When we were developing SPDY, we wanted to know if SPDY was always faster or just sometimes faster than HTTP. The following chart is what convinced us that SPDY is indeed almost always faster. I didn’t publish this at that time because I didn’t like looking at web performance as a single number. “Is it faster” includes many variables, such as the network simulated (bandwidth & latency), the packet loss rate, the content chosen, and the measurement (total PLT, first PLT, second PLT, or time-to-first-render). You’d really want a whole stack of these charts, rather than just a single combination.
What I like about this chart is how easy it is to compare two protocols. If the two protocols are identical in performance, all points would be on the midline (red). If one protocol is slower, then the points will fall closer to that axis.
Notes about this test:
- Used a static copy of the Alexa Top-300 websites (excluded porn sites), full content, unchanged
- Simulated 2Mbps download, 386Kbps upload, 100ms RTT, 0% packet loss
- No SSL
- The average speedup was ~40% on this test
- This test predates CWND changes in the kernel
- Server was linux, client was chrome on Windows 7