device that captures and interprets the network traffic
between two or more connected computer systems. The traffic
can then be decoded so that it is possible to see what
processes are occurring.
By examining the flow of traffic, protocol analysers can be
used to find out where problems (such as bottlenecks or the
failure of a network device) are on a LAN.
Advanced protocol analysers can also provide statistics on
the traffic that can help to identify trends that may in
future lead to further problems with the network.