Passive acquisition mechanism and initiative connections
The passive acquisition mechanism is characterized by the initiative of providing data to the SCADA-system from the data source. This mechanism is rare, but can occur in certain conditions or restrictions of the possibility of using the direct data acquisition mechanisms, Figure 5. An example of such situation can be the geographically allocated systems of the data acquisition through mobile networks GPRS/EDGE/3G/4G. In such networks, the allocation of all client nodes to individual real and static IP-addresses or the formation of a corporate mobile network may prove to be expensive, therefore, the initiative of the data transferring from client dynamic IP-addresses to one real IP-address of the SCADA-server is more accessible. Modification actions are transmitted to the data source at the time of the data transmission session by the source — reading. Although, typical requests are possible here through a VPN connection from a data source and working through a network intermediate DBMS.