• Windows Phone Area
• On July 15, 2016

TCP Fast Open can speed up the page loading up to 40%

TCP Fast Open is among the new experimental features in Microsoft Edge for Windows 10 and Windows 10 Mobile. The feature is currently available only for Windows Insiders on the Fast & Slow Rings, but Microsoft will make it available for the general public after the Anniversary Update in August.

TCP Fast Open is not enabled by default, but you can turn it on manually by typing ‘about:flags’ in the address bar. Then scroll down to the Networking section and mark ‘Enable TCP Fast Open’. Restart the browser and if the server supports TCP Fast Open you should see an improvement in the page loading. Keep in mind that not all websites support sending a ‘Fast Open Cookie’ and you may not even notice an improvement for certain pages. TCP Fast Open currently works in Microsoft Edge version 14.14361 or higher.

From the Microsoft Blog:

The next improvement comes from the TCP Fast Open procedure, defined in RFC 7413. The RFC defines a new TCP option, containing a “Fast Open Cookie.” When a “Fast Open capable” client connects to a server for the first time, it inserts an empty cookie in the initial TCP SYN message, prompting the server to send back a valid cookie in the response. For the subsequent connections, the client copies the cookie in the TCP SYN message, and then sends data immediately. If the server recognizes the data as valid, it will accept the data and pass them to the application. When TCP Fast Open is enabled, data can be sent before the connection complete, and the responses will arrive immediately. When we combine TCP Fast Open and TLS False Start, the key negotiation is performed simultaneously with the initial TCP handshake. There is just 1-RTT before the HTTP traffic starts.
Read more