TCP/IP Protocol Architecture ICSSCADA Practice Questions (Page 5)

Questions 21–25

1. 21application · medium

   A technician captures a packet on an Ethernet link and sees the destination MAC address of the local gateway, an IP header with a destination address of a remote server, and a TCP segment with a destination port of 443. What does this sequence of headers indicate about the packet's journey?

   • AThe packet has been fully de-encapsulated and is now at the application layer.
   • BThe packet is using UDP because the destination port is 443.
   • CThe packet is being sent to the gateway, which will strip the Ethernet header and forward it based on the IP address.
   • DThe packet is destined for the gateway itself, because the destination MAC is the gateway's address.
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2. 22expert · hard

   A SCADA engineer is designing a communication link between a control center and a remote pumping station. The link is a low-bandwidth satellite connection with high latency. The engineer must choose a transport protocol for sending real-time telemetry data (e.g., pressure, flow) and for transferring configuration files. The telemetry data is critical and must be as current as possible, but a few lost samples are acceptable. The configuration files must be transferred without errors. Which approach best balances the requirements?

   • AUse UDP for both telemetry and configuration files
   • BUse UDP for telemetry and TCP for configuration files
   • CUse TCP for both telemetry and configuration files
   • DUse TCP for telemetry and UDP for configuration files
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4. 23foundation · easy

   What is the role of a port number in TCP/IP communication?

   • AIt determines the route a packet takes across the network
   • BIt identifies the physical network interface of the host
   • CIt identifies the specific application or service on a host
   • DIt provides encryption for the data being transmitted
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5. 24expert · easy

   A network analyst is examining a packet capture from a SCADA historian that receives data from multiple PLCs. The analyst sees an Ethernet frame containing an IP packet, which contains a TCP segment, which contains a Modbus TCP payload. The analyst wants to document the layer at which the Modbus TCP payload is processed. Which layer of the TCP/IP model should the analyst identify?

   • AInternet layer
   • BNetwork interface layer
   • CApplication layer
   • DTransport layer
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6. 25foundation · easy

   When a host receives an Ethernet frame, what is the first step in the de-encapsulation process?

   • APass the raw data directly to the application
   • BCheck the destination IP address in the Ethernet header
   • CRemove the Ethernet header and trailer to reveal the IP packet
   • DRemove the TCP header to reveal the application data
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