NETWORK MONITORING DEVICE, NETWORK MONITORING PROGRAM, AND NETWORK MONITORING METHOD

PROBLEM TO BE SOLVED: To calculate accurate estimation values of the number of accommodation users and the number of influenced users in each network component of a monitoring target.SOLUTION: In a monitoring system 300, a traffic collection unit 33 collects information showing the number of registration users for each domain and traffic information for each monitoring target network component from a traffic collection device and a registration user management device, and an operation unit 34 acquires the traffic information for each monitoring target network component, traffic information for each domain including the monitoring target network component, and information on the number of registration users corresponding to each domain, from the traffic collection unit 33. In the operation unit 34, a calculation unit for the number of estimated accommodation users calculates the number of estimated accommodation users, which is an estimation value of the number of accommodation users for each monitoring target network component, by proportionately dividing the number of registration users corresponding to each domain using a ratio of the sum of the traffic information for each monitoring target network component and the sum of the traffic information for each domain.