This topic describes the metrics for site monitoring and the detection process.

The following table describes the metrics for site monitoring based on HTTP. The metrics for site monitoring based on other protocols, such as Simple Mail Transfer Protocol (SMTP), FTP, Transmission Control Protocol (TCP), User Datagram Protocol (UDP), are similar to those described in the following table.
Metric Unit Description
total_time ms The total time spent on detection, which includes the value of the redirect_time metric.
http_dns_time ms The time spent on resolving the domain name into an IP address.
curl_connect_time ms The time spent on setting up the curl connection after the detection request is sent, which includes the value of the http_dns_time metric.
tcp_connect_time ms The time spent on setting up the TCP connection after the detection request is sent, which includes the value of the http_dns_time metric.
ssl_connect_time ms The time spent on SSL-based authentication after the detection request is sent.
curl_pretransfer_time ms The time spent on writing the HTTP request after the detection request is sent.
curl_starttransfer_time ms The time spent on receiving the first byte of the response returned by the web server after the detection request is sent.
http_connect_time ms The time spent on setting up the HTTP connection. The time is calculated by deducting the value of the http_dns_time metric from the value of the curl_pretransfer_time metirc.
http_download_time ms If the version of the detection point is earlier than V1.8, the value of this metric is 0. If the version of the detection point is V1.8 or later, the value of this metric indicates the time spent on reading the first 64 bytes of the HTTP response message. If the HTTP response message is encrypted, the time includes that spent on decryption.
http_download_size byte The size of the HTTP response message. If the HTTP response message contains the Content-Length header, the value of this metric indicates the size of the HTTP response message. Otherwise, the value of this metric indicates the bytes that are read.
http_download_speed byte/s The network speed at which the HTTP response is downloaded.
redirect_time ms The time spent on sending the first redirected request after the detection request is sent.
redirect_count count The number of redirects.
Note If redirects occur during the detection, the metrics apply to the last detection.