Ping: The Network Troubleshooter's Favorite Tool

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Did you know that Internet troubleshooting techniques borrow important terminology and processes from unrelated technologies? We've all seen old war movies in which submarine crews use - "sonar" - to sense the location of other subs or underwater objects.

Modern sonar sets work by driving a powerful speaker with a loud - "ringing" - pulse that sends shock waves radiating outward at the speed of sound. When those waves strike a nearby object, some of their energy is reflected back. An array of sensitive, directional microphones mounted back on the original submarine can hear the reflected sound waves and, by measuring the time interval between the outgoing sound and the detected reflection, can also be used to estimate the distance between underwater objects. Because reflected sound waves will strike some of the receiving microphones sooner than others, the received time intervals can even be used to estimate the direction from which each reflection is received. Thus, - "sonar" - becomes the - "eyes and ears" - or primary - "sensors" - through which the submarine crew learns of their underwater surroundings and avoids trouble.

Submarine crewmembers report that they can always hear the sound pulses emanating from the sonar equipment. They often use the word - "Ping" - to describe the penetrating, ringing sound, and once a crewmember becomes accustomed to it, the sound of a - "ping" - can bring a sense of comfort and well-being, as if it could reassure the entire crew that the outside world is constantly being assessed and understood.

The world of computer networking and internetworking also uses a tool like this. It allows one computer to generate a pulse-like - "signal" - message that can be - "bounced" - back from some other computer, router, or other piece of networking equipment. The official name of this network diagnostic tool is - ICMP Echo Request / Reply (where - ICMP - stands for - "Internet Control Message Protocol"), but the analogy with submarine sonar is so strong that it has become universally known by it's informal nickname - "Ping".

Every modern computer operating system includes some implementation of the - "ping" - utility.

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