I know that 3 way handshake is used. But, the first time a connection is established and there is no RTT data, what is the expected time before sending another packet?

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How does the client know how long to wait for the first confirmation? Is there any calculation or previous procedure?

PS: English is not my native language: :P

1 Answer 1


Before SYN-ACK is received from the destination, the socket is still in the SYN-SENT state. The timeout used and possible SYN retries depend on the initial connection timeout, not the retransmission timeout. The RTO is only used for an already established socket.

  • And this initial connection timeout is standard or is there any way to calculate it?
    – toborochi
    Nov 24, 2019 at 14:02
  • @toborochi That initial timeout is system/implementation specific. I'm not aware of any standard. There's no way to calculate it because you have no data.
    – Zac67
    Nov 24, 2019 at 14:19
  • Thanks dude. You will not have any link to know the value of each system/implementation or some kind of reference.?
    – toborochi
    Nov 25, 2019 at 1:34

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