Possible changes to grading

[pmeenan]

The CDN change is now live and I'm working on the first byte logic (at which point the JS/CSS will be demoted). Right now I'm thinking that the grading for the first byte will look something like this:

Base time = 3 * rtt to server (allow for DNS + socket connect + http request)
If TTFB <= base + 100ms then it get's an A
and then deduct a grade for every 100ms beyond that

SSL would also be accounted for and the extra round trips would be factored in for a https request.

That way the connection latency will not be a factor and it will purely be a measurement of back-end processing time (<= 100ms = really good). It will also penalize for redirects.

The end result for the default DSL connection profile would be:

TTFB <= 250ms = A
250ms - 350ms = B
350ms - 450ms = C
450ms - 550ms = D
> 550ms = F

The actual times will be slightly more generous because these times don't include the additional latency to get to the actual server which will be included in the actual grading (using the socket connect time).