An apparatus has a receiver module configured to receive packets including multiple different identifiers, an aggregation module configured to classify each packet, which is received by the receiver module into a certain aggregate flow and generate aggregate statistical information including number of packets belonging to the certain aggregate flow, and a statistical processing module configured to perform an updating process arranged to classify the certain aggregate flow into a specific statistical flow and to update statistical information including number of packets belonging to the specific statistical flow based on corresponding aggregate statistical information, the statistical processing module repeating the updating process for multiple aggregate flows, into which packets are classified by the aggregation module, so as to update the statistical information in each of the multiple different statistical conditions.