Clocking Settings

In order to enable synchronous clocking across domains that span multiple subnets, devices must be assigned as unicast clocks for each subnet in the domain. This can be done automatically, or manually.

Unicast clocks distribute clocking between subnets via unicast PTP. They can act as a unicast master or a unicast slave, depending on their proximity to the grand master clock. For example, a unicast clock in the same subnet as the grand master clock for the domain has the role of unicast master, transmitting PTP to a unicast slave in another subnet - which then distributes multicast PTP for the other devices in its subnet.

See also: Synchronous Clocking

A unicast clock will often (but not always) also act as the multicast clock master for its own subnet.

If all PTP unicast clocks for a domain are removed from the network, powered down, or unenrolled from the domain, the subnet will lose its clock connection to other subnets, and media between subnets may begin to glitch until a new unicast clock is assigned. The DDM dashboard will provide a notification in this event.

Note:  Clocking configuration is only required for domains that span two or more subnets.

Note:  Legacy Ultimo devices cannot function as unicast clocks, but Ultimo X devices can. To determine if a device is legacy Ultimo or Ultimo X: In Dante Controller, open the Device View > Status tab for the device, and check the Model type in the Dante Information panel. Legacy Ultimo devices are listed as 'Ultimo' or 'Ultimo4', and Ultimo X devices are listed as 'UltimoX' or 'UltimoX4'.

Auto-configure

The Auto-configure function assigns one device in each subnet to act as the active unicast clock, and also where possible a secondary unicast clock to act as backup if the active unicast clock is disconnected, powered off or unenrolled.

Auto-configure is applied at the point of configuration. The DDM will not independently reconfigure unicast PTP in the event of a device failure.

To configure clocking for a domain automatically:

  1. In the Domains menu, select the domain.
  2. In the Settings section of the Domain Details panel, click Auto-Configure.

To see or change which devices have been assigned as unicast clocks, click Advanced Settings.

Unicast Clocking Limit

In unicast clocking, the device acting as the Grand Master clock must provide PTP clocking information individually to each device in another subnet that is acting as a unicast clock slave.

Dante hardware devices acting as Grand Master clocks can support a maximum of 40 unicast clock slaves.

Typically, in a routed DDM network where a domain spans multiple subnets, there will be a Grand Master clock device in one subnet, and the auto-configure clocking feature will automatically assign 2 unicast clock devices in each of the other subnets. This means that up to 20 additional subnets per domain can be supported by one Grand Master clock.

Via the clocking Advanced Settings, you can choose to manually assign only 1 unicast clocking device for each subnet, which will allow the Grand Master clock to support up to 40 additional subnets. However, this approach should be used with caution – if the unicast clocking device for any subnet goes offline, clocking (and therefore media) will be broken for the rest of the subnet until the unicast clock device comes back online, or a new unicast clock device is assigned for that subnet.