1 The Internet Etc Lecture 1
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University of Guyana • Faculty of Natural Sciences • Department of Computer Science
CSI225 Internet Computing (lecture 1) The Internet – An Introduction What is the Internet? In short, the Internet is a revolutionary global medium. More specifically it is a worldwide, publically accessible network of other computer networks – a network of networks. Most networks that interconnect to make up the Internet can be classified as academic-related, government-related, businessrelated, or domestic-related. Regardless of what specific purpose the Internet may facilitate, it always relates (in some way or the other) to the exchange of information across great distances. How did the Internet come about? The history of the Internet is quite a lengthy one; however, the significant events will be chronologically listed to give you a quick idea of how the Internet came to be what it is today (i.e. 2007). In 1957, the Soviet Union launched Sputnik I, the first satellite. This made the US nervous (things were tense then with the threat of nuclear war and all) so the US Department of Defense formed ARPA (Advanced Research Projects Agency) to do research to ensure national security. The IPTO (Information Processing Techniques Office), affiliated with ARPA and headed by J.C.R. Licklider discussed the potential benefits of a country-wide
Page 1
E Marks 1/29/2007
University of Guyana • Faculty of Natural Sciences • Department of Computer Science
communications network to securely share research information under ARPA. Licklider suggested to his superiors that Lawrence Roberts would be perfect for the job to develop such a network. So, Roberts took up the offer and led the development of the network based on Paul Baran’s and Donald Davies’ new concept of packet switching. A special computer called the Interface Message Processor was developed to implement the design and ARPAnet went “online” in October of 1969. The first communications were between a research centre at the University of California (UCLA) and that of the Standford Research Institute (SRI) (California). Shortly afterwards, more Institutions were added to the group of “interconnected nodes” namely: UCSB, University of Utah, Harvard, NASA etc; bringing the total to 15 by 1971. All this time ARPAnet was using the NCP (network control program) to act as a protocol for their network, however in 1983, it was replaced by the TCP/IP protocol (the protocol we use today) developed by Robert Khan, Vinton Cerf and others. This leads to one of the first definitions of an “internet” as being a connected set of networks. By the early 1990s the Soviet Union was no more and ARPAnet went into retirement and became NSFnet (National Science foundation network). The NSFnet was soon connected
Page 2
E Marks 1/29/2007
University of Guyana • Faculty of Natural Sciences • Department of Computer Science
to the CSnet (Conputer Science network), which linked universities throughout North America and then to the EUnet (European network) which connected research facilities in Europe. Shortly afterwards, the popularity of the Internet grew exponentially along with the number of hosts, partially due to NSFnet’s management but mostly because of the advent of the World Wide Web in 1991. This persuaded the US Government to transfer management to independent organisations (listed below) in 1995 and that’s the history. The organisations that marshal the Internet are: 1. ICANN – Internet Corporation for Assigned Names & Numbers a. IANA – Internet Assigned Numbers Authority b. ASO – Address Support Organisation c. CCNSO – Country Code Names Supporting Organisation d. GNSO – Generic Names Supporting Organisation e. NSI – Network Solutions f. Accredited Domain Name Registrars 2. ISOC – Internet Society a. IAB – Internet Architecture Board i. IETG / IESG – Internet Engineering Task Force ii. IRTF / IRSG – Internet Research Task Force 3. Others
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E Marks 1/29/2007
University of Guyana • Faculty of Natural Sciences • Department of Computer Science
The Infrastructure of the Internet The technical infrastructure of the Internet comprises a hardware side and a software side. Hardware Set-Up The global network of networks which is the Internet is physically interconnected by cable, routers and servers that are essentially used to form ISPs and Wide Area Networks. At the endpoints of the interconnected networks lie a series of Clients (End-User computers). The following diagram (fig 1.) illustrates this:
Page 4
E Marks 1/29/2007
University of Guyana • Faculty of Natural Sciences • Department of Computer Science
Software Set-Up The physical structure depicted in fig. 1 can be thought of as primarily comprising computers (clients and servers) that share all types of information. The sharing of such information is facilitated by the data packet. For instance, one computer at an endpoint is able to transfer information to another computer at another endpoint by converting the information into packets and posting them across the series of ISPs, Backbones etc, to the intended destination. But a few technical questions arise: 1- How do these packets find their way across the vast Internet to their destination? 2- How is the destination computer singled out from all the other computers? 3- How is the communication between these computers coordinated for an effective transfer? The answer to question 1 relates to the presence of routers throughout the Internet. A router is the hardware element of the Internet that directs Internet traffic by basically reading the destination address on a data packet, and routing the packet through the appropriate sub-networks to reach its destination in the shortest time possible. This brings us to question 2. Every computer that belongs to a network is given a unique address, to help identify it. This unique address is known as its IP address (e.g 65.199.203.58)
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University of Guyana • Faculty of Natural Sciences • Department of Computer Science
and is embedded in every packet sent, so that routers know which computer of which network to direct the particular packet. Finally, we come to question 3. Since any information sent over the Internet is broken up into several discrete packets to be transferred, there needs to be some common system of control to coordinate and ensure that all of these packets reach their destination safely to reconstruct the information initially sent. This system of control, known as a protocol, essentially facilitates the effective communication of all elements of the Internet. As stated earlier, the primary protocol of the Internet is TCP/IP which represents a stack of all the protocols used over the Internet such as FTP (file transfer protocol) and HTTP (Hypertext transfer protocol) the protocol of the Web. The Internet and the World Wide Web (WWW) The success and popularity of the Internet was primarily brought on by the advent of the World Wide Web in 1991, however, the concepts of the web originated many decades before. In the 1960’s Ted Nelson discovered and popularized the Hypertext concept. The hypertext concept is a user interface paradigm employed today in hyperlinks throughout the web as well as electronic documents that overcomes the linearity in traditional documents. Douglas Engelbart, in accordance with Nelson’s research, developed the first mouse, GUI and hypertext system.
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University of Guyana • Faculty of Natural Sciences • Department of Computer Science
Many years after in the 1980s, the web, in its initial state, was developed in Europe by Tim Berners-Lee and Robert Cailliau and subsequently gained its worldwide popularity in the 1990s through the efforts of Marc Andreesen and NCSA (National Center for Supercomputing Applications) that developed Mosaic and Netscape Browsers. The web, as we know it today, runs on the Internet and consists of: 1- Hyperlinked Web pages 2- Web browsers to view the hyperlinked web pages. 3- Web addresses or Uniform Resource Identifiers (URIs)(e.g. http://www.yahoo.com) to locate the hyperlinked web pages or other file resources. 4- Web servers to host the hyperlinked collection of web pages known as websites and other resources. 5- Domain Name Servers (DNSs) that assist in locating web servers via their URIs instead of a cryptic IP address. The web, however, is coordinated and driven by three particular standards. They are: i. The Uniform Resource Identifier (URI) ii. The Hypertext Transfer Protocol (HTTP), which specifies how the browser and web server communicate with each other. iii. The Hypertext Markup Language (HTML), used to define the structure and content of hypertext documents.
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University of Guyana • Faculty of Natural Sciences • Department of Computer Science
References:
Stewart, William. (2006). Living Internet. Available online at < http://www.livinginternet.com/> Bolter, Jay David (2001). Writing Space: Computers, Hypertext, and the Remediation of Print. New Jersey: Lawrence Erlbaum Associates. ISBN 0-80582919-9.
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CSI225 Internet Computing (lecture 1) The Internet – An Introduction What is the Internet? In short, the Internet is a revolutionary global medium. More specifically it is a worldwide, publically accessible network of other computer networks – a network of networks. Most networks that interconnect to make up the Internet can be classified as academic-related, government-related, businessrelated, or domestic-related. Regardless of what specific purpose the Internet may facilitate, it always relates (in some way or the other) to the exchange of information across great distances. How did the Internet come about? The history of the Internet is quite a lengthy one; however, the significant events will be chronologically listed to give you a quick idea of how the Internet came to be what it is today (i.e. 2007). In 1957, the Soviet Union launched Sputnik I, the first satellite. This made the US nervous (things were tense then with the threat of nuclear war and all) so the US Department of Defense formed ARPA (Advanced Research Projects Agency) to do research to ensure national security. The IPTO (Information Processing Techniques Office), affiliated with ARPA and headed by J.C.R. Licklider discussed the potential benefits of a country-wide
Page 1
E Marks 1/29/2007
University of Guyana • Faculty of Natural Sciences • Department of Computer Science
communications network to securely share research information under ARPA. Licklider suggested to his superiors that Lawrence Roberts would be perfect for the job to develop such a network. So, Roberts took up the offer and led the development of the network based on Paul Baran’s and Donald Davies’ new concept of packet switching. A special computer called the Interface Message Processor was developed to implement the design and ARPAnet went “online” in October of 1969. The first communications were between a research centre at the University of California (UCLA) and that of the Standford Research Institute (SRI) (California). Shortly afterwards, more Institutions were added to the group of “interconnected nodes” namely: UCSB, University of Utah, Harvard, NASA etc; bringing the total to 15 by 1971. All this time ARPAnet was using the NCP (network control program) to act as a protocol for their network, however in 1983, it was replaced by the TCP/IP protocol (the protocol we use today) developed by Robert Khan, Vinton Cerf and others. This leads to one of the first definitions of an “internet” as being a connected set of networks. By the early 1990s the Soviet Union was no more and ARPAnet went into retirement and became NSFnet (National Science foundation network). The NSFnet was soon connected
Page 2
E Marks 1/29/2007
University of Guyana • Faculty of Natural Sciences • Department of Computer Science
to the CSnet (Conputer Science network), which linked universities throughout North America and then to the EUnet (European network) which connected research facilities in Europe. Shortly afterwards, the popularity of the Internet grew exponentially along with the number of hosts, partially due to NSFnet’s management but mostly because of the advent of the World Wide Web in 1991. This persuaded the US Government to transfer management to independent organisations (listed below) in 1995 and that’s the history. The organisations that marshal the Internet are: 1. ICANN – Internet Corporation for Assigned Names & Numbers a. IANA – Internet Assigned Numbers Authority b. ASO – Address Support Organisation c. CCNSO – Country Code Names Supporting Organisation d. GNSO – Generic Names Supporting Organisation e. NSI – Network Solutions f. Accredited Domain Name Registrars 2. ISOC – Internet Society a. IAB – Internet Architecture Board i. IETG / IESG – Internet Engineering Task Force ii. IRTF / IRSG – Internet Research Task Force 3. Others
Page 3
E Marks 1/29/2007
University of Guyana • Faculty of Natural Sciences • Department of Computer Science
The Infrastructure of the Internet The technical infrastructure of the Internet comprises a hardware side and a software side. Hardware Set-Up The global network of networks which is the Internet is physically interconnected by cable, routers and servers that are essentially used to form ISPs and Wide Area Networks. At the endpoints of the interconnected networks lie a series of Clients (End-User computers). The following diagram (fig 1.) illustrates this:
Page 4
E Marks 1/29/2007
University of Guyana • Faculty of Natural Sciences • Department of Computer Science
Software Set-Up The physical structure depicted in fig. 1 can be thought of as primarily comprising computers (clients and servers) that share all types of information. The sharing of such information is facilitated by the data packet. For instance, one computer at an endpoint is able to transfer information to another computer at another endpoint by converting the information into packets and posting them across the series of ISPs, Backbones etc, to the intended destination. But a few technical questions arise: 1- How do these packets find their way across the vast Internet to their destination? 2- How is the destination computer singled out from all the other computers? 3- How is the communication between these computers coordinated for an effective transfer? The answer to question 1 relates to the presence of routers throughout the Internet. A router is the hardware element of the Internet that directs Internet traffic by basically reading the destination address on a data packet, and routing the packet through the appropriate sub-networks to reach its destination in the shortest time possible. This brings us to question 2. Every computer that belongs to a network is given a unique address, to help identify it. This unique address is known as its IP address (e.g 65.199.203.58)
Page 5
E Marks 1/29/2007
University of Guyana • Faculty of Natural Sciences • Department of Computer Science
and is embedded in every packet sent, so that routers know which computer of which network to direct the particular packet. Finally, we come to question 3. Since any information sent over the Internet is broken up into several discrete packets to be transferred, there needs to be some common system of control to coordinate and ensure that all of these packets reach their destination safely to reconstruct the information initially sent. This system of control, known as a protocol, essentially facilitates the effective communication of all elements of the Internet. As stated earlier, the primary protocol of the Internet is TCP/IP which represents a stack of all the protocols used over the Internet such as FTP (file transfer protocol) and HTTP (Hypertext transfer protocol) the protocol of the Web. The Internet and the World Wide Web (WWW) The success and popularity of the Internet was primarily brought on by the advent of the World Wide Web in 1991, however, the concepts of the web originated many decades before. In the 1960’s Ted Nelson discovered and popularized the Hypertext concept. The hypertext concept is a user interface paradigm employed today in hyperlinks throughout the web as well as electronic documents that overcomes the linearity in traditional documents. Douglas Engelbart, in accordance with Nelson’s research, developed the first mouse, GUI and hypertext system.
Page 6
E Marks 1/29/2007
University of Guyana • Faculty of Natural Sciences • Department of Computer Science
Many years after in the 1980s, the web, in its initial state, was developed in Europe by Tim Berners-Lee and Robert Cailliau and subsequently gained its worldwide popularity in the 1990s through the efforts of Marc Andreesen and NCSA (National Center for Supercomputing Applications) that developed Mosaic and Netscape Browsers. The web, as we know it today, runs on the Internet and consists of: 1- Hyperlinked Web pages 2- Web browsers to view the hyperlinked web pages. 3- Web addresses or Uniform Resource Identifiers (URIs)(e.g. http://www.yahoo.com) to locate the hyperlinked web pages or other file resources. 4- Web servers to host the hyperlinked collection of web pages known as websites and other resources. 5- Domain Name Servers (DNSs) that assist in locating web servers via their URIs instead of a cryptic IP address. The web, however, is coordinated and driven by three particular standards. They are: i. The Uniform Resource Identifier (URI) ii. The Hypertext Transfer Protocol (HTTP), which specifies how the browser and web server communicate with each other. iii. The Hypertext Markup Language (HTML), used to define the structure and content of hypertext documents.
Page 7
E Marks 1/29/2007
University of Guyana • Faculty of Natural Sciences • Department of Computer Science
References:
Stewart, William. (2006). Living Internet. Available online at < http://www.livinginternet.com/> Bolter, Jay David (2001). Writing Space: Computers, Hypertext, and the Remediation of Print. New Jersey: Lawrence Erlbaum Associates. ISBN 0-80582919-9.
Page 8
E Marks 1/29/2007
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