What is QUIC?

Since its inception, the Internet has seen countless improvements. From the introduction of encryption via the SSL and TLS protocols to faster and more reliable connections via HTTP/2, the Internet we know now is nothing like it was back in the 1990s when it first opened to the public. It is now more secure, quick, and reliable than ever. Fortunately for us, though, the improvements have not stopped coming. This article will explore one of the newest transport layer protocols: QUIC.

Developed by Google, QUIC is the newest transport layer protocol, designed to improve upon HTTP/2 and overcome the limitations posed by TCP and UDP. QUIC itself stands for Quick UDP Internet Connection, and the name could not be more perfect. It exists to combine the best parts from both TCP with TLS encryption and UDP to make the ultimate transport layer protocol.

Naturally, taking the best parts of those things means leaving their worst behind, and that is what separates QUIC from the other protocols. Here is what QUIC does better than TCP and UDP and why people consider it the future.

• Shorter Connection Times - During a typical TCP connection, a client and server must perform a TLS handshake, ensuring the connection between them is secure and encrypted. That usually takes three round-trips (RTT) before it is established. On top of that, when data is transferred over TCP, even more checks and steps are made because it ensures packet delivery and order of arrival. To us, those processes take mere seconds, but that is a long time in networking terms;
  • QUIC aims to shorten those connection times. Firstly, the encryption handshake is reduced to a single round-trip(1-RTT), dramatically shortening the time it takes for the browser and server to confirm the connection is secure;
  • Secondly, for repeat connections, that handshake is done even faster (0-RTT), meaning QUIC can skip the entire thing and continue from where it left off;
• Eliminating Head-on-Line Blocking - Head-on-Line blocking can occur during a typical TCP connection. This happens when a packet is lost, and all subsequent packets in the connection must wait for it to be retransmitted. Imagine a store with a single cashier and a line of people, with the person at the front fumbling for change. The line cannot move until that first packet is finished. QUIC avoids this by using independent data streams, so if a packet is lost, it only affects the stream to which it belongs. Just like when you have multiple cashiers in a store. HTTP/2 tried to solve this by introducing Multiplexing, but it could still fall victim to Head-on-Line blocking;
• Security - QUIC is inherently encrypted, meaning the connection does not require an HTTPS layer to be secure. By default, QUIC connections utilize TLS 1.3. That is how the TLS handshake is reduced to a single round-trip;
• Better Connection Migration - QUIC can maintain a connection even if the client's IP changes. This is perfect for mobile device users or switching from Wi-Fi to LAN. QUIC can prove to the server that the client is still the same and resume the connection from where they got interrupted. With TCP, such a thing is not possible, as the connection is terminated when the IP changes;
• Congestion Control - QUIC can utilize different "pluggable" congestion control algorithms as long as they are added to the Application Layer. Since they are "pluggable," they will activate when necessary without manual intervention. Additionally, different application connections can use separate algorithms independent of one another.

QUIC has a lot of advantages over HTTP/2 and TCP, and while it is still relatively new, all modern browsers and operating systems have support for it. Naturally, this does not mean it has completely replaced the more traditional HTTP/2 over TCP connection since that is still the default across the Internet. However, it is steadily becoming more and more popular, and rightfully so. Our FastCloud Extra packages all support QUIC for the best performance possible.

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