. What is the Best Master Clock Algorithm?

    The Best Master Clock Algorithm is a software mechanism that determines which Grand Master clock with the same subnet has the best resolution. The comparison is done according to several criteria such as the priority, the clock class, the clock accuracy…

  10. What are transparent clocks?

    The transparent clock is generaly implemented in the switch. Its purpose is to compensate for the residual latency generated by the switch itself. The Transparent clock will modify the time stamp generated by the Grand Master with its actual time. In the point of view of a slave clock it will appear that it is directly connected to the Grand Master. Together with the Best Master clock algorithm, this implementation avoids that 2 Grand master act as Master in the same network.

  11. What environment are OnTime Networks’ devices primarily designed for?

    The OnTime Networks’ devices are specifically designed to operate in the harsh and climatically demanding environments of the aerospace and defense industry, today the systems are widely used in FTI network. Our rugged systems are at the forefront of technology and provide innovative solutions that address complexity, enable modularity while delivering optimal performance for SWaP-C (Space/Weight/Power/Cost) constrained applications.