Table of contents of the article:
User experience is one of the key elements for the success of any website, and loading speed is a crucial factor affecting user perception. In addition, website speed has a significant impact on search engine rankings, as search engines place more and more weight on website speed in their ranking algorithm.
To improve the speed of the website, one of the important factors to consider is the TTFB (Time To First Byte), i.e. the time elapsed between the client's request to the server and the receipt of the first response from the server. A low TTFB can help increase website loading speed and improve the user experience.
However, the connection process between client and server can be a major limitation for TTFB. TCP's three-way handshake requires three messages to establish a connection, and this process can take additional time, increasing TTFB and slowing down the website.
To overcome this problem, it was developed TCP Fast Open, a technology that allows you to reduce the time required to establish a TCP connection, improving network performance and website loading speed. By implementing TCP Fast Open, the server can send data to the client already during the handshake phase, reducing the time it takes to establish the connection and improving TTFB and website latency.
What is TCP Fast Open?
TCP Fast Open (TFO) is a network performance optimization technology of the Transmission Control Protocol (TCP) that helps reduce the time it takes to open network connections. In practice, TFO provides for the sending of critical data during the opening phase of the connection itself, without having to wait for the outcome of the three-way handshake, which normally takes place between the client and the server. This reduces connection opening delays, improving overall network performance.
Goals of the post
The goal of this post is to provide a complete overview of TCP Fast Open, explaining how the technology works, its advantages and disadvantages, and how to enable it on servers and clients. In particular, the post is aimed at those who have a basic knowledge of the TCP protocol and want to learn more about the subject, for example to improve the performance of their network or to better understand the protocol's operating mechanisms.
This post aims to have both an introductory and an implementation purpose for general users and insiders such as computer systems engineers who would like to improve the efficiency of their network, the performance of TCP/IP and improve its speed especially in a context in which you want to use the HTTP or HTTP/2 rather than HTTP3 or QUIC protocol which normally uses UDP rather than TCP connections.