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A protocol is a method of communication between computers and other electronic devices on the same network. It defines the rules or processes to exchange data. Protocols are a common language so communication can happen despite differences in hardware, software, and so on. There are several kinds of protocols that work together at the same time. Each protocol, or network communication layer, has a different role. They work together to provide a flexible model for sending and receiving data. For example, protocols in the Internet layer break data into packets when sending and reassemble them when receiving. The Internet Protocol (IP), is an example of a protocol in this layer.

A port refers to a communication endpoint through which processes on a computer can exchange data with other processes or devices over a network. Ports are identified by numerical values and are used in conjunction with IP addresses to enable communication between different applications or services. Each port is associated with a specific protocol, such as TCP (Transmission Control Protocol) or UDP (User Datagram Protocol), and serves as a unique identifier for directing network traffic to the appropriate application or service running on a device.

The following are transport-layer protocols, which are not assigned to specific ports. The application-layer protocols work with one of the transport layer protocols, depending on the application's specific needs.

• Transmission Control Protocol (TCP): Creates a secure connection before sending data, then verifies the transmission after it's complete to ensure the entire message was sent. It can resend data if needed. It's reliable but slower than the User Datagram Protocol (UDP) because it requires a connection before sending data. TCP is often used for email, texting, web browsing, and file transfers.
• User Datagram Protocol (UDP): Sends data without first establishing a connection. Unlike TCP, UDP does not confirm receipt or check for errors. It's faster than TCP but less reliable. UDP is often used for real-time data transfers, such as streaming or video chat because it avoids delays.

The application-layer protocols work with one of the transport-layer protocols, depending on the application's specific needs.  

• Hypertext Transfer Protocol (HTTP): A protocol for transmitting hypermedia documents, such as HTML files, over the World Wide Web. It defines how messages are formatted and transmitted and how web servers and browsers should respond to various commands.

• Hypertext Transfer Protocol Secure (HTTPS): An extension of HTTP that adds a layer of security through SSL/TLS (SSL (Secure Sockets Layer) and TLS (Transport Layer Security)) encryption. It is used to secure communication over the Internet, particularly for sensitive transactions like online banking, e-commerce, and login sessions.
• File Transfer Protocol (FTP): A protocol for transferring files between a client and a server on a computer network. It provides a set of rules for uploading, downloading, and managing files on a remote server.
• SSH File Transfer Protocol (SFTP): An SSH (Secure Shell) that provides secure file transfer capabilities over a network. It encrypts the commands and data to ensure confidentiality and integrity during file transfers.
• Session Traversal Utilities for NAT (STUN): A protocol used to assist devices behind a NAT (Network Address Translation) or firewall in establishing communication for real-time communication applications, such as VoIP (Voice over Internet Protocol) or video conferencing.
• Session Initiation Protocol (SIP): A signaling protocol for initiating, maintaining, and terminating communication sessions in IP-based networks. It is widely used for voice and video calls, instant messaging, and multimedia conferencing over the Internet.
• WebSocket Secure (WSS): An extension of the WebSocket protocol that adds a layer of security through SSL/TLS encryption. It enables full-duplex communication between a client and a server over a single, long-lived connection.
• VoIP Load Simulator: While not a standard protocol like the others listed, a VoIP load simulator is a tool used to simulate many VoIP calls or sessions to test the performance, scalability, and reliability of VoIP systems and networks.
• Real-time Transport Protocol (RTP) / Secure Real-time Transport Protocol (SRTP): RTP is used for real-time audio and video delivery over IP networks. SRTP adds encryption, authentication, and integrity checks to RTP to ensure secure communication for sensitive data.

TCP/UDP Port Requirements 

Below are the application-layer protocols along with their corresponding standard port numbers used to configure network connectivity.