Pings

Pings refer to signals or packets used to test reachability and measure latency between networked devices, and in other contexts to describe short sonar impulses used for underwater sensing. In computing, the term most often denotes a diagnostic utility that sends a brief, structured packet and waits for a reply. The common network implementation uses ICMP Echo Request and Echo Reply messages, with IPv4 defined by RFC 792 and ICMPv6 Echo Request/Reply used in IPv6. A responding host confirms it is reachable, and the time between sending the request and receiving the reply is used to calculate round-trip time. Statistics typically include the number of replies, total packets sent, and packet loss.

The ping command usually allows configuring the number of requests, payload size, and timeouts. On Windows and Unix-like systems, it reports minimum, maximum, and average round-trip times, along with a packet loss percentage. Pings are routinely used to diagnose connectivity, estimate latency to a host, identify routing issues, and infer path characteristics such as basic reachability and lag.

Limitations include that a ping test only verifies ICMP reachability, not the full suitability of a connection for specific applications. Some networks or devices block or rate-limit ICMP traffic, which can render pings misleading. Latency can be affected by intermediate devices, congestion, queuing policies, and prioritization of ICMP packets. In IPv6 networks, ICMPv6 Echo messages perform a similar role, with the same caveats.

History and naming: the ping utility was created by Mike Muuss in 1983 to model sonar ping signals, and the term has since become a standard descriptor for echo-request diagnostics. Beyond networking, a ping can also refer to a short sonar signal or a periodic heartbeat in monitoring systems to verify liveness.