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Tip

By design, the use of MQTT removes the requirement for periodic publishing of infrequently changing data whilst maintaining data integrity.

Each time an MQTT Client connects, a BIRTH message is published which contains all metrics with a current time stamp. After that initial BIRTH message, metric changes are published using DDATA messages. If there are no metric changes for a data point, the timestamp provided in the BIRTH message is a valid timestamp for that data point.


By default the MQTT messages from Transmission are sent only upon Value or Quality changes and there is no provision to resend a tag(s) at an interval if the values have not changed. 

However, MQTT Transmission has control tags that allow you to request the Edge to perform either a Node or Full Transmission refresh. This forces the Edge Node(s) to disconnect and reconnect resulting in the sending of NDEATH, NBIRTH and DBIRTH messages for Edge Node(s). 

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