DEPLOYABILITY

Question 1

If a SYN packet with TCP Fast Open option set does not elicit a response within the timeout period

Answer 1

TFO falls back on a regular TCP 3WHS and connectivity with the server is not lost.

Question 2

If a SYN packet with TCP Fast Open option set does not elicit a response within the timeout period

Answer 2

The client also caches the RTT to the
server in its cookie cache and sets the SYN retransmit timeout to 1.5 × RTT, thereby reducing the ordinarily longer SYN timeout.

Question 3

If a SYN packet with TCP Fast Open option set does not elicit a response within the timeout period

Answer 3

If TFO fails repeatedly to a given server, the

client remembers the server’s IP address and disables TFO for that server in the future.