CIS 1203 Web Technologies Introduction to the Internet and the WWW

Lesson Objectives  Students should: –Understand the Internet and its history –Understand the WWW, its history and how it relates to the Internet –Discuss the evolution of the WWW –Identify and describe the fundamental technologies of the Web –Explain how the Web works

Information Technology  IT  all aspects of managing & processing information using technology –Mainly computers and computer networks: Hardware Software Connectivity (Networks)

Hardware Software Navigation software  Steer clear of danger Image compression software  More image returns

Hardware Software Operating system  Control HW and other SW Web browser  Surf the net Photo gallery  Organize photos Text editor  Compose and manage text messages

Connectivity  Computer networks and telecommunications infrastructure allow multiple hardware devices to connect and share data and information Transmits voice and data to other devices Transmits data back to earth

Computer Networks  A network is a group of two or more computers connected –Why connected? To communicate, share resources and exchange information

Types Of Networks  LAN –Local Area Network »Computers are connected in a confined geographical area  WAN –Wide Area Network »Computers span a large geographical area

The Internet  A network of networks –A worldwide collection of computer networks, cooperating with each other to exchange data using a common software standard  Multiple data systems – –FTP (File Transfer Protocol) –TELNET –The World Wide Web (WWW) –And more

History of The Internet  The Advanced Research Projects Agency (ARPA  A Department of Defense project to establish US lead in science and technology applicable to the military  Operation ARPANET –A need for a bombproof communications system –Link computers together throughout the US –Gradual shift from a military pipeline to communications tool for scientists  In late 1980s, DOD decommissioned the ARPANET to NSF (National Science Foundation) Network called NSFnet –Large telecommunication companies created high speed data lines and connected to NSFnet  The rest is history…

But What is The WWW?  Created in 1989 in CERN  The “information superhighway” –A method of posting and accessing interactive multimedia information  Hyper what? –The WWW is based on a concept called hypertext The organization of information units into connected associations that a user can choose to make (links)

Web 1.0  Web pages connected together via hyperlinks  Mostly static and very little interaction between the user and the webpage  Focus is companies that own create and own their content

Web 2.0  Dynamic web pages that are data-driven and user-centric  High level of interactivity with user-generated content (blogs, forums, social networks, video sharing, etc.)  Rich interfaces made possible through AJAX –AJAX  Asynchronous JavaScript And XML

Mobile Web  Web resources are being accessed via mobile devices  Companies are developing mobile versions for their websites  Mobile commerce is an emerging trend

The Client-Server Model Internet Server Side Client Side Client-Server Model: describes the relationship between two computer programs in which one program, the client, makes a service request from another program, the server, which fulfills the request HTTP request HTTP response Web BrowserWeb Server

What is HTTP?  HTTP (Hypertext Transfer Protocol) is the foundation of data communication for the WWW  A protocol defines a set of rules that enable effective communications between computers  HTTP is part of a protocol framework called the Internet Protocol Suite which includes TCP/IP

TCP/IP  Transmission Control Protocol (TCP): –Establishes connections among sending and receiving Web computers –Handles assembly of packets at point of transmission, and reassembly at receiving end  Internet Protocol (IP): –Provides the Internet’s addressing scheme

Internet Protocol (IP) Addresses  IPv4: –32-bit number –Expressed as series of four sets of separate numbers marked off by periods Class C address: Network identified by first three sets, computer identified by last set  New version: IPv6 has 128-bit addresses, able to handle up to 1 quadrillion addresses (IPv4 can only handle 4 billion)

Routing Internet Messages: TCP/IP

Web Browser Overview  A tool for “traveling” the internet  A “client” software for “surfing” the WWW  Browser war –Different vendors –Non standard extensions –Different viewing experience of the same web page  Then came the standards –World Wide Web Consortium (w3c) Internet Explorer Safari FireFox Mozilla Opera Lynx

Web Browsers and Devices The way a webpage is displayed depends on the monitor size and screen resolution Some browser might not support flash or other multimedia objects Some browsers are so small, the whole webpage layout must be different

How Browsers Work  Enter URL or click a link  The browser breaks the address into 3 parts 1.Protocol 2.Server and domain name 3.The resource name (webpage) 1 2 3

How Browsers Work  The browser then communicates with a domain name system (DNS) server that translates the domain name into IP address DNS Server 1 Sorry I don’t know this address. Let me check another server DNS Server 2 I found it. The IP address is: Du Web Server

How Browsers Work  Your browser sends an HTTP request to the server using its IP address  Some level of authentication takes place  The server sends the requested page coded in HTML  Your browser reads the markup of HTML and interprets it into the web page that you view

Domain Names, DNS, and URLs  Domain name –IP address expressed in natural language  Domain name system (DNS) –Allows numeric IP addresses to be expressed in natural language  Uniform resource locator (URL) –Address used by Web browser to identify location of content on the Web –E.g.

Top-Level Domain (TLD) Names

URL  Uniform Resource Locator File Name Path Domain Name Double slash means a system address will follow Access method or Protocol A separator