Wednesday 30 May 2012

INTERNET INFRASTRUCTURE

Internet is a global network connecting millions of computer using a common sets of communications protocols called internet protocol (IP).

INTERNET PROTOCOL (IP)
~ provides a common layer over dissimilar networks
~ used to move packets among host computer
~ consist of 32 bits
~ 4 octets of no. from 0-255
~ represented in decimal form instead of binary form
~ easy to remember the decimal no. rather than binary form
~ consist of two parts ; identify network and identify nodes
~ eg : 168.223.210.221

Class A Network
~ binary address start with 0
~ no. can be anywhere from 1-126
~ first octet is the identify network
~ eg : 108.187.212.206

Class B Network
~ binary address start with 10
~ no. can be anywhere from 128-191
~ first two octets is the identify network
~ 127 is reserved for loopback
~ eg : 187.202.226.212

Class C Network
~ binary address start with 110
~ no. can be anywhere from 129-223
~ first three octets is the identify network
~ eg : 212.167.203.224

Class D Network
~ binary address start with 1110
~ no. can be anywhere from 224-239
~ used to support multicasting

Class E Network
~ binary address start with 1111
~ no. can be anywhere from 240-255
~ used for experiment and never been documented

DOMAIN NAME SYSTEM (DNS)
~ an internet service that translate domain namesinto numerical IP
~ eg : www.yahoo.com into 210.168.223.211
~ fx ; easier to remember


INTERNET SERVICE PROVIDER (ISP)
~ provides access to the internet
~ monthly fee ; provide software package, username, password and access phone no.
~ equipped with modem

HTTP
~ Hyper Text Transfer Protocol
~ define how messages are formatted and transmitted
~ command to the Web server to fetch and transmmit the request web page
~ transfer the contents of a web page into browser for viewing

Friday 11 May 2012

TRANSMISSION MEDIA

UNGUIDED/UNBOUNDED MEDIA
- transport electromagnetic wave without physical conductor
- signal broadcasting through air or water
- types of media : microwave, satellite and wireless

1. TERRESTRIAL MICROWAVE
~ require line-of-sight transmission and reception microwave
~ the taller the antennas, the longer the sight distance
~ signals are propagate in one direction in a time
~ consist of repeater which function to increase the distance
~ two types of antenna :

a) Parabolic Dish
~ catching a wide range of waves and directing to a focus
~ higher frequencies for higher data rates
~ 10-60 GHz

b) Horn
~ looks like a gigantic scoop
~ deflected the waves outward in a series of narrow parallel beams
~ received transmission are collected by the scooped shape

2.  SATELLITE
~ acting as a super tall antenna and repeater
~ relay station : receive on one frequency, amplifies and repeats signal and transmits on another frequency
~ geosynchronous : orbital speed is based on distance from planet
~ 35.784km away from the planet
~ uplink : transmission from earth to the satellite
~ downlink : transmission from satellite to earth

3. WIRELESS @ Wi-Fi
~ transmits computer data over distances using radio waves
~ most commonly used is 802.11 b (11MBps)
~ 802.11 a (54MBps)
~ to communicate over the network, computer must be equipped with a Wi-Fi card
~ types of Wi-Fi card : Wi-Fi PC Cards, USB Adapter, PCI and ISA Adapter etc.