Topic 3: Networks

Server and Client

• Server: Central piece of hardware or system in a network (holds data, sends/receives instructions).
• Client: Requests a service or connects to a server on the same network (e.g., kiosk in an airport).
• Analogy: Clients are bar patrons, the bartender is the server.

Computer Networks

• Definition: Multiple computers connected, can send/receive data.
• Types of Connections:
  • Hub: Sends data to all devices, not efficient.
  • Switch: Sends data from one specific computer to another.
  • Router: Connects multiple networks (e.g., home network to the internet).
• Internet: Large network using TCP/IP protocol, decentralized system.
• World Wide Web vs. Internet: WWW is the information (websites), Internet is the physical infrastructure.

ISPs and Internet Exchanges (IX)

• ISP: Provides Internet access, connects to Internet Exchanges.
• IX: Academic or nonprofit organizations that glue ISPs together, enabling global connectivity.
• Data Transmission: Uses packets (units of information) via packet switching.
  • Packet Structure: Payload (data), header (source/destination), footer.

Types of Networks

• LAN (Local Area Network): Covers a single building, high transfer rate, lower cost/setup.
• WAN (Wide Area Network): Covers larger areas, multiple LANs connected.
• PAN (Personal Area Network): Immediate user's area (e.g., Bluetooth).
• VLAN (Virtual LAN): Software-based, mimics physical LANs for security and configuration.
• SAN (Storage Area Network): Network of storage devices, not accessible via LAN/Wi-Fi.
• Wi-Fi (Wireless LAN): Uses radio waves for connectivity, easy setup.
• Intranet/Extranet: Private/internal networks, extranet accessible via an online portal.
• VPN (Virtual Private Network): Secure connection to a server, uses tunneling and encryption.
• Peer-to-Peer Network: Direct connection between computers without central server.

Network Protocols

• Role: Rules for data transmission (e.g., TCP/IP for internet, HTTPS for web data).
• Functions:
  • Data integrity
  • Flow control
  • Prevent deadlock
  • Ensure error-free transmission

OSI Model

• Seven Layers: Physical, Data Link, Network, Transport, Session, Presentation, Application.

Transmission Media

• Types: Wired (Ethernet, fiber optic) and Wireless (radio waves, microwave).
• Factors: Security, reliability, cost, speed.
• Comparison: Wi-Fi vs Ethernet; Fiber vs Copper.
• Speed Influencers: Traffic, time of day, distance, infrastructure quality.

Data Compression

• Lossy Compression: Removes data, irreversible, smaller file sizes (useful for multimedia).
• Lossless Compression: Uses algorithms, no data loss, reversible (useful for text).

Network Security

• Methods:
  • Authentication: 1FA (password), 2FA (password + SMS), 3FA (password + SMS + biometrics).
  • Encryption: Encodes data for secure transmission (SSL/TLS protocols).
  • MAC Address Control: Whitelisting MAC addresses to restrict network access.
  • Firewalls: Control incoming/outgoing traffic based on data packet analysis.
  • Physical Security: Secure physical access to network hardware (locks, guards, etc.).