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11. When your configuration is complete, enter Y in the Process selections field and press <return>. SCADA MULTICAST 19 Utility Features The DYNASTAR has two multicast functions specifically designed for SCADA applications where a modem multidrop type of environment is replaced by a digital network approach. These are the Frame Relay multicast and the TCP/IP multicast. In the analog modem environment, the Host port is directly connected to multiple remote IEDs via analog circuits and modems. The analog circuits are physically bridged together and, via RS-485 interfaces, can provide a multi-drop environment where a single host port is fanned out concurrently to multiple remote devices. This is illustrated in Figure 19-5. Modem IED Modem Modem Server Modem Modem IED IED IED Punchdown block Figure 19-5 Analog Multi-Drop Environment In a digital or networking approach, the bridged analog circuits are replaced by a gateway product that has a serial connection to the host. The gateway is then connected over a WAN connection to remote IEDs, each IED having its own dedicated connection rather than a shared connection. In this environment, the gateway is responsible for making virtual connections to the remote IEDs (for example, over frame relay). The gateway must multiply or multicast messages received from the host port to each remote device. All remote devices receive the host’s message; however, only the single IED that matches the message address will respond. This response must be routed back over the multicast network and 19-9
