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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
3 Computing System Fundamentals

  • 3.4 Networked Computer Systems



The network interface
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.


Connection media
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.








Network hardware
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.


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.


Switch
Switch

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


Bridge
Bridge

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


Gateway
Gateway

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


Router
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.


Modem
Modem

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


Modems
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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