WEEK 1 Networking Fundamentals .....

What is Internet?

It is a global network of interconnected computers and devices that communicate using standardized protocols. It enables data exchange, online communication, and access to information from anywhere in the world. It involve the huge amount of optic fiber cables under the oceans which is owned by tier 1 companies likes AT&T, Verizon. This companies rent their cables to tier 2 companies like BSNL, Jio, Airtel. And thereafter we get this internet services into our devices.

🌐 Understanding OSI and TCP/IP Models, Common Protocols, and AWS EC2 Security Groups

🔹 OSI & TCP/IP Models: An Overview

📌 OSI Model (Open Systems Interconnection)

The OSI model is a conceptual framework used to understand network interactions in seven layers:

1. Physical Layer ⚡ - Deals with physical connections (cables, switches, etc.)

2. Data Link Layer 📶 - Handles MAC addresses and error detection (e.g., Ethernet, Wi-Fi)

3. Network Layer 🌎 - Manages IP addressing and routing (e.g., IPv4, IPv6)

4. Transport Layer 🚚 - Ensures reliable data transfer (e.g., TCP, UDP)

5. Session Layer 🔄 - Manages sessions between applications (e.g., RPC, NetBIOS)

6. Presentation Layer 🎨 - Formats and encrypts data (e.g., SSL, TLS)

7. Application Layer 🌍 - Interface for end-users (e.g., HTTP, FTP, SMTP)

📌 TCP/IP Model

A simplified version of OSI, the TCP/IP model consists of four layers:

1. Network Interface Layer ⚡ (Combines Physical & Data Link layers)

2. Internet Layer 🌐 (Equivalent to OSI's Network layer)

3. Transport Layer 🚀 (Handles data transport, similar to OSI Transport layer)

4. Application Layer 📩 (Includes OSI's Application, Presentation, and Session layers)

🌎 Real-World Examples of Each Layer

OSI Model:

• Application Layer (🌍): Web browsing using HTTP/HTTPS

• Transport Layer (🚀): Sending an email using TCP

• Network Layer (🌐): Routing data via IP

• Data Link Layer (📡): Wi-Fi communication

• Physical Layer (⚡): Ethernet cables

TCP/IP Model:

• Application Layer (📨): Using SMTP for sending emails

• Transport Layer (📡): Streaming video via UDP

• Internet Layer (🌎): Web browsing using IP routing

🔑 Commonly Used Protocols & Their Port Numbers

🔐 AWS EC2 Security Groups: Securing Your Cloud Instances

📌 What are Security Groups?

Security Groups act as virtual firewalls for your AWS EC2 instances, controlling inbound and outbound traffic.

📌 Security Group Rules

• Inbound Rules 📥: Define what traffic is allowed to enter the instance (e.g., Allow SSH on port 22)

• Outbound Rules 📤: Specify allowed outgoing traffic (e.g., Allow HTTP requests to the internet)

📌 Importance of Security Groups

✅ Enhanced Security 🔒 - Blocks unauthorized access ✅ Granular Control 🎛️ - Configurable rules for different instances ✅ Default Deny 🚫 - Restricts all traffic unless explicitly allowed

📌 Example Security Group Configuration

🎯 Best Practices for AWS Security Groups

• Use Least Privilege 🚫 - Only allow necessary ports

• Restrict SSH Access 🔑 - Limit to known IPs

• Enable Logging & Monitoring 📊 - Track access logs

🔹 By understanding the OSI and TCP/IP models, commonly used network protocols, and AWS EC2 security best practices, you can build and secure robust network architectures! 🚀