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Question

Difficulty: EasyEncapsulation and De-encapsulation

A network interface card (NIC) on a destination host receives an incoming Ethernet frame from the physical medium. After the NIC verifies the frame check sequence and strips off the Layer 2 header and trailer, which Protocol Data Unit (PDU) is passed up to Layer 3 for processing?

  1. PacketAnswer
  2. B
    Segment
  3. C
    Datagram
  4. D
    Bit stream

Answer

The Protocol Data Unit (PDU) passed up to Layer 3 after removing the Layer 2 Ethernet header and trailer is a Packet.
During the de-encapsulation process, as data moves up the protocol stack, each layer removes its corresponding header and trailer. When Layer 2 (Data Link) removes the Ethernet frame header and frame check sequence trailer, the payload revealed is the Layer 3 (Network layer) Protocol Data Unit, which is called a Packet.

Step-by-Step Solution

1
Identify the current OSI layer performing de-encapsulation.
The network interface card processes the Layer 2 (Data Link layer) frame.
De-encapsulation moves up the stack from Layer 1 to Layer 7.
2
Determine the PDU associated with the next higher layer (Layer 3).
Stripping the Layer 2 header and trailer exposes the Layer 3 (Network layer) payload, which is an IP Packet.
Each layer strips its respective encapsulation headers to reveal the higher-layer PDU inside.

Key Concept

Protocol Data Unit (PDU) De-encapsulation Order
Estimated Time:45s
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Topics

Encapsulation and De-encapsulation

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