Connecting to a computer NetworkConnecting to a computer NetworkConnecting to a computer NetworkConnecting to a computer Network

• Network interface Card (NIC)

• Connecting Devices

• Network Cables

• Wireless Networks

• Network Topology

• Network Operating System

Network Interface Card (NIC)

• Transferring message from computer to network cables

• Is an expansion card (or built-in) to motherboard

• is the KEY hardware component for connecting the computer to a network– of course need software setting too …

• Each NIC has a unique hardware number– MAC Address (Medium Access Control)– used to identify the computer in a network– e.g. 00-10-B5-59-CF-56

• already burnt in by manufacturer

• Network Card Classification– by type of connectors

• AUI / BNC / RJ-45

– by Expansion bus• ISA / PCI / PCMCIA / USB

– by Bandwidth• 10Mbps / 100Mbps / 1000Mbps• 10/100 Mbps (Combo)

Connecting Device

• For connecting the computers and devices in a network– repeater– hub– bridge– switch– router

• Repeater– one-port to one-port– a device that

• amplifies the signal it receives and then resend it– because there has signal attenuation during the

transmission of signal over long distance

• remove unwanted noise

– do not consider to forward the signal or not

• Hub– a repeater with multi-ports (multi-ports

repeater)– also do not consider to forward the signal or

not– disadvantage :

• shares bandwidth– broadcast the signal to all other ports– for heavy traffic network, the performance degrade

• Bridge– one-port to one-port– used to interconnect LAN segment– with the advantage of repeater plus

• when receiving a signal, will consider to forward the signal or not

Yes / No ?

• Switch– a bridge with multi-ports (multi-ports bridge)– unlike hub, it does not broadcast signal to all

ports• but just send the signal to destination port• because it contains a switching tables

A

B

C

F

E

D

To E

• Router – a device used to connect multiple networks– an essential device for connecting a LAN to

the internet– To translate information between LAN and the

Internet• LAN - private IP address• Internal - real IP address

– A router also has the function of choosing the best route (path) for information flow

• best path = shortest distance, shortest time– depending on the protocol used

WAN LAN

Network cables

• Used to connect computers and other devices

• Common types :– twister pair cable– coaxial cable– optical fibre

• Twisted-Pair Cable– like telephone cables– has a square, plastic head

• RJ-45 connector– telephone … RJ-11 connector

– often used in LAN– Type of twisted-pair cable

• shielded twisted pair (STP)• unshielded twisted pair (UTP) …. Most common

• Shielded Twisted Pair cable (STP)– has a metal wrapper around each wire

• to reduce noise due to electromagnetic (EM) wave– i.e. to reduce interference

• Unshielded Twisted Pair cable (UTP)– do not has a metal wrapper around each wire– Types of UTP :

• Category 1, 2, 3, 4, 5

• Most common : Cat. 5– data transfer rate up to about 100Mbps

• Coaxial Cable– commonly used for VCR and cable TV

connections– uses BNC connector– Adv :

• retain the strength of signal over long distance transmission (c.f. twisted pair cable)

– Structure of a coaxial cable• Innermost = copper wire• then ===== a sheath of insulation• then ===== a metal wire mesh

– conducts and shields against interference

• Outermost = coating (plastic)

– More insulation of coaxial cable• allow coaxial cable to carry more information than

twisted pair cable

• Crosstalk– because twisted pair and coaxial cable use

copper conductors• transmit electrical signals• generate EMI

– electromagnetic interference

• EMI disturb the quality of transmission• = CROSSTALK

• Optical fibre cable– made of a bundle of glass threads that transm

it light beams• using the principles of total internal reflection

– Adv (c.f. twisted pair and coaxial)• greater signal carrying capacity• faster data transmission• less susceptibility to noise / interference

– from other device

– Adv (cont’d)• Better Security for signal during transmission• much thinner• less heavy

– Disadv :• more expensive• more technique is require during the installation• more easy to break