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Global Discovery
February 16, 2021
13:04, EET
Forum Posts: 19
Member Since:
June 2, 2019
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Been on a mission to get a more clear understanding of the discovery mechanisms.
I am very confused with the Global Discovery service. I see that it can be used to identify the services across the administrative domain. Does this mean it can find the servers across multiple networks? GDS in Network A, can find all the OPC UA applications in network B,C etc.. provided they are registered to the GDS?
Does it by any chance replace the subnet discovery? I can see that GDS can also incorporated in the single network. I actually do not seem to understand as to how would it be beneficial.
I see that mDNS is not so secure, however GDS in a single network still uses multicast extension faciltiies to register the servers.

I understand there is a certificate management system, which would produce the signed certificates for all the applciations registered to the GDS, so that they can communicate between each other, without having to manually transfer the certficates prior to the communication.

But such a thing is never a concern if we are using a security mode of NONE in a communication scenario right?
I could be wrong here. Please do correct me.

The specification for the GDS part just kicks of too technical, leaving behind a lot of questions.
Could you clarify please.


February 17, 2021
12:25, EET
Bjarne Boström
Forum Posts: 620
Member Since:
April 3, 2012
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I wish you great luck in your quest 🙂

This particular question might be better suited for https://opcfoundation.org/forum. But I can see https://opcfoundation.org/forum/opc-ua-standard/regarding-global-discovery-service/, which has similar username to yours, so maybe you already did.

Short answer is that we have not yet done much related to GDS nor seen it being used (like, not even normal LDS is that much being used). I would assume if a GDS is needed, then you’ll also have a scenario where you really wouldn’t use NONE security mode.

Not every feature of OPC UA is implemented or used in the real world. It is also not exactly helping that the OPC Foundation is continuously adding stuff to the specification. Also, OPC UA is like 15 years old at this point. Some stuff might not make sense in today’s context, but are as is since changing those would break interoperability. OPC UA 1.01 had a lot less stuff when compared to 1.04 (+amendments to it).

February 17, 2021
16:01, EET
Forum Posts: 19
Member Since:
June 2, 2019
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Hi Bjarne,

Thank you so much. Regarding the speciffication, yes i totally agree. It is really difficult to correlate and make sense of it.
Anyway, thanks again!


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