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What is the Internet? Introduction about internet...
Chapter 1 Introduction to the Internet 1.1 What is the Internet? 1.1.1 Deﬁnition A network is a collection of computers interconnected through some kind of medium so that they can communicate. This medium can be a copper cable, ﬁber optic cable, or a wireless medium such as electromagnetic waves (light, radio waves, etc.). We can classify these networks depending on their geographical extent; a Local Area Networks (LAN) spreads over a limited geographical area and in contrast a Wide Area Network 1 (WAN) connects computers over a much larger geographic area An internetwork connects independent LANs and WANs to form one large network. Such a network is called an internet. There is one such global internet (ﬁgure 1.1) that stemmed from an experimental network started by the Advanced Research Project Agency of the United States Department of Defense in 1960s. Now this network spans over political and geographical boundaries. That particular internet is called the Internet. When we refer to this particular internetwork we always capitalize the ﬁrst letter “I”. The individual networks on the internet are administered and owned by different persons and organizations and they use diﬀerent technologies to connect computers. The Internet uses diﬀerent technologies to connect these networks together; some networks 1 1 There is no pre-determined distance to diﬀerentiate a WAN from a LAN. 1 1. INTRODUCTION TO THE INTERNET are connected to each other over a public telephone networks while others are connected over satellite links. It is a wonder that computers communicate over this widely diverse and most often incompatible collection of networks. This is possible because of a common set of rules that they all adhere to despite the differences in the individual LAN or WAN technologies. Such a set of rules used for communication is called a protocol and the protocol used in the Internet is called the TCP/IP protocol suite. Figure 1.1: Internet is the worldwide, publicly accessible network of interconnected computer networks 1.1.2 Global infrastructure The Internet is a giant network spread through out the world by connecting diﬀerent types/levels of computers (from personal computers to high end work-stations). Although these computers are at homes, oﬃces, schools/universities and government departments, it appears as an Information retrieval system with communication facilities to all users of the Internet. At the same time, it is a system which is available on demand at all times. 2 1.1 What is the Internet? 1.1.3 Communication system Not like the telephone system which has very limited number of services (voice phone, fax etc.), the Internet has unlimited number of services. At the same time, these services can be oﬀered simultaneously (multi tasking environment) based on the users demand. Applications which run (execute) at computers connected to the Internet can provide these services. Examples: 1. Email 2. Instant messaging 3. Discussion forums (forums on website, news groups etc.) 1.1.4 Information retrieval system Information can be sent from any computer to any other if it is connected through a network. There are various types of resources available for information retrieval. One major resource is web sites or home pages of organizations or individuals like www.cnn.com. Another resource that can be used for information retrieval is search engines. www.google.com is a very popular search engine. You can also find books and reports and repositories of software applications and so much more. 1.1.5 Who pays for it? Who pays for the Internet? Do you have to pay for the Internet Access? There are no owners for the Internet. Then you do not want to pay for it. However, these networks should be developed and maintained by the providers. Therefore those who provide network connectivity (we call them Internet Service Providers) have to charge individuals/organizations when they want to access the Internet through their network. Generally, there are two types of fees: One for the access time and the other one for the internet connectivity. Access time is usually based on the local telephone charges (e.g. Dial up Connection) or a fixed amount irrespective of access time (e.g. ADSL Connection In some countries, Internet connection can be obtained through Cable TV networks. In some countries, Internet connection can be obtained through Cable TV 3 1. INTRODUCTION TO THE INTERNET networks. At the same time, an individual or organization can obtain a dedicated direct connection to the Internet (e.g. Leased line provided by SLT) if they want to have very high speed connection and the charges for such connections are usually high. 1.1.6 The Impact of the Internet The Internet is creating a big impact on the society by revolutionizing the way people live and work in the everyday life. There is a huge impact in several key areas like the Government sector, Commerce or Business sector, and also in Education sector. The impact continues beyond what mentioned above. Entertainment is an-other area which has started to make a direct impact on the life. On the other hand, the cost of some of services could bring to zero once they are provided through the Internet. For example, consider, voice calling to a long distance location through the Internet. The Internet globalizes communication by allowing users from around the world to connect with each other. Ultimately, we hope that the Internet would bring people, services and diﬀerent cultures together into a small village. 188.8.131.52 eGovernment Many government services have been made available through the Internet and this initiative is known as eGovernment (ﬁgure 1.2). eGovernment is a tool for governments to use new technologies to provide people with more convenient access to government information and services to improve quality of services and provide opportunities to participate in democratic institutions and processes. eGovernment provides opportunities to move forward in the 21st century with high quality, cost eﬀective government services delivery and the creation of better relationships between the people and the government. 4 1.1 What is the Internet? Figure 1.2: People do not want to spend many hours to obtain government services 184.108.40.206 eCommerce / eBusiness People do not have to visit physical stores/super markets to buy products. They can query about products through online stores and can order them immediately by paying through Electronic Fund Transferring Cards (Eg: Visa, Master, Diners Club Etc.). This buying and selling process is described as e-commerce (ﬁgure 1.3). In fact, the process of buying and selling goes more than two party interaction when customers pay through credit cards (your bill will be settled probably through a bank) and get those goods through a delivery service like DHL, Fedex or normal postal service. This whole business process can be powered through Internet by providing an interface through the Word Wide Web (described later). This revolution is termed as the e-Business. To many people the term ”electronic commerce” means shopping on the part of the internet called World Wide Web (The web). However, it also includes many other activities such as business trading with other businesses and internal processes that companies use to support their buying, selling, hiring, planning etc. In many cases the term eBusiness is used in this broader sense. 5 1. INTRODUCTION TO THE INTERNET Figure 1.3: You don’t have to visit supermarkets to buy goods 220.127.116.11 eLearning Going beyond the government services and business transactions, the Internet is penetrating into the education sector and it will be creating the biggest impact in the society. E-Learning is the framework which integrates the power of Information Communication Technology to provide learning solutions through the Internet (ﬁgure 1.4). E-Learning probably minimizes much discrimination in society due to education privileges, especially in rural communities. 1.2 History of the Internet 1.2.1 Early years of the Internet In the early years of the Internet, by the late 1970s, many independent LAN networks were emerged due to two reasons. First is due to the introduction of the inexpensive minicomputers. Second reason is introduction of the inexpensive easy to install LAN technologies. LAN technologies (ﬁgure 1.5) solve the problem of computer communication in a way that is inexpensive and reliable. LAN technology changed the way people worked by enabling resource sharing. Before LAN technologies, 6 1.2 History of the Internet Figure 1.4: By linking universities, colleges, schools and homes into a world wide network, the Internet is creating a big impact in the society each computer had speciﬁc input/output devices like printers and one copy of the data or software. But with the introduction of the LAN technology a set of computers could share resources like printers. As there were many diﬀerent LAN technologies companies installed the LAN technology that best met their needs. Most large organizations had several LAN technologies in use in diﬀerent departments Suppose an organization has two LANs one in the accounting department and one in the Human Resource (HR) division. If one needs to transfer information that is stored on a computer in the HR division to a computer in the accounting department connecting the two cables may not make it possible if the two LANs are using diﬀerent technologies. So there was a problem in sharing information between diﬀerent LANs. 1.2.2 Emergence of WANs It is not always possible to connect multiple LANs together as diﬀerent LAN technologies can be incompatible. 7 1. INTRODUCTION TO THE INTERNET Figure 1.5: A Local Area Network spreads over a limited geographical area In 1960s and 1970s scientists came out with WANs that connected multiple computers across large geographical distances. So with this a company with oﬃces in several cities can install a WAN that links computers in each city. All attached computers can communicate with each other. However WANs cost much more than LANs. Hence LANs were much popular than WANs. Engineers invented many WAN technologies most of them were incompatible with one another. 18.104.22.168 A Single Network Still there were many problems in accessing resources. For example, say in an organization if one computer attaches to a LAN and another attaches to a WAN, neither has access to all resources in the organization. The goal was to have a usable single network where each computer in an organization has access to all resources, with some restrictions on the resources a given computer or user can access. 8 1.2 History of the Internet Figure 1.6: A Wide Area Network connects computers over a much larger geographic area 1.2.3 ARPANET By the late 1970s, the U.S. department of Defense through Advanced Research Project Agency (ARPA) (ﬁgure 1.7) had several computer networks to pass technology on to the military. Its goal was to support military research about how to build a network that could continue to function in the midst of partial outages that could be caused by bomb attacks. It included a WAN called ARPANET. ARPA also had the same problem in sharing resources. ARPA research examined how to interconnect all machines to form a large single network. 22.214.171.124 ARPANET Backbone ARPANET also called as the backbone network, allowed smaller local networks to connect to it. Once these smaller networks were connected to the backbone, they were in eﬀect connected to each other. In 1969 the Internet, then known as the ARPANET, was brought online under a contract let by the ARPA which initially connected four major computers at universities in the southwestern US. They are UCLA, Stanford Research Institute, UCSB, and the University of Utah. 9 1. INTRODUCTION TO THE INTERNET Figure 1.7: The ARPA network Useful URLs • http://www.w3c.rl.ac.uk/primers/history/origins.htm 1.2.4 Internet Standards: TCP/IP Internet standards forms an important part of the technology that makes it possible to interconnect networks. Two pieces of the Internet standards are, The Internet Protocol (IP) software which Provides basic communication, Transmission Control Protocol (TCP) software which provides additional facilities that applications need. Most of the time, the entire set of Internet Communication Software is identified as TCP/IP by the initials of the two components with a slash in between. More formal name is The TCP/IP Internet Protocol Suite and it’s more accurate as it points out that, the entire set contains more than just the two protocols. 10 1.2 History of the Internet 126.96.36.199 Protocol When two persons want to communicate with each other, they must know the same language. Just like that, computers on the Internet must know the same language or adapt to a set of standard rules to communicate with one another and the term, protocol, is used to refer the standard rules of communication. Hence, the standards or rules of communication on the Internet (i.e. The Internet Protocol) are known as TCP/IP. 1.2.5 Open system ARPA made the research results public to encourage vendors to adopt Internet technology. Whenever a researcher discovered some thing important took measures to document the results in a report. ARPA made all reports available to public. Researchers who devised the Internet published technical information also in a series of reports that describe the Internet and the TCP/IP it uses. As the project documentation was accessible across the network the researchers could coordinate their activities easily. 1.2.6 Military uses TCP/IP By 1982, a prototype Internet was used and the TCP/IP technology had been tested. Some of the academic and industrial research sites were using TCP/IP regularly. U. S. military also started to use TCP/IP and chose the internet as its primary computer communication system. By 1983, ARPA expanded the Inter-net to include all military sites connected to the ARPANET. The date, Marked a transition for the Internet as it changed the Internet from an experiment to a useful network. 11 1. INTRODUCTION TO THE INTERNET 1.2.7 Doubles In Size In a Year Before 1982, the Internet interconnected approximately 200 computers. One year later, it had doubled in size. Increase in Internet size uncovered limits in TCP/IP. As more and more computers connected to the Internet the TCP/IP couldn’t accommodate all. There was a need to update TCP/IP to increase the capacity and also required tuning of administrative procedures by professional staff. The National Science Foundation funded a project (CSNET) to build the Computer Science Network. CSNET encouraged institutions to use TCP/IP to connect to the Internet. 1.2.8 Adaptability Many services face difficulties when the demand increases and if they cannot support all their customers. When service provider increases its capacity, it may ask their customers to acquire new equipments and their old equipments become obsolete. This issue is known as backward compatibility. However, this is not an issue in the Internet, although new equipments are integrated to the system. Simply we can say, continual expansion of the Internet is possible by adapting to both technical and political changes. What we can observe is that, the Internet continues to expand (figure 1.8). 1.2.9 NSF’s Approach The Internet changed the way scientists do research. They could exchange documents or experimental data instantly and also used the Internet to disseminate data as experiments proceed. So the scientists could analyze the results of experiments done at a remote place without travelling and also used the Internet for informal, unpublished discussions. Recognizing the importance of the Internet to the science, NSF decided to fund Internet growth and TCP/IP technology. In 1986, the National Science Foundation funded NSFNET as a cross country 56 Kbps backbone for the Inter-net. This network was much smaller and not much faster than the ARPANET. Later NSF decided to extend network access to every scientist. 12 1.2 History of the Internet Figure 1.8: Internet is growing rapidly They maintained their sponsorship for nearly a decade, setting rules for its non- commercial government and research uses. And because the NSF Network was so successful, ARPANET was dissolved in 1990 and many of the sites connected to it were absorbed by the NSFNET. 1.2.10 Exponential Growth Internet has grown rapidly during the recent past. This is mainly due to the fact that the services and opportunities available through the Internet are growing very fast. According to the recent statistics, a computer is added to the Internet in every second. It is expected the number of computers connected to the Internet will be doubled every 10 months and the growth has an exponential trend now. 188.8.131.52 Accommodating the access growth In order to accommodate this access growth of the Internet, it is necessary to develop technological capabilities and infrastructure of the Internet. Many inter national organizations and governments are contributing to improve the Internet. 13 1. INTRODUCTION TO THE INTERNET 1.2.11 The Future of the Internet The incubator for many of the emerging technologies shaping the future is known as Internet2. 184.108.40.206 Internet2 Formed in 1996 and administered by the University Corporation for Advanced Internet Development (UCAID), Internet2 is a partnership between universities, corporations and government agencies. Internet2 is not a single network, but a consortium of hundreds of high-speed networks linked by fiber optic backbones that span the United States and links to other countries. The network transmits data at speeds up to 2.4 gigabits per second–45,000 times faster than a 56 Kbps modem– allowing scientists to test their laboratory discoveries in the real world. 1.3 Why do people use the Internet? 1.3.1 Who is using the Internet? Everyday the numbers of users are increasing. Current statistics say that the largest portion is from US and Europe. However, Asian users are rising rapidly. The Internet has become a resource irrespective of profession or status. At the same time, their usage objective varies and some individuals may have different objectives. For example, children, parents, teachers and researchers may access the Internet mainly for education purposes and stockbrokers and different business professionals for business purposes. Anyone can connect to the Internet through telephone lines since these two networks are connected. You need a device called a modem to connect your computer to Internet through a telephone line. 14 1.3 Why do people use the Internet? 220.127.116.11 Why would YOU want to use it? Besides, individuals, business, trade, commerce and industry, the Internet also provides tremendous opportunities to students, researchers and professionals for getting information on matters related to academic and professional topics. In addition to that the Internet is a source of information. It is a good source of entertainment too. We will look into the facilities provided by the Internet in brief. 1.3.2 Internet Facilities The Internet makes it possible to communicate and share information in a number of ways. Two of the most popular uses of the Internet are electronic mail and the World Wide Web. We can also find several other useful services like Instant messaging, video conferencing, FTP, newsgroups, etc. 1.3.3 WWW WWW stands for the World Wide Web which is sometimes called as w3 or Web is the most popular and powerful application on the Internet. It was originally created to build the infrastructure for sharing documents on the Internet. Since different types of computers will access these documents, it was decided to have a standard structure for them. This standard was called HTML (HyperText Markup Language). Today the web is a huge collection of documents stored on computers around the world. 18.104.22.168 HTML HTML was derived based on another document language called SGML(Standard Generalized Markup Language). Hence web documents usually have html mark up commands to format these documents. It was called web since html gives facilities to link documents with respect to specific locations. These locations are identified using file addressing mechanism called URL (Uniform Resource Locator). 15 1. INTRODUCTION TO THE INTERNET URL identifies a file using its physically stored location, file name and if necessary segment name in the file. 1.3.4 Email If you are a user of the Internet, you can get an address called the email address. Then others can send you messages to your email address and you can read them when ever you want. This is like when you give the postal address of your home, others can send mail to your address. Postal Mail takes time and more costly than emails. Emails are instant and the cost of delivery is very small. Do you have an email address? If not, do you like to get one? How much will it cost? It is just few keystrokes and you can get one for free too. We will learn more about emails later. 1.3.5 Chat Chatting is a method of communication and is a very popular activity that people engage through the Internet. When two or more people are online (i.e. they are connected to the Internet at the same time), they can exchange messages as a private group or in an open chat room where anyone else can participate with or without their permission. Email based communication is considered as the asynchronous method of communication where participants do not want to be online. Whereas, chatting is considered to be synchronous method of communication and it opens a direct interactive environment. Earlier, chatting was done using simple text messages since it didn’t take much time for the transmission. With the development of the Internet speed and band-width, people can now do chatting using audio and video streams just like in a real-time communication. Irrespective of the medium of chatting, it is almost free except the charges to access the Internet. 1.3.6 Video conferencing It is usually a bi-directional communication between two or more parties using video streams and special hardware in a real time communication. Since video 16 1.3 Why do people use the Internet? stream requires better (bandwidth) and faster (speed) connection, it is not a very popular way of communication on the Internet in early days. Video conferencing is more than mere communication and it may involve more collaborative activities. Video conferencing tools provide additional facilities for active collaboration, for example white boards. Examples for video conferencing include MSN messenger for video conferencing or Microsoft Netmeeting 22.214.171.124 Special Hardware Video conferencing is now becoming a common mechanism due to the better technological infrastructure of the Internet. You need a video camera, microphone attached to a computer to start video conferencing with another party on the Internet. 1.3.7 Newsgroups When you want to send a message to one or very few individuals you can send it by email. However, if you want to start a discussion based on these messages, emailing is not the best option. Newsgroups serve this purpose and it provides an interface for such discussions. Simply, you can send a message to a newsgroup and then all people who are in this group can see your posting and reply to it. Such replies also appear in this newsgroup. It also can be considered as an electronic bulletin board. Usenet is one such famous newsgroup but there are several others. Most of the time, these groups are based on some specific interest which is identified by the topic given to the group. 1.3.8 FTP FTP which stands for File Transfer Protocol is a standard way to copy files from one location to another (i.e. from one machine location to another location in the same or different machine). You can use FTP to download files to your machine from a location in another machine. 17 1. INTRODUCTION TO THE INTERNET However, you need to login into these machines in order to obtain the per-mission. There are some public locations on the Internet from which you can download files by just giving your identification information if you like. In order to simplify the process of accessing files through FTP, there are several applications just like web browsers. Then, users do not need to know complicated commands and they can copy files or directories just like copying files on the desktop. We will be exploring these Internet services in detail in upcoming chapters. 18
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