Specifically, how are RTOs calculated?

I wanted to find out if there is more specific information on how RTOs are calculated. Based on content found on ExtraHop’s website, when the sender is missing “too many” or an “excessive” amount of acknowledgements, a RTO is triggered.

Can someone provide more specifics on how many failed acknowledgements to a sender would trigger a RTO?



“A retransmission timeout (RTO), on the other hand, is quite a different beast. An RTO occurs when the sender is missing too many acknowledgments and decides to take a time out and stop sending altogether. After some amount of time, usually at least one second, the sender cautiously starts sending again, testing the waters with just one packet at first, then two packets, and so on.”

This is really dependent on several things. But if I remember right you can adjust this in windows and probably linux. Here is the registry key value for windows 7 . cpMaxConnectRetransmissions : Defines the number of retransmissions before timing a connection out. Defaults to 5. But this may change per operating system or if there is a patch. And I believe that the default value is 3 seconds. but again this can be adjusted based on operating system.
I am not sure how Extrahop is measuring this but assume it is off the default value of 3 seconds.

This might help a little more.