1. Internet és a Web Történelme, Bevezetés Kecskeméti Gábor A/1 336-os szoba – fizika tanszék Konzultációs idő: Csütörtök 9-11 Előadás: XX. Előadó, Csütörtök 14-16 Gyakorlat: 207-es terem, Csütörtök 12-14

2. Ütemterv – vázlat 1. Hálózati alapfogalmak, a web történelme 2. FTP protokoll 3. HTTP protokoll 4. HTML alapozó 5. HTML űrlapok 6. Formázás CSS segítségével 7. ZH 8. DOM modell 9. Javascript 10. HTML 5 11. CGI 12. PHP 13. Ajax Szeptember 29.-én mind az előadás mind a gyakorlat elmarad! Pótlást később beszéljük meg.

3. Számonkérés - vázlat 1 ZH – Az előadás idejében 7. alkalommal – Pótlása az utolsó előadás idejében 1 Gyakorlati feladat – Kiadása: 5. hét – Beszedése: 10. hét – Pótálására félév közben van lehetőség Vizsga: írásbeli + szóbeli

4. 4 What is the Internet? The internet is a publicly available, global network of computers It interconnects billions of Users. For example: –Businesses –Citizens –Governments –Academic Institutions –Research Centers –Libraries –Etc. Provides a Common Communications System for Diverse Computing and Network Environments Still Rapidly Expanding Involves Numerous Technologies (Not a Single Technology)

5. 5 Internet History Milestones ARPANETINTERNET 1969 ARPANET R&D Project 1991 World Wide Web Released by Tim-Berners Lee 1974 Vinton Cerf and Robert Kahn Initiated TCP/IP 1983 DOD Mandated Adoption of TCP/IP 1983 ARPANET Split into ARPANET and MILNET 1985 NSFNET founded by The National Science Foundation 1993 Web Browser “ Mosaic ” invented by Mark Andreesen

6. ARPANET Advanced Research Projects Agency Network The precursor to the Internet Developed in the late 60’s and early 70’s by the US Department of Defense as an experiment in wide-area-networking that would survive a nuclear war.

7. The Path of ARPANET  December 1969 July 1977  Images from Heart, F., McKenzie, A., McQuillian, J., and Walden, D., ARPANET Completion Report, Bolt, Beranek and Newman, Burlington, MA, January 4, 1978

8. A brief history of the Internet 1961: Kleinrock - queueing theory shows effectiveness of packet-switching 1964: Baran - packet-switching in military nets 1967: ARPAnet conceived by Advanced Research Projects Agency 1969: first ARPAnet node operational 1972: – ARPAnet public demonstration – NCP (Network Control Protocol) first host-host protocol – first e-mail program – ARPAnet has 15 nodes 1961-1972: Early packet-switching principles

9. 1969 ARPANET was born. 4 nodes were inter-connected: UCLA,SRI,UCSB, U. of Utah Charley Kline from UCLA sent 1 st packet. First RFC by Steve Crocker.

10. 1970 RFC maintained by Jon Postel (the RFC-editor). ARPANET used NCP (Network Control Protocol), first end-to- end protocol

11. 1971 15 nodes were connected. Ray Tomlinson of BBN invented email program.

12. 1972 @ was chosen by Ray Tomlinson to separate the userid and hostname. First computer-to-computer chat program at UCLA.

13. 1973 Ethernet was invented by Bob Metcalfe's (Harvard PhD Thesis)

14. 1974 TCP (Transmission Control Protocol) was invented by Vint Cerf and Bob Kahn.

15. 1975 First mailing list was created by Steve Walker.

16. 1978 TCP splited into TCP and IP.

17. A brief history of the Internet 1983: deployment of TCP/IP 1982: smtp e-mail protocol defined 1983: DNS defined for name- to-IP-address translation 1985: FTP protocol defined 1988: TCP congestion control New national networks: Csnet, BITnet, NSFnet, Minitel 100,000 hosts connected to confederation of networks 1980-1990: new protocols, a proliferation of networks

18. 1982 DoD used TCP/IP to inter- connect networks. Thus, the Internet!!!

19. 1983 NCP → TCP/IP. ARPANET was split into ARPANET and MILNET. BSD included TCP/IP.

20. 1984 DNS (Domain Name System) was introduced. > 1000 hosts.

21. 1986 NSFNET was created, connecting 5 super-computers. IETF was formed. NNTP was created.

22. NSFnet National Science Foundation Network The National Science Foundation followed on the earlier ARPANET by creating NSFNet in 1986 as a 56 Kbps backbone for the Internet. –A Backbone is a very-high-speed connection with huge bandwidth Commercialization of the nets began in 1992. By 1995, the National Science Foundation withdrew its sponsorship.

23. 1987 > 10,000 hosts.

24. 1988 First Internet Worm released by Morris. CERT (Computer Emergency Response Team) was formed as a result. IRC was created.

25. 1989 > 100,000 hosts

26. A brief history of the Internet Early 1990’s: ARPAnet decommissioned 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) Early 1990s: Web – hypertext [Bush 1945, Nelson 1960’s] – HTML, HTTP: Berners-Lee – 1994: Mosaic, later Netscape – late 1990’s: commercialization of the Web Late 1990’s – 2000’s: – more killer apps: instant messaging, P2P file sharing – network security to forefront – est. 50 million host, 100 million+ users – backbone links running at Gbps 1990, 2000’s: commercialization, the Web, new apps

27. 1990 ARPANET ceased. AOL, CompuServe provided dial- up service.

28. 1991 WWW was created by Tim Berners-Lee from CERN. Linux was released by Linus Torvalds.

29. CERN Centre Européen de Recherche Nucléaire (European Center of Nuclear Research) Announced World Wide Web in Aug 1991, invented by English scientist Tim Berners- Lee in 1989 Developed a system to share documents in a multi-platform environment. Three major developments came from this: –Hyper Text Transfer Protocols –Hyper Text Markup Language –Web Browsers

30. 1992 > 1,000,000 hosts. MBONE was created.

31. 1993 Network Solution, Inc was chosen to provide domain name registration. www.whitehouse.govwww.whitehouse.gov online. Mosaic was created.

32. 1994 NSFNET was transformed to commercial network. Shopping mall. Can order pizza online.

33. NSFnet in Action Byte traffic into the ANS/NFSNET T3 backbone from its client networks for the month of December 1994, the last heavy usage month prior to the NSFNET’s decommissioning in April 1995. Backbone service has now transitioned to a number of commercial centers.

34. 1995 NSFNET was reverted back to research-only network. Realaudio started. Netscape IPO. Win95 released. Bob Metcalfe predicted the Internet would collapse.

35. 1996 Browser war (Netscape vs. IE) began. tv.com sold to CNET for $15,000.

36. 1998 2M domain names registered. Compaq bought altavista.com for $3.3M. Google founded. Jon Postel (RFC-editor) died.

37. 2000 Millennium bug. Dotcom → dotgone. Clinton made first webcast.

38. 2001 Wikipedia launched.

39. 2003 Facebook launched.

40. 2006 > 439M hosts. 10 new computers joined the Internet every second.

41. http://en.wikipedia.org/wiki/Image:Internet_map_1024.jpg Internet Map

42. 42 How the Internet works

43. PACKETS

44. 44 Underlying principle of the Internet: Packet Switching The internet was first conceived in 1969 as ARPANET (Advanced Research Projects Agency Network) which was used to connect computers in geographically dispersed research centers ARPANET was the first major implementation of a packet switched network Previously, data communications were based on circuit switching as in traditional telephone networks, where a dedicated link is set up for the duration of the call The invention of packet switching in the early 1960 ’ s enabled the transmission of data over links that are not established beforehand. In packet switching, data is assembled into packets which are then independently routed (using routers) to their destination through various links over the network. This leads to the distribution of resources, an increase in resource utilization, and increased fault tolerance since a packet may take alternative routes to reach its destination The destination node receives these packets and re-assembles them to construct the original message This breakthrough was what made internet a reality

45. 45 One possible route for a data packet Source Destination Source: http://howstuffworks.com

46. Packets Pieces of data divided up for transit Packets contain information about the computer that sent the data and where the data is going. If a packet runs into a problem in transit, it can attempt to find another route. When all the packets arrive at their destination, the recipient computer reassembles them. photo copyright Star Trek

47. Internet Communications Data to be transferred is broken up into packets Packets are addressed with IP address for delivery Packets travel over the Internet backbone Routers give directions along the way, choosing paths at intersections When packets arrive at the destination IP address, they are delivered through the firewall to specific ports

48. ADDRESSING

49. 49 Addressing Schemes We know that packets are sent over the network, but how does a packet reach its destination? Three addressing schemes are used concurrently in sending information across the Internet – Organizationally-Unique Identifier (OUI) This is the 48-bit (MAC) unique address stamped on Network Interface Cards – IP Address All devices connected to the internet are identified by a unique 32-bit IP address It is via IP addresses that computers in the internet can identify each other – Domain Name System (DNS) Hierarchical, alphanumeric addressing scheme that is a “ synonym ” of an IP address

50. IP Address Internet Protocol (IP) address A unique number assigned to every computer connected to the Internet (current version is IPv4) Four sets of numbers separated by periods, called dot-decimal notation Each number in the sequence ranges from 0 to 255 Example: 53.160.248.99 Running out of numbers

51. 51 The IP Address Unique 32-bit (4 byte) logical address –129.174.1.8 (This one belongs to GMU) Made up of two parts –Network Number Identifies a network Must be assigned by the Internet Network Information Center (InterNIC) –Host Number Identifies a host on a network Assigned by the local network administrator Decimal IP address

52. 52 IP Address Classes There are 5 different classes of IP addresses: A, B, C, D and E. A, B, and C are available for commercial use For example, a Class A network could support 126 networks, each with 16,777,216 hosts

53. 53 IPv4 to IPv6 The number of IP addresses provided by a 32-bit code (IPv4) is insufficient for the Internet’s current growth trajectory How many different addresses does a 32-bit number provide? –2 32 = 4,294,967,296 How can we be running short? –Rapid global diffusion –Rapid proliferation of wireless devices that require an IP address –Voice over IP will only increase the shortage Is there a solution? –IPv6 is going to increase the address space to 128 bits –How many addresses will that provide? Short term work-arounds like Network Address Translation have helped stall the need to migrate to IPv6, and many predict the transition will be a rough one.

54. IPv6 Internet Protocol Version 6 Designed to replace 20-year-old IPv4 (current IP address standard) Number sequence has 8 places of hex with colons instead of the standard 4 places of decimal with dots Will allow more computers to connect to the Internet Example: 3ffe:ffff:101::230:6eff:fe04:d9ff

55. Assigning IP Addresses Static – address assigned permanently to that computer Dynamic – new address assigned to that computer each time it connects to the Internet DHCP – Dynamic Host Configuration Protocol, software that assigns IP address to the computer when it connects

56. Ports Each IP address is subdivided into ports, each port assigned to a single program You can browse the Internet using one port while receiving e-mail using another port, with a single IP address

57. NAMING

58. Internet Address Names IP addresses for a particular computer or web server can change Names are assigned to identify Internet locations, called Domain Names Example: www.google.comwww.google.com

59. 59 The Domain Name System We would go crazy if we would have to remember the IP addresses of all the web sites that we wanted to visit The Domain Name System translates between domain names and IP addresses of devices connected to the Internet –A domain name (a part of the URL) is a unique alphanumeric name such as gmu.edu –The top level domain name is edu and the secondary level domain name is gmu in the above example (there could be up to 127 levels, but more than 4 is rare)

60. DNS Domain Name Server Used to map domain names to IP addresses and vice versa. Example: www.website.com = 255.255.222.22

61. Top Level Domains.com – commercial.net – on the Internet.org – non-profit organizations.gov – government agencies.edu – educational organizations.mil – military locations Example: top level domain for www.google.com is com www.google.com

62. Regional Domains.uk.jp.de.ru.kr.br.it.fr.ca.ar.es.pl Regional domain is a top level domain. Example: www.british-library.ukwww.british-library.uk

63. Subdomains Any domain to the left of the top level domain name Example: www.weather.com has top level of com, subdomain of weatherwww.weather.com Example: www.weber.k12.ut.us has top level of us, which has a subdomain of ut, which has a subdomain of k12, which has a subdomain of weberwww.weber.k12.ut.us

64. 64 How DNS works When you type a URL into the address portion of your browser, the browsers ’ first task is to convert the domain name into an IP address so that it can send a request to the appropriate web server at that IP address for the web page that you are requesting To accomplish this task, the browser interacts with a name server, a machine that maintains lists to translate the domain names into IP addresses Once the browser receives the IP address from the name server, it sends a request for the web page that you are requesting Let us retrieve the IP address of the name server that we are using…

65. 65 DNS IP ADDRESSESDOMAIN NAMES Every device connected has a unique 32-bit address Machine Readable e.g. 151.196.19.22 DNS Translation Between domain Names and IP Addresses Every device connected has an alphanumeric address p IP address and domain name allocation requires central administration to avoid duplication p Previously administered by U.S. government contract (NSI) p In 1998, technical coordination assigned to ICANN (Internet Corporation for Assigned Names and Numbers). Human Readable cnn.com

66. ICANN Internet Corporation for Assigned Names and Numbers Provides domain name registration services “Cyber Squatting” – the practice of buying names and selling them back to companies who wanted to use them, or buying names very similar to well-known names to profit from visitors looking for that well-known name.

67. Virtual Domain A single IP address shared between multiple domains Multiple Web sites at one IP address Multiple domain names that access the same server Example: www.wikipedia.com all go to www.wikipedia.org the same www.wikipedia.net IP address www.wikipedia.com www.wikipedia.org www.wikipedia.net

68. URL Uniform Resource Locator The address of a site on the Internet The name of an Internet site (Domain name) Example: http://www.irs.gov

69. 69 The Universal Resource Locator (URL) Each page of information on the web has a unique address called the URL at which it can be found http://faculty.uscupstate.edu/atzacheva/lecture1.html The document can be obtained using the Hypertext Transfer Protocol (HTTP) Host Name - The Name of Web Server Path to the Web Page Denotes that the File is Written in HTML HyperText Markup Language File Name 123 ProtocolHost Name File Name

70. Anatomy of a URL Example: http://www.irs.gov Begins with protocol needed to transfer the requested file – http or https for Web Next is main location on the Internet; for the Web, that is “www” Next is the Web server location; in the example above, it’s the server named “irs.gov” If there is a slash and more data, this specifies the path and file of the data on the Web server

71. Example of a URL http://www.schools.utah.gov/cte/it.ht mlhttp://www.schools.utah.gov/cte/it.ht ml Protocol: http Web server: schools.utah.gov on World Wide Web File named it.html in folder named cte, located on that Web server Top level domain: gov (government) Subdomains: schools sub to utah

72. PROTOCOLS

73. Internet protocol stack application: supporting network applications – FTP, SMTP, HTTP transport: process-process data transfer – TCP, UDP network: routing of datagrams from source to destination – IP, routing protocols link: data transfer between neighboring network elements – PPP, Ethernet physical: bits “on the wire” application transport network link physical

74. source application transport network link physical HtHt HnHn M segment HtHt datagram destination application transport network link physical HtHt HnHn HlHl M HtHt HnHn M HtHt M M network link physical link physical HtHt HnHn HlHl M HtHt HnHn M HtHt HnHn M HtHt HnHn HlHl M router switch Encapsulation message M HtHt M HnHn frame

75. Protocols Sets of rules or standards that let computers communicate over the Internet Type or size or brand of computer doesn’t interfere with communication if the protocol is used

76. Protocols Main protocol is TCP/IP -- Transmission Control Protocol / Internet Protocol More specific protocols: –HTTP (Hypertext Transfer Protocol) allows transfer of Web pages via a browser. –HTTPS (Secure HTTP) allows transfer of Web pages with encryption and authentication –FTP (File Transfer Protocol) allows transfer of files through the Internet from one computer to another.

77. SMTP Simple Mail Transfer Protocol The Internet standard protocol for transferring electronic mail messages from one computer to another.

78. POP Post Office Protocol A protocol used to retrieve e-mail from an e-mail server. Must have this to get your e-mail POP3, a newer version, can be used with or without SMTP.

79. E-mail Messages, usually text, sent from one person to another via the Internet. E-mail can also be sent automatically to a large number of addresses. (including spam) E-mail is never anonymous and never really private.

80. USES OF THE INTERNET

81. Telnet Protocol for remote computing on the Internet Allows a computer to act as a remote terminal on another machine, anywhere on the Internet Many library and information resources are accessible through telnet Transfers in plain text on unsecured channels More secure protocol is Secure Shell or SSH

82. Newsgroups Discussion groups on the Internet (not on the Web, which is only one area of the Internet). Newsgroups are classified by subject matter and do not necessarily deal with journalism or "news." Like a message board but not Web based Text only

83. Gopher A widely successful method of listing material available over the Internet Invented in 1993 as the Internet started exploding in size Designed to be much easier to use than FTP, while still using a text-only interface, like a table of contents Gopher is a client-server system Although Gopher spread rapidly across the globe in only a couple of years, it has been largely supplanted by the Web

84. Internet Usage Today World Wide Web File transfer and file sharing Communication such as e-mail and VOIP (Voice-Over-IP) Online chat, Instant Messaging Online gaming Commerce (banking, shopping)

85. Understanding the Web

86. 86 Applications of the Internet The internet is used for a many of applications. For example: – WWW – Email – Instant messaging

87. 87 The World Wide Web (WWW) The world wide web is a sophisticated system for universal information capture and delivery The world wide web consortium (W3C) definition of the web: "The World Wide Web is the universe of network-accessible information, an embodiment of human knowledge" Provides information access in ways not previously possible –Hyperlinked (Hypertext) –Graphical user interface –Pictorial and non-text information –Information that changes rapidly –Immediate access –Anyone can author a web site –Multi-user access to the same information (try that with a book) –Easily searchable information

88. WWW World Wide Web A system of Internet servers that uses HTTP to transfer HTML documents These documents (Web pages) support links to other documents, as well as graphics, audio, and video files One can jump from one document to another simply by clicking on hyperlinks Not all Internet servers are part of the World Wide Web

89. 89 The functionality of the WWW is based on 3 main standards: – URL (Universal Resource Locator) – HTML (Hypertext Markup Language) – HTTP (Hypertext transfer Protocol)

90. HTTP Hyper Text Transfer Protocol The most important protocol used in the World Wide Web Protocol for moving hypertext files across the Internet. Requires an HTTP client program on one end and an HTTP server program on the other end.

91. 91 HTTP The standard Web transfer protocol is HTTP (HyperText Transfer Protocols). It is used for document exchange between servers and clients (typically browsers) in the WWW. To retrieve a document, the client first sends a request to the web server and waits for a reply An HTTP daemon/service (a program that waits for http requests) on the server then handles the request and the document is sent to the client (over a connection established using TCP/IP – Transmission Control Protocol / Internet Protocol) We recall from previous lectures, that a Protocol is “ Agreed upon sets of rules that provide order to a system or situation. ” In this case, a set of rules/standards for communicating on the Internet.

92. 92 Web Client/Server Architecture

93. HTML Hypertext Markup Language The coding language used for creating and designing hypertext documents on the World Wide Web Must be interpreted by software for Web browsers Example: My Page

94. 94 HTML HTML is a universal, simple language for formatting text. It also allows embedding of graphics, and linking of documents via ‘ hyperlinks ’. ‘ Hypertext ’ documents allow readers to freely move around the document, following links to subjects of interest. HTML is a language that is used to specify the structure of documents for retrieval across the Internet using browsers.

95. Hypertext The text that makes up Web page files. Hypertext can contain hyperlinks, which are words or phrases in the document that can be chosen by a reader (clickable text), which causes another document to be retrieved and displayed Example: Click here to go to next page.here

96. Web Browsers Software that interprets and displays documents using HTML located on the World Wide Web Web browsers provide a graphical interface that lets users click buttons, icons, and menu options to view and navigate Web pages Microsoft Internet Explorer, Netscape and Mozilla Firefox are popular Web browsers