Unit-1 Network, Topic: Internet Protocols
Internet protocols: TCP/IP, SMTP, POP3, HTTP, HTTPS.
Remote login and file transfer protocols: SSH, SFTP, FTP, SCP TELNET, SMTP, TCP/IP.
🌐 TCP/IP (Transmission Control Protocol/Internet Protocol)
- Foundation of the internet and most networks.
- Defines how data is packetized, addressed, transmitted, routed, and received.
- Comprises four layers: Application, Transport, Internet, and Network Access.
- TCP ensures reliable, ordered delivery of data.
- IP handles addressing and routing of packets.
- Supports protocols like HTTP, FTP, SMTP.
- Enables interoperability across diverse systems.
- Developed by DARPA in the 1970s.
- Uses IP addresses to identify devices.
- Highly scalable and platform-independent.
📧 SMTP (Simple Mail Transfer Protocol)
- Used for sending emails between servers.
- Operates at the application layer of TCP/IP.
- Uses port 25 (or 587 for secure transmission).
- Push protocol: sends emails from client to server.
- Works with Mail Transfer Agents (MTAs).
- Cannot retrieve emails—used only for sending.
- Often paired with POP3 or IMAP for receiving.
- Supports plain text; MIME extends it for multimedia.
- Stateless and connection-oriented.
- Vulnerable to spam unless secured with SMTP Auth.
📥 POP3 (Post Office Protocol v3)
- Used to retrieve emails from a mail server.
- Downloads emails to local device and deletes from server.
- Operates at the application layer.
- Uses port 110 (or 995 for SSL).
- Simple protocol, ideal for offline access.
- Does not support folder synchronization.
- Messages are stored locally after download.
- Limited support for multiple device access.
- Often used in personal email setups.
- Superseded by IMAP in modern systems.
🌍 HTTP (Hypertext Transfer Protocol)
- Protocol for transferring web pages and resources.
- Operates at the application layer.
- Uses port 80 by default.
- Stateless and text-based.
- Supports methods like GET, POST, PUT, DELETE.
- Client-server model: browser requests, server responds.
- Used for HTML, CSS, JS, and media files.
- No encryption—data is sent in plain text.
- Basis of the World Wide Web.
- Easily intercepted without HTTPS.
🔒 HTTPS (HTTP Secure)
- Secure version of HTTP using SSL/TLS.
- Encrypts data between client and server.
- Uses port 443.
- Prevents eavesdropping and tampering.
- Essential for secure transactions and logins.
- Provides authentication via digital certificates.
- Widely adopted across websites.
- Supports same HTTP methods securely.
- Improves trust and SEO rankings.
- Mandatory for modern web applications.
🔐 SSH (Secure Shell)
- Protocol for secure remote login and command execution.
- Encrypts all data exchanged.
- Uses port 22.
- Replaces insecure protocols like TELNET.
- Supports password and key-based authentication.
- Enables tunneling and port forwarding.
- Used for server administration and automation.
- Includes tools like
scpandsftp. - Highly secure and widely supported.
- Essential for managing Linux/Unix systems remotely.
📂 SFTP (SSH File Transfer Protocol)
- Secure file transfer protocol built on SSH.
- Encrypts both commands and data.
- Uses port 22.
- Replaces FTP for secure environments.
- Supports file upload, download, and management.
- Works in client-server model.
- Authentication via SSH keys or passwords.
- Supports GUI and CLI clients (e.g., FileZilla).
- Ensures data integrity and confidentiality.
- Ideal for enterprise-grade file transfers.
📁 FTP (File Transfer Protocol)
- Transfers files between client and server.
- Uses ports 20 (data) and 21 (control).
- Operates in active or passive mode.
- No encryption—data sent in plain text.
- Supports anonymous login for public access.
- Commands include GET, PUT, LS, CD.
- GUI clients available (e.g., WinSCP, FileZilla).
- Can be secured using FTPS or replaced by SFTP.
- Useful for bulk file transfers.
- Less secure without additional encryption.
🖥️ TELNET
- Protocol for remote login to another computer.
- Uses port 23.
- Sends data in plain text—no encryption.
- Client-server model.
- Allows command-line access to remote systems.
- Replaced by SSH due to security concerns.
- Useful for testing network services.
- Supports Network Virtual Terminal (NVT).
- Lightweight and simple.
- Not recommended for secure environments.
📦 SCP (Secure Copy Protocol)
- SCP is a secure file transfer protocol based on SSH (Secure Shell).
- It allows copying files between a local host and a remote host or between two remote hosts.
- Uses TCP port 22 for encrypted communication.
- Combines SSH’s encryption with RCP’s file transfer capabilities.
- Ensures confidentiality and integrity of data during transfer.
- Supports authentication via passwords or SSH keys.
- Preserves file attributes like permissions and timestamps.