Chapter13 Network Management Applications Autodiscovery can be done by using the broadcast ping on each segment and following up with further SNMP queries to gather more details on the system.A more efficient method is to look at the ARP cache in the local router.The ARP cache table is large and contains the addresses of all the hosts and nodes used in recent communications.Use of this table also allows subsequent ARP queries to be sent to other routers.This process is continued until the desired information is obtained on all IP addresses defined I by the scope of the autodiscovery procedure
Chapter13 Network Management Applications Autodiscovery can be done by using the broadcast ping on each segment and following up with further SNMP queries to gather more details on the system. A more efficient method is to look at the ARP cache in the local router. The ARP cache table is large and contains the addresses of all the hosts and nodes used in recent communications. Use of this table also allows subsequent ARP queries to be sent to other routers.This process is continued until the desired information is obtained on all IP addresses defined by the scope of the autodiscovery procedure
Hub 1 Port A Segment A Router Port B Segment B 口口 Hub 2 source of th se B2 Figure 13.2 LAN Physical Configuration
A1 (hub 1) A2(hub 2) B50908) Router Switch baviso9T jon 916 asanodasT 9viuogano B1 (hub 1) B2(hub 2) Figure 13.5 Logical Configuration of Two VLAN Segments
13.3 Performance Management Network performance is a nebulous term,which is hard to define or quantify in terms of global metrics.Performance management actually is (data) traffic management.It involves following data monitoring,problem isolation,performance tuning, analysis of statistical data for recognizing trends, and resource planning. 13.3.1 Performance Metrics The parameters that can be attributed to defining network performance on a global level are throughput,response time,network availability, and network reliability.The metrics of these parameters depend on what,when,and where the measurements are made
13.3 Performance Management Network performance is a nebulous term, which is hard to define or quantify in terms of global metrics. Performance management actually is (data) traffic management. It involves following data monitoring, problem isolation, performance tuning, analysis of statistical data for recognizing trends, and resource planning. 13.3.1 Performance Metrics The parameters that can be attributed to defining network performance on a global level are throughput, response time, network availability, and network reliability. The metrics of these parameters depend on what, when, and where the measurements are made
13.3.2 Data Monitoring Data monitoring in the network for abnormal performance behavior,such as a high collision rate in an Ethernet LAN and excessive packet drop because of overload,are detected by traps generated by agents and RMON.Performance-related issues are detected primarily with trap messages generated by RMON probes.Thresholds are s set for important SNMP parameters in the RMON,which then generate alarms when the preset thresholds are crossed.For example,the parameters in the alarm group and the event group in the RMON MIB [RFC 1757]may be set for the object identifier to be monitored.The time interval over which the data are to be collected for calculation and the rising and falling thresholds are specified
13.3.2 Data Monitoring Data monitoring in the network for abnormal performance behavior, such as a high collision rate in an Ethernet LAN and excessive packet drop because of overload, are detected by traps generated by agents and RMON. Performance-related issues are detected primarily with trap messages generated by RMON probes. Thresholds are set for important SNMP parameters in the RMON, which then generate alarms when the preset thresholds are crossed. For example, the parameters in the alarm group and the event group in the RMON MIB [RFC 1757] may be set for the object identifier to be monitored. The time interval over which the data are to be collected for calculation and the rising and falling thresholds are specified