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Difficulty: EasyOSI Model Layers and Functions

Arrange the following Protocol Data Units (PDUs) in the correct sequential order as data moves down the Open Systems Interconnection (OSI) model during the encapsulation process, starting from the application layer down to the physical transmission medium.

  1. 1Data (Application, Presentation, and Session layers)
  2. 2Segment (Transport layer)
  3. 3Packet (Network layer)
  4. 4Frame (Data Link layer)
  5. 5Bits (Physical layer)

Answer

The correct encapsulation sequence from top to bottom is: Data → Segment → Packet → Frame → Bits.
During encapsulation, data moves down the OSI model from Layer 7 to Layer 1. The PDU sequence is Data at the upper layers (Application, Presentation, Session), Segment at the Transport layer (Layer 4), Packet at the Network layer (Layer 3), Frame at the Data Link layer (Layer 2), and Bits at the Physical layer (Layer 1).

Step-by-Step Solution

1
Identify the starting point of data creation in the OSI model.
Information originates at the Application, Presentation, and Session layers as raw Data.
Encapsulation begins at the upper layers before being prepared for network transport.
2
Determine the PDU created at the Transport layer (Layer 4).
Data is segmented and wrapped with transport protocol headers to create Segments (or Datagrams).
Layer 4 manages end-to-end communication and port numbers.
3
Determine the PDU created at the Network layer (Layer 3).
Segments are encapsulated with IP headers containing source and destination IP addresses to create Packets.
Layer 3 handles logical addressing and path selection across networks.
4
Determine the PDU created at the Data Link layer (Layer 2).
Packets are encapsulated with MAC headers and frame check sequence trailers to create Frames.
Layer 2 facilitates node-to-node transfer on the local network segment.
5
Determine the final state at the Physical layer (Layer 1).
Frames are encoded into raw Bits for transmission across physical medium.
Layer 1 transmits binary signals over copper cables, fiber optics, or wireless mediums.

Key Concept

OSI Model Data Encapsulation and PDU Sequence
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Topics

OSI Model Layers and Functions

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