Overview RMON

One important function of the network management is to monitor the element performances of the network. In the traditional SNMP network management mode, the initiative of the management is mainly mastered by the network management station. Usually, the network management work station regularly polls the data of the device and then measures and analyzes in the network management system, so as to get the desired information of the administrator. In this mode, the network management work station needs to send and receive lots of packets to the network devices. When there are many devices in the network, it causes the additional load for the network. Meanwhile, the network blocking and other factors take various accidents to the running of the network management system. As for this, we put forward the RMON (Remote Network Monitoring) concept.

The realizing of RMON still needs the supporting of the SNMP protocol. In fact, it is one group of MIBs, distributed in MIB-2, and the object ID is 1.3.6.1.2.1.16. Compared with other general MIB, RMON adds the calculation at Agent during realizing, that is, put the processing, such as performance statistics in the device. This realizes the distributed processing in the whole network, reducing the disadvantages brought by the polling of the network management work station.

RMON needs to realize lots of calculation functions, so the previous RMON proxy (also called Probe) is acted by a special device, distributed in the network to monitor the corresponding target. With the improvement of the processing capability of the network device, RMON is gradually integrated to the network devices, so as to realize the RMON requirement high-efficiently. However, this also puts forward higher performance requirement for the network devices. After all, the calculations of RMON occupy lots of system resources, reducing the system performance. This is also the additional cost brought by the management, so RMON is mainly realized in the hardware with the network processing capability, such as switching chip.

RMON MIB has 10 groups:

• statistics: Measure all Ethernet interfaces of the device, such as broadcast and conflict;
• history: Record the samples of the periodical statistics information that is taken out from the statistics group;
• alarm: Permit the administration Console user to configure the sampling interval and alarm when the values of any counters or integers (recorded by the RMON proxy) exceed the threshold value;
• host: Include the input/output traffics of various types of hosts adhering to the subnet;
• hostTopN: Contain the stored statistics information of hosts, some parameters in the host tables of these hosts are the highest;
• matrix: Indicate the error and utilization information in the form of matrix, so that the operator can use any address pair to search for information;
• filter: Permit the monitor to monitor the packets matched with the filter;
• capture: The captured groups set up one group of buffer area, used to store the groups captured from the channel.
• event: Present the table of all events generated by the RMON proxy;
• tokenRing: Maintain the statistic and configuration information of a subnet which is a token ring