yser can perform a health 1. The number of packets sent or received. check on the physical network. 2. The number of bytes sent or received. The analyser can locate problems such as faulty connectors, 3. How many of the packets were in some way erroneous, poss- improperly terminated cables or network devices operating out of ibly with a breakdown of errors by type. Data communications network measurement 61/13 Such a detailed table may be displayed without further processing, the trends in usage of the network for the management team to or stored on disc to enable subsequent analysis. Alternatively, by forecast future purchasing requirements. taking periodic samples of, say, the total number of bytes trans- mitted by each station, the monitor can display a table or histogram 61.4.3 Reporting alarm conditions showing how the relative activity of the stations on the network changes over time. The experienced user of a network monitor will be able to spot a fault or potential problem on the network merely by studying the various statistical displays. However, more effective use may be 61.4.2.2 Manipulation made of the monitor by configuring it to watch certain network parameters and raise an alarm if an invalid condition arises. Network monitors can perform a limited amount of manipulation on the statistical data before recording it. This manipulation, under the control of the user, means that the monitor can focus on specific 61.4.3.1 Thresholds areas of concern. A filter could be applied such that the monitor only records Network parameters that may be monitored include the network information for certain types of packets and discards the rest. For load and rate at which errors occur. Both of these parameters have example, the filter could be programmed such that only packets of a time component, and hence it is important that the user under- a particular type are noted. Where there are a number of proto- stands the sampling period used by the network monitor. cols in use on a network, this facility enables the us