Computer Networks

Peer-to-Peer Network

• In a peer-to-peer network, if one computer stops working, the others will not be affected.
• Each computer manages itself, making it easy to set up and maintain.
• Disadvantages include:
  • No centralized system for data backup.
  • Security issues since each device manages itself.

Client/Server Network

• A client/server network is designed for end users (clients) to access resources from a central computer (server).
• The server manages all resources, including security and network management.
• Clients communicate with each other through the server.
• Advantages include:
  • Centralized system for data backup.
  • Improved performance and security.
  • Faster resource sharing.
• Disadvantages include:
  • High cost of the server and its operating system.
  • Requires a dedicated server with large memory.

Network Layer (Layer 3)

• Manages device addressing and tracking.
• Determines the best path for data transmission based on network conditions and priority.
• Responsible for routing and forwarding packets.
• Routers are layer 3 devices used for routing services.
• Protocols used for routing include IP and IPv6.
• Functions include:
  • Internetworking: connecting different devices.
  • Addressing: adding source and destination addresses to packets.
  • Routing: determining the best path for data transmission.
  • Packetizing: dividing data into packets.

Transport Layer (Layer 4)

• Ensures that messages are transmitted in the correct order and without duplication.
• Responsible for complete data transfer.
• Provides error-free transfer of data.

Guided Media

• Types:
  • Twisted Pair:
    • Made up of two insulated copper wires twisted together.
    • Categories: 1, 2, 3, 4, 5, with increasing speeds.
    • Advantages: cheap, easy to install, lightweight.
    • Disadvantages: limited distance due to attenuation.
  • Shielded Twisted Pair (STP):
    • Has a mesh surrounding the wire for higher transmission rates.
    • Advantages: higher capacity, easier to install, shielded.
    • Disadvantages: more expensive than UTP.

Microwave

• Frequency range: 4-6 GHz to 21-23 GHz.
• Bandwidth: 1-10 Mbps.
• Short distance: inexpensive.
• Long distance: expensive due to tower requirements.
• Attenuation: affected by environmental conditions and antenna size.
• Advantages:
  • Cheaper than cable transmission.
  • No land acquisition required.
  • Easy communication in terrains.
  • Communication over oceans possible.
• Disadvantages:
  • Susceptible to eavesdropping.
  • Out of phase signal.
  • Weather conditions affect signal.
  • Limited bandwidth.

Satellite Microwave Communication

• A satellite is a physical object that revolves around the earth.
• Satellite communication is more reliable and flexible than cable and fiber optic systems.
• How it works:
  • Signal is transmitted from earth station to satellite.
  • Satellite amplifies the signal.
  • Multiplexing is used to combine multiple data streams.
  • Signal is transmitted back to earth station.
• Multiplexing:
  • Why: to avoid collision and share bandwidth.
  • Concept: combining multiple signals into one.
  • History: originated in telegraphy in the 1870s.
  • Types: many-to-one, one-to-many.