DNS (short for Domain Name System) is a distributed Internet directory service. DNS is used to translate between domain names and IP addresses, and to control Internet email delivery. Domain names are alphabetic as they're easier to remember. The Internet however, is based on IP addresses. Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address. For example, the domain name www.somesite.com might translate to 198.105.105.7. DNS is a globally distributed system consisting of thousands of servers sharing information.

If DNS fails, websites cannot be found and email delivery stops. The speed of Web addresses look-up is important to the DNS system as a whole. The monitoring centers measure the speed of looking up your Web server's address using the DNS system.

DNS lookup shows the time needed to find your site's virtual domain name in a DNS database and resolve it to your Web server's IP address (in msec.).

Connect Time is the measure of time needed setting up a network connection to your Web server over HTTP (in msec.).

Host Ping is the service that checks your server's IP address for accessibility. The monitoring center sends an ICMP packet to your server's echo port and listens for a response. When the echoed packet is received from the host server, it is compared with the original packet sent. If the data matches, the host server is considered accessible.

Time required downloading a 20 Kb file from your server (in msec.). Download time shows how long it takes to retrieve the requested file and send it over the Internet. The monitoring center downloads a 512- byte portion of your page. The download has a "no-cache" cache-control directive to exclude the caching effect, and therefore measure the exact loading time.

This parameter indicates the number of time-outs, i.e.the number of times your server failed to respond. This includes all the time-outs recorded by all the Site Monitoring tests within the selected period.

This is the total time that your server had the Alert status (in minutes). This number is a grand total of all the intervals your server was not reachable by all the tests conducted. If several tests failed round about the same time, the interval includes the earliest and the latest time your server was not working. For example, if the ping test failed at 11.25 a.m. then was successful again at 12.20 a.m. , and the test connection over HTTP also failed at 11.30 a.m. and then was back at 12.21 a.m. , the 'Time on Error' report would reflect the interval between 11.25 a.m. and 12.21 a.m.

Score is a mark for certain parameter of a service

Rating is an average value for the number of scores.

Score and Rating are calculated with the help of the following formula:

Score = ROUND(10-(Ps/((Pmax-Pmin)/10))),

where Ps is the index for the given site, Pmax and Pmin - maximum and minimum values for all sites subscribed for the Monitoring service. The numbers are rounded to integer.