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Difficulty: HardOSI Model Layers and Functions

A network security analyst is monitoring how an inbound HTTPS session is processed by a host system during decapsulation. Arrange the following data processing actions in the correct sequential order as the received data moves up the OSI reference model, starting from Layer 1 (Physical) to Layer 7 (Application).

  1. 1Converting incoming electrical pulses on the network interface transceiver into a raw binary bitstream
  2. 2Evaluating the Frame Check Sequence (FCS) to detect transmission errors and validating the destination MAC address
  3. 3Inspecting the IP header to verify the Time to Live (TTL) value and evaluate packet routing parameters
  4. 4Reassembling out-of-order TCP segments using sequence numbers and verifying destination port 443
  5. 5Decrypting the TLS cryptographic wrapper and uncompressing the presentation data formatting
  6. 6Parsing the HTTP GET request payload within the target web server application daemon

Answer

The correct sequence follows the bottom-up decapsulation process of the OSI model: Physical (Layer 1) → Data Link (Layer 2) → Network (Layer 3) → Transport (Layer 4) → Presentation (Layer 6) → Application (Layer 7).
Decapsulation proceeds from Layer 1 up to Layer 7. Incoming physical signals are first converted to bits (Physical / L1), framed and verified using MAC/FCS (Data Link / L2), processed for IP routing and TTL (Network / L3), reassembled by TCP sequence and port numbers (Transport / L4), decrypted from TLS wrappers (Presentation / L6), and finally processed as an HTTP payload by the application (Application / L7).

Step-by-Step Solution

1
Identify Layer 1 operation
Converting physical signals (electrical pulses) into binary bits occurs at the Physical layer (Layer 1).
Layer 1 is responsible for the physical interface, encoding, and raw bit transmission.
2
Identify Layer 2 operation
Checking the Frame Check Sequence (FCS) and verifying the MAC address occurs at the Data Link layer (Layer 2).
Layer 2 encapsulates network packets into frames containing hardware MAC addresses and CRC error checking.
3
Identify Layer 3 operation
Inspecting IP headers, checking TTL, and handling logical address routing occurs at the Network layer (Layer 3).
Layer 3 operates on packets and processes IP addresses and routing fields.
4
Identify Layer 4 operation
TCP segment reassembly using sequence numbers and reading port numbers occurs at the Transport layer (Layer 4).
Layer 4 provides flow control, connection management, port multiplexing, and reliable segment reassembly.
5
Identify Layer 6 operation
Decrypting TLS/SSL wrappers and formatting data occurs at the Presentation layer (Layer 6).
Layer 6 manages syntax formatting, encryption/decryption, and data compression.
6
Identify Layer 7 operation
Processing the HTTP GET request by the web application service occurs at the Application layer (Layer 7).
Layer 7 directly interfaces with end-user software applications and protocol payloads.

Key Concept

OSI Model Layer Decapsulation Order and Layer Functions
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Topics

OSI Model Layers and Functions

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