Computer Networking: LAN, WAN, MAN, PAN

• Computer networking involves the exchange of data between devices over a communication medium
• It enables resource sharing, communication, and access to information

Network Types

• Local Area Network (LAN): Connects devices in a limited area like a home, school, or office
• Wide Area Network (WAN): Connects devices over a large geographical area, like the internet
• Metropolitan Area Network (MAN): Connects devices within a city or metropolitan area
• Personal Area Network (PAN): Connects devices in a small area, typically around an individual

Network Topologies

• Bus Topology: All devices are connected to a central cable, called the bus
  • Simple to implement but a break in the bus can disrupt the entire network
• Star Topology: All devices are connected to a central node, like a hub or switch
  • Easy to troubleshoot, but the central node's failure can affect the entire network
• Ring Topology: Each device is connected to two other devices, forming a ring
  • Data travels in one direction, but a break in the ring can disrupt the network
• Mesh Topology: Each device is connected to many other devices
  • Highly redundant and reliable, but complex and expensive
• Tree Topology: Combines characteristics of linear bus and star topologies, consists of groups of star-configured workstations connected to a linear bus backbone cable
  • Provides scalability and hierarchy

Key Network Devices

• Router: Forwards data packets between networks
  • Operates at the network layer
• Switch: Connects devices within a network
  • Operates at the data link layer
• Hub: Connects devices within a network
  • Operates at the physical layer, broadcasts data to all connected devices
• Modem: Modulates and demodulates signals for transmission over communication channels

Communication Protocols

• TCP/IP (Transmission Control Protocol/Internet Protocol): Suite of protocols governing internet communication
• HTTP (Hypertext Transfer Protocol): For web communication
• FTP (File Transfer Protocol): For file transfer
• SMTP (Simple Mail Transfer Protocol): For email transmission
• DNS (Domain Name System): Translates domain names to IP addresses

IP Addressing

• IPv4: 32-bit address, represented in dotted decimal notation
• IPv6: 128-bit address, represented in hexadecimal notation
• Private IP addresses: Used within private networks and not routable on the internet
• Public IP addresses: Used for communication on the internet

Subnetting

• Dividing a network into smaller subnetworks for better management and security
• Involves borrowing bits from the host portion of an IP address to create subnetworks
• Subnet mask: Used to identify the network and host portions of an IP address

Network Security

• Firewall: A network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules
• VPN (Virtual Private Network): Establishes a secure connection over a public network
• Encryption: Encoding data to protect its confidentiality

Wireless Networking

• Wi-Fi: Wireless communication technology based on the IEEE 802.11 standards
• Bluetooth: Wireless technology for short-range communication

The OSI Model

• The Open Systems Interconnection (OSI) model is a conceptual framework
• It standardizes the functions of a telecommunication or computing system
• Characterized by a layered approach
• This model divides the communication system into seven abstract layers

Seven Layers of the OSI Model

• Each layer has specific functions

Layer 7: Application Layer

• Provides network services to applications
• Examples: HTTP, FTP, SMTP, DNS
• Provides interfaces for applications to access network services
• Deals with high-level protocols and data interpretation for applications
• It's the layer closest to the end user

Layer 6: Presentation Layer

• Handles data representation, encryption, and decryption
• Ensures that data is in a usable format for the application layer
• Converts data formats between different systems
• Handles character encoding, data compression, and encryption

Layer 5: Session Layer

• Manages connections between applications
• Establishes, maintains, and terminates sessions
• Provides mechanisms for synchronization and dialogue control
• Handles authentication and authorization

Layer 4: Transport Layer

• Provides reliable and unreliable data delivery between hosts
• Uses protocols like TCP (reliable) and UDP (unreliable)
• TCP provides flow control, error correction, and retransmission
• UDP provides fast, connectionless communication
• Segments data into smaller units for transmission

Layer 3: Network Layer

• Handles routing of data packets between networks
• Uses IP addresses to identify hosts
• Determines the best path for data to travel
• Uses protocols like IP, ICMP, and routing protocols
• Implements logical addressing

Layer 2: Data Link Layer

• Provides error-free transmission of data between adjacent nodes
• Uses MAC addresses to identify devices
• Divides data into frames
• Implements error detection and correction mechanisms
• Protocols: Ethernet, PPP, Frame Relay

Layer 1: Physical Layer

• Transmits raw bit stream over the physical medium
• Defines physical characteristics of the network
• Specifies voltages, data rates, and physical connectors
• Deals with cables, connectors, and network interface cards

Data Encapsulation and Decapsulation

• Encapsulation: Adding headers and trailers to data as it moves down the OSI model
• Decapsulation: Removing headers and trailers as data moves up the OSI model
• Each layer adds its own control information to the data

Advantages of the OSI Model

• Provides a standard framework for network communication
• Allows modular design and development
• Facilitates troubleshooting and problem isolation
• Promotes interoperability between different devices and networks

TCP/IP Model vs. OSI Model

• TCP/IP model is a simplified model with four layers: application, transport, internet, and link
• OSI model has seven layers, providing a more detailed framework
• TCP/IP model is the foundation of the internet, while the OSI model is a conceptual reference model