TCP Deep Dive: Understanding TCP Fast Open
In today’s fast paced digital word, miliseconds count. The traditional way that TCP connections are established, known as the three-way handshake (3WHS), introduces a significant latency cost: at least one full Round-Trip Time (RTT) before any actual data can be exchanged. For applications like web browsing, where many connections are short-lived or frequently re-established, this delay can severely impact user experience. This is where TCP Fast Open (TFO) comes in. Documented in RFC 7413, TFO is an experimental TCP mechanism designed to save up to one full RTT by allowing data to be carried in the initial SYN and SYN-ACK packets of a TCP connection, enabling the receiving end to consume it during the handshake itself. ...