Abstract: A system for monitoring metropolitan area network traffic flow is designed and a warning model is studied. Based on SNMP protocol, the network performance and error are monitored, which can achieve the acquisition of network traffic flow for varieties of device ports, and the monitoring data is automatically saved in the database file. In addition, the recorded data can be transformed into the grapy by computer technology. Finally the rates of aggregation group are obtained by time. Through this software, the rates of recorded objects can be monitored and analyzed. If there are unbalanced or abnormal rates, this system will give warning prompts.

Key words: MAN, bandwidth, rate control