Connecting 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 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 transmit 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