A CCecho option can only be seen in a segment that is received in the SYN-SENT or the SYN-SENT* state and has the SYN and the ACK flags set.
The CCecho value needs to be checked against the CCsent value stored in the routing cache for that host. This means that the destination host has acknowledged the correct connection request and is using T/TCP. State processing in this situation can be seen from the code in appendix A.2.7.2. The TAO cache for this host is updated since the TAO test has passed.
If there is data in the SYNACK we delay our acknowledgement. If not, and there is no FIN, that means that the server is forcing a 3-Way Handshake and we need to resend our FIN.
If there is no CCecho option in the SYNACK then the destination host is not using T/TCP and processing falls back onto normal TCP/IP processing.