Explain the four layers of the TCP/IP Protocol stack and their functions.

The TCP/IP Protocol stack is a set of protocols that are used for communication over the internet. It is composed of four layers, each with its own specific functions.

1. Network Interface Layer: This is the lowest layer of the TCP/IP stack and is responsible for the physical transmission of data. It deals with the hardware aspects of communication, such as network cards, cables, and network devices. Its main function is to transmit and receive data packets over the network.

2. Internet Layer: The internet layer is responsible for addressing and routing data packets across different networks. It uses IP (Internet Protocol) to assign unique IP addresses to devices and ensures that data packets are delivered to the correct destination. It also handles fragmentation and reassembly of data packets if they are too large to be transmitted in a single frame.

3. Transport Layer: The transport layer is responsible for the end-to-end delivery of data packets. It provides reliable and efficient data transfer between devices. The two main protocols used in this layer are TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). TCP ensures reliable delivery by establishing a connection, breaking data into smaller segments, and reassembling them at the destination. UDP, on the other hand, provides a connectionless and faster delivery method, but without guaranteed reliability.

4. Application Layer: The application layer is the topmost layer of the TCP/IP stack and is responsible for providing services to end-users. It includes protocols such as HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), SMTP (Simple Mail Transfer Protocol), and DNS (Domain Name System). These protocols enable functions like web browsing, file transfer, email communication, and domain name resolution.

Overall, the TCP/IP Protocol stack provides a standardized framework for communication over the internet, ensuring that data is transmitted reliably and efficiently between devices. Each layer has its own specific functions, working together to enable seamless communication across networks.