A real-time monitor for token ring networks

The authors describe a real-time monitor for IEEE 802.5 token ring LANs (local-area networks). Unlike a protocol analyzer that first records network traffic and later disassembles packets and replays them, this monitor displays network traffic and statistics in real time. All user interaction with the monitor is controlled by pop-up menus, which select various modes. In graphic mode the monitor displays current network statistics, scroll graphs of network load, and a histogram of network packet lengths. In trace mode it displays the contents of packets in a format specified by the user. The monitor will report on all network traffic or, using user-specified pattern-matching filters, will select a subset of network traffic based on any combination of packet source address, destination address, or packet content. An alarm option provides notification when a specific event first occurs or when a repeated event deviates from a user-specified minimum or maximum frequency