CyberCertPrepOT Security FundamentalsOT Fundamentals: Network Architecture & ProtocolsMEDIUMFree question
A Modbus TCP client sends requests with transaction IDs 7, 8, and 9 on one connection before reading any replies. What do the IDs let the client do?
- A.Route the frame to the correct serial slave address
- B.Pair each response with its request when replies arrive late
- C.Authenticate the PLC through a shared secret held in the ID
- D.Select the function code table the PLC should read from
Why B is correct
The MBAP transaction identifier is echoed in the response so a client with several requests outstanding can pair them. Routing to a serial slave uses the unit ID, and nothing in the field authenticates anyone.
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