Clock Synchronization

In Standard Dante Networks

All Dante-enabled devices use the IEEE 1588 Precision Time Protocol (PTP) across the network to synchronize their local clocks to a leader clock, providing sample-accurate time alignment throughout the network.

One Dante device will be elected as the PTP Leader Clock for the network; all other Dante devices act as a PTP Follower Clocks to the elected leader clock. Although many Dante devices may be capable of becoming PTP Leader Clock, only one device will win the election. Devices with clock inputs (e.g. Word Clock or AES3) will be preferred in the election process. A gigabit connected device is preferred over a device connected via 100Mbps. A tie-breaker rule of the lowest MAC address is used if several equivalent candidate leader clocks are available. The election process may be overridden by manually setting 'Preferred Leader' on a device.

Dante Clock Types

Each Dante hardware device can derive its clock from either its high-quality onboard clock circuit, or an externally connected word clock. In the case of Dante Virtual Soundcard, the computer’s clock will be used.

Clock Settings

Enable Sync To External

A Dante device set to 'Enable Sync To External' will use the external word clock from its host equipment to tune its onboard VCXO. A Dante device with this attribute set will become the PTP Leader Clock, unless there is another Dante device present with 'Preferred Leader' set.

Preferred Leader

Sometimes it may be necessary to force a particular device to provide the PTP Leader Clock. A Dante device with 'Preferred Leader' set will always be chosen as the PTP Leader Clock. If more than one device has 'Preferred Leader' set, the device with the lowest MAC address will be chosen.

Note:  If device A is deriving its clock from an external word clock source ('Enable Sync To External'), but device B is set as Preferred Leader, device A will lose sync with the Dante network and will eventually be muted - unless device B is also deriving its clock from the same external source as device A.

Clock Status

Clocking and Synchronization in Redundant Networks

In a redundant network, the clock synchronization protocol operates over both primary and secondary networks. Each network will have a designated PTP leader clock; usually this will be the same device on both networks. If this is not the case (e.g. if a non-redundant device is designated Preferred Leader) then one device will bridge the clock synchronization information from the primary to the secondary network, ensuring that all devices derive their clock from the same source. Redundant PTP Follower clocks will synchronize their local clocks based on information from one of the networks they are connected to. In event of a failure on one network, a redundant device will continue to receive clock synchronization information over the other network.

In Dante Domains

In Dante domains, there is one Primary Leader clock, and if the domain spans IP subnets, an additional 'subnet leader' clock for each subnet, plus one or more boundary clocks for each subnet. The subnet leader may also be a boundary clock for its own subnet.

Boundary clocks use PTP v2 (IEEE 1588-2008) for unicast clocking between subnets. Boundary clocks can be manually or automatically specified using the DDM web interface.

Each Dante domain will use its own individual clock domain, unless media sharing between domains is configured, in which case all domains in the shared media group share the same clock domain.

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