TCP timeout after receiving a RST

Question

I am trying to understand an issue between an NFS client and Server. When the server application crashes, the kernel sends a RST packet to client to which the client closes the old connection and initiates a new one by sending a SYN. Since the application is not ready at this point, the server again responds with a [RST, ACK]. After this, the client only sends SYN packets every 15 seconds.

I wanted to understand where this 15 seconds timeout is coming from? Is this something that TCP enforces or is it an application timeout that is totally application specific?

Thanks in advance!!!

Answer 1

Since TCP does not initiate a new connection attempt if a connection fails (as it does here, assuming the RST makes it back to the TCP stack), that's an application timer.

TCP will only re'send a SYN, if it doesn't get any reply to it, normally doubling the time between each attempt, up to a fixed limit of retries.