How many layers are defined in the OSI model?

The OSI model, which stands for Open Systems Interconnection model, is a conceptual framework used to understand and implement networking protocols in seven distinct layers. These layers, listed from the top to the bottom, are the Application, Presentation, Session, Transport, Network, Data Link, and Physical layers.

Understanding that there are seven layers is crucial for comprehending how different network protocols interact and operate at various levels within a network. Each layer serves its specific function and relies on the layers below it to provide comprehensive services that allow for effective data communication. This model helps network professionals troubleshoot issues and design networks by clearly delineating responsibilities between the layers.

The other options do not accurately reflect the number of layers in the OSI model, which is firmly established as seven. Thus, recognizing that the OSI model consists of these seven layers is essential for anyone working in networking or IT.