3.1.2.5 Retry Timer

The Retry Timer is used to track when a message is considered to have been dropped and either needs to be retried or causes a send mask to be sent. The recommended values are for the first retry to be 2.5 round-trip time (RTT) plus the delayed acknowledgment (ACK) time-out (nominally 100 milliseconds). It is also recommended that there be linear backoff for the second and third retries, exponential backoff for the fourth through the eighth retries, and an overall cap at 5 seconds and 10 retries.