TCP/IP vs OSI Model Layer Differences

H12-811 By islever Editorial Last updated

Network Reference Models

Short answer

ABD Session, Network, and Presentation layers are not part of the TCP/IP model; TCP/IP uses the Internet layer instead of Network, and merges Session/Presentation into Application.

Question

Which of the following are not layers in the TCP/IP model? (Choose all that apply.)
  1. Session layer Correct Answer
  2. Network layer Correct Answer
  3. Application layer
  4. Presentation layer Correct Answer
  5. Transport layer

Key Takeaways

The main trap is assuming 'Network layer' is valid for TCP/IP; it is actually called the 'Internet layer' in TCP/IP, while Session and Presentation are entirely omitted and merged into the Application layer.

This question identifies which layers do not belong to the TCP/IP model. The correct answers are Session, Network, and Presentation layers, as TCP/IP uses different naming conventions and fewer layers than the OSI model.

Common mistake: Many candidates select only A and D, missing B. They incorrectly assume 'Network layer' is synonymous with TCP/IP's Internet layer without recognizing that exam questions often test the precise nomenclature difference between the two models.

Expert Analysis

The TCP/IP model is a four-layer protocol suite that serves as the practical foundation of internet communication, distinct from the theoretical seven-layer OSI model. The layers in the TCP/IP model are typically defined as the Application layer, Transport layer, Internet layer, and Network Access layer (sometimes called Link or Network Interface layer). Understanding this distinction is critical for network certification exams.

To identify the correct options, we must evaluate each choice against the TCP/IP architecture:

  • A. Session layer: This is an OSI-specific layer responsible for establishing, managing, and terminating sessions between applications. In the TCP/IP model, session management functions are handled by the Application layer. Therefore, it is not a TCP/IP layer.
  • B. Network layer: While the concept exists in TCP/IP, the specific terminology used is the Internet layer. The term "Network layer" is strictly associated with Layer 3 of the OSI model. In strict academic and certification contexts distinguishing between the two models, "Network layer" is considered incorrect because it mislabels the TCP/IP Internet layer. Comments in the source material highlight this semantic trap, noting that TCP/IP uses "Internet layer," not "Network layer."
  • C. Application layer: This is a core component of the TCP/IP model, encompassing data representation, encoding, and session control (which includes OSI's Session and Presentation functions).
  • D. Presentation layer: Like the Session layer, this is an OSI-only layer dealing with data translation and encryption. These functions are merged into the TCP/IP Application layer.
  • E. Transport layer: This is a standard TCP/IP layer responsible for end-to-end communication and error recovery.

The question asks which are not layers in the TCP/IP model. Based on the strict definition where "Network layer" is replaced by "Internet layer," options A, B, and D are the correct selections. Option A and D are absent due to functional merging, while Option B is absent due to nomenclature differences between the OSI and TCP/IP models.

Key Insight: The primary trap here is confusing OSI terminology with TCP/IP terminology. Students often assume "Network layer" is acceptable because it maps to IP routing, but exam questions testing model comparisons require precise adherence to the specific layer names defined by the TCP/IP suite.

Exam Strategy

When comparing network models, always verify the exact layer names. For TCP/IP, remember the acronym "AINT" (Application, Internet, Network/Link, Transport) or simply recall the four specific layers: Application, Transport, Internet, and Network Access. If an option uses OSI terms like 'Session', 'Presentation', or 'Network', treat them as incorrect unless the question explicitly allows loose mapping. Prioritize precision over conceptual similarity.

Frequently Asked Questions

Why is 'Network layer' not a TCP/IP layer?

While TCP/IP has a layer that performs network functions (IP routing), it is specifically named the 'Internet layer'. The term 'Network layer' belongs exclusively to the OSI model.

What happens to Session and Presentation layers in TCP/IP?

These OSI layers are not separate in TCP/IP. Their functionalities (session management, data formatting, encryption) are integrated into the single TCP/IP Application layer.

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Community Votes

A
50%
D
33%
B
17%

50% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 4 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 4

  1. konyuz 👍 1
    A. Session layer → Not in TCP/IP (it's part of OSI, merged into Application in TCP/IP) B. Network layer → Careful: TCP/IP doesn’t use the term Network layer; instead, it has Internet layer. So Network layer is NOT strictly a TCP/IP layer. C. Application layer → Is in TCP/IP D. Presentation layer → Not in TCP/IP (also OSI-only, merged into Application) E. Transport layer → Is in TCP/IP
  2. Fmoura17 👍 1
    Answer: A and D The TCP/IP model has only 4 layers: TCP/IP ModelApplication LayerTransport LayerNetwork LayerNetwork Access Layer
  3. Mze 👍 1
    Correct answer is ABD, We have internet on the TCP not Network
  4. Creyes1495 👍 1
    Pag. 41

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