Google, Inc. Google, Inc. Google, Inc. Google, Inc. TCP Fast Open (TFO) allows data to be carried in the SYN and SYN-ACK packets and consumed by the receiving end during the initial connection handshake, thus providing a saving of up to one full round trip time (RTT) compared to standard TCP requiring a three-way handshake (3WHS) to complete before data can be exchanged. Terminology