INTERNET1
INTERNET
 
 
 
 
 
 
Objectives
 
After completing this unit, you will be able to:
 
·         Understand exactly what the Internet is.
·         Understand how Web Technologies are Advancing.
·         Understand Email, Telnet, FTP, Chat and Instant Messaging.
·         Understand Web Pages and URL.
·         Describe the Domain Name System along with the Plugins and ActiveX.
 
Structure
 
1.1   Introduction
 
1.2   Components of the Internet
 
1.3   World Wide Web
 
1.4   Pages on the Web
 
1.5   Retrieving Documents from the Web
 
1.6   Web Browsers
 
1.7   Advancements in Web Technologies
 
1.8   Summary
 
 
 
 
 
 
 
 
 
 
 
 
 
1.1 INTRODUCTION
 
The Internet is a computer network made up of thousands of networks sharing resources worldwide. No one knows exactly how many computers are connected to the Internet. It is certain, however, that these numbers are in millions and are growing day by day.
 
There are organizations which develop the technical aspects of this network and set standards for creating applications on it. The Internet backbone, through which Internet traffic flows, is usually owned by private companies known as Internet Service Providers (ISP).
 
All computers on the Internet communicate with one another using the ‘Transmission Control Protocol/Internet Protocol suite’ (TCP/IP). Computers on the Internet use a client/server architecture. This means that the remote server machine provides files and services to the user’s local client machine. Software can be installed on a client computer to take advantage of the latest access technology.
 
An Internet user has access to a wide variety of services such as electronic mail, file transfer, vast information resources, interest group membership, interactive collaboration, multimedia displays, real-time broadcasting, breaking news, shopping opportunities, and many more.
 
The Internet consists primarily of a variety of access protocols. Many of these protocols feature programs that allow users to search for and retrieve information made available by the protocol.
 
 
1.2 COMPONENTS OF THE INTERNET
 
Let us now have a look at the different components of the Internet.
 
1.       World Wide Web
The World Wide Web (WWW) is a system of Internet servers that supports hypertext to access several Internet protocols on a single interface. Almost every protocol type available on the Internet is accessible on the Web. This includes e-mail, FTP, Telnet, etc. In addition to these, the World Wide Web has its own protocol known as ‘HyperText Transfer Protocol’ (HT TP).
 
The World Wide Web provides a single interface for accessing all these protocols. This creates a convenient and user-friendly environment. It is not necessary to be conversant in these protocols within separate, command-level environments, as was the case earlier. The Web gathers together these protocols into a single system. Because of this feature, and because of the Web's ability to work with multimedia and advanced programming languages, the Web is the fastest-growing component of the Internet today.
 
The operation of the Web relies primarily on hypertext as its means of information retrieval. HyperText is a document containing words that connect to other documents. These words are called links and are selectable by the user. A single hypertext document can contain links to many documents. In the context of the Web, words or graphics may serve as links to other documents, images, video and sound. Links may or may not follow a logical path, as each connection is programmed by the creator of the source document. Overall, the Web contains a complex virtual web of connections among a vast number of documents, graphics, videos and sounds.
 
Producing hypertext for the Web is accomplished by creating documents with a language called ‘HyperText Markup Language’ (HTML). With HTML, tags are placed within the text to accomplish document formatting, visual features such as font size, italics and bold and the creation of hypertext links. Graphics and multimedia may also be incorporated into an HTML document as a part of the document.
 
HTML is an evolving language, with new tags being added as each upgrade of the language is developed and released. For example, visual formatting features are now often separated from the HTML document and placed into Cascading Style Sheets (CSS). This has several advantages, including the fact that an external style sheet can centrally control the formatting of multiple documents. The World Wide Web Consortium (W3C), co-ordinates the efforts of standardizing HTML. The W3C now calls the language XHTML and considers it to be an application of the XML language standard.
 
The World Wide Web consists of files, called pages or home pages, containing links to documents and resources throughout the Internet.
 
The Web provides a vast array of experiences including multimedia presentations, real-time collaboration, interactive pages, radio and television broadcasts, and the automatic “flow” of information to a client computer. Programming languages such as Java, JavaScript, Visual Basic, Cold Fusion and XML are extending the capabilities of the Web. A growing amount of information on the Web is served dynamically from content stored in databases. The Web is therefore not a fixed entity, but one that is in a constant state of development and flux.
 
 
2.      E-Mail
Electronic mail, or e-mail, allows computer users locally and worldwide to exchange messages. Each user of e-mail has a mailbox address just like our post mailbox address to which messages are sent. Messages sent through e-mail can arrive within a matter of seconds.
 
A powerful aspect of e-mail is the option to send electronic files to a person's e-mail address. Non-ASCII files, known as binary files, may be attached to e-mail messages. These files are referred to as MIME attachments. MIME stands for Multimedia Internet Mail Extension, and was developed to help e-mail software handle a variety of file types. For example, a document created in Microsoft Word can be attached to an e-mail message and retrieved by the recipient with the appropriate e-mail program. Many e-mail programs, including Eudora, Netscape Messenger, and Microsoft Outlook offer the ability to read files written in HTML, which is itself a MIME type.
 
 
3.       Telnet
Telnet is a program that allows you to log into computers on the Internet and use online databases, library catalogs, chat services, etc. To Telnet to a computer, you must know its address, rather an IP address. Some services require you to connect to a specific port on the remote computer. In this case, type the port number after the Internet address to have access to that particular resource.
 
Telnet is available on the World Wide Web. Probably the most common web-based resources available through Telnet are library catalogs, though most catalogs have since migrated to the Web. A link to a Telnet resource may look like any other link, but it will launch a Telnet session to establish the connection. A Telnet program must be installed on your local computer and configured to your Web browser in order to work properly.
 
With the increasing popularity of the Web, Telnet has become less frequently used as a means of access to information on the Internet.
 
4.       File Transfer Protocol (FTP)
FTP is both a program and a method used to transfer files between computers. Anonymous FTP is an option that allows users to transfer files from thousands of host computers on the Internet to their personal computers. FTP sites contain books, articles, software, games, images, sounds, multimedia, course work, data sets, etc.
 
If your computer is directly connected to the Internet via an Ethernet cable, you can use one of several PC software programs such as WS_FTP for Windows to conduct a file transfer.
 
FTP transfers can be performed on the World Wide Web without the need for special software. In this case, your Web browser will suffice. Whenever you download software from a Web site to your local machine, you are using FTP. You can also retrieve FTP files via search engines because in this case you do not need to know FTP program commands.
 
5.       E-Mail Discussion Groups
One of the benefits of the Internet is the opportunity it offers to people worldwide to communicate via e-mail. The Internet is home to a large community of individuals who carry out active discussions organized around topic-oriented forums distributed through e-mail. These are administered by software programs. The most common program is the listserv.
 
This program handles subscription information and distributes messages to and from subscribers. You must have an e-mail account to participate in a listserv discussion group.
 
6.       Usenet News
Usenet News is a global electronic bulletin board system in which millions of computer users exchange information on a vast range of topics. The major difference between Usenet News and e-mail discussion groups is the fact that Usenet messages are stored on central computers, and users must connect to these computers to read or download the messages posted to these groups. This is distinct from e-mail distribution, in which messages arrive in the electronic mailboxes of each list member.
 
Usenet itself is a set of machines that exchange messages or articles from Usenet discussion forums called newsgroups. Usenet administrators control their own sites, and decide which (if any) newsgroups to sponsor and which remote newsgroups to allow into the system.
 
There are thousands of Usenet newsgroups in existence. While many are academic in nature, numerous newsgroups are organized around recreational topics. Much serious computer-related work takes place in Usenet discussions. A small number of e-mail discussion groups also exist as Usenet newsgroups. For example, the Netscape suite comes with a newsreader program called Messenger. Newsreaders are also available as standalone products.
 
 
 
7.       Chat and Instant Messaging
Chat programs allow users on the Internet to communicate with each other in real time. They are sometimes included as a feature of a web site, where users can log into the “chatroom” to exchange comments and information about the topics addressed on the site. Chat may take other, more wide-ranging forms also. For example, America Online is well known for sponsoring a number of topical chat rooms.
 
Internet Relay Chat (IRC) is a service through which participants can communicate to each other on hundreds of channels. These channels are usually based on specific topics. While many topics are frivolous, substantive conversations are also taking place. To access IRC, you must use an IRC software program.
 
A variation of chat is the phenomenon of instant messaging. With instant messaging, a user on the Web can contact another user currently logged in and initiate a conversation. The most famous today is America Online’s Instant Messenger. ICQ, MSN and Yahoo also offer chat programs.
 
 
1.3 WORLD WIDE WEB
 
The World Wide Web was developed in 1989 by Tim Berners-Lee in Switzerland. The initial purpose of the Web was to use networked hypertext to facilitate communication among its members, who were located in several countries. In addition to hypertext, the Web began to incorporate graphics, video and sound. The use of the Web has reached global proportions and has become a defining aspect of human culture in an amazingly short period of time.
 
Almost every protocol type available on the Internet is accessible on the Web. Internet protocols are sets of rules that allow for inter-machine communication on the Internet. The following are some of the major protocols accessible on the Web:
 
E-mail(Simple Mail Transport Protocol or SMTP):
Distribute electronic messages and files to one or more electronic mailboxes.
               
 
Telnet (Telnet Protocol):
Facilitates login to a computer host to execute commands and share resources.
 
FTP (File Transfer Protocol):
Transfer text or binary files between an FTP server and client.
 
Usenet (Network News Transfer Protocol or NNTP):
Distributes Usenet news articles derived from topical discussions on newsgroups.
 
 HTTP (HyperText Transfer Protocol):
Transmit hyptertext over networks.
 
Many other protocols are also available on the Web. To name just one example, the Voice over Internet Protocol (VoIP) allows users to place a telephone call over the Web.
 
The World Wide Web provides a single interface for accessing all these protocols. This creates a convenient and user-friendly environment. Earlier it was necessary to be conversant in these protocols within separate, command-level environments. The Web gathers these protocols together into a single system. Because of this feature and also because of the Web's ability to work with multimedia and advanced programming languages, the Web is by far the most popular component of the Internet.
 
1.4 PAGES ON THE WEB
 
The World Wide Web consists of files, called web pages, containing information and links to resources throughout the Internet.
 
Web pages can be created by user activity. For example, if you visit a web search engine and enter keywords on the topic of your choice, a page will be created containing the results of your search. In fact, a growing amount of information found on the Web today is served from databases creating temporary web pages “on the fly” in response to user queries.
 
Access to web pages may be accomplished by:
1.       Entering an Internet address and retrieving a page directly.
2.       Browsing through pages and selecting links to move from one page to another.
3.       Searching through subject directories linked to organized collections of web pages.
4.       Entering a search statement at a search engine to retrieve pages on the topic of your choice.
 
 
 
 
1.5 RETRIEVING DOCUMENTS FROM THE WEB
 
The URL and Domain Name System
 
URL stands for Uniform Resource Locator. The URL specifies the Internet address of a file stored on a host computer connected to the Internet. Every file on the Internet, no matter what its access protocol, has a unique URL. Web browsers use the URL to retrieve the file from the host computer and the specific directory in which it resides. This file is downloaded to the user's client computer and displayed on the monitor connected to the machine.
 
URLs are translated into numeric addresses using the Domain Name System (DNS). The DNS is a worldwide system of servers that stores location pointers to web sites. The numeric address, called the IP (Internet Protocol) address, is actually the “real” URL. Since numeric strings are difficult for humans to use, alphanumeric addresses are employed by end users. Once the translation is made by the DNS, the browser can contact the web server and ask for a specific file located on its site.
 
Anatomy of a URL
 
This is the format of the URL:
 
protocol://host/path/filename
 
For example, this is a URL on the Website: http://www.yahoo.com/news.html
 
This URL is typical of addresses hosted in domains and the structure of this URL is:
1.       Protocol: http
2.       Host computer name: WWW
3.       Second-level domain name: Yahoo
4.       Top-level domain name: Com
5.       File name: news.html
 
 
 
Table 1.1: Top Level Domain
 
ComCommercial enterprise
EduEducational institutions
GovGovernment Entity
MilMilitary Entity
NetNetwork Access Provider
OrgUsually non-profit Organizations

 
 
 
 
New domain names were approved in November 2000 by the Internet Corporation for Assigned Names and Numbers (ICANN). They are as follows:
 
.biz,.museum, info, .pro(for professionals), .name (for individuals), .aero (for the aerospace industry) and .coop (for cooperatives).
 
ICANNcontinues to investigate proposals for adding additional domain names; for example, .mobi for sites designed for mobile devices and .jobs for the human resources community.
 
In addition, dozens of domain names have been assigned to identify and locate files stored on host computers in countries around the world. These are referred to as two-letter Internet country codes.
 
Table 1.2: Examples of two letter Internet country codes
 
InIndia
ChSwitzerland
DeGermany
JpJapan
UkUnited Kingdom
NzNew Zealand
UsUnited States

 
 














As the technology of the Web evolves, URLs have become more complex. This is especially the case when content is retrieved from databases and served onto web pages. The resulting URLs can have a variety of elaborate structures describing the data that has been displayed on the screen using HTML tags and additives.
 
 
1.6 WEB BROWSERS
 
To access the World Wide Web, you must use a web browser. A browser is a software program that allows users to access and navigate the World Wide Web. There are two types of browsers: graphical and text.
 
1.       Graphical
 
Text, images, audio and video are retrievable through graphical software programs such as Internet Explorer, Firefox and Netscape. These browsers are available for Windows, Apple, Linux and other operating systems. Navigation is accomplished by pointing and clicking with a mouse on highlighted words/hyperlinks and graphics.
 
2.       Text
 
The web pages are usually accessed by typing the web page name and using the enter key.
 
EXTENDING THE BROWSER
 
Plug-Ins:
 
Software programs may be configured to a web browser in order to enhance their capabilities. When the browser encounters a sound, image or video file, it hands off the data to other programs, called plug-ins, to run or display the file. Working in conjunction with plug-ins, browsers can offer a seamless multimedia experience. Many plug-ins are available for free.
 
File formats requiring plug-ins are known as MIME types. MIME stands for Multimedia Internet Mail Extension and was originally developed to help e-mail software handle a variety of binary (non-ASCII) file attachments. The use of MIME has expanded to the Web. For example, the basic MIME type handled by Web browsers is text/html associated with the file extension.html.
 
A common plug-in utilized on the Web is the Adobe Acrobat Reader. The Acrobat Reader allows you to view documents created in Adobe’s Portable Document Format (PDF).
 
These documents are the MIME type “application/pdf” and are associated with the file extension .pdf. When the Acrobat Reader has been downloaded to your computer, the program will open and display the file requested when you click on a hyperlinked filename with the suffix.pdf.
 
Web browsers are often standardized with a small suite of plug-ins, especially for playing multimedia content. Additional plug-ins may be obtained at the browser’s website, at special download sites on the Web, or from the websites of the companies that created the programs.
 
Once a plug-in is configured to your browser, it will automatically launch when you choose to access a file type that it uses.
Beyond Plug-Ins:
 
ActiveXis a technology developed by Microsoft which makes plug-ins less necessary. ActiveX offers the opportunity to embed animated objects, data and computer code on web pages with ease. A web browser supporting ActiveX can render most items encountered on a web page. As just one example, ActiveX allows you to view and edit PowerPoint presentations directly within your web browser. ActiveX works best with Microsoft's Internet Explorer.
 
 
 
1.7 ADVANCEMENTS IN WEB TECHNOLOGIES
 
Today's World Wide Web presents an ever-diversified experience of multimedia, programming languages and real-time communication. There is no question that it is a challenge to keep up with the rapid pace of developments. Some of the more important trends are described below:
 
1.       Multimedia
 
The Web has become a broadcast medium. It is possible to listen to audio and video over the Web, both pre-recorded and live. For example, you can visit the sites of news organizations and view the same videos shown on the nightly news. Several plug-ins are available for viewing these videos.
 
At one time, the entire multimedia file had to be downloaded before viewing. Since these types of files tend to be quite large, download time can be lengthy. This problem has been answered by are revolutionary development in multimedia capability: streaming media. In this case, audio or video files are played as they are downloading, or streaming, into your computer. Only a small wait, called buffering, is necessary before the file begins to play.
 
The Windows Media Player, RealPlayer and QuickTime plug-ins play streaming audio and video files. Extensive files such as interviews, speeches and hearings work very well with these players. They are also ideal for the broadcast of real-time events which may include live radio and television broadcasts, concerts, and so on.
 
Shockwave andFlash are plug-ins that provides another multimedia experience. They offer the creation and implementation of an entire multimedia display combining graphics, animation and sound.
 
Sound files, including music, are also a part of the Web experience. Sound files may be incorporated into websites, and are also available for downloading independent of website visits. Sound files of many types are supported by the Web with the appropriate plug-ins. The MP3 file format, and the choice of supporting plug- ins, is one of the most popular music trends to sweep the Web.
 
Live camsare another aspect of the multimedia experience available on the Web. Live cams are video cameras that send their data in real time to a web server. These cams may appear in all kinds of locations, both serious and whimsical: an office, on top of a building, a scenic locale, a special event, and so on.
 
 
2.       Programming Languages and Functions
 
The use of existing and new programming languages has extended the capabilities of the Web. What follows is a basic guide to a group of the more common languages and functions in use on the Web today.
 
CGI, Active Server Pages: CGI (Common Gateway Interface)refers to a specification by which programs can communicate with a web server. A CGI program, or script, is any program designed to accept and return data that conforms to the CGI specification. The program can be written in any programming language, including C, Perl and Visual Basic Script. A common use for a CGI script is to process a form on a web page. For example, you might fill out a form to order a book from Amazon.com. The script processes your information and sends it to Amazon.com to process your order.
 
Another type of dynamically generated web page is called a Active Server Page (ASP). Developed by Microsoft, ASP is a programming environment that processes scripts on the web server. The scripts run on the server, rather than on the web browser, to generate the HTML pages sent to browsers. Visual Basic and JScript (a subset of JavaScript) are often used for the scripting. ASPs end in the file extension .asp or.aspx.
 
Java/Java Applets:Java is an object-oriented programming language similar to C++. Developed by Sun Microsystems, the aim of Java is to create programs that will be platform independent. The Java motto is, "Write once, run anywhere". A perfect Java program should work equally well on a PC, Macintosh, UNIX, and so on, without any additional programming. This goal has yet to be realized. Java can be used to write applications for both Web and non-Web use.
 
Web-based Java applications are usually in the form of Java applets. These are small Java programs called from an HTML page that can be downloaded from a web server and run on a Java-compatible web browser. A few examples include live news feeds, moving images with sound, calculators, charts and spreadsheets, and interactive visual displays. Java applets tend to load slowly, but programming improvements should lead to a shortened loading time.
 
JavaScript/JScript:JavaScript is a programming language created by Netscape Communications. Small programs written in this language are embedded within an HTML page, or called externally from the page, to enhance the page’s functionality. Examples of JavaScript include moving tickers, drop-down menus, real-time calendars and clocks and mouse-over interactions. JScript is a similar language developed by Microsoft and works with the company’s Internet Explorer browser.
 
XML:XML (eXtensible Markup Language) is a mark-up language that enables Web designers to create their own customized tags to provide functionality not available with HTML alone. XML is a language of data structure and exchange, and allows developers to separate form from content. With XML, the same content can be formatted for multiple applications. In May 1999, the W3 Consortium announced that HTML 4.0 has been recast as an XML application called XHTML. This move is slowing having an impact on the future of both XML and HTML.
 
3.       Real-Time Communication
 
Text, audio and video communication can occur in real time on the Web. These capabilities allow people to conference and collaborate in real time. In general, the faster the Internet connection, the more successful is the experience.
 
At its simplest, chat programs allow multiple users to type to each other in real time. Internet Relay Chat and America Online's Instant Messenger are prime examples of this type of program. The development of messaging protocols is underway. Such a protocol would allow for the expansion of this capability throughout the Internet.
 
Featured collaboration tools include:
 
Audio:Conduct a telephone conversation on the Web.
 
Video:View your audience.
 
File transfer:Send files back and forth among participants.
               
Chat:Type in real time.
 
Whiteboard:Draw, mark up and save images on a shared window or board.
 
Document/application sharing:View and use a program on another's desktop machine.
 
Push:A technology that sends data to a program without the program's request.
 
4.       Current Trends: Blogs and RSS
 
The Web is a welcoming medium for experimentation and user participation. It is becoming easier to post web content and share comments with other users. The idea of the website is still very much alive, but web participation is taking new forms and being driven by new technologies. Here are two of the latest trends.
 
Blogs: A blog is an easy-to-create website that allows users to share their thoughts with the world and is managed by a lightweight content management system. The word “blog” comes from “Weblog” because a blog consists of a signed and dated log of individual postings.
 
What is important about blogs is the content management system that manages the content. This system can offer a variety of features that can make the blog a useful tool. Examples include a calendar view of postings, organization of postings into categories, archived postings, options to send e-mail notification of new postings, and so on.
 
Blogging can be an interactive activity. Readers can add comments to a blogger's postings, other can respond, and a conversation ensues. Lately, bloggers have become well-known commentators on the political scene; blogging can encompass any topic or no topic at all. If the blogging software allows it, bloggers can use RSS to distribute their postings.
 
RSS:RSS allows people to place news and other announcement-type items into a simple XML format that can then be pushed to RSS readers and web pages. The initials RSS can stand for different things, including Rich Site Summary or Really Simple Syndication. RSS is used for all kinds of purposes, including the news itself and announcing new content on websites.
 
RSS content may be read by using an RSS reader or aggregator. This is usually free software that you can install on your computer that posts new items and stores old ones in a graphical interface. An RSS reader is similar to e-mail software in that it displays incoming items and can store content for offline reading. Subscribing to a news feed is usually as simple as entering the address of the RSS document.
 
It is also possible to subscribe to and read your own collection of RSS feeds on websites devoted to this purpose. The advantage here is that you can access your RSS feeds from any computer that is connected to the Web.
 
 
 
1.8 SUMMARY
 
The Internet is a computer network made up of thousands of networks worldwide that share resources. All computers on the Internet communicate with one another using the Transmission Control Protocol/Internet Protocol suite (TCP/IP).
 
The World Wide Web (WWW) is a system of Internet servers that supports hypertext to access several Internet Protocols on a single interface. It offers a varied nature of services such as e-mail, FTP, Chat and Instant Messaging, Usenet News, etc. It is progressing higher by encompassing new web technologies so that the sharing of information and resources can be accomplished more easily.