You are on page 1of 14

1

B.Sc (Computer Sc ience) Web Technologies Unit- II 1. What is Internet? Explain the history of Inte rnet. A. The Internet is a global system of networked computers together w ith their users and data. It is a global communication network consisting of thousands of networks typically interconnected. 1960s Te lecommunications: ARPANET, 1969: In 1969, a network called Advanced Research Projects Agency Network for the United States Depart ment of Defense. The military created ARPA to enable researchers to share super-computing power. Initially, only four nodes comprised the ARPANET. The ARPANET later became know n as Internet. 1970s Te lecommunications: In this decade, the ARPANET was used primarily by the military, some of the larger companies such as IBM and universities (for email). The general population was not yet connected to the system. The use of LANs became more prevalent during the 1970s. UUCP, 1976: AT & T Bell Labs developed UNIX to UNIX CoPy. In 1977, UUCP was distributed with UNIX. USENET, 1979: User Network was started by using UUCP to connect Duke University and the University of North Carolina. 1980s Te lecommunications: In this decade, Transmission Control Protocol/Internet Protocol (TCP/IP), a set of rules governing how network making up the ARPANET communicate was established. For the first time, the term Internet was being used to describe the ARPANET. CSNET, 1980: The Computer Science Network connected all university computer science depart ments in the United States. Computer Science depart ments were relatively new and only a limited number existed in 1980. CSNET joined ARPANET in 1981. BITNET, 1981: The Because It’s Time Network formed at the City University of New York and connected to Yale University. Many mailing lists originated with BITNET. TC P/IP 1983: The United States Defense Communications Agency required that TCP/IP be used for all ARPANET hosts. Since TCP/IP was distributed at no charge, the Internet became what is called an open system. Internet Work, 1988: The v irus called Internet Worm (created by Robert Morris while he was a computer science graduate student at Cornell University) was released. It infected 10 percent of all Internet hosts.

IIMC

Prasanth Kumar K

2
1990s Te lecommunications: During the 1990s, lots of commercial organizations started getting online. Graphical browsing tools were developed and the programming language HTML allowed users all over the world to publish on WWW. Gopher, 1991: Gopher allowed the users to fetch files on the Internet using a menu based system. Gopher is still available and accessible through Web Browsers. World Wide Web, 1991: The World Wide Web was created by Tim Beerners Lee as a simple way to publish information and make it available on the Internet. It became available to the public in 1992. Mosaic, 1993: Mosaic, a graphical browser for the Web. It was first released under Windows and graphical UNIX. Netscape communications, 1994: Netscape released a browser called Netscape Nav igator, a web browser that captured the imagination of everyone who used it. Yahoo, 1994: Stanford University students David F ilo and Jerry Yang developed their Internet search engine and directory called Yahoo which is now world famous. Java, 1995: The internet programming language, Java was released by Sun Microsystems. This language was originally called Oak which allowed programmers to develop Web pages that were more interactive. Mic rosoft discovers the Inte rnet, 1995: The software giant Microsoft developed its browser, Internet Explorer. Google indexes over 1. 3 Billion Web Pa ges, 2001: The search engine Google has a huge index of more than 1.3 billion Web Pages. 2. Explain the way Inte rnet Works. A. Network Be nefits: The follow ing are the benefits of networks in general.

Provide Convenience: Computers on a network can back up their files over the network. Allow Sharing: Networked computers can share resources such as disks and printers. Facilitate communication: Sending and receiving email, transferring f iles and videoconferencing are examples of how networks promote communication. Generate Savings: Networked computers can provide more computing for less money. Several small computers connected on a network can provide as much as or more computing power than a singe computer. Also, since resources can be shared, not everyone needs their own peripherals w hich can result in a substantial cost savings. Provide Reliability: If one part of a network is down, useful work may still possible using a different network path. Simplify scalability: It is relatively easy to add more computers to an existing network. Interconnected Networks a nd Communication: The internet is essentially a network of networks and its success depends upon cooperation. Since no one person, organization or government is responsible for the Internet, cooperation among the networks and computers that compose the Internet is paramount. This is

IIMC

Prasanth Kumar K

3
accomplished by a common set of protocols. The protocol that determines how computers connect, send and receive information on Transmission Control Protocol/Internet Protocol (TCP/IP). TCP/IP consists of about 100 different protocols and new ones are developed and added regularly. TCP/IP has been described as the language of the Internet. TCP/IP allows many different kinds of computers from personal computers to mainframes to exchange information. If TCP/IP software is installed in the computer, then the information to be sent is split into IP Packets The advantages of packets are as follows: Error Recovery: If a packet gets corrupted, only that packet needs to be resent, not the entire message. Load Distribution: If one area of the network is congested, packets can be rerouted to less busy areas. Flexibility: If the network experiences failure or disruption in one locale, packets can be rerouted. In addition to the message pieces, each packet of data also contains information about the computer that sent it, the computer it is being sent to, a sequence number indicating where the packet fits in the overall message and error checking information to ensure that packet is not corrupted while in transit. The packets are reassembled after being received at the destination computer. A message is sent from the destination computer to the sending computer to resend any missing or corrupted packets. This method of packet switching does not require the packets to be sent in sequential order.

Physica l Compone nts In addition to various software protocols, Internet includes a host of physical components as well: · · · Servers Routers Communication Media

Server: Servers are the computers that answers the requests for serv ices, such as list servers, mail servers, & news servers.

IIMC

Prasanth Kumar K

4
Route r: Routers are the special-purpose computers that direct data packets along the network. Routers can detect whether the part of the network is down or congested and can then reroute traffic just like a traffic cop. Communication Media: Communication media prov ides means to transport packets of information like: · Copper Wires – transmit messages as electrical impulses. · Fiber Optic Cables – uses light waves to transmit messages. · Radio waves, Microwaves, Infrared Light & Visible Light – all carry messages through air. Network Connections: Connecting to the Internet from homes generally requires the use of a modem and a regular telephone line (copper wire) to connect to an Internet Serv ice Provider (ISP). A second modem at the ISP’s end completes the connection and slower the two modem speeds determines the maximum connection speed, usually 56 kbps. Modem (Modulator – Demodulator), is a device needed to convert data from digital to analog and analog to digital. Business, organization, network typically uses Network Interfa ce Cards (NIC) instead of modems. These systems have a higher speed connection, usually 56 kbps or better, to their ISPs. Such connections are usually leased from the telephone company. Another option is an Integrated Serv ices Digita l Network (ISDN) which is slightly more expensive but uses regular telephone lines and replaces modems w ith special adaptors upto five times faster than traditional modems. Sender’s Computer.

Client – Se rver Model The client – server model consists of two parts: · Client, that request for some serv ice · Server, that serves the client for any request.

IIMC

Prasanth Kumar K

5

The client makes a request to the server for any information or resources over network by sending a request message. Then the server serves the client on his request by providing the required information or resources.

IP Addresses Each computer connected over a network must have a unique name or address to be identified uniquely. Computers are best suited to manipulate numbers, thus every computer is assigned a numeric address, called IP Address. An IP Address is a 32 bit or four byte address, each byte separated by a dot. One byte represent a number f rom 0 (00000000) to 255 (11111111). Each IP Address consists of a network component and a Host Component.

IP Address plays an important role in the routing of packets over the Internet. Source and Destination IP Addresses are included in each packet. In essence, the address prov ides direction on where the packets should go. A central authority manages IP Addresses; otherw ise conflicts might arise. The Network Information Cente r (NIC) is in charge of assigning IP Addresses. IP Addresses are 32 – bit numbers, whereas Domain Names are easy – to – remember sy mbolic strings. A program called a Resolver takes care of the translation i.e., conversion of a sy mbolic name into its corresponding IP Address. Types of IP Addresses: Static IP Address. A permanently assigned IP Address, one that is given to a computer or router connected to the Internet is called a static IP a ddress. Dynamic IP Address. If one is connected to the Internet through an ISP, then typically each time the user connects, he will be assigned a different IP address, called a dy namic IP address, from the ISPs pool of IP addresses.

IIMC

Prasanth Kumar K

6
3. What is Internet Congestion? A. Inte rnet Congestion The number of users and their demands continue to grow almost without bound, causing the congestion on the Internet. Once a user get a network connection, the factor limiting how quickly one can view Web Pages often becomes the speed w ith which the computer renders the pages. The computer speed depends on a complex balance of CPU speed, bus speed, memory quantity, disc speed, and so on. The slowest link speed involved in a connection determines the overall level of performance. 4. Explain World Wide Wait Problem. A. “World Wide Wait” refers to the ever – increasing delays experienced when trying to access information on the Internet. The literal translation of this phrase is “wait in the world network”. With the advent of the WWW and the development of graphical browsers came a surge of interest in the Internet. This increase in the number of Internet users, coupled w ith the accompany ing requests for Web Pages containing elaborate in – line images, sound, and v ideo clips, has degraded the speed of the Internet to the point where the Information Superhighway sometimes appear to have a traffic jam. 5. Explain a bout Internet Culture. A. Internet has emerged f rom being a research medium to one that includes advertising, commerce, and forums for exchanging ideas on a nearly infinite set of subjects. Critica l Eva luation of Information Since the Internet is not regulated for content, anything and everything can be found on the Web. To find valuable information, one needs to go through several Web pages, and separate the useful from the useless, the valid from the invalid information. To evaluate the valuable information, one must consider several issues as mentioned below: · Who wrote the information? – Was the person who wrote the material know ledgeable and careful? Was he aware of what others have written? Can he be trusted? Is the writing quality high? – A document riddled with types is more likely to have inaccurate content than carefully created Web page. Is the doc ument up – to – date? – Try to determine whether the information is current or up – to – date.

·

·

IIMC

Prasanth Kumar K

7
· Are the re obvious errors in the content? – For example, if the user knows that the same of baseball requires 9 players on a team and the document says it only requires 6 players, be vary ing.

Freedom of Expression The Internet facilitates the interchange of ideas. Anyone with an Internet connection can express their v iews globally. This also allows small groups of people with something in common to share their views. Internet provides the facility of personal expression, but it is not necessary that everything and anything should be published. For example, some people f ind the availability of offensive material like articles encouraging violence (such as encouraging terrorism). Unfortunately, some people lose sight of all the great benefits that the Internet prov ides: · · · · · More educational opportunities Sharing of research ideas and information. Convenience of performing many functions, such as banking and shopping on – line. Opportunity for entertainment like playing games, listening to music. World Wide discussion forums to promote solutions to global problems.

Communication Mechanism People f rom all over the world can exchange ideas via email, Internet Relay Chat (IRC), Instant Messaging, Mailing Lists, newsgroups, and so on. Since there are no facial expressions, voice inflections, or body language to convey or interpret these communications, users must avoid ambiguity or misunderstanding by either spelling things out completely or using emoticons like: O:-) >:-) :-( :-[ angel devil frown grim :-D :-) :-o ;-) laugh smile Surprise wink

To save time when typing messages, users sometimes employ a friendly shorthand for commonly used phrases like: BRB – Be Right Back BTW – By The Way LOL – Laughing Out Loud TTYL – Talk To You Later GM – Good Morning HRU – How Are You Advertising Ads generate huge incomes for companies like Yahoo, Rediff mail, India Times, and so on. The web pages of these companies get millions of hits per day, so an ad placed on one of their web pages has a tremendous audience and provides the marketing experts a potential consumer base. · Most of the ads shown on web pages are clickable images.

IIMC

Prasanth Kumar K

8
· Many of the most popular web pages have revolving advertisements; i.e. each time the user revisit the page, or while the user is visiting the page, he gets a different ad. Many users manage to browse the web w ithout pay ing too much attention to the advertisements, other than noticing that the ads slow down the loading process. Obviously, the ads influence some people, because companies continue to invest huge amounts of money in them. The style, forms and content of ads is a rapidly emerging part of the Internet culture.

·

· ·

Societal Impact The Internet has had an enormous impact on society, and its influence will be continued. Nearly all facets of life have been affected. · Many people work in Internet – related jobs, either building computer network components, writing software, creating web pages, performing marketing research, designing graphics, or conducting business on the web. · Many people obtain required information and perform most of their communication using the Internet. · Weather, news, stock prices, and travel information are accessed by millions of users every day. 6. Explain a bout Business Culture a nd Inte rnet. A. On – line Business The Internet provides a way to facilitate communications both within and between companies. Internet is an excellent venue for advertising and conducting trade with consumers. It is currently possible to shop goods and services through on – line catalogs; subscribe to on – line versions of magazines and newspapers; and purchase software. These are just a few types of business transactions taking place on the on – line market place. For companies, this means potential customers. For consumers, this means a greater selection of services and products. Internet prov ides various options for business like: · Advertising · Marketing · Partnership · Retail · Service · Software · Subscription

IIMC

Prasanth Kumar K

9
On – line Business Hurdles The most signif icant consumer concerns about doing business on – line are privacy and security. When disclosing personal information and revealing spending habits on – line, consumers want assurance that the information will go no further. Some users could also get nervous if their favorite on – line catalog remembers their hat sizes, shoe sizes, and credit card numbers. What is to prevent this information from falling into the wrong hands? These data are actually stored on the hard disk in a file usually called cookies. Cookies. Sometimes when a user visit a Web page, information about the user is collected. · · It might be the name, password, preferences, credit card number, phone number, address, etc. A web server sends this information to the user’s browser, and the data is written to the cookies file stored on the user’s disk. This process is known as setting a cookie. Using cookies file, a web server can keep track of the web page the user visits. The next time the user visit a particular web page, the server will search the cookies file, retrieve the information stored there, and use that to customize its web page to accommodate the user.

· ·

As the amount of data that can be stored in a cookie is very limited, the server stores an “id” for the user, fetches that id from the cookie, and then looks up in the server database for user’s more detailed profile and history. The purpose of putting information in the cookies f ile on the hard disk is to reduce the server’s search time in locating a specific cookie, as the cookies file is limited in size. The information stored in cookies file may be retrieved and used to determine one’s personal habits. Credit card security is a valid concern, but such numbers are encrypted. But it is generally considered to be harmf ul. Business and Safety / Security on web The biggest concern of consumers conducting business on – line is the issue of secure pay ments. Is it safe to use credit card on – line? Mechanisms for ensuring secure pay ments are currently being developed in the private sector. Secure Electronic Transaction (SET) is a new technical standard to be implemented by Visa and MasterCard to make credit card pay ments over Internet more secure. Other pay ment option being developed includes Electronic Money.

IIMC

Prasanth Kumar K

10
Business transactions over Internet are becoming more widespread and also more secure. 7. Define Web. A. Web: The World Wide Web or Web is a software application that makes it easy and possible for nearly anyone to publish and browse hypertext documents on the Internet. The information on Web is transported over the Internet. 8. Explain a bout Web Browser Details. A. Most Web Browsers have a number of options: · Cookies: User can decide whether to use cookie or not. · Disk Cache: User can set the size of the cache. The cache stores the HTML source code and images of Web Presentation which are visited. If user reloads one of these pages, the browser can load the cached copy and the page will appear very quickly. · Fonts: User can select a font specification and also set a default font size. · Helper Applications: User can configure helper applications to handle certain types of data that the browser is unable to process. · Homepage Location: User can specify the page that loaded when the browser if first launched. · Ima ges: User can specify whether or not images are loaded. Options for color selection are also available. · JavaScript and Java: User can enable or disable these types of programs from running within the browser. · Messages: User can specify a default signature file or default carbon copy address for outgoing messages. This can be set for regular email or for posts to newsgroups. · Bookmarks: A convenient feature of browser allows the user to save the URL of any webpage to display. The saved URL is called Bookma rk or Favorite. The bookmark is a pointer to a location on the Web. A collection of bookmarks is sometimes referred to as a hot list, list of favorites or simply bookmark list. The two main reasons for sav ing a bookmark are: 1. It is a page user expects to visit often. 2. It is a page user may never find again.

9. Compa re the features of Plug-ins a nd Helper Applications.

A. Browsers are equipped with many features. New web products and file formats are constantly being developed. When a browser is designed, it cannot handle every product and file format that currently exists or may exist in the future. Furthermore, browsers are not built to handle all existing data formats. Browsers are already huge programs and bundling in more features makes them even larger. To overcome this problem, we use two closely related mechanisms: plug-ins and helpe r applications. Plug-ins and Helper Applications do the same thing – they extend the power of browser. Plug-ins are tightly integrated with the browser, so there is less work for the user to do. User has to drag plug-ins into the browser’s plug-ins folder so

IIMC

Prasanth Kumar K

11
that it will f ind them and load them at start-up. However, there is a memory cost to use plug-ins. There are plug-ins that are capable of playing audio, show ing mov ies, and running animations. The Adobe Acrobat plug-in is an example of such program. Normally, plug-in runs inside the browser. Helper Applications or Helpers are stand-alone programs that are used to process or display data that is directly integrated into a web page. Helpers don’t display their information inside the browser’s window; instead, they are launched in their own window. The browser activates the appropriate helper application when the browser encounters a file type that it doesn’t handle. The Helper Applications must be downloaded and placed in appropriate directory.

Plug-ins
Closely tied to browser Displays inside browser window Installation involves downloading the plug-in and running Broad selection available Launches quickly

Helper Applications
Program stands alone. Displays in separate window Configuring involves downloading the helper application Broad selection available May launch more slowly than plug-in

9. Explain the comparison of Microsoft and Netscape We b browse rs. A. The two most popular graphical browsers are Navigator from Netscape and Internet Explorer f rom Microsoft. The Netscape release includes the browser as well as many other features; the entire suite is referred as Netscape Communicator. The two browsers are actually quite similar and they include many of the same features. Both browsers are large programs and are approximately the same size, depending on the exact versions. The number of HTML tags they support is large; however we cannot assume that because Web Presentations looks great under Nav igator, it looks equally impressive using Internet Explore or v ice versa. Both companies have always incorporated some of their own features. For example, Netscape introduced tables and frames whereas Microsoft supports marquees and a wide range of font faces. Currently for every person using Netscape, about two people use Internet Explorer. Netscape’s market share used to be much greater than Internet Explorer’s but it has decreased in recent years. Netscape is usually downloaded off the Web or brought from a software-vendor as a stand-alone product. However, Internet Explorer is packaged and distributed w ith a variety of other Microsoft products like Windows 98, XP, Vista, etc. 10. Ex pla in about We b Writing Styles and Writing Genres.

A. Web Writing Styles: The writing style required for a typical web page is different than the writing style for the average printed page because: · Readers usually spend less time looking at a web page than they do reading an off-line magazine or newspaper article. · Web pages are typically very short, only one or two screens in length. · Off-line material has greater longev ity than on-line material. · Web designers usually try to grab the reader’s attention. If a presentation is not cleverly designed, a reader can easily move. · Web pages are hyperlinked documents, so readers typically do not go through them in sequential order.

IIMC

Prasanth Kumar K

12
· Published off-line material is generally written and edited by professionals, whereas Web pages may be published by anyone, sometimes with little or no writing and editing skills. Web pages are dynamic and they often involve multimedia. With off-line material, the quality of the writing holds the reader’s attention. The appearance and form of writing are secondary. However, appearance and form are critical components of a web page.

· ·

Writing Genres: The key points that made writing genres effective are: · A theme and clear goals for the presentation. · The ability to permit exploration, while providing sufficient nav igation so that user can easily avoid getting lost. · Good choice of colors with the text easy to read. · Consistent and careful page design w ith hyperlinks normally situated near the top of the page. · User-friendly navigation. · Short, descriptive writing. 11. Ex pla in the process of registering a web page. A. Registering a web page means having the page indexed by a search engine. The goal is to have the page v iewed by more users. If a search engine indexes a page, then the search engine can return the page to user’s queries. The more search engines that know about the page, the more likely the page will be accessed. Many search engines allow the designer to fill out and submit an on-line form telling the search engine about the page. Search engine designers want their programs to know about the more web pages than any other search engine. Program performance is judged by the speed of the search and the number of hits a search engine found a page that matched a query. By registering the web page, we are helping a search engine to expand its knowledge base. There are some businesses on the web whose pages get visited often. Usually, a business will add a hyperlink to a specific page for a fee. This service is most commonly used by people w ith commercial pages. Another consideration to registration and publicity is tra ffic. The person responsible for the server on which the pages reside may not be prepared to handle an enormous bulge in traffic. 12. Ex pla in brie fly about outline, design and ma nagement of a web presentation. A. Web Presentation: A web presentation is a collection of associated, hyperlinked web pages that usually have some underlying theme. Some of the key elements in an effective web presentation are: · Details: A presentation that includes well-thought-out touches can make a positive impression on the reader. Good choice of background color, headers, footers and appropriate font size are all important. Typos, poorly aligned images and a clashing color scheme create a negative image. Carefully prepared pages help to enhance the credibility and readability of the presentation. · Coding: A competent HTML programmer uses the appropriate elements of style to contribute to the overall quality of the presentation. Overly simplistic pages could indicate a lack of knowledge by the designer and cluttered pages indicate poor design.

IIMC

Prasanth Kumar K

13
· Features: A few “bells and whistles” can improve the feel of a set of pages. For example, splash screens, applets or JavaScript can add things up. Remember each feature takes extra time to download and display. Gra phics: A modest use of in-line images is probably one of the most significant ways to enhance the design. Many free images found on the web. It is important to integrate the images effectively into the presentation. Randomly positioning images usually doesn’t enhance the design. Layout: If the pages are visually appealing and if they provide convenient navigation, they are likely to be visited by more users. A poor layout w ill discourage people from spending too much time on the presentation. Writing Qua lity: Good writing and an interesting style are also necessary for a solid presentation. Load Time: Since some users have dial-up connections, care should be taken not to include too many graphics or any large graphics. Also, users should be given the option of downloading large images separately. If users get frustrated during the loading process, they are likely either to stop loading the page altogether or be more critical of the page when it finally arrives. Hyperlinks: Nav igation is a key element to any good web presentation. If readers can move around the pages easily, they w ill be more impressed. If they can easily get lost and are not able to find the desired information, they may become frustrated.

·

·

· ·

·

Goal Setting: The object of goal setting is to decide on specific parameters for the web presentation. A number of issues are considered before creating the web presentation. · Audience: Who are the intended audience? Are you w riting for children, business executives, retired persons or general audience? Are you intended visitors scattered throughout the world? · Date: What is the time frame? Many things published on the web need to be displayed in a timely manner. Time constraint affects the depth and extensiveness of the project. · Gra phics: How many graphics do you intend to include? Do you want to impress the audience? Graphics take a long time to download. If the audience is local, we can use more graphics than if they are global. · Length: How much material is going to be included in the presentation? Is the goal to produce a comprehensive presentation? · Maintenance: Is the goal to design a presentation that doesn’t need any maintenance or the nature of the material such that items w ill need to be modified from time to time? · Money: Are you trying to earn money from the presentation? Is the goal to impress people to obtain other jobs? Are you building an on-line gallery? · Objective: What is the main objective? Is it designed for personal satisfaction, for a class, for a friend or for a business? · Resea rch: Does the project require a lot of research? Can the research be accomplished on-line? The time frame w ill influence the level of research you can conduct. · Writing: Is the goal to have accurate and error-free writing? Do you want high-quality content? Do you want visitors to read everything you write? Outlining: It is a good idea to produce an outline. This can be done in many ways. Generally it is a two-step process: 1. Develop the writing for the presentation 2. Then code it in HTML.

IIMC

Prasanth Kumar K

14
These two steps can be completely independent, but experience shows that writing and coding together leads to an incremental development process and a better design. Navigation: The navigational tools provide hy perlinks that allow the readers to move more smoothly through the pages. It should be convenient for the users to return to either the main page or an index. General organizational arrangement of web presentation is as follows: Circular: The circular arrangement of web pages supports forward and backward movement through the pages. This format is especially good for describing step-by-step procedures or instructions or for dividing up text that should be read sequentially. Exploratory: The exploratory arrangement allows jumping from nearly every page to nearly every other page in an order determined by the user. This form is similar to spider web and it works best for describing things like geographical areas or maps. Hiera rchical: The hierarchical arrangement permits a more limited number of hyperlinks from the introductory page and each succeeded page leads to additional hyperlinks. This arrangement yields a treelike or directory structure.

·

·

·

Design a nd Coding: To write an effective web presentation, set the goals and develop an outline and a global nav igational design. Producing an HTML document from a design involves coding as well as writing. The design and coding process is as follows: · Navigating: Design the strategy based on navigation. Once a strategy is designed, add the HTML code. Set up the appropriate number of pages and the hyperlinks between them. Migrate the relevant parts of the outline into each page, but keep a copy of the original outline. · Coding and Writing: With the outlining and coding, we have created places for the writing. If we are experts in w riting block, continue coding. If not, do more writing. Periodically view what we have created. · Rev ising: After completion of the first draft of the presentation, revise the project with a new perspective.

IIMC

Prasanth Kumar K