Connection management links the DNP3 layers with the IP layers in addition to

Connection management links the dnp3 layers with the

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Figure 6-2Protocol Stack for Transporting Serial DNP3 SCADA over IP In Figure 6-2, the master side initiates connections by performing a TCP active open.
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Module 3: Internet of Things [15CS81] © Mr. Nischaykumar Hegde, Dept. of CSE, VCET Puttur 203 The outstation listens for a connection request by performing a TCP passive open. Dual endpoint is defined as a process that can both listen for connection requests and perform an active open on the channel if required. Master stations may parse multiple DNP3 data link layer frames from a single UDP datagram, while DNP3 data link layer frames cannot span multiple UDP datagrams. Single or multiple connections to the master may get established while a TCP keepalive timer monitors the status of the connection. Keepalive messages are implemented as DNP3 data link layer status requests. If a response is not received to a keepalive message, the connection is deemed broken, and the appropriate action is taken. Tunneling Legacy SCADA over IP Networks Native support for IP can vary and may require different solutions. Ideally, end-to-end native IP support is preferred, using a solution like IEEE 1815-2012 in the case of DNP3. Otherwise, transport of the original serial protocol over IP can be achieved either by tunneling using raw sockets over TCP or UDP or by installing an intermediate device that performs protocol translation between the serial protocol version and its IP implementation. A raw socket connection simply denotes that the serial data is being packaged directly into a TCP or UDP transport. A socket in this instance is a standard application programming interface (API) composed of an IP address and a TCP or UDP port that is used to access network devices over an IP network. More modern industrial application servers may support this capability, while older versions typically require another device or piece of software to handle the transition from pure serial data to serial over IP using a raw socket. Figure 6-3 details raw socket scenarios for a legacy SCADA server trying to communicate with remote serial devices.
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Module 3: Internet of Things [15CS81] © Mr. Nischaykumar Hegde, Dept. of CSE, VCET Puttur 204 Figure 6-3 Raw Socket TCP or UDP Scenarios for Legacy Industrial Serial Protocols In all the scenarios in Figure 6-3, notice that routers connect via serial interfaces to the remote terminal units (RTUs), which are often associated with SCADA networks. An RTU is a multipurpose device used to monitor and control various systems, applications, and devices managing automation. From the master/slave perspective, the RTUs are the slaves.
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  • Winter '19
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  • Computer Science, Internet Protocol Suite, VCET PUTTUR, Mr. Nischaykumar Hegde

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