Analyzing IEC 61850 SCADA communication

28/08/2018
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Looking inside the client/server communication with IEDScout 3

The communication between the station control and the IEDs is performed over a sophisticated protocol. The possibility to look into this from the IEC 61850 view supports an efficient top-down analysis. Only if required, the option to drill down into the details may be use

Client/server communication

Client/server (C/S) communication is a generic term for parts of the abstract communication services defined in IEC 61850-7-2. In a substation, the client is typically the station controller and the server is typically an IED (Intelligent Electronic Device) such as a protection relay. The term MMS (Manufacturing Message Specifi  – cation) is often used when C/S is actually meant. But in fact MMS is just the specific transport protocol described in IEC 61850-8-1. In the future IEC 61850-8-2 shall provide an alternate mapping by using Web-Services instead.

Accessing client/server traffic

The C/S communication is performed over explicitly established connections and the corresponding Ethernet packets are only forwarded on those links that actually establish the path between the involved client and server. Without special precautions, an analysis tool will not receive the packets to be analyzed. The access to the traffic of interest must be first established. A mir- ror port, which can be typically found on a managed Ethernet switch, is used to replicate the traffic from other ports on the switch.

Recovering the context

The C/S communication generally consists of request/ response sequences. The matching and combined representation of these request/response sequences is a challenge, but delivers great value for the user. The combined, time aligned view of C/S traffic and GOOSE messages, is more than a list of events from a SCADA system.

Top level representation

OMICRON´s IEDScout 3 makes the circumstances vis – ible on the top layer, represented as closely as possible to the way they are defined in the standard. Thus, the need to look into the complex MMS protocol is typically eliminated. The option to drill down to lower protocol layers comes second. For special examina – tion with external protocol analyzers or for docu – mentation, the exporting of data is a complementary feature.

OMICRON Magazine

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