CSI315 Lecture 1CSI315 Lecture 1CSI315 Lecture 1CSI315 Lecture 1

WEEK 1WEEK 1

The Internet• A world-wide network of millions of

computers connected to share information and communication.

• The interconnected computers allow information transfer based on standardized protocols.

• Internet computers are connected to each other by telecommunications links.

• Internet is not a single network, but a collection of networks that are connected to each other.

Internet HistoryLate 1960’s, US Defence network.Funded ARPA (Advanced Research

Projects Agency) of the DOD.Objectives:• To network main computers of ARPA funded

projects in universities and research institutes• ARPAnet: allow multiple users to communicate

simultaneously over the same communication paths

• Using packet switching technique• No centralized Control• Transmission Control Protocol (TCP) adopted

later TCP/IP Internetworking Protocol

FACTS ABOUT THE INTERNET

• Developed in 1960’s from just a few to millions of connections today.

• No one knows exactly how many computers are connected to the Internet.

• No one is in charge of the Internet • There exists organizations which

develop technical aspects and set standards for creating applications

• TCP/IP is an agreed upon standard for computer communication over Internet.

• The Internet uses the client-server model

Internet Technologies

• The Internet Backbone• Communication protocols• Communication Software• Telecommunication Hardware

The Backbone

Internet Backbone: A major set of computers on the internet

• Structured hierarchically, comprising three main levels of participants:

–End users( bottom)– ISP Internet Service Providers (middle)

– IBP Internet Backbone Providers /Network Service Providers (top)

Network Service Providers: • Owns and maintain routings at (Network

Access Point),NAP a point on the Internet where several connections converge.

• Own high speed and high capacity networks to provide global access and interconnectivity

• Sell wholesale internet connectivity services to ISP’s e.g. AT&T, BT.

Internet Service Providers: • Provide individuals, busiss, organization access

to the internet)

• Re-Sell or add value to and sell new services to customers

e.g AOL , UUNET, Mega, Botsnet, BBi (Broadband Botswana), Infotec Botswana

End Users: Include Residential, Business, Orgs

Communication Protocols

A set of rules that every computer follows to transfer information:

Most widely used on the internet:• TCP/IP-primary• http-movement of info over the web• ftp-transfering files btwn computers• PPP-for direct connection btwn

computers

Communications Software

Connectivity Software: helps connect to your ISP, standard in most computers

Web Browser Software: Netscape, Intert Ex. BTInert, AOL

Email Software: Outlook express,

Telecommunication hardware

Direct Network connection. Internet point

A telephone modemDigital Subsrciber Line:Cable modemSattellite modem

How does the Internet Work

The following concepts make the Internet work

• Internet Protocols• Client-Server Computing• Internet Adressing

Internet Protocols

• TCP/IP: Transmission Control Protocol/Internet Protocol

• A universal language that makes it possible to send information between computers regardless of their location or platform

Client-Server Computing

Servers: Computers that provide services by

over the internet. They are usually called hosts. Main types Include, Web Server, Mail Server, FTP Server IRC, server, UseNet Server

Clients: Computers that request and receive information from the servers

Internet Addressing

• Every Computer on the Internet has unique address( IP address)

• IP addresses are translated into a domain name

168.167.140.30 debian.mopipi.bw(IP address) (Domain name)

Intranets and ExtranetsIntranets:

• A network inside an organization that uses Internet technologies to provide Internet-like environment for information sharing, communications, collaboration and support of business processes.

• It is protected by security measures and accessed by authorized users through the internet

Extranets

• Network links that use Internet technologies to interconnect the intranet of a business with the intranets of its customers

USES OF THE INTERNET

• WORLD WIDE WEB• E-MAIL • TELNET• FTP• E-MAIL DISCUSSION GROUPS• USENET NEWS• FAQ, RFC, FYI• CHAT & INSTANT MESSAGING

USES OF THE INTERNET

WORLD WIDE WEB (WWW OR WEB)A system of Internet servers that

supports hypertext to access several Internet protocols on a single interface.

• Internet protocols are sets of rules that allow for inter-machine communication on the Internet

• Hypertext is a document containing words that connect to other documents.

Facts about the WWW• 1989 : Tim Berners-Lee invented it

for internal use at CERN (European Lab for Particle Physics)

• a protocol (http) for document transfer

• a language (html) for document layout, including embedded links to other documents, on that server or any other

• links to other media...graphics, sound ..

The WWW vs Internet

The web is not synonymous with the internet, though some people may think so. Actually, the web is one way to utilize the infrastructure of the internet. In other words, the web is a subset of the internet.

USES OF THE INTERNET Ctnd

• Electronic mail, or e-mail, allows computer users locally and worldwide to exchange messages. Each user of e-mail has a mailbox address to which messages are sent. Messages sent through e-mail can arrive within a matter of seconds

• Telnet is a program that allows you to log into computers on the Internet and use online databases, library catalogs, chat services, and more. To telnet to a computer, you must know its address.

• FTP stands for File Transfer Protocol. This is both a program and the method used to transfer files between computers.

USES OF THE INTERNET

• E-MAIL DISCUSSION GROUPS: The Internet is home to a large community of individuals who carry out active discussions organized around topic-oriented forums distributed by e-mail. These are administered by software programs.

• Usenet News is a global electronic bulletin board system in which millions of computer users exchange information on a vast range of topics Usenet messages are stored on central computers, and users must connect to these computers to read or download the messages posted to these groups.

USES OF THE INTERNET

• FAQ stands for Frequently Asked Questions

• RFC stands for Request for Comments.

• FYI stands for For Your Information.

• CHAT & INSTANT MESSAGING: Allow users on the Internet to communicate with each other by typing in real time. They are sometimes included as a feature of a Web site, where users can log into the "chat room" to exchange comments and information about various topics e.g Internet Relay Chat (IRC)