Stream of Knowledge

A port number is a unique identifier for specific processes or services on a networked server, crucial for directing incoming internet or network messages to the appropriate application. In the context of Transmission Control Protocol (TCP) and User Datagram Protocol (UDP), a port number is a 16-bit integer included in the message header. Key Port Numbers and Their Functions: 1. FTP - File Transfer Protocol Port Number: TCP 20, 21 Function: Facilitates the transfer of files between a client and a server. 2. SSH - Secure Shell Port Number: TCP 22 Function: Provides a secure login and command execution on remote machines. 3. Telnet Port Number: TCP 23 Function: Allows for unencrypted text-based communication for remote login services. 4. SMTP - Simple Mail Transfer Protocol Port Number: TCP 25 Function: Handles the routing of emails across networks. 5. DNS - Domain Name System Port Number: TCP/UDP 53 Function: Translates domain names to IP addresses for locating and identifying

protocols at each layer of OSI model The OSI (Open Systems Interconnection) reference model is a conceptual framework used to understand network interactions in seven distinct layers. Each layer has specific protocols that facilitate communication and data exchange. Let’s dive into the OSI model and explore the protocols that operate at each layer. Application layer It’s responsible for providing an interface for the user to interact with application services or network services. Ex- Web browser (HTTP), Telne Presentation layer It’s responsible for defining a standard format to the data. The major functions described at this layer are: - Encoding-Decoding Ex- AVI-(video), WAV-(voice), JPEG (graphite), ASCII (text) Encryption-Decryption Session layer It’s responsible for establishing, maintaining, and terminating the sessions. Session ID is used to identify a session or interaction. Ex- Remote procedural call, Apple talk session protocol. Transport Layer It provides data delivery me