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HTTP/2 notes (taken from https://www.nginx.com/wp-content/uploads/2015/09/NGINX_HTTP2_White_Paper_v4.pdf)

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http2.md

General features

HTTP/2 adds five key features:

SSL

How does HTTP/2 overcome the performance overhead imposed by SSL on HTTP/1.x? There are four key techniques:

  1. Having a single connection minimizes SSL handshaking.
  2. Headers are compressed, reducing the time needed to send them.
  3. Multiplexing means file transfers don’t wait on other requests.
  4. Files don’t need to be in-lined, concatenated, or sprited, so caching can work optimally.

When compared to a non-SSL implementation, there is still SSL performance overhead for authenticating the single connection and for encrypting and decrypting data, but this remaining overhead should be more or less offset by the performance improvements in HTTP/2.

Note: The HTTP/2 specification also includes server push, in which the server sends files listed in a page’s HTML before they’re requested