High-resolution network monitoring with ping
Stopwatch Timing
© Lead Image © Sergey-Jarochkin, 123RF.com
The Pinger network monitoring tool uses ping to look for switches and estimate cable lengths.
The ping command is used to determine whether a particular host on the network is accessible and to reveal the packet turnaround time, usually known as the round trip time (RTT). The RTT of a ping request is longer when packets need to pass through network devices or long stretches of wire. In this article, I develop a utility that uses the ping RTT to track down switches and transparent bridges and determine cable lengths.
Known Pings
Common ping programs under Linux, like that from the iputils package [1], create RTT statistics with a mean value. However, the average of thousands of pings can vary so greatly that it is impossible to achieve high resolution within the framework of a few microseconds to nanoseconds.
These subtleties, however, are interesting when exploring the network and the equipment in it. Expert evaluation, that is, filtering out RTT outliers before computing an average, can return a resolution of less than one microsecond (1µs). Several available ping programs offer additional features that remain mostly unused, such as the ability to send a bit pattern in the ping packet to determine data rot (i.e., damage to data on the network).
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