35.1 Best-effort Delivery Model

By default, Connext uses the best-effort delivery model: there is no effort spent ensuring in-order delivery or resending lost DDS samples. Best-effort DataReaders ignore lost DDS samples in favor of the latest DDS sample. Your application is only notified if it does not receive a new DDS sample within a certain time period (set in the 59.7 DEADLINE QosPolicy).

The best-effort delivery model is best for time-critical information that is sent continuously. For instance, consider a DataWriter for the value of a sensor device (such as a the pressure inside a tank), and assume the DataWriter sends DDS samples continuously. In this situation, a DataReader for this Topic is only interested in having the latest pressure reading available—older DDS samples are obsolete.