CHAPTER 2 The Internet and the Web Irfan

CHAPTER 2 The Internet and the Web Irfan A. Ilyas Ch 8 1

Points to cover § Internet Backbone § Internet Administration § Details of World Wide Web § Details of Web Standards § Document Format § Web Addressing § Details of Emailing § Email Structure § Mechanism used § Domain Name Addressing (DNS) Ch 8 2

…Internet Architecture § Internet Backbone § A collection of relatively fast computers on the internet, mainly responsible for providing high speed data communication across regional or national distances § Public computers will then be connected to these compu § Video Clip Demo (Web Publishing CD) Ch 8 3

Who Owns the Internet Now? ? ISOC: Created in 1992 IAB is a voluntarily based Technical Advisory Group. Consists of members of ISOC & IETF. Ch 8 4

Introducing World Wide Web § WWW is a collection of dissimilar computers on Internet. § These computers can participate in exchanging information objects (text/ pictures/ sound etc. ) among each other § In other words, WWW is an interface of Internet contents (stuff on Internet Computers) § This information exchange is made possible by implementing some web standards like: § § § Ch 8 Standard for Web document format (HTML) Standard for Web transaction mechanisms (HTTP) Standard for Web addressing (URL) 5

Details of Web Standards 1. Web Document Format: HTML § All web documents are required to be in a standard (agreed upon) format § Named as Hyper Text Marked Up Language (HTML) § Lets a Web Author to write a formatted hypertext document in form of simple text codes (tags) § The document file should have an extension. html or. htm § Reading an HTML Document § A HTML document in its simple form is not smoothly Ch 8 readable by humans. § Can only be shown by a browser program (web client programs) after proper interpretation of HTML codes. 6

…HTML: The Web Document Format § Explaining HTML Capabilities § Formatted: § Produces visual effects (bold/ underline/ different fonts/ blinking etc. ) on different document units <H 1> This is a first-level heading </H 1> § Hypertext: § A hypertext document allows the reader to read in n-dimensions (freely), using cross-referencing of topics being discussed. § Different from sequential reading. § A hyperlink is used to access a cross-referenced document. Ch 8 <A HREF="http: //www. yahoo. com"> Link to Yahoo 7

Example: A HTML Code An example HTML Code [example. html] Ch 8 Example. html when seen inside a Web Browser [Internet Explorer] 8

… Details of Web Standards § Web Transaction Mechanisms (HTTP) § For a smooth web transaction, some internal handshake of messages are needed § The set of rules governing these handshakes (request -response), are collectively called Hyper Text Transfer Protocol (http) § Complete list of messages included in HTTP rules are well known. § In case a problem happens (broken link etc. ), client will wait for server response for a fixed period, then print a “Request Timeout” Message Ch 8 9

…Web Transaction Mechanisms (HTTP) A List of HTTP request/ response messages for Web Transactions Ch 8 10

…Details of Web Standards § Web Addressing (URLs) § To access resources (html files/ jpeg images/ sounds etc. ) saved on different WWW computers § A unique address is assigned to each resource, called Universal Resource Locator (URL) § To be unique in addressing, a standard addressing format is used. Ch 8 11

…Web Addressing (URLs) URL Format: http: //computer_name/ path where § http: Name of the mechanism used to access the resource. § Computer_name a unique computer name for the Internet computer * § path file path of the resource (html code/ picture etc. ) on that computer Ch 8 Example: http: // www. yahoo. com / index. html *A domain based naming scheme, called DNS is used to assign this name 12

WWW: Important Terms § Hyperlinks § Active sentences on a web document § Let the user to jump on another web page § Home page § On any web site (web document collection), the Grand Central Station (the place users start their hypertext journey) § Browsing § The process of reading hypertext documents § May not be organized (wild hyperlink clicks) § Navigation § An organized browsing experience § Make use of tools [Favorite list, History, Next, Back etc. ] to help the user in the event of “Getting Lost” on a web system Ch 8 13

…. WWW: Important Terms § Browser § A computer program (web client) which let the user to start browsing a web system § Web Page Authoring § The process of creating hypertext documents § Recent authoring tools (Front Page, Dream weaver, Home Site etc. ) makes the experience easy and joyful Ch 8 14

Details of Emailing § Most common & first of its kinds Internet activity § Allows global access to all Internet Users § Basic elements of an email message § Header § Composed of Subject, Addresses, Date, Attachments Ch 8 § Message § The body of the email § Signature § More details about the sender 15

…Details of Emailing § A basic emailing activity involves three computers § Email Server Computer § § The computer runs an email server program. It is connected permanently to the Internet. The computer has a unique Internet address attached with it. Also, there are more than one user email accounts (mail boxes, maintained in different folders) on the server computer. Computer Internet Address kfupm. edu. sa Ch 8 User Email Accounts irfan saraza iskhan 16 A Server Computer running the email server program

…Details of Emailing § Email Sender (Client) Computer § The computer runs an email client program {like Outlook Express} § The computer doesn’t need to be connected permanently, gets connected whenever needs to do an emailing activity § The client program lets the user to send an email message to any server computer connected on the Internet. § The email address used in the mail header, tells exactly § Which computer is being addressed? § Which user account of that computer will receive this mail? Ch 8 A Server Computer running the email server program To: irfan@kfupm. edu. sa Subject: blah… Hello, ………………… ………. . 17 An Email Client Computer

…Details of Emailing § Email Receiver (Client) Computer § The computer also runs an email client program {like Outlook Express} § The computer doesn’t need to be connected permanently, gets connected whenever needs to do an emailing activity § The program lets the user to receive his email by contacting the server computer {Outlook Express should be setup with the address of the server computer} To: irfan@kfupm. edu. sa § The server computer lets client computer receive its mails Subject: blahthe blah… Hello, after authenticating it with a username & password. ………………… ………. . Ch 8 A Server Computer running the email server program User: irfan Passwd: *** 18 An Email Client Computer

Explaining E-Mail Addresses § Domain name system (DNS) § An addressing scheme used by Internet authorities to assign names (addresses) to computers and people. § The main theme of the scheme is “Unique Name” § The name is assigned in chunks by dividing the whole address space into different addressing domains § An addressing domain represents a set of all possible names which Domain Code: sa with the trailing part as. domain can be assigned pk edu. sa edu kfupm kfu Ch 8 irfan saraza com org net edu com org net ksu Domain : kfupm 19

… Explaining E-Mail Addresses § An Email Address has three parts § Domain code § Domain name § User name user name domain code dcoats@usc. edu Ch 8 domain name 20

Common Internet Domain Codes Ch 8 com Commercial org Other organizations gov Government 21

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