Which OSI layer is *not* part of TCP/IP model ?

Which OSI layer is *not* part of TCP/IP model ?

Application layer
Session layer
Network layer
Physical layer
This question was previously asked in
UPSC CISF-AC-EXE – 2020
The OSI (Open Systems Interconnection) model has seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.
The TCP/IP model is typically described with four layers: Network Interface (or Link), Internet, Transport, and Application. Sometimes a five-layer model is used, splitting the Network Interface layer into Physical and Data Link.
Comparing the models:
– OSI Physical and Data Link correspond to TCP/IP Network Interface/Link (or Physical and Data Link).
– OSI Network corresponds to TCP/IP Internet.
– OSI Transport corresponds to TCP/IP Transport.
– OSI Application corresponds to TCP/IP Application, but the TCP/IP Application layer encompasses the functions of the OSI Session, Presentation, and Application layers.
The OSI Session layer and Presentation layer do not have distinct corresponding layers in the standard TCP/IP model; their functions are integrated into other layers (primarily the Application layer). Among the options provided, the Session layer is the one from the OSI model that is not a separate layer in the TCP/IP model.
– OSI has 7 layers, TCP/IP has 4 or 5 layers.
– TCP/IP combines functions of some OSI layers into its own layers.
– OSI Session and Presentation layers are not distinct layers in the TCP/IP model.
While TCP/IP is the dominant model for the internet, the OSI model is still valuable for understanding networking concepts and relationships between different functions.