Multiple RAVENNA devices - PTP Priorities considerations.

According to IEEE1588-2008, the PTP Master can be elected via its priority value.

To access Merging devices PTP settings, open the device advanced pages > PTP Tab.

• PTP Domain : allow to define a specific PTP domain, usually when several PTP masters are required in the same network (default value for Merging devices and programs is 0).
  

  Supported since :
  MassCore : Pyramix V11.1.5 / Ovation 7.1.5
  Ravenna ASIO : V12
  Merging Audio Device : V1.0
  ALSA : V1.0
  CoreAudio / Virtual Audio Device : 2.0.37746
  Horus - Hapi : firmware v 3.9.2

• To modify the PTP setting, you must first tick the "Manual" checkbox.
• Priority 1 is the main priority value.
• Priority 2 is only used if the other parameters do not allow to elect a PTP master.
• Class - Delay Mech. - Announce - Sync : those values should NOT be modified
• Slave only  : forces the Merging device to always be PTP slave.

Example :

To set the PTP priorities on a network :
A: Main Master priority 
B: Secondary Master priority (if Main Master device fails)
C: Other devices priority

Priorities should be set as A < B < C
C should probably be 128, but as some devices may no have a manual PTP priority, it could be even lower.

See also:
https://standards.ieee.org/content/dam/ieee-standards/standards/web/documents/interpretations/1588-2008_interp.pdf
https://en.wikipedia.org/wiki/Precision_Time_Protocol