Week 1 - Networking

1. Understand OSI & TCP/IP Models

What Is the OSI Model?

The OSI (Open Systems Interconnection) model is a framework that explains how computers communicate over a network. It is divided into seven layers, each with a specific role, from physical connections to application interactions.

Why Is It Important?

The OSI model helps people understand how data moves through a network. It also aids in troubleshooting by allowing network professionals to pinpoint issues at specific layers.

The OSI 7 Layers

We’ll describe OSI layers “top down” from the application layer that directly serves the end user, down to the physical layer.

1. Application Layer:
   This is where users interact with software (e.g., web browsers, email). It helps applications communicate over the network.

2. Presentation Layer:
   It formats and translates data so different systems can understand each other. It also handles encryption and compression for secure and efficient data transfer.

3. Session Layer:
   Manages connections between computers, making sure they start, stay active, and end smoothly. It also helps resume connections if interrupted.

4. Transport Layer:
   Ensures data is sent completely and accurately. It breaks data into smaller parts and checks for errors to provide reliable communication.

5. Network Layer:
   Routes data to its destination using IP addresses. It decides the best path for data to travel across different networks.

6. Data Link Layer:
   Transfers data between devices on the same network. It also detects and corrects errors that occur during transmission.

7. Physical Layer:
   Involves the actual hardware (cables, switches, etc.) that transmit data as electrical, optical, or radio signals.

What Is the TCP/IP Model?

The TCP/IP model is a fundamental framework for computer networking. It stands for Transmission Control Protocol/Internet Protocol, which are the core protocols of the Internet.

This model defines how data is transmitted over networks, ensuring reliable communication between devices.

Why Is It Important?

It enables global communication by connecting different devices and networks. It ensures reliable data delivery with error-checking and scalability for growing networks. Its flexibility and standardization make it the backbone of the Internet.

Layers of TCP/IP Model

1. Network Interface Layer: Handles the physical transmission of data over a network.

2. Internet Layer: Manages the routing of data packets across the network.

3. Transport Layer: Ensures reliable data transmission between devices.

4. Application Layer: Provides protocols for specific data communication services on a process-to-process level.

How is the TCP/IP Model different from the OSI Model?

The OSI Model has seven layers, while the TCP/IP Model has four layers. The TCP/IP Model is simpler and more practical, making it more widely used in real-world networking.

What are the most commonly used protocols?

1. HTTP (Hypertext Transfer Protocol) - Port 80
   Used for transferring web pages and other resources over the internet.

2. HTTPS (HTTP Secure) - Port 443
   Secure version of HTTP with encryption for safe data transfer.

3. FTP (File Transfer Protocol) - Ports 20 (Data), 21 (Control)
   Used for transferring files between client and server.

4. SSH (Secure Shell) - Port 22
   Provides secure remote login and command execution.

5. DNS (Domain Name System) - Port 53
   Translates domain names into IP addresses.

Conclusion

The OSI and TCP/IP models are essential frameworks for understanding network communication. The OSI model provides a detailed, layered approach that helps in learning and troubleshooting networks, while the simpler TCP/IP model is the backbone of the modern Internet. Together, they offer a clear structure for data transmission, ensuring compatibility and reliability across different systems and devices. Understanding both models is crucial for effective network design, management, and communication.