Abstract: An LAN parameter measuring instrument is provided for measuring at least one physical parameter of a wired, packet based, baseband LAN. The instrument comprises input means for providing a connection to the LAN transmission medium to enable measurements to be made while the LAN is active and voltage measuring means arranged to connect to the LAN transmission medium through said input means and operative to measure the voltage on the LAN transmission medium during inter-packet gaps. The instrument may determine the resistance of the LAN by measuring the inter-packet voltage during the injection of a known current into the transmission medium.

Abstract: The network monitoring device is provided for monitoring the activity on a network carrying message packets each of which contains source and destination addresses. The monitoring device includes a network interface for sending and receiving message packets carried on the network, and a processor for collecting and processing data from the packets received by the network interface. In order to minimize processor memory requirements for the monitoring device, only randomly selected packets detected by the network interface are processed by the processor of the device. Preferably, the monitoring device is further simplified by providing a central measurement station to analyze data collected from the randomly sampled packets. As a result, the only processing required to be done by the monitoring device is the construction of collected-data packets for transmission to the central measurement station.