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18-10-2007, 19:17
Internet
From: Encyclopedia of Computer Science and Technology.
The Internet is the worldwide network of all computers (or networks of computers) that communicate using a particular protocol for routing data from one computer to another. As long as the programs they run follow the rules of the protocol, the computers can be connected by a variety of physical means including ordinary and special phone lines, cable, fiber optics, and even wireless or satellite transmission.
HISTORY AND DEVELOPMENT
The Internet's origins can be traced to a project sponsored by the U.S. Defense Department. Its purpose was to find a way to connect key military computers (such as those controlling air defense radar and interceptor systems). Such a system would require a great deal of redundancy, routing communications around installations that had been destroyed by enemy nuclear weapons. The solution was to break data up into individually addressed packets that could be dispatched by routing software that could find whatever route to the destination was viable or most efficient. At the destination, packets would be reassembled into messages or data files.
By the early 1970s, a number of research institutions including the pioneer networking firm Bolt Beranek and Newman (BBN), Stanford Research Institute (SRI), Carnegie Mellon University, and the University of California at Berkeley were connected to the government-funded and administered ARPANET (named for the Defense Department's Advanced Research Projects Agency). Gradually, as use of the ARPANET's protocol spread, gateways were created to connect it to other networks such as the National Science Foundation's NSFnet. The growth of the network was also spurred by the creation of useful applications including email ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]) and Usenet, a sort of bulletin-board service.
Meanwhile, a completely different world of online networking arose during the 1980s in the form of local bulletin boards, often connected using a store-and-forward system called FidoNet, and proprietary online services such as CompuServe and America Online. At first there were few connections between these networks and the ARPANET, which had evolved into a general-purpose network for the academic community under the rubric of NSFnet. (It was possible to send email between some networks using special gateways, but a number of different kinds of address syntax had to be used.)
In the 1990s, the NSFnet was essentially privatized, passing from government administration to a corporation that assigned domain names. However, the impetus that brought the Internet into the daily consciousness of more and more people was the development of the World Wide Web ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]) by Tim Berners-Lee ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]) at the European particle research laboratory CERN. With a standard way to display and link text (and the addition of graphics and multimedia by the mid-1990s), the Web is the Internet as far as most users are concerned. What had been a network for academics and adventurous professionals became a mainstream medium by the end of the decade.
APPLICATIONS
A number of applications are (or have been) important contributors to the utility and popularity of the Internet.
Email was one of the earliest applications on the ancestral ARPANET and remains the single most popular Internet application. Standard email using SMTP (Simple Mail Transport Protocol) has been implemented for virtually every platform and operating system. In most cases once a user has entered a person's email address into the "address book," email can be sent with a few clicks of the mouse. While failure of the outgoing or destination mail server can still block transmission of a message, email today has a high degree of reliability.
Netnews (also called Usenet, for UNIX User Network) is in effect the world's largest computer bulletin board. It began in 1979, when Duke University and the University of North Carolina set up a simple mechanism for "posting" text files that could be read by other users. Today there are tens of thousands of topical "newsgroups" and millions of messages (called articles). Although still impressive in its quantity of content, many Web users now rely more on discussion forums based on webpages.
FTP (File Transport Protocol) enables the transfer of one or more files between any two machines connected to the Internet. This method of file transfer has been largely supplanted by the use of download links on webpages, except for high-volume applications (where an ftp server is often operated "behind the scenes" of a Web link). FTP is also used by Web developers to upload files to a website.
Telnet is another fundamental service that brought the Internet much of its early utility. Telnet allows a user at one computer to log into another machine and run a program there. This provided an early means for users at PCs or workstations to, for example, access the Library of Congress catalog online. However, if program and file permissions are not set properly on the "host" system, telnet can cause security vulnerabilities. The telnet user is also vulnerable to having IDs and passwords stolen, since these are transmitted as clear (unencrypted) text. As a result, some online sites that once supported telnet access now limit access to Web-based forms. (Another alternative is to use a program called "secure shell" or ssh, or to use a telnet client that supports encryption.)
Gopher was developed at the University of Minnesota and named for its mascot. Gopher is a system of servers that organize documents or other files through a hierarchy of menus that can be browsed by the remote user. Gopher became very popular in the late 1980s, only to be almost completely supplanted by the more versatile World Wide Web.
WAIS (Wide Area Information Service) is a gateway that allows databases to be searched over the Internet. WAIS provided a relatively easy way to bring large data resources online. It, too, has largely been replaced by Web-based database services.
The World Wide Web as mentioned above, is now the main means for displaying and transferring information of all kinds over the Internet. Its flexibility, relative ease of use, and ubiquity (with Web browsers ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]) available for virtually all platforms) has caused it to subsume most earlier services. The utility of the Web has been further enhanced by the development of many search engines that vary in thoroughness and sophistication.
Streaming Media protocols allow for a flow of video and/or audio content to users. Player applications for Windows and other operating systems, and growing use of high-speed consumer Internet connections have made it possible to present "live" TV and radio shows over the Internet.
E-commerce or the carrying out of business transactions on the Web was the most highly touted application of the late 1990s. While a few companies such as Amazon.com and eBay have managed to create large revenue streams with expectations of eventual profitability, other entrepreneurs have concentrated on business-to-business (B2B) commerce applications, such as the replacement of traditional forms of wholesale distribution with online-brokered systems. The stock market declines of the early 2000s have cast doubt on the projected rate of growth of e-commerce ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]).
CURRENT AND FUTURE TRENDS
After the rapid growth of the late 1990s, Internet access in the United States seems to be reaching saturation levels with a declining rate of growth. Internationally, Internet growth has been strong through the developed world, particularly in Europe and Asia. Unless it can be heavily subsidized (including the provision or upgrading of basic infrastructure), it is unlikely that Internet access will become a mass phenomenon in the developing world for the foreseeable future.
Increasingly, proprietary local area network ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]) (LAN) systems have been replaced by networks using the same protocols as the Internet. This means that the same software (Web servers, browsers, search engines ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]), and so on) used to connect to the Internet is used to manage an organization's internal network. This seamless connection raises security concerns and requires the deployment of effective measures to protect the local network from intruders.
In the United States, the transition from relatively slow dial-up access to broadband ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]) (mainly cable or DSL) is likely to be steady. In the early 2000s, the continuing growth in bandwidth-hungry applications such as streaming video and audio is likely to increase congestion as its demands increase faster than the provision of new high-speed "backbone" connections. Initiatives based on the Internet 2 proposal are likely to relieve congestion in the long run.
Security remains a pressing concern in the wake of well-publicized "denial of service" attacks that have occasionally brought down major sites such as Yahoo! as well as the continuing spread of viruses, particularly through exploiting vulnerabilities in the dominant Microsoft server and client products. Together with concerns about terrorism in the post-9/11 world and threats to privacy, security issues are likely to keep the growing Internet under critical scrutiny and invite further government regulation.
In the longer term, however, what we call the Internet today is likely to become so ubiquitous that people will no longer think of it as a separate system or entity. Household appliances, cars, cell phones, televisions, and virtually every other device used in daily life will communicate with other devices and with control systems using Internet protocols. In effect, people may eventually live "inside" a World Wide Web.
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ] Information
Hafner, K., and M. Lyon. Where Wizards Stay Up Late: The Origins of the Internet. New York: Simon & Schuster, 1996.
Juliussen, Egil, and Karen Petska Juliussen. Internet Industry Almanac. Glenbrook, Nev.: Computer Industry Almanac, 1998.
Segaller, S. Nerds 2.0.1: A Brief History of the Internet. New York: TV Books, 1998.
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ] Information
Record Citation: Henderson, Harry. "Internet." Encyclopedia of Computer Science and Technology. New York: Facts on File, Inc., 2003. Science Online. Facts On File, Inc.
برای مشاهده محتوا ، لطفا وارد شوید یا ثبت نام کنید comptechi0191&SingleRecord=True (accessed October 18, 2007).
From: Encyclopedia of Computer Science and Technology.
The Internet is the worldwide network of all computers (or networks of computers) that communicate using a particular protocol for routing data from one computer to another. As long as the programs they run follow the rules of the protocol, the computers can be connected by a variety of physical means including ordinary and special phone lines, cable, fiber optics, and even wireless or satellite transmission.
HISTORY AND DEVELOPMENT
The Internet's origins can be traced to a project sponsored by the U.S. Defense Department. Its purpose was to find a way to connect key military computers (such as those controlling air defense radar and interceptor systems). Such a system would require a great deal of redundancy, routing communications around installations that had been destroyed by enemy nuclear weapons. The solution was to break data up into individually addressed packets that could be dispatched by routing software that could find whatever route to the destination was viable or most efficient. At the destination, packets would be reassembled into messages or data files.
By the early 1970s, a number of research institutions including the pioneer networking firm Bolt Beranek and Newman (BBN), Stanford Research Institute (SRI), Carnegie Mellon University, and the University of California at Berkeley were connected to the government-funded and administered ARPANET (named for the Defense Department's Advanced Research Projects Agency). Gradually, as use of the ARPANET's protocol spread, gateways were created to connect it to other networks such as the National Science Foundation's NSFnet. The growth of the network was also spurred by the creation of useful applications including email ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]) and Usenet, a sort of bulletin-board service.
Meanwhile, a completely different world of online networking arose during the 1980s in the form of local bulletin boards, often connected using a store-and-forward system called FidoNet, and proprietary online services such as CompuServe and America Online. At first there were few connections between these networks and the ARPANET, which had evolved into a general-purpose network for the academic community under the rubric of NSFnet. (It was possible to send email between some networks using special gateways, but a number of different kinds of address syntax had to be used.)
In the 1990s, the NSFnet was essentially privatized, passing from government administration to a corporation that assigned domain names. However, the impetus that brought the Internet into the daily consciousness of more and more people was the development of the World Wide Web ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]) by Tim Berners-Lee ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]) at the European particle research laboratory CERN. With a standard way to display and link text (and the addition of graphics and multimedia by the mid-1990s), the Web is the Internet as far as most users are concerned. What had been a network for academics and adventurous professionals became a mainstream medium by the end of the decade.
APPLICATIONS
A number of applications are (or have been) important contributors to the utility and popularity of the Internet.
Email was one of the earliest applications on the ancestral ARPANET and remains the single most popular Internet application. Standard email using SMTP (Simple Mail Transport Protocol) has been implemented for virtually every platform and operating system. In most cases once a user has entered a person's email address into the "address book," email can be sent with a few clicks of the mouse. While failure of the outgoing or destination mail server can still block transmission of a message, email today has a high degree of reliability.
Netnews (also called Usenet, for UNIX User Network) is in effect the world's largest computer bulletin board. It began in 1979, when Duke University and the University of North Carolina set up a simple mechanism for "posting" text files that could be read by other users. Today there are tens of thousands of topical "newsgroups" and millions of messages (called articles). Although still impressive in its quantity of content, many Web users now rely more on discussion forums based on webpages.
FTP (File Transport Protocol) enables the transfer of one or more files between any two machines connected to the Internet. This method of file transfer has been largely supplanted by the use of download links on webpages, except for high-volume applications (where an ftp server is often operated "behind the scenes" of a Web link). FTP is also used by Web developers to upload files to a website.
Telnet is another fundamental service that brought the Internet much of its early utility. Telnet allows a user at one computer to log into another machine and run a program there. This provided an early means for users at PCs or workstations to, for example, access the Library of Congress catalog online. However, if program and file permissions are not set properly on the "host" system, telnet can cause security vulnerabilities. The telnet user is also vulnerable to having IDs and passwords stolen, since these are transmitted as clear (unencrypted) text. As a result, some online sites that once supported telnet access now limit access to Web-based forms. (Another alternative is to use a program called "secure shell" or ssh, or to use a telnet client that supports encryption.)
Gopher was developed at the University of Minnesota and named for its mascot. Gopher is a system of servers that organize documents or other files through a hierarchy of menus that can be browsed by the remote user. Gopher became very popular in the late 1980s, only to be almost completely supplanted by the more versatile World Wide Web.
WAIS (Wide Area Information Service) is a gateway that allows databases to be searched over the Internet. WAIS provided a relatively easy way to bring large data resources online. It, too, has largely been replaced by Web-based database services.
The World Wide Web as mentioned above, is now the main means for displaying and transferring information of all kinds over the Internet. Its flexibility, relative ease of use, and ubiquity (with Web browsers ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]) available for virtually all platforms) has caused it to subsume most earlier services. The utility of the Web has been further enhanced by the development of many search engines that vary in thoroughness and sophistication.
Streaming Media protocols allow for a flow of video and/or audio content to users. Player applications for Windows and other operating systems, and growing use of high-speed consumer Internet connections have made it possible to present "live" TV and radio shows over the Internet.
E-commerce or the carrying out of business transactions on the Web was the most highly touted application of the late 1990s. While a few companies such as Amazon.com and eBay have managed to create large revenue streams with expectations of eventual profitability, other entrepreneurs have concentrated on business-to-business (B2B) commerce applications, such as the replacement of traditional forms of wholesale distribution with online-brokered systems. The stock market declines of the early 2000s have cast doubt on the projected rate of growth of e-commerce ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]).
CURRENT AND FUTURE TRENDS
After the rapid growth of the late 1990s, Internet access in the United States seems to be reaching saturation levels with a declining rate of growth. Internationally, Internet growth has been strong through the developed world, particularly in Europe and Asia. Unless it can be heavily subsidized (including the provision or upgrading of basic infrastructure), it is unlikely that Internet access will become a mass phenomenon in the developing world for the foreseeable future.
Increasingly, proprietary local area network ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]) (LAN) systems have been replaced by networks using the same protocols as the Internet. This means that the same software (Web servers, browsers, search engines ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]), and so on) used to connect to the Internet is used to manage an organization's internal network. This seamless connection raises security concerns and requires the deployment of effective measures to protect the local network from intruders.
In the United States, the transition from relatively slow dial-up access to broadband ([ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]) (mainly cable or DSL) is likely to be steady. In the early 2000s, the continuing growth in bandwidth-hungry applications such as streaming video and audio is likely to increase congestion as its demands increase faster than the provision of new high-speed "backbone" connections. Initiatives based on the Internet 2 proposal are likely to relieve congestion in the long run.
Security remains a pressing concern in the wake of well-publicized "denial of service" attacks that have occasionally brought down major sites such as Yahoo! as well as the continuing spread of viruses, particularly through exploiting vulnerabilities in the dominant Microsoft server and client products. Together with concerns about terrorism in the post-9/11 world and threats to privacy, security issues are likely to keep the growing Internet under critical scrutiny and invite further government regulation.
In the longer term, however, what we call the Internet today is likely to become so ubiquitous that people will no longer think of it as a separate system or entity. Household appliances, cars, cell phones, televisions, and virtually every other device used in daily life will communicate with other devices and with control systems using Internet protocols. In effect, people may eventually live "inside" a World Wide Web.
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ]
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ] Information
Hafner, K., and M. Lyon. Where Wizards Stay Up Late: The Origins of the Internet. New York: Simon & Schuster, 1996.
Juliussen, Egil, and Karen Petska Juliussen. Internet Industry Almanac. Glenbrook, Nev.: Computer Industry Almanac, 1998.
Segaller, S. Nerds 2.0.1: A Brief History of the Internet. New York: TV Books, 1998.
[ برای مشاهده لینک ، لطفا با نام کاربری خود وارد شوید یا ثبت نام کنید ] Information
Record Citation: Henderson, Harry. "Internet." Encyclopedia of Computer Science and Technology. New York: Facts on File, Inc., 2003. Science Online. Facts On File, Inc.
برای مشاهده محتوا ، لطفا وارد شوید یا ثبت نام کنید comptechi0191&SingleRecord=True (accessed October 18, 2007).