[hdhzy]

Oh I wasn't clear - I meant that for the same connection headers are not sent for every page but just references for previous values (see [0]). The initial page load is a different matter but that's part of the cost/risk analysis if you need CSP or HPKP (I agree it's not necessary and very easy to mess up).

[0]: https://http2.github.io/http2-spec/compression.html#indexed....

> When you take into account that you can only send 10 packets down the first response (in almost all cases today) due to TCP congestion window specifications (google: CWND), they get more expensive as a percentage of what you can send. It may be that you can't send enough of the page to render, or the browser isn't getting to a critical stylesheet link until the second wave of packets after the ACK. This can greatly affect load times.

I wonder how much of the page can be rendered in 10 packets...

Do you send Link preload headers?

[DamonHD]

I explicitly try to ensure that for my sites the first 10kB sent (so less than 10 packets typically) is enough to render all the information above the fold. Anything essential should make it out in the first 2 packets for old TCP slow-start rules. (Lipstick and ads can arrive later, once the user is happy reading or whatever, IMHO.) Has been my policy since about the mid '90s!