(ISC)2 Certified in Cybersecurity Practice Exam

How many layers does the OSI model have?

1. A) 2

2. B) 1

3. C) 4

4. D) 7

The correct answer is: D) 7

The OSI (Open Systems Interconnection) model consists of seven distinct layers, each designed to handle specific aspects of network communication. These layers are: 1. **Application Layer** - This layer interacts directly with software applications to provide communication services. 2. **Presentation Layer** - It translates data between the application layer and the network format; it is also responsible for data encryption, decryption, and compression. 3. **Session Layer** - This layer establishes, manages, and terminates connections between applications. 4. **Transport Layer** - It provides reliable or unreliable delivery and error recovery, managing end-to-end communication. 5. **Network Layer** - This layer is responsible for routing and forwarding packets through the network. 6. **Data Link Layer** - It handles error detection and correction from the physical layer, and defines the protocol for data transfer across a physical link. 7. **Physical Layer** - The lowest layer, it deals with the physical connection between devices, including hardware elements like cables and switches. Each of these layers has specific functions and communicates with the layers directly above and below it. The significance of having multiple layers is to provide a modular approach to network design, allowing for interoperability and simplification in troubleshooting and maintenance.