Protocol Layering Concepts and TCP/IP Layering ICSSCADA Practice Questions (Page 1)

Questions 1–5

1. 1foundation · easy

   What is the process called when each layer of the protocol stack adds its own header (and possibly trailer) to the data as it moves down the stack?

   • AMultiplexing
   • BEncapsulation
   • CDe-encapsulation
   • DFragmentation
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2. 2application · medium

   A training document for new ICS network engineers includes a diagram that maps common protocols to the OSI model. The diagram shows Modbus TCP at the application layer, TCP at the transport layer, IP at the network layer, and Ethernet at the data-link layer. Which statement correctly describes how this mapping relates to the TCP/IP model?

   • AEthernet maps to the TCP/IP network layer, and IP maps to the link layer.
   • BModbus TCP maps to the TCP/IP application layer, and TCP maps to the transport layer.
   • CModbus TCP and TCP are both in the TCP/IP application layer.
   • DIP and Ethernet are both in the TCP/IP network layer.
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4. 3foundation · easy

   Which statement accurately describes a similarity between the OSI and TCP/IP models?

   • ABoth models use a layered approach to networking
   • BBoth models were developed by the same organization
   • CBoth models define exactly the same protocols
   • DBoth models have a dedicated session layer
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5. 4application · medium

   An engineer is troubleshooting a problem where a SCADA application on a workstation can ping the PLC's IP address, but the application cannot establish a TCP connection to the PLC's Modbus port. The ping succeeds, so IP connectivity exists. Which layer interaction is most likely the cause of the failure?

   • AThe network layer is not routing the TCP segments to the PLC.
   • BThe transport layer is unable to complete the TCP handshake because the PLC is not listening on the expected port.
   • CThe data-link layer is dropping frames because of a MAC address mismatch.
   • DThe application layer is not sending the correct Modbus function code.
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6. 5application · medium

   A technician is using a protocol analyzer to troubleshoot a communication failure between a DCS controller and a remote I/O rack. The analyzer shows that the DCS is sending frames, but the remote I/O rack is not responding. The technician checks the cabling and finds no physical issues. At which layer should the technician next look to determine whether the frames are being processed correctly?

   • ATransport layer, to check TCP or UDP port numbers
   • BData-link layer, to check for MAC address mismatches or frame check sequence errors
   • CNetwork layer, to verify that IP routing is functioning
   • DApplication layer, to verify the DCS application is sending the correct data
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