per comments, add a better hint about what %D/%T measure / do not measure
to the server. Only version 0 cookies are fully supported.</td></tr>
<tr><td><code>%D</code></td>
- <td>The time taken to serve the request, in microseconds.</td></tr>
+ <td>The time taken to serve the request, in microseconds. See %T for details.</td></tr>
<tr><td><code>%{<var>VARNAME</var>}e</code></td>
<td>The contents of the environment variable
</td></tr>
<tr><td><code>%T</code></td>
- <td>The time taken to serve the request, in seconds.</td></tr>
+ <td>The time taken to serve the request, in seconds. The time measured
+ begins when the first line of the HTTP request is read from the host
+ operating system by by the HTTP server and ends when the last byte of
+ the response is written by the HTTP server to the host operating system.
+ <p> The time measured does <em>not</em> include any of the following:
+ <ul>
+ <li> Time spent in TCP or TLS handshakes.</li>
+ <li> The time before a webserver thread is able to read the first
+ line of the request.</li>
+ <li> Delays in the operating system putting the response data out
+ onto the network.</li>
+ <li> Time taken for the response to arrive at the client host.</li>
+ <li> Time taken for the the useragent to read and process the
+ response.</li>
+ </ul></p>
+ </td></tr>
<tr><td><code>%{<var>UNIT</var>}T</code></td>
<td>The time taken to serve the request, in a time unit given by
