Ieee1588 Precision Time Protocol - FibroLAN Falcon-RX/812/G/A User Manual

Falcon R-Class | User Guide

4.12 IEEE1588 Precision Time Protocol

PTP is an acronym for Precision Time Protocol, a network protocol for synchronizing the clocks of
Network systems. Regarding Ethernet Backhaul, PTP is considered the technology of choice to deliver
clock synchronization to remote telecom base stations. PTP defines synchronization message used
between a Master and Slave clock. The Master provides the time, and the slave synchronizes to the
Master
Multiple slaves can synchronize to a single Master. The Master clock provides synchronization
message that the slaves use to correct their local clocks. This section allows the user to configure and
inspect the current PTP Clock settings. In Synchronous mode of operation, the Synchronous Ethernet
interface processes the SSM (Synchronization Status Messages) and recovers the clock quality level
information. The ESMC channel is a logical communication channel which transmits SSM information
that is the quality level of the transmitting synchronous Ethernet equipment clock.
When a Synchronous Ethernet port is selected, the SSM are transmitted through this port, indicating
the quality level of the clock it can drive. The messages are received (if the other remote unit supports
SyncE) with the quality level of the transmitting clock. The remote end unit receiving the messages
on its configured Synchronous Ethernet port extracts the clock quality level and transmits it to the
Clock Master Unit. The Clock Master Unit receives the SSM data from many Synchronous Ethernet
ports and establishes the clock sources. The device internal state logic (clock selector) monitors all
reference clocks and automatically selects the best available reference clock based on configured
priority and revertive priorities. There are different synchronization methods as described below
The Auto-Revertive is the default mode of operation. This mode includes two functions: automatic
reference clock selection (the highest priority qualified clock is selected) and the occurrence of the
Revertive function when needed.
The clock selection process supports revertive and non-revertive modes of operation. If the Auto-
revertive mode is enabled: when the clock selection process has selected -a primary clock, and the
active primary clock source has failed o degraded over a certain period and then is later recovered,
this primary clock source becomes again the active clock source. If Auto non-revertive mode is
selected and a secondary clock source is active (due to a previous degradation of the primary clock
source), the primary clock source is not reactivated even after its quality has been improved.
Methods of Operation
Note: the following modes of operation can be selected under SyncCenter Configuration.
Auto Revertive: In this mode, the highest priority qualified reference clock is selected. If this selected
clock fails or it is degraded, the next priority qualified clock is selected, and the lock acquisition will
begin. If the previous primary clock is restored and qualified, then the revertive function will compel
the previous primary clock to become again the active clock source.
Auto Non Revertive: Clock Selection of the best clock source is only done when the selected clock
fails. The primary clock source is not reactivated in this case.
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