Wednesday, December 28, 2011

MMS (ISO 9506) Introduction – Why to focus on the API?

Jan Tore Sørensen and Martin Gilje Jaatun (SINTEF ICT, Trondheim, Norway) have published a nice introduction to the basic architecture and definitions of MMS in a 46 page document – easy to read and understand.

This documents demonstrates that MMS is not complex. IEC 61850-8-1 (and IEC 61850-9-2) use MMS for specifying the message exchange between IEC 61850 servers (publishers) and clients (subscribers).

Implementing IEC 61850 compliant systems comprising SCL tools, servers, clients, publishers, and subscribers means to implement:

  1. Upper layers on top of TCP/IP (or on Ethertype for publisher/subscriber)
  2. Protocol machine (MMS, GOOSE and SV)
  3. Encoding/Decoding ASN.1 BER messages
  4. ACSI services (LD, LN, Control Blocks (reporting, Logging, service tracking, GOOSE, and SV), DataSets, Control, LOG –> mapped to protocols, mainly MMS)
  5. Object model (dictionary in IED and behavior according to IEC 61850-7-4)
  6. API (application program interface) for server, client, publisher, and subscriber
  7. IED configuration using SCL file
  8. SCL tool for system engineering and IED configuration

A ballpark estimate of the efforts needed to implement a reasonable subset of IEC 61850 (if one develops the software from scratch) is in the range of some 10 man-years. Only a small part of efforts (likely less than 10 per cent) deals with MMS and the underlying protocols required by MMS.

A different solution for the client-server messaging, e.g., by using a webservice, would have a minor impact on the total efforts. From a application point of view an efficient API should be in the focus when implementing of using IEC 61850!

Click HERE for the complete paper on MMS [pdf, 446 KB]

Note that IEC 61850 is much more than a protocol – and much more than MMS. MMS is just an international standard like Ethernet or TCP/IP.

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