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08/31/2020
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While going thru 7.1.2.1 structure of a Message placed on the wire- I see this image:
[I had difficulty in adding the image hence describing the same below]
It has 3 chucks – Chunk 1 , Chunk 2 and Chunk 3 and with legend.
However it is completely un-clear of what UPC UA message structure looks like – is there a generic message format that I can refer to and please describe the structure outlines?
Thanks in advance
08/31/2020
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Thanks so what does it means in all –
It is a TCP packet and the payload of the TCP Packet has below components:
Message + Security + Sequence header followed by body , padding and signature.
Further TCP itself gives SSL security feature before any connection get established so what does this additional security header is it for? Please provide a general Ethernet packet structure for a OPC UA message on wire – I believe all messages would be same except the message content itself stating which operation to do?
05/30/2017
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TCP and SSL/TLS are different standards. TLS runs over TCP in the same way UA runs over TCP. The TLS message structure is similar to UA.
OPC UA client-server is an application level protocol. Applications provide message bytes to the TCP stack which then creates multiple TCP packets that are not controlled or specified by OPC UA. The same process repeats when TCP packets are passed to the Ethernet layer. IOW, each Ethernet packet will contain some random subset of one or more UA messages and will not be a useful thing to know if you want to understand the protocol.
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