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1. Introduction to Internet 1.1. Introduction By the turn of the century, information, including access to the Internet, will be the basis for personal, economic, and political advancement. The popular name for the Internet is the information superhighway. Whether you want to find the latest financial news, browse through library catalogs, exchange information with colleagues, or join in a lively political debate, the Internet is the tool that will take you beyond telephones, faxes, and isolated computers to a burgeoning networked information frontier. The Internet supplements the traditional tools you use to gather information, Data Graphics, News and correspond with other people. Used skillfully, the Internet shrinks the world and brings information, expertise, and knowledge on nearly every subject imaginable straight to your computer. 1.2. What is the Internet? The Internet links are computer networks all over the world so that users can share resources and communicate with each other. Some computers have direct access to all the facilities on the Internet such as the universities. And other computers, eg privately- owned ones, have indirect links through a commercial service provider, who offers some or all of the Internet facilities. In order to be connected to Internet, you must go through service suppliers. Many options are offered with monthly rates. Depending on the option chosen, access time may vary. The Internet is what we call a metanetwork, that is, a network of networks that spans the globe. It's impossible to give an exact count of the number of networks or users that comprise the Internet, but it is easily in the thousands and millions respectively. The Internet employs a set of standardized protocols which allow for the sharing of resources among different kinds of computers that communicate with each other on the network. These standards, sometimes referred to as the Internet Protocol Suite, are the rules that developers adhere to when creating new functions for the Internet. The Internet is also what we call a distributed system; there is no central archives. Technically, no one runs the Internet. Rather, the Internet is made up of thousands of smaller networks. The Internet thrives and develops as its many users find new ways to create, display and retrieve the information that constitutes the Internet. 1.3. History & Development of the Internet In its infancy, the Internet was originally conceived by the Department of Defense as a way to protect government communications systems in the event of a military strike. The original network, dubbed ARPANet (for the Advanced Research Projects Agency that developed it) evolved into a communications channel among contractors, military personnel, and university researchers who were contributing to ARPA projects. 1 The network employed a set of standard protocols to create an effective way for these people to communicate and share data with each other. ARPAnet's popularity continued to spread among researchers and in the 1980 the National Science Foundation, whose NSFNet, linked several high speed computers, took charge of what had come to be known as the Internet. By the late 1980's, thousands of cooperating networks were participating in the Internet. In 1991, the U.S. High Performance Computing Act established the NREN (National Research & Education Network). NREN's goal was to develop and maintain high- speed networks for research and education, and to investigate commercial uses for the Internet. The rest, as they say, is history in the making. The Internet has been improved through the developments of such services as Gopher and the World Wide Web. Even though the Internet is predominantly thought of as a research oriented network, it continues to grow as an informational, creative, and commercial resource every day and all over the world. Birth of Internet - Key terms:  1960 most universities and Government agencies had individual mainframe computers, which were not interconnected.  1968 The national Physical Laboratory in Great Britain was the first to set up the test network.  1969 Pentagon’s Department of ARPA came out with the first infant network with four nodes.  Which was named as ARPANET  1971 there were fifteen nodes in ARPANET.  1972 thirty seven nodes were added.  1980 NSF net (National Science Foundation). 1.4. Features of internet a. Key Web Features b. Key Usenet Newsgroups Features c. Key Email Features d. Key Mailing List Features a) Key Web Features  Ease Of Use  Universal Access  Search Capabilities 2 The web leverages the key features of the Internet and makes them widely accessible to the public. Key features of the web in particular are its ease of use, universal accessibility, and ability to be quickly searched: • Ease of use. The web can be immediately used by anyone already familiar with a computer window. The only special features are links, which are as natural and intuitive to use as pressing a button. This ease of use enabled the rapid adoption of the web in the 1990's, and led to the establishment of the Internet around the world. • Universal access. The open design of the web makes it easy to build web browsers for a wide range of devices. Web browsers have been deployed on cell phones and personal organizers, and the web is now the standard interface for providing access to information. • Search capabilities. The development of search sites greatly multiplied the power and usefulness of the web by providing the capability to effectively search the content of millions of web pages in seconds. Search sites significantly enabled the web to realize Vannevar Bush's vision of an automated library system. b) Key Usenet Newsgroups Features  Group Communications  Common Space • Group communications. The Usenet is a powerful facilitator of group communication across time and geographic space. One person can post a message on the Usenet, another person reply to it, and a third person reply to either message, no matter where they are in the world, and whenever is convenient to them. Usenet messages are organized in newsgroups and threads that are stored in Usenet archives indefinitely for later retrieval by anyone that wishes to access them, even years later, connecting people across generations. Mailing lists, IRC, and MUD's also provide group communications, although on a lessor scale. • Common space. The Usenet is the second largest common public space in existence, next to the Internet itself. Anyone can post anything they wish to any newsgroup, and anyone can read any message they wish from any newsgroup. Like most common spaces, the Usenet therefore reflects the best and worst of human nature, from community newsgroups where people are focused on selflessly helping each other, to less worthwhile groups where the postings are filled with pointless and counterproductive information. 3 Like most common spaces, messages posted on the Usenet are public property and can be freely copied and reused in other sources, although Usenet netiquette mandates that credit should always be provided. c) Key Email Features  Email Is A Push Technology  Email Waits For You  Email Is One-To-Many  Email Is A Push Technology Email is delivered to the recipient so they don't have to work to get it they just open their Inbox and there it is. Technologies are sometimes labeled push or pull as described below: • Pull . These technologies require the user to actively go and retrieve the information. A library, the Web, and the Usenet are pull technologies, requiring active participation of a human being to retrieve the information. • Push . These technologies deliver information to the user so all they have to do is receive it. Radio, television, and email are push technologies. One of the reasons email has been such a big success is because it is a push technology. The person that sends the email writes it, then POP3 and SMTP transmit it, and all the recipient has to do is open his email program and double-click on the email to read it. An advantage of push technologies is their ease of use they require a minimum of effort on the part of the recipient, which greatly supports adoption because they get used more often. Partly because of this feature, the use of email has greatly outstripped all other Internet applications since its creation, even after the explosive development of the Web  Email Waits For You Email is particularly convenient because it is asynchronous; it waits for you and fits into your schedule instead of demanding that you structure your activities to synchronize with those you communicate with. For example, an email recipient doesn't have to be available when you compose and send an email you can send it at the time that is most convenient to you. Similarly, you don't have to be available or even connected to the Internet when someone else sends you email it waits on your server until you log in and download it when most convenient to you. 4 Email provides the convenience that voice mail later provided for telephones except that voice mail is more ephemeral, cannot be conveniently edited, and is usually accompanied by a preference to talk to the other party in real time. With email you know that the medium is inherently asynchronous, so you tend to write down all the information the addressee needs so they can respond when they are able.  Email Is One-To-Many You can send an email to several people in one simple action. Communications can be divided into four types depending on the number of parties participating in the information transfer: (1) one-to-one, (2) one-to-many, (3) many-to-one, and (4)many-to- many. Each type of communication has its own attributes and strengths. For example, the typical phone call is one-to-one, and the typical meeting is many-to-many. Email is the most successful one-to-many technology, with respect to both sending and receiving: • Sending . You can send an email to more than one person at a time, for example to everyone in your family, or to a group of friends. • Receiving . You can receive information that has been mailed to more than one person, for example an announcement sent to hundreds of people on a mailing list. The key advantage of this one-to-many communication is efficiency, since instead of sending emails individually; you can save large amounts of time by sending one email to several people at once. Similarly, when you receive an email from an Internet mailing list you are getting information that would probably be impractical to receive any other way, since most organizations don't have the time or resources to send out paper based notices individually to hundreds or even thousands of people. e. Key Mailing List Features  One-to-many communication. Mailing lists enable powerful one-to-many communications. Because mailing lists are based on email, they share the key features of email. Mailing lists also build on that technology to create a new capability called "one-to- many" functionality, enabling one person to communicate with many people at the same time. This feature is a virtual Internet extension of the real-world communication power of a person speaking to a group, except that the members of the audience may be located anywhere in the world. 5 The reverse is also true: mailing lists can give one person unique access to the informed opinion of a diverse group of people on various subjects with little effort the email arrives from the groups they have subscribed to, and they then read the ones they want. Like so many of the Internet technologies, mailing lists are important primarily because of their power to bring people around the world together in a single communication setting. Features of internet  Decentralized  Non proprietary  Platform independent  Packet Switching.  Self maintenance.  Democracy 1.5. Types of Connection • Dial Up Connection. (telephone line) • DSL (Digital Subscriber Line). (broadband) – Asymmetric digital Subscriber line (ADSL). – Symmetric digital Subscriber line (SDSL). – Depending upon the speed • High-data-rate DSL (HDSL). • Very high DSL (VDSL). • RF Link. (radio frequency) • ISDN (Integrated Services Digital Network). • A Cable modem.( cable TV line) 1.6. What makes the internet work? The unique thing about the Internet is that it allows many different computers to connect and talk to each other. This is possible because of a set of standards, known as protocols that govern the transmission of data over the network: TCP/IP (Transmission Control Protocol/Internet Protocol). Most people who use the Internet aren't so interested in details related to these protocols. They do, however, want to know what they can do on the Internet and how to do it effectively. 1.7. The Client/Server Model The most popular Internet tools operate as client/server systems. You're running a program called a Web client. This piece of software displays documents for you and carries out your requests. If it becomes necessary to connect to another type of service 6 say, to set up a Telnet session, or to download a file your Web client will take care of this, too. Your Web client connects (or "talks") to a Web server to ask for information on your behalf. The Web server is a computer running another type of Web software which provides data, or "serves up" an information resource to your Web client. All of the basic Internet tools including Telnet, FTP, Gopher, and the World Wide Web are based upon the cooperation of a client and one or more servers. In each case, you interact with the client program and it manages the details of how data is presented to you or the way in which you can look for resources. In turn, the client interacts with one or more servers where the information resides. The server receives a request, processes it, and sends a result, without having to know the details of your computer system, because the client software on your computer system is handling those details. The advantage of the client/server model lies in distributing the work so that each tool can focus or specialize on particular tasks: the server serves information to many users while the client software for each user handles the individual user's interface and other details of the requests and results. Characteristics of a client • Initiates requests • Waits for replies • Receives replies • Usually connects to a small number of servers at one time • Typically interacts directly with end-users using a graphical user interface Characteristics of a server • Never initiates requests or activities • Waits for and replies to requests from connected clients • A server can remotely install/uninstall applications and transfer data to the intended clients 1.8. Electronic mail on the internet: Electronic mail, or e-mail, is probably the most popular and widely used Internet function. E-mail, email, or just mail, is a fast and efficient way to communicate with friends or colleagues. You can communicate with one person at a time or thousands; you can receive and send files and other information. You can even subscribe to electronic journals and newsletters. You can send an e-mail message to a person in the same building or on the other side of the world. 7 1.9. How does E-mail Work E-mail is an asynchronous form of communication, meaning that the person whom you want to read your message doesn't have to be available at the precise moment you send your message. This is a great convenience for both you and the recipient On the other hand, the telephone, which is a synchronous communication medium, requires that both you and your listener be on the line at the same time in order for you to communicate (unless you leave a voice message). It will be impossible to discuss all the details of the many e-mail packages available to Internet users. Fortunately, however, most of these programs share basic functionality which allows you to:  Send and receive mail messages.  save your messages in a file  print mail messages  reply to mail messages  attach a file to a mail message 1.10. WWW (World Wide Web) • WWW was found in the year 1989 by Tim Berners-Lee of CERN (the European Organization for Nuclear Research) • He founded the basic HTML to use on the web. • In October 1994 Time Berners-Lee founded the World Wide Web consortium organization for developing nonproprietary. WWW (World Wide Web)-Key Terms Web pages, Web Site, Portal, Web Servers, Mail Server, File Server, News Server, DNS. 8 2. HTML 4 Protocols Protocols Introduction • A protocol is a program written as per mutually accepted standard that two computers use to communicate with each other. • Computers use protocols to format consistently their message so that other computer can understand them. The Protocols determines the following: • The type of error checking to be used. • Data compression method, if any • How they sending device will indicate that it has finished sending a message. • How they receiving device will indicate that it has received a message. • There are varieties of standard protocols from which programmers can choose. • Each has particular advantages and disadvantages, • Ex: Some are simpler than others. Some are most reliable, and some are faster Some standard protocols • Simple Mail Transfer protocol (SMTP). • Post Office Protocol version3 (POP3). • Transmission Control Protocol/Internet Protocol (TCP/IP). • Hyper Text Transfer Protocol (HTTP). • File Transfer Protocol (FTP). • Internet Mail Access Protocol (IMAP). • Multipurpose Internet Mail Extensions (MIME). • Network News Transfer Protocol (NNTP). 2.1. Hyper Text Transfer Protocol (HTTP). HTTP is the network protocol of the Web. It is both simple and powerful. Knowing HTTP enables you to write Web browsers, Web servers, automatic page downloader’s, link-checkers, and other useful tools. 2.1.1. What is HTTP HTTP stands for Hypertext Transfer Protocol. It's the network protocol used to deliver virtually all files and other data (collectively called resources) on the World Wide Web, whether they're HTML files, image files, query results, or anything else. Usually, HTTP takes place through TCP/IP sockets (and this tutorial ignores other possibilities). A browser is an HTTP client because it sends requests to an HTTP server (Web server), which then sends responses back to the client. The standard (and default) port for HTTP servers to listen on is 80, though they can use any port. 9 2.1.2. What are "Resources" HTTP is used to transmit resources, not just files. A resource is some chunk of information that can be identified by a URL (it's the R in URL). The most common kind of resource is a file, but a resource may also be a dynamically-generated query result, the output of a CGI script, a document that is available in several languages, or something else. While learning HTTP, it may help to think of a resource as similar to a file, but more general. As a practical matter, almost all HTTP resources are currently either files or server-side script output. 2.1.3. Structure of HTTP Transactions Like most network protocols, HTTP uses the client-server model: An HTTP client opens a connection and sends a request message to an HTTP server; the server then returns a response message, usually containing the resource that was requested. After delivering the response, the server closes the connection (making HTTP a stateless protocol, i.e. not maintaining any connection information between transactions). The format of the request and response messages is similar, and English-oriented. Both kinds of messages consist of: • an initial line, • zero or more header lines, • a blank line (i.e. a CRLF by itself), and • an optional message body (e.g. a file, or query data, or query output). Put another way, the format of an HTTP message is: <initial line, different for request vs. response> Header1: value1 Header2: value2 Header3: value3 <optional message body goes here, like file contents or query data; it can be many lines long, or even binary data $&*%@!^$@> Initial lines and headers should end in CRLF, though you should gracefully handle lines ending in just LF. (More exactly, CR and LF here mean ASCII values 13 and 10, even though some platforms may use different characters.) 10 [...]... window.toolbar - the browser toolbar window.document.link - an array containing all of the links in the document window.document.anchor - an array of all the anchor points in the document Window.document.layer - a named document layer window.document.applet - a named java applet area window.document.image- a named image tag window.document.area - a named area window.document.form - a named form or the default... (relieving the server of this task) – web site navigation 3.4 Object based scripting Objects refer to windows, documents, images, tables, forms, buttons or links, etc Objects should be named Objects have properties that act as modifiers 3.4.1 • • • • • • • • • • • • Objects window - the current browser window window.history - the Netscape history list window.document - the html document currently in the browser... data These documents were refined and expanded two years later in RFCs 1521, 1522 and 1523 The last RFC talked only about enriched text in MIME Two years ago, December 1996 MIME related RFCs were reworked once again and this time into a group of five RFCs 2045 through 2049 After these documents more extensions to MIME such as security has been proposed, but they have remained in separate documents 2.4.4... type="text/javascript"> and tells where the JavaScript starts and ends: Example: document.write("Hello World!"); The word document.write is a standard JavaScript command for writing output to a page By entering the document.write command between the and tags, the browser will recognize it as a JavaScript command and... getMonth B getTimeZoneoffset B setDate B setMonth B setYear B UTC B getHours B getSeconds B getYear B setHours B setSeconds B toGMTString Document Object Contains information on the current document, and provides methods for displaying HTML output to the user Syntax To define a document object, use standard HTML syntax: 32 . your Web client will take care of this, too. Your Web client connects (or "talks") to a Web server to ask for information on your behalf. The Web. the web by providing the capability to effectively search the content of millions of web pages in seconds. Search sites significantly enabled the web