return to the Quality of Service (QoS) Parameters
The TRANSPORT_PRIORITY QoS policy allows the application to take advantage of transports capable of sending messages with different priorities.
This policy is considered a hint. The policy depends on the ability of the underlying transports to set a priority on the messages they send. Any value within the range of a 32-Bit signed integer may be chosen; higher values indicate higher priority. However, any further interpretation of this policy is specific to a particular transport and a particular implementation of the Service. For example, a particular transport is permitted to treat a range of priority values as equivalent to one another. It is expected that during transport configuration the application would provide a mapping between the values of the TRANSPORT_PRIORITY set on DataWriter and the values meaningful to each transport. This mapping would then be used by the infrastructure when propagating the data written by the DataWriter.
Source: DDS 1.4 Spec