3.1.6.3 Retry Timer

When the retry timer elapses without having been canceled, and the associated packet was marked as reliable, the TRANS_USERDATA_HEADER prefixed message SHOULD be resent, and the retry timer SHOULD then be scheduled for the next period. It is recommended that the retry period start at 2.5 RTT + 100 ms and that there be linear backoff for the second and third retries, exponential backoff for subsequent retries 4 through 8, and an overall cap at 5 seconds and 10 retries.

If the maximum number of retries has already been attempted when the timer expires, the connection SHOULD be considered as lost. All other in-progress sends SHOULD be discarded, and the upper layer SHOULD be informed of the disconnection.

When the retry timer elapses without having been canceled, and the associated packet was not marked as reliable, the packet's sequence ID SHOULD be remembered as requiring a send mask to be used in future transmissions.