Computer Networking Overview

Computer Networking

• Computer networking links computers for shared resources through the internet
• Networks allow web browsing, email, file sharing, image sharing, and downloading
• Organizations (companies, schools, governments) use networks for general purpose computing
• Networks categorized by geographic scope

Network Categories

• Personal Area Network (PAN): Smallest, connects personal devices (e.g., earbuds to phone, computer to printer)
• Local Area Network (LAN): Connects devices in a limited area (e.g., building, house) for shared resources
• Campus Area Network (CAN): Connects multiple buildings in a campus environment (e.g., universities)
• Metropolitan Area Network (MAN): Connects city buildings, devices, and wirelessly within a city area
• Wide Area Network (WAN): Largest, connecting vast areas (e.g., cities, countries); often composed of LANs and MANs

Network Architecture

• A diagram displaying network structure and services to meet connectivity needs
• Common enterprise network types:
  • Access networks: Connect users and devices within a building or branch location
  • Data center networks: Connect servers and applications for easy access
  • Wide area networks (WANs): Connect users to various services and programs (e.g., hospital employees to health applications)

The Open Systems Interconnection (OSI) Model

• A seven-layer model for communication systems allowing different network types to interlink
• Layers describe networking functions, from physical to application level
• Aims for compatibility and advancement of networking technologies

OSI Model Layers

• Physical Layer: Electrical and mechanical connections to the network
• Data Link Layer: Handles error recovery, flow control, and sequencing; includes MAC addressing
• Network Layer: Network controller handling outgoing messages and routing information
• Transport Layer: End-to-end message integrity and delivery between devices
• Session Layer: Controls connections, starts, manages, and ends them
• Presentation Layer: Converts messages to appropriate formats for applications (e.g. encryption, compression)
• Application Layer: Interacts with applications for tasks such as web browsing and email

Network Types and Devices

• Wired Networks: Use cables and connectors for connections (e.g., LAN cables)
• Wireless Networks: Use radio signals for connections (e.g., Wi-Fi)
• Wired Devices:
  • Hub: Interconnects devices but broadcasts all data; less privacy-focused
  • Switch: Initiates a direct connection between devices
  • Cable Modem: Connects home networks to the internet
  • Servers: Provide resources, data, and programs to clients
  • Firewall: Monitors and controls network traffic; establishes security policies
• Wireless Devices:
  • Access Point: Connects wireless devices and provides access to wired LANs
  • Wireless Router: Connects wireless devices to other networks (e.g., internet)

Network Topologies

• Point-to-Point: Simplest; direct connection between two devices
• Token Ring: Each device has a fixed time interval for transmission
• Bus: Sharing media for communication in a single line; vulnerable to data transmission interruptions
• Star: Most common in LANs; all devices connect to a central switch or hub
• Mesh: Direct connection between all devices (fully) or through multiple paths between some devices (partially)