tl;dr

★★★★☆ - Highly recommended! But, a bit replaceable with other books or articles.

This book provides valuable practical handson examples and clear explanations of the progress of HTTP protocols. It also offers a clear comparison between HTTP 2 and HTTP 1.

The link about this book is Learning HTTP/2.

Impressions

• I appreciated the book’s inclusion of the history of HTTP protocols.
  • What I value most in technical books like this is actually the inclusion of historical context. While I can learn about the specifications and features of technologies through videos and articles in the internet, understanding the history of a technology is something I can only achieve through books.
  • It included the progress of HTTP protocol from versions 0.9, 1.0 and 1.1 to 2.0
• I found the detailed explanations about HTTP/2 headers and accompanying examples to be highly valuable.
• The book was super easy to read. Despite of my slower reading pace, I managed to finish it within a few days.
• I highly recommend this book to students who are students looking for a job or engineers who may be unaware or unconsciously using HTTP 2.
  • I, too, didn’t know much about HTTP2 but now I’ve gained some confidence in the subject.
• I intend to revisit this book serveral more times later!
  • Through this book, I was able to become somewhat familiar with HTTP 2, but honestly speaking, I still don’t fully understand it.

Summaries

The history of HTTP protocols

1. The birth of HTTP 0.9
   • A simple protocol with limited features
   • Only supports the GET method
   • No headers are included.
   • Desipite its poor features, HTTP 0.9 was widely used.
2. The birth of HTTP 1.0
   • Developed a few years after HTTP 0.9.
   • Introduced significant enhancements compared to HTTP0.9, including headers, response codes, redirects, errors, conditional requests, contents encoding and compressions and various methods
   • Cannot keep connections.
   • The Host headers is optional, not required.
   • Limited caching capabilities.
3. The birth of HTTP 1.1
   • Dominated web communications for over 20 years.
   • Allows to keep connections using the Connection directive.
   • Introduction of the Host header enables virtual hosting, serving multiple web services with a single IP address.
   • The Upgrade header allows negotiation for higher-level protocols.
   • Improved caching features
4. The birth of HTTP 2.0
   • Multiplexing - Enables the use of a single TCP connection for multiple requests to the same destination with the same domain name and certificate.
   • Framing - The unit of data transmitted. Data transmission occurs in framed units.
   • Header compression - Optimizes transmitting similar headers by compressing them using HPACK.

Transition from HTTP 1 to HTTP 2

When transitioning our services from HTTP 1 to HTTP 2, we need to consider certain cases where performance optimization tips for HTTP 1 may deteriorate the performances in HTTP 2.

• A pattern integrating files for fewer requests - In HTTP 2, there’s no need to integrate files because we can request each files concurrently even with just 1 TCP connection.
• A pattern using domain sharding for increased concurrent connections - In HTTP 2, typically, a single TCP connection is sufficient, making the pattern of domain sharding less necessary.
• A pattern using specific domains without HTTP cookies - In HTTP 2 those specific domains aren’t as efficient because HPACK effectively compresses HTTP Headers well.
• Spriting which means integrating multiple images into a huge image and then cut it in-place in the memory - In HTTP 2, multiple contents can be requested concurrently, reducing the need for spriting.

Headers which are used in HTTP 2

The content related to organizing headers in HTTP 2 is so extensive that I decided to skip this part in this article.

Miscellaneous

Technically, TLS is not required but recommend to use TLS.