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Difficulty: MediumOSI Model Layers and Functions

During a routine security audit of host communications, a technician inspects raw protocol headers passing through a socket interface. The payload header contains source and destination port multiplexing fields along with window size parameters for flow control, but contains no IP routing headers or hardware physical addresses. At which layer of the OSI model does this data unit function?

  1. Transport LayerAnswer
  2. B
    Network Layer
  3. C
    Data Link Layer
  4. D
    Session Layer

Answer

Transport Layer
The Transport Layer (Layer 4) of the OSI model manages end-to-end transport services. Key functions at this layer include service multiplexing using port numbers (e.g., TCP/UDP ports), segmentation, error control via checksums, and flow control using mechanisms like sliding window size.

Step-by-Step Solution

1
Analyze the header fields described in the scenario.
Identified port numbers (source/destination) and window size parameters (flow control).
Port numbers provide service multiplexing, and window sizes regulate data transmission rates.
2
Map identified protocol functions to the OSI model layers.
Port assignment and flow control are core duties of Layer 4.
The Transport Layer manages end-to-end communication control between end hosts.

Key Concept

OSI Layer 4 (Transport Layer) Functions and Protocol Data Units
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Topics

OSI Model Layers and Functions

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