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CISSP · Question #869

CISSP Question #869: Real Exam Question with Answer & Explanation

The correct answer is B: Physical Layer. The OSI model divides network communication into seven layers, each with a distinct responsibility. The Physical Layer (Layer 1) is specifically responsible for transmitting raw binary data as electrical, optical, or radio signals over a physical medium.

Submitted by thandi_sa· Mar 5, 2026Communication and Network Security

Question

In the Open System Interconnection (OSI) model, which layer is responsible for the transmission of binary data over a communications network?

Options

  • AApplication Layer
  • BPhysical Layer
  • CData-Link Layer
  • DNetwork Layer

Explanation

The OSI model divides network communication into seven layers, each with a distinct responsibility. The Physical Layer (Layer 1) is specifically responsible for transmitting raw binary data as electrical, optical, or radio signals over a physical medium.

Common mistakes.

  • A. The Application Layer (Layer 7) provides network services directly to end-user applications such as HTTP, FTP, and DNS, and is not involved in the physical transmission of binary data.
  • C. The Data-Link Layer (Layer 2) is responsible for node-to-node data transfer and error detection/correction in frames between directly connected nodes, not the raw binary transmission over the physical medium.
  • D. The Network Layer (Layer 3) handles logical addressing and routing of packets between different networks (e.g., IP addressing), and does not deal with the physical transmission of binary signals.

Concept tested. OSI model Physical Layer binary data transmission

Reference. https://learn.microsoft.com/en-us/windows-server/networking/technologies/nic-teaming/osi-model

Topics

#OSI model#physical layer#data transmission#network fundamentals

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