Web Performance: SPDY Protocol and the Foundation of HTTP/2

The Limitations of HTTP/1.1

HTTP/1.1 (standardized in 1997) is blocking page speed in 2012. It limits browsers to a maximum of 6 concurrent TCP connections per domain, and only allows one request per connection at a time (Head-of-Line Blocking).

To optimize load times, web developers hack layouts: combining images into sprites, splitting assets across domains, and minifying files.

Google's SPDY protocol addresses these issues natively.

How SPDY Optimizes Performance

SPDY does not replace HTTP; it acts as a session layer on top of TCP:

• ◆Multiplexing: Executing concurrent requests and responses over a single TCP connection.
• ◆Header Compression: Reducing header sizes to minimize network payloads.
• ◆Server Push: Allowing the server to push assets (like CSS files) to the client cache before they are requested, reducing round-trips.