Adobe Scan 18-Feb-2025

Computer networks enable data transfer between computers, analogous to train networks facilitating travel.
They connect people, shrinking the world and enhancing communication, collaborative efforts, and information sharing.
A network consists of two or more connected computers sharing resources, which can range from home setups to global networks like the Internet.

Resource Sharing: Devices share resources like printers and scanners within a network.
File Sharing and Remote Database Access: Allows easy access and collaboration on files without the need for physical storage devices (e.g., CDs). Example: Railway reservation systems where user access data simultaneously.
Ease of Communication: Facilitates communication through emails and instant messaging, making information transmission efficient and affordable.
Data Backup: Important files can be backed up across different locations, ensuring data safety in case of individual computer failures.
Software Cost and Management: Network versions of software are more economical than individual copies, reducing overhead costs.

ARPANET: The foundation of the Internet, established by the US Department of Defence.

Personal Area Network (PAN): Organised around an individual; connects devices like phones and laptops in close proximity.
Local Area Network (LAN): Covers a small area like a school or office; uses cables or radio waves for connection.
Campus Area Network (CAN): Connects multiple LANs within a limited geographical area, typically in an educational or office setting.
Metropolitan Area Network (MAN): Covers larger areas than a LAN, connecting multiple offices within a city.
Wide Area Network (WAN): Spans extensive geographical areas, connecting LANs and MANs, such as the Internet, often using fibre optic cables and satellite links.

Topology: The arrangement of computers in a network. Each computer is a node.

Bus Topology: All computers connected to a single backbone cable; data shares in both directions.
Ring Topology: Each computer connects to two others in a closed loop, transmitting data in one direction. A breakdown can disable the network.
Star Topology: All nodes connect to a central node (hub/switch); easy to add computers but a failure at the central node affects the whole network.
Mesh Topology: Each computer connects to every other one, very robust but costly to implement.

Twisted Pair Cable: Consists of pairs of insulated wires; comes in shielded and unshielded versions (UTP is most common).
Coaxial Cable: Has a central conductor surrounded by insulation and shielding; used for cable internet.
Optical Fibre Cable: Contains a glass core transmitting data as light; faster and capable of covering longer distances than other cables.

Microwave Transmission: Used for line-of-sight communication; suitable for terrestrial and satellite links.
Radio Wave Transmission: Omnidirectional, allows easy communication over long distances, can penetrate buildings; used in Wi-Fi and Bluetooth technologies.

Bluetooth: Short-range communication technology, effective for data exchange between close devices (around 30 feet).
Wi-Fi: Popular high-speed wireless networking technology allowing internet connections through radio waves.
WiMAX: Similar to Wi-Fi but with higher speeds and coverage.

NIC (Network Interface Card): Hardware that enables computers to connect and communicate over networks, carrying a unique MAC address.
Hub: Connects multiple computers, broadcasting data to all connected devices.
Switch: An intelligent device that forwards data only to the intended recipient.
Router: Connects different networks, forwarding packets based on address info.

TCP/IP: Standard for sending data over the internet, where TCP breaks data into packets and IP finds optimal routes for them.
HTTP/HTTPS: Protocols for transferring web pages, with HTTPS providing secure communication.

Data is split into packets before transmission; each packet contains headers for routing.
Packets may travel different paths to reach their destination and are reassembled upon arrival.

Threats: Viruses, worms, and Trojan horses pose risks to network safety.
Security Measures:
- Antivirus Software: Protects against malware and should be regularly updated (examples: Norton, McAfee).
- Firewalls: Prevent unauthorized access; can be software, hardware, or a mix.
General Awareness: Understanding hacker types (white and black) is vital for network protection.

Computer Network: A system of interconnected computers for resource sharing.
Topology: Configuration of a network.
Optical Fibre Cable: Transmits data using light signals.
WLAN: Wireless Local Area Network.
Packet Switching: Method for routing data in small packets based on address.