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Cybersecurity Essentials Lecture One ​

What is a Network? ​

A computer network is a system that connects multiple independent computers and devices to share data and resources. It enables easier communication and collaboration among users.

  • A network can be established using cable (wired) or wireless media.
  • It uses both hardware and software to facilitate connections and operations.

Types of Computer Networks ​

1. Local Area Network (LAN) ​

  • Most commonly used network type.
  • Connects computers within a limited area (e.g., home, office, school).
  • Range: Up to 2 km.
  • High transmission speed, easy to maintain, and low cost.
  • Example: Networking in libraries, labs, schools, and offices.

2. Wide Area Network (WAN) ​

  • Connects computers across large geographical distances.
  • Not restricted to a single location.
  • Essentially a group of LANs connected together.
  • Range: Over 50 km.
  • Low transmission speed, high maintenance, and high cost.
  • Example: The Internet.

3. Metropolitan Area Network (MAN) ​

  • Larger than LAN, smaller than WAN.
  • Connects computers across a city or town.
  • Range: 5 km to 50 km.
  • Moderate transmission speed, high cost, and harder to maintain.
  • Example: Networking within a city or across multiple buildings in a campus.

4. Personal Area Network (PAN) ​

  • Basic type of network used around a single person.
  • Connects personal devices like smartphones, tablets, laptops.
  • Range: 1 to 100 meters.
  • High transmission speed, very low cost, and easy maintenance.
  • Typically uses Bluetooth.
  • Example: Connections between a phone and a Bluetooth headset or printer.

5. Body Area Network (BAN) / Body Sensor Network (BSN) / Wireless Body Area Network (WBAN) ​

  • A system of low-power wearable or implanted devices operating around the human body.
  • Communicates wirelessly and can transmit data via gateways to the Internet or base stations.
  • Commonly used in healthcare to monitor patient data remotely.
  • Uses technologies like WPAN for broader connectivity.

What is Data Communication? ​

Telecommunication refers to communication over a distance, while data communication is the exchange of data between two devices using a transmission medium (e.g., cable or wireless).

Characteristics of Effective Data Communication ​

  1. Delivery – Data must reach the correct destination.
  2. Accuracy – Data should be delivered without errors.
  3. Timeliness – Data should be delivered in real-time (especially for audio/video).
  4. Jitter – Variation in packet arrival time should be minimized.

Network Criteria ​

  • Performance: Evaluated by throughput and delay.
  • Reliability: Includes accuracy, failure frequency, recovery time, and robustness.
  • Security: Involves protecting data from unauthorized access, corruption, and implementing recovery measures.

Network Devices ​

Network devices are hardware components that allow communication between computers and other devices on a network.

Repeater ​

  • Operates at the physical layer.
  • Regenerates weak or corrupted signals to extend transmission distance.
  • 2-port device used in star topologies.

Hub ​

  • Multiport repeater.
  • Connects multiple devices in a network.
  • Broadcasts data to all connected devices (no filtering or routing).
  • Lacks efficiency and intelligent data forwarding.

Bridge ​

  • Operates at the data link layer.
  • Filters traffic by MAC address and connects two or more LAN segments.
  • Modern bridges are often called Layer 2 switches.

Switch ​

  • Multiport bridge with buffers for better efficiency.
  • Operates at the data link layer.
  • Performs error checking and forwards data only to the intended port.

Router ​

  • Operates at the network layer.
  • Routes data based on IP addresses.
  • Connects multiple networks (e.g., LAN to WAN).
  • Divides broadcast domains and dynamically updates routing tables.

Modem ​

  • Stands for modulator/demodulator.
  • Converts digital signals to analog (and vice versa) for transmission over telephone lines or cables.
  • Commonly used for internet access via ISPs.

Access Point (AP) ​

  • Wireless networking device that connects wireless devices to a wired network.
  • Creates Wireless Local Area Network (WLAN).
  • Useful in large offices and buildings to provide mobile access with reduced infrastructure cost.