devices lack much of the sophistication of the monitors that have been described here. In particular, they possess no means of providing for direct user interaction. 61.4.5.3 Traffic patterns A central monitoring station can interrogate each of the remote monitors and present the information as if it had been gathered If a network monitor is able to transmit packets whose contents are locally. The communication with the remote devices may be in defined entirely by the user, or copied from a packet captured from band, using the same network that is being monitored, or out of the network, then the monitor can be used to send out a series of band, using an alternative route. 61/16 Telecommunication system measurements The central monitoring station, in addition to being able to act as Figure 61.13) and the Primary Rate Access (PRA) (see Figure if it were connected to a single monitor at another point of the 61.14). network, will be able to summarise data gathered from all of the remote devices. In this way, the user can gain an overall view of how the network is operating. exchange 61.4.7.2 Network management More and more devices are becoming available with support for one of the network management protocols, such as SNMP (Simple 4 wire 2B+D 4 wire 2B+D 2 wire twisted Network Management Protocol). An increasing number of net- 144kbit/s 144kbit/s pair, line code works have a central management station to gather information 2B1Q, 4B3T, Standard from these devices. In such networks, the function of network interfaces e.g. monitors may be unclear. RS 232 Certainly, network management stations will be able to perform detailed analysis of how network devices are behaving by directly Figure 61.13 ISDN Basic Rate Access interrogating tables maintained by the device. By collating such information for all devices on the network, the management station will gain a detailed view of how the devices on the network are interacting. exchange However, the data supplied to the management station by network devices is only pertinent 