Frequency synchronous method of transparent clock and storage and forward method of synchronous messages

Abstract

The invention discloses a frequency synchronous method of an IEEE1588 transparent clock and a storage and forward mode of synchronous messages. The frequency synchronous method includes that (1) a main clock periodically sends Sync messages, and the transparent clock passively receives and forwards the Sync messages; (2) the transparent clock records a receiving timestamp when the Sync messages reach the transparent clock and a sending timestamp when the Sync messages leave the main clock; (3) the transparent clock also records a sending timestamp and a receiving timestamp of next Sync message; (4) the method respectively obtains time that one Sync message gap uses to pass the main clock and the transparent clock; (5) the time ratio is utilized to obtain ratio of clock crystal oscillator frequency between the main clock and the transparent clock; and (6) the ratio of the clock crystal oscillator frequency is utilized to modify residence time. The method can improve accuracy for calculating residence time of the transparent clock. Simultaneously, forwarding of the synchronous messages adopts the storage and forward mode on the premise that the frequency is synchronous, and orderly forwarding of the Sync messages and FollowUp messages is strictly guaranteed.

Description

technical field [0001] The invention relates to IEEE1588V2 transparent clock technology, in particular to an IEEE1588V2 transparent clock frequency synchronization technology. Background technique [0002] The transparent clock (TC) is an important part of the IEEE1588v2 clock synchronization network, which can effectively prevent the error accumulation in the cascaded topology. Considering the processing delay of the switching device and the asymmetry of the physical link, the synchronization message will inevitably introduce errors through network switching. The transparent clock calculates and corrects the delay caused by the message passing through the device (called dwell time), and presents each switch as a "wire", thereby effectively reducing the error introduced by network switching. [0003] In fact, there must be a small error in the clock crystal frequency of different devices. Assuming that the error is 0.02%, and the dwell time is 1ms, then an error of 200ns wi...

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Problems solved by technology

[0008] The present invention aims at the problem that the frequency of the transparent clock is inconsistent with that of the main clock, resulting in an error in the calculation result of the dwell time, which ultimately affects the synchronization accuracy of the slave clock, and provides a clock frequency synchronization method, which can improve the dwell time of the transparent clock correction the accuracy of

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