Understanding Computer Networks: Transmission Media, Topologies, and Communication Standards

Posted on May 3, 2024 in Technology

1. Transmission Media

1.1. Electrical Leads

Electrical leads convey information as electrical signals through metal cables (copper or aluminum). Two common types are:

  • Twisted Pair: Pairs of insulated copper wires twisted together to minimize interference. Used for Ethernet networks with RJ-45 connectors.
  • Coaxial Cables: A central conductor surrounded by insulation, a metallic shield, and an outer insulation. Used for cable TV, telephone networks, and Ethernet with BNC connectors.

1.2. Optical Fiber

Optical fibers transmit data as light pulses through a glass core and a plastic cladding. They offer high speed and data capacity over long distances but are expensive to install. Common connectors are ST and SC.

1.3. Electromagnetic Waves

Electromagnetic waves propagate through space without a physical medium. They are used for various communication purposes:

1.3.1. Radio and Television Waves

These waves carry information by modulating a carrier wave. Two modulation techniques are:

  • Amplitude Modulation (AM): Varies the amplitude of the carrier wave.
  • Frequency Modulation (FM): Varies the frequency of the carrier wave.

A radio system consists of a microphone, transmitting antenna, repeater stations (if needed), receiving antenna, and a radio receiver with a speaker.

1.3.2. Microwaves for Terrestrial Communications

Microwaves are used for point-to-point communication using satellite dishes. The receiving antenna must be aligned with the transmitting antenna.

1.3.3. Microwaves for Satellite Communications

Satellite networks use microwaves to provide various services. Key components include:

  • Satellites: Receive and transmit data between ground stations.
  • Control Center: Monitors satellite operations.
  • Ground Stations: Send and receive data to/from satellites.

Different types of satellites based on their orbit include:

  • Geostationary Earth Orbit (GEO): High altitude, circular orbit for long-distance communication, weather forecasting, and TV broadcasting.
  • Highly Elliptical Orbit (HEO): Elliptical orbit for cartography.
  • Medium Earth Orbit (MEO): Lower altitude than GEO, used for positioning and mobile communication.
  • Low Earth Orbit (LEO): Lowest altitude, requiring many satellites for global coverage. Used for mobile communication, data collection, etc.

1.3.4. Infrared

Infrared waves have a lower frequency than visible light. They are used for short-range communication between devices, such as remote controls.

2. Computer Networks

Computer networks connect computers and devices to share information and resources.

2.1. LAN, MAN, WAN

Networks are classified based on their geographical coverage:

  • Local Area Network (LAN): Connects devices within a limited area like a building or campus.
  • Metropolitan Area Network (MAN): Covers a larger area like a city or region.
  • Wide Area Network (WAN): Spans a large geographical area, connecting LANs across countries or continents. The internet is an example of a WAN.

2.2. Network Topology

Network topology refers to the arrangement of devices and connections. Common topologies include:

  • Bus Topology: All devices connect to a single cable. A break in the cable disrupts the entire network.
  • Ring Topology: Devices are connected in a closed loop. Failure of one device affects the entire network.
  • Star Topology: Devices connect to a central hub or switch. Failure of one device does not affect others.

2.3. Client-Server Networks

Two main network models are:

  • Peer-to-Peer Networks: All devices have equal capabilities and can share resources.
  • Client-Server Networks: Dedicated servers provide services to client devices.

2.4. Communication Standards

The Institute of Electrical and Electronics Engineers (IEEE) develops communication standards for networks. Some important standards include:

  • Ethernet: The most common standard for wired LANs, typically using twisted pair cable with RJ-45 connectors.
  • Wi-Fi: Enables wireless connectivity for mobile devices with a range of 100-300 meters.
  • Bluetooth: A standard for short-range wireless communication between devices (around 10-15 meters).

2.5. Components of a Local Area Network

A LAN consists of both hardware and software components:

  • Network Interface Card (NIC): Connects a computer to the network. Wireless NICs have antennas for Wi-Fi connectivity.
  • Switch: A device that directs data between devices connected to it.
  • Hub: Similar to a switch but less efficient, as it broadcasts data to all connected devices.
  • Wireless Access Point: Allows wireless devices to connect to a wired network.
  • Peripherals: Shared devices like printers and hard drives.
  • Cables: Twisted pair and coaxial cables are commonly used in LANs.
  • Operating System: Provides network functionality and resource sharing.
  • Networking Software: Enables communication services like email, file transfer (FTP), and remote access (Telnet).

2.6. Interconnecting Networks

Several devices are used to connect networks or extend their reach:

  • Repeaters: Regenerate signals to extend the transmission distance.
  • Bridges: Connect two networks and filter traffic between them.
  • Gateways: Connect networks of different types.
  • Routers: Connect multiple networks and determine the best path for data transmission. They are commonly used to connect LANs to the internet.