Packet InterNet Groper

(ping, probably originally contrived to

match submariners' term for the sound of a returned sonar

pulse) A program used to test reachability of destinations by

sending them one, or repeated, {ICMP} echo requests and

waiting for replies. Since ping works at the {IP} level its

server-side is often implemented entirely within the

{operating system} {kernel} and is thus pretty much the lowest

level test of whether a remote host is alive. Ping will often

respond even when higher level, {TCP}-based services cannot.

The term is also used as a verb: "Ping host X to see if it is

up."

The {Unix} command "ping" can be used to do this manually and

to measure round-trip delays.

The funniest use of "ping" was described in January 1991 by

Steve Hayman on the {Usenet} group comp.sys.next. He was

trying to isolate a faulty cable segment on a {TCP/IP}

{Ethernet} hooked up to a {NeXT} machine, and got tired of

having to run back to his console after each cabling tweak to

see if the ping packets were getting through. So he used the

sound-recording feature on the NeXT, then wrote a {script}

that repeatedly invoked ping, listened for an echo, and played

back the recording on each returned packet. Result? A

program that caused the machine to repeat, over and over,

"Ping ... ping ... ping ..." as long as the network was up.

He turned the volume to maximum, ferreted through the building

with one ear cocked, and found a faulty tee connector in no

time.

See also {ACK}, {ENQ}, {traceroute}, {spray}.

{Unix manual page}: ping(8).

(1995-03-28)