RMON Overview

RMON

SNMP is a widely used network management protocol. It collects statistics about network communication by using the agent software embedded in the managed devices. The NMS polls the agent to provide network communication information. The agent then searches the Management Information Base (MIB) and returns the required information to the NMS. The NMS can manage the network based on returned information. The MIB counter only records the statistics, but cannot analyze history information about routine communication. To display traffic volume and changes on a whole day, the NMS has to keep on polling and analyze network traffic based on the obtained information.

SNMP polling has the following disadvantages:

• Occupies a large number of network resources. Polling generates many communication packets. On a large-sized network, congestion may occur or even the network is blocked. Therefore, SNMP is not applicable to large-sized networks and cannot recycle large amount of data, such as routing information.
• Increases the burden of network administrators. The network administrators are responsible for collecting all data using the NMS software. It is difficult for an administrator to monitor more than three network segments.

IETF develops RMON to improve usability of network management information and lighten the burden on the NMS and network administrators. Compared with SNMP, RMON is more applicable to large-sized networks and can monitor traffic on one or multiple network segments. The characteristics of RMON are as follows:

• SNMP is the basis of RMON, and RMON is an enhancement of SNMP. RMON is implemented based on the SNMP structure and compatible with SNMP. It consists of NMS and agents. Network administrators can use the SNMP NMS to implement RMON without additional training.
• RMON agent collects statistics on network traffic. For example, it counts the number of packets sent and received on a network segment within a period or the number of packets correctly sent to a host. Compared with SNMP, RMON monitors remote network devices more efficiently and actively. It provides an efficient solution to monitor the running of sub-networks, which reduces the communication traffic between the NM Station and the agent. Large-sized networks can thus be managed in a simple and effective manner.

RMON defines multiple monitors to collect network management information in either of the following ways:

• The NMS obtains management information directly from the RMON probe and controls network resources. This allows the NMS to obtain all RMON MIB information.
• A RMON agent is embedded into a network device, such as a switch, so that the device can provide the RMON probe function. The NMS uses basic SNMP commands to exchange data with the RMON agent and collect network management information. Due to the limitation on resources, the NMS can only obtain information about statistics, history, alarms, and events.

Huawei devices have embedded RMON agent. The management device can obtain information including traffic volume, error packet statistics, and performance statistics of the entire network segment connected to the interfaces on the managed devices.