If a port is using the SETG output as its timing reference, the port transmits the SSM corresponding to the QL of the SETG.
On the port that is selected as the reference for the SETG, the port transmits the DNU/DUS value in the SSM/ESMC.
If a BITS port is selected as the reference for the SETG, both BITS ports transmit DNU/DUS value.
An Ethernet port with a copper SFP always transmits DNU/DUS when SSM is enabled on the port. When SSM is enabled on a copper-based RJ45 Ethernet port, DNU/DUS is transmitted if the port phy-tx-clock is not configured as master. When SSM is enabled on a copper-based RJ45 Ethernet port and the port phy-tx-clock is configured as master, the port transmits the SSM value corresponding to the determined by the SSU.