Curl - расширенная проверка времени ответа сайта

# vi curl-format.txt
    time_namelookup:  %{time_namelookup}s\n
       time_connect:  %{time_connect}s\n
    time_appconnect:  %{time_appconnect}s\n
   time_pretransfer:  %{time_pretransfer}s\n
      time_redirect:  %{time_redirect}s\n
 time_starttransfer:  %{time_starttransfer}s\n
                    ----------\n
         time_total:  %{time_total}s\n

Проверка ответа сайта с VPS сервера:

#  curl -w "@curl-format.txt" -o /dev/null -s 2ip.ru
    time_namelookup:  0.010397s
       time_connect:  0.010914s
    time_appconnect:  0.000000s
   time_pretransfer:  0.010946s
      time_redirect:  0.000000s
 time_starttransfer:  0.011244s
                    ----------
         time_total:  0.011268s

Что означают параметры:

time_appconnect - The time, in seconds, it took from the start until the SSL/SSH/etc connect/handshake to the remote host was completed.
time_connect - The time, in seconds, it took from the start until the TCP connect to the remote host (or proxy) was completed.
time_namelookup - The time, in seconds, it took from the start until the name resolving was completed.
time_pretransfer - The time, in seconds, it took from the start until the file transfer was just about to begin. This includes all pre- transfer commands and negotiations that are specific to the particular protocol(s) involved. 
time_redirect - The time, in seconds, it took for all redirection steps including name lookup, connect, pretransfer and transfer before the final transaction was started. time_redirect shows the complete execution time for multiple redirections.
time_starttransfer - The time, in seconds, it took from the start until the first byte was just about to be transferred. This includes   time_pretransfer and also the time the server needed to calculate the result. 
time_total -  The total time, in seconds, that the full operation lasted.

Исходящие запросы должны быть через ipv4 и использовать ДНС сервера на ipv4.