CHAPTER

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

2. 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)

3. …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)

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

5. 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: • Standard for Web document format (HTML) • Standard for Web transaction mechanisms (HTTP) • Standard for Web addressing (URL)

6. Details of Web Standards • 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 formattedhypertextdocument 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 readable by humans. • Can only be shown by a browser program (web client programs) after proper interpretation of HTML codes.

7. …HTML: The Web Document Format • Explaining HTML Capabilities • Formatted: • Produces visual effects (bold/ underline/ different fonts/ blinking etc.) on different document units • 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. <H1> This is a first-level heading </H1> <A HREF="http://www.yahoo.com"> Link to Yahoo

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

9. … 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

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

11. …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.

12. …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 Example: http:// www.yahoo.com / index.html *A domain based naming scheme, called DNS is used to assign this name

13. 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

14. ….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

15. 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 • Message • The body of the email • Signature • More details about the sender

16. A Server Computer running the email server program …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 User Email Accountsirfansarazaiskhan

17. An Email Client Computer 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? To: irfan@kfupm.edu.saSubject: blah blah…Hello,…………………………..

18. An Email Client Computer A Server Computer running the email server program …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} • The server computer lets the client computer receive its mails after authenticating it with a username & password. To: irfan@kfupm.edu.saSubject: blah blah…Hello,………………………….. User: irfanPasswd: ***

19. sa pk edu com org net edu org net com kfupm ksu kfu irfan saraza 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 nameis assigned in chunks by dividing the whole address space into different addressing domains • An addressing domain represents a set of all possible names which can be assigned with the trailing part as .domain Domain Code: edu.sa Domain : kfupm

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

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