Which option lists all the layers that exist as separate layers in the OSI…
2025
Which option lists all the layers that exist as separate layers in the OSI model but not in the TCP/IP model?
Answer: D. Session and Presentation layer — Concept: A layered network model assigns a distinct responsibility to each layer and specifies how neighboring layers interact. Comparing two models requires…
- A.
Application layer
- B.
Presentation layer
- C.
Session layer
- D.
Session and Presentation layer
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Correct answer: D
Concept: A layered network model assigns a distinct responsibility to each layer and specifies how neighboring layers interact. Comparing two models requires checking which responsibilities exist as separate layers and which are consolidated into a broader layer.
Application
The OSI upper stack separates application services, data representation, and session control into the Application, Presentation, and Session layers. The TCP/IP model groups these application-facing responsibilities under its Application layer instead of defining separate Presentation and Session layers.
Contrast
Application layer: provides network services to user applications and appears as a named layer in both model families.
Presentation layer: handles representation tasks such as translation, compression, and encryption in OSI.
Session layer: handles dialog establishment, synchronization, and termination in OSI.
Cross-check and result
OSI has seven layers, whereas the traditional TCP/IP model has four. Consolidating the two OSI-specific upper-layer functions explains the smaller TCP/IP count. Therefore, the complete choice is Session and Presentation layer.