The OSI model is the most common networking model used in the industry. Applications, network functions, and protocols are typically referenced using one or more of the seven OSI layers. Of the follow

Question

Options

• ALayers 1 and 2 deal with application functionality and data formatting. These layers reside at
• BLayers 4 through 7 define the functionality of IP Addressing, Physical Standards, and Data
• CLayers 5, 6, and 7 focus on the Network Application, which includes data formatting and
• DLayers 1, 2, 3, and 4 deal with physical connectivity, encapsulation, IP Addressing, and Error

• A
  3% (1)
• B
  3% (1)
• C
  94% (32)

Explanation

Options C and D correctly split the OSI model into its two functional halves. Layers 1–4 (Physical, Data Link, Network, Transport) handle the "how data moves" concerns: physical connectivity, frame encapsulation, IP addressing, and end-to-end error/flow control - exactly what D describes. Layers 5–7 (Session, Presentation, Application) handle the "what the application needs" concerns: session management, data formatting/encryption, and the user-facing application interface - which is what C captures.

Option A is wrong because it inverts the model - Layers 1 and 2 are the bottom layers responsible for physical signals and data-link framing, not application or formatting functions. Option B is wrong because IP Addressing belongs to Layer 3 and Physical Standards belong to Layer 1, neither of which falls in the Layer 4–7 range described.

Memory tip: Think of the OSI stack as a building - the foundation (Layers 1–4) is infrastructure (wires, frames, IP, transport), while the penthouse (Layers 5–7) is where the users and apps live (sessions, formatting, applications). Anything ending in "addressing," "physical," or "encapsulation" lives in the lower four; anything involving "application," "formatting," or "sessions" lives in the upper three.

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