In the early days when there were some dozen computers machine on the network, it was done individually but now as we have looked that there are millions of computers on the internet so how can we determine the number of computers connected to the internet. This is perform through probing the Internet. Now an automated tool is needed that tests to see whether the given computer is online or offline.

We see that 5 data packets of 64 bytes are sent to Google.com and 5 data packets are received. We see that ping has also shown some additional information such the IP addresses of sears.com, the sequence of packets and the times of transmission called as the round-trip time, as there is no packet loss so it seems that Google.com is connected to the internet.

PROBLEM WITH 'PING':

Ping, as a tool looks like to be simplistic. Now look what are the causes attached with ping. If ping does not view any responses from host machine it can not tell the reason of cause. Because one of the following reasons happen but ping will not specify the reason.

• Remote computer may have a problem.
• Local computer may have a problem.
• Ping sometimes removed because of congestion.

Some computers or networks reject the ping messages. They do this to avoid removal of service of flooding attack. Inspite of these causes ping is still heavily used as a diagnostic tool. Network administrators need ping as soon as they learn about the failure.