Explain OSI Model and TCP/IP: How is Data Sent Over the Internet?

The OSI Model and TCP/IP are fundamental to understanding how data travels over the internet.

The OSI Model consists of seven layers:

1. **Physical Layer**: Handles physical connection and transmission. Example: Cables and switches.

2. **Data Link Layer**: Provides node-to-node data transfer. Example: MAC addresses.

3. **Network Layer**: Routes data packets. Example: IP addresses.

4. **Transport Layer**: Ensures reliable transmission. Example: TCP and UDP.

5. **Session Layer**: Manages sessions between applications. Example: Establishing a connection.

6. **Presentation Layer**: Translates data formats. Example: Encryption and compression.

7. **Application Layer**: Closest to the user. Example: Web browsers and email clients.

TCP/IP, on the other hand, consists of four layers:

1. **Link Layer**: Similar to the physical and data link layers in OSI.

2. **Internet Layer**: Routes packets using IP.

3. **Transport Layer**: Provides TCP and UDP protocols for data transfer.

4. **Application Layer**: Contains protocols like HTTP, FTP, etc.

Data is sent over the internet by encapsulating it in packets. Each layer adds its header information, enabling accurate delivery.