OPC layers respect to ISO OSI Reference Model

General topics regarding OPC Foundation and communication technology in general.

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sshoghi61
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Joined: 27 Mar 2015, 13:57

OPC layers respect to ISO OSI Reference Model

Post by sshoghi61 »

Hi there,
I have a question regarding OPC network layers respect to ISO OSI Reference Model
I couln't find anything in the net in this regard
I mean something like following link for CAN BUS:
http://www.ifak-system.com/uploads/pics/Schema_CAN.jpg[^]
or for PROFINET:
http://image.slidesharecdn.com/introduc ... 1377682945[^]
or other fieldbuses:
http://www.processonline.com.au/article ... iew-Part-2[^]

for OPC, I have just found following stack overviews:
http://www.digitalbond.com/wp-content/u ... Opcua2.png[^]

so my question is:
is OPC (Classic/UA) not following ISO OSI model?

Thanks
Regards
Saeed

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Support Team
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Joined: 18 Mar 2011, 15:09

Re: OPC layers respect to ISO OSI Reference Model

Post by Support Team »

Hi,

It is hard to not follow the ISO OSI model if something is based on TCP/IP.

But other than field busses who mainly transport byte blobs, OPC UA is an application layer protocol where most of the definitions are on ISO OSI layer 7 and above.

The transport protocols of OPC UA defined in OPC UA Part 6 Mappings (mapping of OPC UA services to network protocols) covers ISO OSI layers 5 and 6, using layer 4 TCP.

The services defined in OPC UA Part 4 - Services defines the abstract API between OPC UA clients and servers. It covers ISO OSI layer 7.

But OPC UA defines also the rules for exposing object oriented information models (Part 3), defines a base information model (Part 5) and also dedicated information models like Part 8 - Data Access and Part 9 - Alarms and Conditions. In addition there is a long list of so called companion information model specifications. Such features are not covered at all by the ISO OSI layers.

Best Regards,
Unified Automation Support Team

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