GIS Time Synchronization (PTP)
- Tim Williams
The various LIC in the GIS are synchronized using CIP Sync an implementation of IEEE-1588 Precision Time Protocol (PTP).
The Grandmaster Clock for the facility is a Spectracom time server in the Computer Room. This distributes the time to the clock card (1756HP-TIME) in the GIC backplane. From the backplane the time is distributed to the GIC controller card and the network card. From the network card the signal propagates throughout the GIS with each Stratix switch configured as a boundary clock.
Each switch is slaved to the previous switch. Then in turn each switch is master for the network card connected to it then to backplane.
Best Master Clock Algorithm
Order | Attribute | Description |
|---|---|---|
1 | Priority 1 | A user-settable value that overrides the natural choice for best clock. |
2 | clock class | A manufacturer or dynamically set value that describes the intended function of the clock. |
3 | accuracy | Represents the expected maximum error |
4 | variance | Represents the inherent precision of the clock. |
5 | Priority 2 | A user-settable value to impose a preference between otherwise-identical clocks. |
6 | identity | A unique manufacturer’s value used as a final tie-breaker. |
7 | Steps removed | Chooses the `shortest’ path when multiple boundary clocks offer different paths to the same Grandmaster. |
