A ping is a type of message that is transmitted across a network from one system to another, usually between a server host and connected user systems. Though different types of messages can potentially be used, the most common type of signal sent for this purpose has been an Internet Control Message Protocol (ICMP) echo request packet. This is basically a signal with little real data contained in it, and serves primarily to transmit to a connected user and then generate an “echo” signal. A ping consists of this process of sending out an ICMP echo request and then receiving the echo.
The term “ping” was initially used when this type of utility was first created in 1983, and was taken from the term used to describe the signal sent out using sonar technology. Active sonar uses generated sound waves, often called pings, which are emitted from a central location and then bounce off of objects and return as an echo. A computer ping utility uses a similar approach for analyzing connectivity of various systems on a network. The server host or other computer on a network, such as a local area network (LAN) or the Internet, sends out an ICMP echo request packet to other systems, which then transmit an echo back to the source.
This entire process is timed, often by including a time stamp in the original ICMP signal that is then compared to the time when the echo reaches the source. Once a ping is issued by a server host or similar system, servers and routers are required, through industry standards, to issue an echo packet in response. Numerous pings can be sent to generate an accurate measurement of how long a signal takes to move between the two systems, as well as gauge any potential signal loss. The information displayed after a ping test will usually include the minimum time for transmission, the average time, the longest time, and any standard deviation between these results. Any loss in signal will typically be indicated as well.
While the use of an ICMP echo request ping was quite standard during early development of the Internet and corporate networks, it became less prevalent in the early 21st century. Pings can be used to create a denial of service attack on a server, by flooding the system with echo requests, and malicious software can use pings to find systems for infection. A number of Internet service providers (ISPs) have blocked echo request messages, and so other methods are often used to evaluate network connectivity. Online video games, for example, often measure ping responses using data transmitted during game play, and then display this information as latency for users to evaluate their connectivity.
