Friday, February 18, 2011

Are Standards changing too fast?

There is are many SCADA users that think standards are changing too fast. I guess this is true for the many interface standards for sensors and actuators (the so-called fieldbusses and sensor interfaces). Lets have a look on the most crucial communication standards used in IEC 61850 and IEC 61400-25:

Layer 7 MMS (ISO 9506) some 20 years; likely to stay unchanged
Layer 5-6 ISO Presentation and Session some 20 years
Layer 4 TCP some 30 years; likely to stay for a long time
Layer 3 IP some 30 years v4; likely that v6 will stay for decades
Layer 2 Ethernet basics: 30 years

One crucial is that wide area monitoring seems to be build on top of TCP/IP - all over. There is no difference in the many different solutions from the transport layer viewpoint. IEC 61850-8-1 (mapping to MMS) is stable since UCA 2.0 (mid of the 90's). RTU protocols like DNP3 or IEC 60870-5-101 have changed from serial links to TCP/IP - became more convergent to IEC 61850!! Guess these protocols will be extended to become convergent at model and configuration levels.

When it comes to the application layers, there seems to be mainly ONE standard profile stable: The profile shown above - which is QUITE STABLE.

There were (and are still) many people criticizing that the communication protocols in IEC 61850 are not following new developments faster (e.g., in the application of webservices)! Most people like what we have. When discussing webservices, the question is: Which one?? There is not an "old" solution like MMS that is around for 20 years. What is discussed is: use IEC 61400-25-2 dedicated webservices, use OPC UA webservices or use DPWS, or ... Reaching consensus in the selection of webservices may take some time. In the meantime we have the stable stack in IEC 61850-8-1. That is what I call: Sustainable Interoperability.

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