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3 Computing System Fundamentals

3 Computing System Fundamentals. 3.4 Networked Computer Systems. 3.4.2 Network Hardware. The network interface. Computers may be directly connected to a LAN, in which case they will need special hardware (the network interface card or NIC ).

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3 Computing System Fundamentals

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  1. 3 Computing System Fundamentals • 3.4 Networked Computer Systems

  2. 3.4.2 Network Hardware

  3. The network interface • Computers may be directly connected to a LAN, in which case they will need special hardware (the network interface card or NIC). • Even if they only connect occasionally to a WAN (e.g. using a dial-up connection via a telephone line) they need a modem. • Direct connections e.g. DSL are faster than dial-up connections.

  4. Connection media • The medium of transmission may be: • an electrical cable (e.g. coaxial or unshielded twisted pair - UTP), • fibre optic cable or • via radio waves.

  5. Coaxial cable

  6. UTP cable

  7. Fibre optic cable

  8. Wifi base station

  9. Microwave link

  10. Satellite link

  11. Network hardware • Various connection boxes co-ordinate the transmission of data with varying degrees of programability. • Of those that follow, the important ones are: • hub, • switch and • router.

  12. Hub • A hub is a junction box, acts as a repeater, amplifying and sending on signals to networked devices, but not discriminating on where they are for or from.

  13. Switch • A switch is similar to a hub but with some ability to filter out irrelevant traffic.

  14. Bridge • A bridge links together LANs, letting through only the data destined for that LAN (thus reducing unnecessary traffic).

  15. Gateway • A gateway is similar to a bridge, but can also translate data from one network protocol to another.

  16. Router • A router can translate and direct the traffic. • They are used to manage internet traffic: data will always be passed on to a router nearer to their destination.

  17. Modem • A modem converts a computer’s digital data (stream of bits) to analogue (continuous wave) sound (DA conversion or DAC) and vice versa.

  18. Modems • Dial-up modem speed theoretically up to 56kbps (bps = bits per sec). • ISDN (Integrates Services Digital Network), transfer rates of up to 144kbps). • ADSL (Asynchronous Digital Subscriber Line), incoming rate ~8Mbps and outgoing ~1Mbps).

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