WORLD WIDE WEB : WEB BROWSER

THE WORLD WIDE WEB

•The World Wide Web, a service of the Internet.

•The Internet was developed in the late 1960s.

•The World Wide Web emerged in the early 1990s.

WORLD WIDE WORLD

THE WORLD WIDE WORLD

• Web pages 

          - Each electronic documents on the Web.

          - Can contain text, graphics, animation, audio and video.

• Types of web pages

          - Static (fixed) : A fixed Web page where visitors all see the same content.

          - Dynamic (changing) : A Web page that allows visitors to customize some of all the viewed                  contents.

WEB BROWSER

• A Web browser, or browser, is application software that allows users to access and view Web pages.
• The purpose of a web browser is to bring information resources to the user.
• With an Internet connection established, you start a Web browser.
• The browser retrieves and displays a starting Web page.

BASIC CONCEPT OF NETWORK

DEFINITION 

• A network is a collection of computers and devices connected together via communications devices and transmission media.

BASIC CONCEPT OF NETWORK

• Usually, the connections between computers in a network are made using physical wires or cables.
• However, some connections are wireless, using radio waves or infrared signals.

APPLICATIONS OF NETWORK

•           Resource Sharing

Ø  Hardware (computing resources, disks, printers)

Ø  Software (application software)

•            Information Sharing

Ø  Easy accessibility from anywhere (files, database)

Ø  Search Capability (www)

•  Communication

Ø  Email

Ø  Message board

COMMUNICATION DEVICES

• A communications device is any type of hardware capable of transmitting data, instructions, and information between a sending device and a receiving device.

TYPES OF COMMUNICATION DEVICES

• Dial-up Modem.
• Digital Modem (ISDN, DSL, Cable Modem).
• Wireless Modem.
• Network Card.
• Wireless Access Point.
• Router.
• Switch.
• Hub.

TRANSMISSION MEDIA

• Materials or substances capable of carrying one or more signals in a communications channel.

TYPES OF TRANSMISSION MEDIA

1. Physical transmission media/Guided media/Wired : Twisted-pair Cable, Coaxial Cable, Fiber-optic Cable.
2. Wireless transmission media/Unguided media : Infrared, Broadcast Radio, Cellular Radio, Microwave, Communications Satellite.

COMPUTER ETHICS : NETIQUETTE

NETIQUETTE 

• Netiquette, or net etiquette, refers to etiquette on the Internet. 
• Is the code of acceptable behaviours users should follow while on the Internet or online or cyberspace.
• It is the conduct expected of individuals while online.
• Rules for all aspects of the:

1. World Wide Web
2. E-mail
3. Instant Messaging
4. Chat rooms
5. Newsgroups & message board.  

• Electronic communication lacks the facial expression, gestures and tone of voice to convey your meaning. It’s easy to misinterpret meaning of words.
• Remember, when you communicate through cyberspace your words are written. 
• Chances are they're stored somewhere and they can come back and haunt you.
• Any message you send could be saved or forwarded by its recipient. You have no control over where it goes. 
• When you enter a domain of cyberspace that's new to you, take a look around and spend a while listening to the chat or reading the archives.
• Get a sense of how the people who are already there act, then go ahead and participate. 
• Don’t expect instant responses to all your questions and don't assume that all readers will agree with or care about your passionate arguments.

NETWORK TOPOLOGY

DEFINITION

• A network topology refers to the layout of the computers and devices in a communication network. 
• It refers to both the physical and logical layout of a network. 

PHYSICAL TOPOLOGY

• The arrangement of a cabling is the physical topology. 

LOGICAL TOPOLOGY

• The path that data travels between computers on a network is the logical topology. 

BUS TOPOLOGY

• A bus network consists of a single central cable (backbone), to which all computers and other devices connect. 
• The bus is the pysical cable that connects the computers and other devices. 
• The bus in a bus network transmit data, instructions, and information as a series of signal. 
• Those signals are sent as electric pulses that travel along the length of the cable in all directions. 
• Each devices is connected to the single bus cable through T-Connecter. 
• A terminator is required at each end of the bus cable to prevent the signal from bouncing back and forth on the bus cable. 
• When a sending device transmits data, the address of the receiving device is included with the transmission. 
• If the device address does not match the intended address for the data, the device ignores the data. 
• If the data does not match the devices address, the data is accepted. 
• All devices receive the data but only the receiving device accept them. 

RING TOPOLOGY

• On a ring network, a cable forms a closed loop (ring) with all computers and devices arranged along the ring. 
• Data transmitted on a ring network travels from device to device around the entire ring, in one direction (clockwise or counterclockwise). 
• Token passing is one method for sending data around a ring. 
• Each device takes a turn sending and receiving information through the use of a token. 
• The token along with any data is sent from the first device to the second device which extracts the data addressed to it and adds any data it wishes to send. 
• Then second device passes the token and data to the third device, etc. until it comes back around to the first device again. 
• Only the device with the token is allowed to send data. 
• All other devices must wait for the token to come to them. 

STAR TOPOLOGY

• All the computers and other devices on the network connect to a central device, thus forming a star. 
• Two types of devices that provide a common central connection point to all the other devices on the network are a hub and a switch.

HUB / SWITCH 

• The device that provides a common central connection point for other devices on a network. 
• All the data that transfers from one device to another passes through the hub or switch. 
• The hub / switch takes a signal that comes from any device and passes it along to all the other devices in the network. 

NETWORK ARCHITECTURE

بِسْمِ ٱللّٰهِ ٱلرَّحْمٰنِ ٱلرَّحِيمِ

DEFINITION

• The design of computers, devices, and media on a network is sometimes called the network architecture.
• There are two categories of network architecture :
• Peer-to-peer
• Client-server

PEER-TO-PEER

• Is a simple, inexpensive network, typically connects fewer than 10 computers.
• Each computer, called a peer, has equal responsibility and capabilities in sharing hardware.
• Each computer on a peer-to-peer network shares its hardware and software with other computers on the network.
• It describes an Internet network on which users access each other's hard disks and exchange files directly over the Internet.
• Each peer, stores files on its own storage devices.

CLIENT-SERVER

• A network in which the shared files applications are stored in the server and network that request services from the server.
• One or more computers act as a server and the clients access the server ; highly capable computer on the network.
• A server controls access to the hardware, software and other resources on the network.
• The other computers on the network, called clients request services from the server.

ADVANTAGES & DISADVANTAGES

	ADVANTAGES	DISADVANTAGES
PEER-TO-PEER	Low cost. Simple to configure. User has full accessibility of the computer.	May have duplication in resources. Difficult to uphold security policy. Difficult to handle uneven loading.
CLIENT-SERVER	Centralized security & backups. Faster access. Single password. Better password security.	Central point of failure. Administrator required. Server and server software required.