in part 14 of the OPCUA Specifications, figure shows a single instance of the LDS residing between a publisher (left hand side) and a subscriber (right hand side), separated by a Message Oriented middleware.
This is my setup tweaked according to the above reference architecture:
OPCUA Servers (publisher) -> MQTT broker1 <-------------------------------> MQTT broker2 <- OPCUA Servers (subscriber)
Can I add 1 LDS-A server to the network (network-1) of the publisher, and another LDS-B server to the network (network-2) of the subscriber in the DMZ.
All the OPCServers at network-1 will announce itself to LDS-A and all the OPCServers at the network-2 will announce itself to LDS-B.
Between LDS-A and LDS-B, it will automatically announce each own group of OPCServers to each other.
In this way, if i add another network (network-C) of OPCServers, I only need to configure the comms between network-1, network-2 and network-3.
Is my understanding correct?
Revised setup according to my description above:
OPCUA Servers (publisher) -> MQTT broker1 <-----------------------> MQTT broker2 <- OPCUA Servers (subscriber)
It is in chapter 5 Pubsub Concepts
Figure 2 Publisher and Subscriber entities
Unless I am looking at wrong place or I am effectively blind, there is no LDS on that figure.
You might be referring to the "Directory" box on Figure 2. In my understanding, that does not refer to any specific implementation or technology - it just shows a concept that publishers can register themselves into some kind of directory service, and other applications can query the directory to find the publishers.
I can imagine that on a single subnet, the "Directory" can be LDS-ME. But in your case you are likely to have multiple subnets, and the following statement:
"Between LDS-A and LDS-B, it will automatically announce each own group of OPCServers to each other."
is not true when LDS-A and LDS-B are on different subnets.
I would say that in your case, the role of "Directory" (if any) is more likely to be fulfilled by a GDS.
Try this link instead: https://app.box.com/s/j2mekiku.....1is3ckwzri