Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Ping is a computer network tool used to test whether a particular host is reachable across an IP network; it is also used to self test the network interface card of the computer, or as a latency test. It works by sending ICMP “echo request” packets to the target host and listening for ICMP “echo response” replies. The "echo response" is sometimes called a pong. Ping measures the round-trip time and records any packet loss, and prints when finished a statistical summary of the echo response packets received, the minimum, mean, max and in some versions the standard deviation of the round trip time.