What is HTTP/3 and How it Works?

HTTP/3 is the next-generation transport protocol on the Internet, aiming to provide faster, more secure, and more reliable network communication. It is based on the QUIC (Quick UDP Internet Connections) protocol, which brings numerous innovations and advantages.

Development of HTTP Protocol

The development of the HTTP protocol has gone through several versions and improvements. Here is a summary of the major milestones in the evolution of the HTTP protocol:

HTTP/0.9: Released in 1991, it was the earliest version of HTTP. It was a simple protocol that only supported the GET method for retrieving HTML documents. It lacked headers, status codes, and advanced features.
HTTP/1.0: Released in 1996, it introduced significant enhancements. It added support for additional request methods (such as POST, HEAD, etc.), introduced headers for requests and responses, and supported status codes and error handling. HTTP/1.0 also introduced persistent connections, allowing multiple requests and responses on a single connection.
HTTP/1.1: Released in 1999, it is the most widely used version of HTTP. It introduced features like pipelining support, cache control, virtual hosting, and chunked transfer encoding. HTTP/1.1 significantly improved performance and efficiency.
SPDY: SPDY was an experimental protocol developed by Google to improve web page loading speed. It introduced features like multiplexing, header compression, and server push. Some of SPDY's features were later incorporated into the HTTP/2 standard.
HTTP/2: Released in 2015, it was a major improvement over HTTP/1.1. It introduced a binary protocol, communication using frames, support for multiplexing, and the ability to send multiple requests and responses on a single connection. HTTP/2 also introduced header compression and server push, further enhancing performance and efficiency.
HTTP/3: HTTP/3 is the next-generation HTTP protocol based on the QUIC (Quick UDP Internet Connections) protocol. QUIC is a UDP-based transport protocol designed to provide faster connection establishment and data transfer. HTTP/3 leverages the features of QUIC to offer faster loading speeds, improved security, and adaptability. HTTP/3 is still under development but has started gaining support in some browsers and servers.

These versions and improvements have allowed the HTTP protocol to continuously adapt and meet the evolving needs of the internet, providing better performance, security, and user experience. The introduction of HTTP/2 and HTTP/3, in particular, has brought significant performance improvements and new features, driving the development and innovation of the web.

What is HTTP/3?

HTTP/3 is the latest version of the Hypertext Transfer Protocol (HTTP), which is the foundation of any data exchange on the Internet. HTTP/3 introduces several important improvements and optimizations over its predecessor, HTTP/2, aimed at enhancing webpage loading speed and overall network performance.

A significant change in HTTP/3 is that it no longer uses the Transmission Control Protocol (TCP) as its underlying transport protocol. Instead, it has switched to Quick UDP Internet Connections (QUIC). QUIC is a transport protocol based on User Datagram Protocol (UDP), combining the reliability of TCP with the speed of UDP. QUIC also introduces new features such as built-in Transport Layer Security (TLS) encryption, as well as improved congestion control and error recovery mechanisms.

One of the main advantages of using QUIC is that it can reduce network latency. In TCP, establishing a new connection requires multiple round-trip communications, which increases network latency. In contrast, QUIC can establish a connection with a single round-trip, thereby reducing latency. Furthermore, QUIC supports multiplexing, meaning multiple requests can be sent in parallel over a single connection, further enhancing network performance.

quic over http/3

However, HTTP/3 also faces some challenges. As it is based on UDP, some network devices may block or limit UDP traffic, potentially affecting the deployment and performance of HTTP/3. Additionally, the implementation and optimization of HTTP/3 require more computational resources, which could increase server load.

What is New in HTTP/3?

HTTP/3 introduces several new features and improvements to provide a faster, more secure, and more reliable network communication experience. Here are some of the new features of HTTP/3:

QUIC Protocol: HTTP/3 utilizes the QUIC (Quick UDP Internet Connections) protocol as the underlying transport protocol. QUIC is a UDP-based transport protocol that offers faster connection establishment and data transmission, lower latency, and better adaptability and congestion control compared to TCP.
Fast Connection Establishment: HTTP/3 enables fast connection establishment through 0-RTT (Zero Round Trip Time) handshake. This allows clients to send data immediately on the first request if they have previously established a connection, reducing handshake latency.
Multiplexing: HTTP/3 supports multiplexing, allowing simultaneous transmission of multiple requests and responses over a single connection. This improves network utilization, reduces connection establishment and closure overhead, and enhances performance.
Low Latency: By minimizing the round trip time for connection establishment and recovery, the QUIC protocol in HTTP/3 reduces latency. This is particularly beneficial in high packet loss network environments, where HTTP/3 can maintain low latency.
Transport Layer Security: HTTP/3 incorporates Transport Layer Security (TLS), ensuring that all data is transmitted encrypted. This provides higher security and privacy protection, preventing data theft or tampering.
Congestion Control: The QUIC protocol in HTTP/3 employs advanced congestion control algorithms, adapting better to network congestion. This results in more stable transmission performance.

These new features and improvements make HTTP/3 faster in connection establishment and data transmission, lower in latency, more adaptable to network conditions, and more secure with enhanced privacy protection. HTTP/3 represents a significant innovation as the next-generation internet transport protocol.

HTTP/3 vs HTTP/2

HTTP/3 and HTTP/2 are both versions of the Hypertext Transfer Protocol, which is used to transfer data on the World Wide Web. While HTTP/2 brought significant improvements over HTTP/1.1, HTTP/3 introduces new features and optimizations. Here is a comparison of the two:

1. Transport Protocol

HTTP/2: Uses TCP (Transmission Control Protocol) as its transport protocol, which is reliable but can suffer from head-of-line (HOL) blocking, where a single lost packet can delay the transmission of subsequent packets.
HTTP/3: Uses QUIC (Quick UDP Internet Connections) as its transport protocol, which is built on top of UDP (User Datagram Protocol). QUIC is designed to minimize latency and eliminate head-of-line blocking, resulting in faster and more efficient data transfer.

2. Connection Establishment

HTTP/2: Requires multiple round trips between the client and server to establish a connection, including the TCP handshake and TLS (Transport Layer Security) negotiation.
HTTP/3: QUIC allows for faster connection establishment by combining the connection and security handshakes into a single round trip, reducing latency.

3. Multiplexing

HTTP/2: Supports multiplexing, allowing multiple requests and responses to be sent over a single TCP connection simultaneously, reducing the need for multiple connections and improving performance.
HTTP/3: Also supports multiplexing but does so over QUIC, which eliminates head-of-line blocking issues and further improves performance.

4. Encryption

HTTP/2: Uses TLS for encryption, but it is not mandatory, and some connections might not be encrypted.
HTTP/3: Encryption is built into the QUIC protocol, making it mandatory for all connections, enhancing security and privacy.

5. Error Handling

HTTP/2: Errors in one stream can potentially affect other streams due to the shared TCP connection, causing performance issues.
HTTP/3: Errors are isolated to individual streams, as QUIC manages streams independently, improving error handling and reducing the impact of errors on other streams.

In summary, HTTP/3 improves upon HTTP/2 by introducing the QUIC protocol, which provides faster connection establishment, eliminates head-of-line blocking, and enhances security with mandatory encryption. These improvements are expected to result in better performance and user experience on the web.

HTTP/3 Compatibility

HTTP/3 is currently available and being implemented by various organizations and internet companies. However, it is important to note that HTTP/3 is still in the development and adoption phase. The QUIC protocol, on which HTTP/3 is based, is being standardized by the Internet Engineering Task Force (IETF).

Here is the support status for some major browsers and servers:

Browser support:

Google Chrome: HTTP/3 is supported starting from Chrome version 79.
Mozilla Firefox: HTTP/3 is supported starting from Firefox version 78.
Microsoft Edge: HTTP/3 is supported starting from Edge version 92.

Server support:

Nginx: HTTP/3 is supported starting from Nginx version 1.19.10.
Apache: Apache currently does not have official support for HTTP/3, but there are third-party modules (such as quiche) available to enable HTTP/3 support.

It is important to note that while HTTP/3 is supported, its widespread adoption and support are still ongoing. Some older versions of browsers and servers may not support HTTP/3, so it is necessary to ensure that both the client and server support the protocol when using HTTP/3.

Additionally, since HTTP/3 is based on the QUIC protocol, it requires support for the QUIC protocol in the network infrastructure (such as routers, firewalls, etc.) to function properly with HTTP/3. Over time, it is expected that support for HTTP/3 will become more widespread and mature.