1. Web Technologies COMP6115 Session 1: Internetworking and the World Wide Web Dr. Paul Walcott Department of Computer Science, Mathematics and Physics University of the West Indies, Cave Hill Campus Barbados © 2006/2007 Dr. Paul Walcott Created 20/11/06

2. 2 Session Objectives After completing this session you will be able to: After completing this session you will be able to: –Briefly describe the Internet and discuss its history –Briefly describe the World Wide Web (WWW) –Describe some of the software required to build an e-commerce Web site –Describe the Open System Interconnection (OSI) model

3. 3 Session Objectives Cont’d –Describe the use of tools in the construction of Web sites –Compare and contrast different types of computer networks –Compare and contrast different methods of connecting to the Internet – Create a simple Web Page

4. 4 The Internet What is the Internet? What is the Internet? The history of the Internet The history of the Internet The growth of the Internet The growth of the Internet

5. 5 What is the Internet 1 The Internet is a large system of inter- connected networks that span the globe The Internet is a large system of inter- connected networks that span the globe Internet-ready computers and personal digital assistants (palm and pocket PCs) can access this network 2 Internet-ready computers and personal digital assistants (palm and pocket PCs) can access this network 2

6. 6 What is the Internet Cont’d The Federal Networking Council (FNC) defines the Internet more formally as the global information system that 3 : The Federal Networking Council (FNC) defines the Internet more formally as the global information system that 3 : –is logically linked together by a globally unique address space based on the Internet Protocol (IP) or its subsequent extensions/follow-ons

7. 7 What is the Internet Cont’d –is able to support communications using the Transmission Control Protocol/Internet Protocol (TCP/IP) suite or its subsequent extensions/follow-ons, and/or other IP- compatible protocols; and –provides, uses or makes accessible, either publicly or privately, high level services layered on the communications and related infrastructure described herein

8. 8 What is the Internet Cont’d The Internet allows: The Internet allows: –communication by e-mail –the reading of on-line newspapers, academic journals and books –the joining of discussion groups, –participation in simulations and games –downloading of software, electronic books, movies and music –businesses to market and sell products and services (e-commerce)

9. 9 The History of the Internet 1 In the early 1960s the US department of defense began investigating ways of creating networks of computers that coordinate and control nuclear weapons In the early 1960s the US department of defense began investigating ways of creating networks of computers that coordinate and control nuclear weapons This network was to withstand attack, so that even if part of it was down it will continue to function This network was to withstand attack, so that even if part of it was down it will continue to function –This network was to have no central control These new networks required multiple channels to send information (leased lines inadequate) These new networks required multiple channels to send information (leased lines inadequate)

10. 10 The History of the Internet Cont’d In 1969 the advanced research agency (ARPA) used this network model to connect four computers In 1969 the advanced research agency (ARPA) used this network model to connect four computers This network was called ARPANET This network was called ARPANET During the 1970s and 1980s the academic community contributed to this network During the 1970s and 1980s the academic community contributed to this network In the late 1980s this network became the Internet In the late 1980s this network became the Internet

11. 11 Internet Growth 1 In 1969 ARPANET (the Internet) connected 4 computers In 1969 ARPANET (the Internet) connected 4 computers In 1990 the Internet connected 300,000 In 1990 the Internet connected 300,000 In 1995 the intranet was privatised In 1995 the intranet was privatised –The structure was based on four network access points (NAPs) operated by different telecom companies in the US –As the Intranet grew, more NAPs were added

12. 12 Internet Growth Cont’d The NAPs began selling Internet access rights to large customers The NAPs began selling Internet access rights to large customers –Internet service providers (ISPs) sold on the service to small businesses and individuals Growth in Internet hosts rose from under 10 million in 1995 to over 180 million in 2004 Growth in Internet hosts rose from under 10 million in 1995 to over 180 million in 2004 Millions of people now use the Internet Millions of people now use the Internet Billions of dollars are exchanged from the sales of products and services Billions of dollars are exchanged from the sales of products and services Estimated number of Web sites is 40 million and billions of web pages Estimated number of Web sites is 40 million and billions of web pages

13. 13 The World Wide Web What is the World Wide Web? What is the World Wide Web? What is hypertext? What is hypertext? Hypertext markup language (HTML) example Hypertext markup language (HTML) example What types of Web sites exist? What types of Web sites exist? www.ransen.com/Repligator/Spider.htm

14. 14 What is the World Wide Web The World Wide Web (WWW) was an Internet-based hypertext project that allowed global information sharing 2 The World Wide Web (WWW) was an Internet-based hypertext project that allowed global information sharing 2 –It is software that runs on machines connected to the WWW The WWW is based on two concepts 1 : The WWW is based on two concepts 1 : –Hypertext and –a graphical user interface (a Web browser)

15. 15 What is Hypertext 1 In 1945, Vannevar Bush wrote an article in the Atlantic Monthly describing a system, called Memex, that would store all a person’s books, records, letters and research results on microfilm In 1945, Vannevar Bush wrote an article in the Atlantic Monthly describing a system, called Memex, that would store all a person’s books, records, letters and research results on microfilm Microfilm and indexes would then be used to quickly access this information Microfilm and indexes would then be used to quickly access this information

16. 16 What is Hypertext Cont’d In the 1960s, Ted Nelson described a similar system: In the 1960s, Ted Nelson described a similar system: –He incorporated a page linking system called hypertext Tim Berners-Lee wrote a hypertext server in 1989 which Tim Berners-Lee wrote a hypertext server in 1989 which stored files written in hypertext markup language (HTML) stored files written in hypertext markup language (HTML) allowed other computers to read these files allowed other computers to read these files

17. 17 What is Hypertext Cont’d Tim Berners-Lee hypertext server was called httpd and his client browser “WorldWideWeb” Tim Berners-Lee hypertext server was called httpd and his client browser “WorldWideWeb”

18. 18 HyperText Markup Language HTML is a markup language that includes a set of tags attached to text HTML is a markup language that includes a set of tags attached to text These tags describe the relationship between text elements These tags describe the relationship between text elements A hypertext link (or hyperlink) points to another location in the same or another HTML document (that might be stored on the same or another computer) A hypertext link (or hyperlink) points to another location in the same or another HTML document (that might be stored on the same or another computer) Given below is an example of a simple HTML document. Given below is an example of a simple HTML document.

19. 19 HTML Example Begins the HTML document HTML docs contain both a head and body section Sets browser’s background colour to blue and font colour to white Creates a bulleted list of items Inserts an image Creates a hyperlink back to the top of the page

20. 20 Activity 1.1 Create a simple web page for your curriculum vitae Create a simple web page for your curriculum vitae

21. 21 XML Markup Language XML or Extensible Markup Language is a markup language that is similar to HTML XML or Extensible Markup Language is a markup language that is similar to HTML HTML and XML, however have different purposes: HTML and XML, however have different purposes: –HTML is primarily used to present (display) data, while –XML is used to describe data

22. 22 XML Example Begin the XML document by specifying the XML version Every XML document must have a root node The user defines tag names A tag can have zero, one or more attributes Every opening tag must have a closing tag.

23. 23 Activity 1.2 Create an XML document with a different structure than the XML document on the previous slide, but with the same data Create an XML document with a different structure than the XML document on the previous slide, but with the same data

24. 24 Graphical Interface for Hypertext A Web browser is a graphical user interface used to read and navigate through files written in HTML A Web browser is a graphical user interface used to read and navigate through files written in HTML In 1993 the first graphical web browser was developed; called Mosiac (http://archive.ncsa.uiuc.edu/SDG/Software/Mosaic/NCSAMosaicHome.html) In 1993 the first graphical web browser was developed; called Mosiac (http://archive.ncsa.uiuc.edu/SDG/Software/Mosaic/NCSAMosaicHome.html) Popular web browsers include: Popular web browsers include: –Microsoft Internet Explorer (http://www.microsoft.com/windows/ie/default.ms px) –Netscape (http://browser.netscape.com) –Mozilla Firefox (http://www.mozilla.com/firefox/)

25. 25 Mosiac Web Browser

26. 26 Internet Explorer Web Browser

27. 27 Netscape Web Browser

28. 28 Mozilla Firefox Web Browser

29. 29 Activity 1.3 Using your favourite search engine, locate, download and install the following web browsers: Using your favourite search engine, locate, download and install the following web browsers: –Mosiac –Netscape –Mozilla Firefox –Opera

30. 30 Hypertext Servers (Web Servers) 1 There are several Web servers available today, however the most popular are (April 2006 survey) 4,8 : There are several Web servers available today, however the most popular are (April 2006 survey) 4,8 : –Apache HTTP Server 67.11% (down from 69.01% in 2004) –Microsoft Internet Information Server (IIS) 20.61% (down from 23.26% in 2004) –Sun Java System Web Server (JSWS) (former names are Sun One, iPlanet Enterprise Server and Netscape Enterprise Server) 2.50% (up from 0.86% in 2004)

31. 31 Apache(“A Patchy” Server) Developed in 1994 by Rob McCool Developed in 1994 by Rob McCool The original core system has many patches applied to it, and thus its name The original core system has many patches applied to it, and thus its name Apache has dominated the Web since 1996 Apache has dominated the Web since 1996 Freely available Freely available Runs on many operating systems including FreeBSD-UNIX, HP-UX, Linux, Microsoft Windows, SCO-UNIX and Solaris Runs on many operating systems including FreeBSD-UNIX, HP-UX, Linux, Microsoft Windows, SCO-UNIX and Solaris

32. 32 Microsoft Internet Information Server (IIS) Comes bundled with Microsoft Windows Server operating system Comes bundled with Microsoft Windows Server operating system IIS used on many corporate intranets (Microsoft standard product) IIS used on many corporate intranets (Microsoft standard product) Originally written to run on Windows NT and Windows 2000; runs on Windows 2003 Server and Windows XP Originally written to run on Windows NT and Windows 2000; runs on Windows 2003 Server and Windows XP Supports ASP, ActiveX Data objects and SQL queries Supports ASP, ActiveX Data objects and SQL queries

33. 33 Sun Java System Web Server This is a descendant of the original NCSA server This is a descendant of the original NCSA server Cost US$1500-per-CPU licensing fee Cost US$1500-per-CPU licensing fee Runs on HP-UX, Solaris and Windows Runs on HP-UX, Solaris and Windows Is ODBC compatible (i.e. full access to ODBC compliant databases) Is ODBC compatible (i.e. full access to ODBC compliant databases) –ODBC is short for Open DataBase Connectivity, a standard database access method which allows access to data from any application (http://www.webopedia.com/TERM/O/ODBC.html)

34. 34 Activity 1.4 Using your favourite search engine, locate, download and install the Apache Web server Using your favourite search engine, locate, download and install the Apache Web server

35. 35 Web Site Types There are numerous different types of Web sites including: There are numerous different types of Web sites including: –Development sites: are used by companies to evaluate web site designs. The initial investment in these sites are small since they use existing hardware (i.e. no special hardware is purchased) – Intranets: these are corporate networks that hold documents such as internal memos, corporate handbooks, expense account worksheets, budgets and newsletters

36. 36 Web Site Types Cont’d –Extranets: which allow external entities, e.g. suppliers and strategic partners to access a subset of the information on the Intranet –Transaction-processing: These sites operate 24 hours a day, seven days a week and require fast, reliable hardware and e-commerce software Web sites hosting B2B and B2C activities must have spare capacity to support an increase in customer volume. Web sites hosting B2B and B2C activities must have spare capacity to support an increase in customer volume.

37. 37 Web Site Types Cont’d –Content-delivery: sites must be available seven days a week, 24 hours a day and require fast and precise search engines to help visitors locate information quickly These sites deliver content such as news, histories and other digital information. These sites deliver content such as news, histories and other digital information.

38. 38 Networking What is a computer network? What is a computer network? What are some of the types of networks? What are some of the types of networks? Characteristics of networks Characteristics of networks –Network topology –Network protocols –Network architectures http://www-structure.llnl.gov/Xray/comp/network.gif

39. 39 What is a Network 5 A network is a group of two or more computer systems linked together A network is a group of two or more computer systems linked together

40. 40 Types of Networks 6 There are several types of computer networks including: There are several types of computer networks including: –Local-area networks (LANs) Computers that are geographically close to each other (in the same building) Computers that are geographically close to each other (in the same building) –Wide-area networks (WANs) Computers are farther apart than LANs; typically connected by telephone lines or radio waves Computers are farther apart than LANs; typically connected by telephone lines or radio waves

41. 41 Types of Networks Cont’d –Campus-area networks (CANs) These computers are within a limited geographic area, e.g. a campus These computers are within a limited geographic area, e.g. a campus –Metropolitan-area networks (MANs) These networks are designed for towns and cities These networks are designed for towns and cities – Home-area networks (HANs) A network created in a person’s home A network created in a person’s home

42. 42 Characteristics of Networks 5,6 A network is characterised by its: A network is characterised by its: –Topology The geometric arrangement of the computer system The geometric arrangement of the computer system –Architecture This refers to the two major type of networks, peer-to-peer or client/server This refers to the two major type of networks, peer-to-peer or client/server –Protocol The set of rules and signals used to communicate (e.g. Ethernet or IBM’s Token Ring) The set of rules and signals used to communicate (e.g. Ethernet or IBM’s Token Ring)

43. 43 Network Topologies 6 Common network topologies include: Common network topologies include: –Star topology –Ring topology –Bus topology –Other topologies include the: Mesh topology Mesh topology Tree topology Tree topology http://www.webopedia.com/TERM/s/star_network.html

44. 44 Network Topologies Cont’d Network topologies are considered either logical or physical Network topologies are considered either logical or physical –The physical layout of a network is its physical topology –The way signals are routed through a network is the logical topology Just because a network has a particular physical topology does not mean that its logical topology must be the same Just because a network has a particular physical topology does not mean that its logical topology must be the same

45. 45 Network Topologies Cont’d For example: For example: –Twisted-pair Ethernet has a logical bus topology on a physical star topology layout –IBM’s token ring has a logical ring topology on a physical star topology layout

46. 46 Star Topology In a Star network all nodes are connected through a central hub In a Star network all nodes are connected through a central hub –A node is a computer or device, e.g. a printer; each node has a unique address called the Data Link Control (DLC) address or the Media Access Control (MAC) address The main advantage of the star network is that a malfunctioning node does not affect the rest of the network The main advantage of the star network is that a malfunctioning node does not affect the rest of the network

47. 47 Star Topology Cont’d The main disadvantage of the star network is that: The main disadvantage of the star network is that: –It requires more cabling than other topologies (e.g. the ring network), and –If the hub goes down, the network no longer functions Standard twisted-pair Ethernet uses a physical star topology Standard twisted-pair Ethernet uses a physical star topology

48. 48 Ring Topology Each node in a ring network is connected to two other nodes to form a closed loop Each node in a ring network is connected to two other nodes to form a closed loop Messages pass around the ring and each node reads the message addressed to it Messages pass around the ring and each node reads the message addressed to it One advantage of a ring network is that it can span larger distances than other networks (e.g. bus) because each node regenerates the signal One advantage of a ring network is that it can span larger distances than other networks (e.g. bus) because each node regenerates the signal One disadvantage is that malfunctioning nodes can make other nodes inaccessible One disadvantage is that malfunctioning nodes can make other nodes inaccessible IBM’s token ring uses a logical ring topology IBM’s token ring uses a logical ring topology

49. 49 Bus Topology The nodes in a bus topology are connected to a central cable called a bus or backbone The nodes in a bus topology are connected to a central cable called a bus or backbone The bus has two end points The bus has two end points One advantage of the bus network is that if one node goes down the network still functions One advantage of the bus network is that if one node goes down the network still functions One disadvantage of the bus network is it can not travel as long a distance as say a ring network due to the diminishing signal strength One disadvantage of the bus network is it can not travel as long a distance as say a ring network due to the diminishing signal strength Ethernet 10Base-2 and 10Base-5 use the bus topology Ethernet 10Base-2 and 10Base-5 use the bus topology

50. 50 Activity 1.5 Using your favourite search engine identify other network topologies Using your favourite search engine identify other network topologies

51. 51 Mesh Topology In the mesh topology many redundant connections exist between nodes; in a true mesh, each node is connected to every other node In the mesh topology many redundant connections exist between nodes; in a true mesh, each node is connected to every other node http://www.webopedia.com/quick_ref/topologies.asp

52. 52 Tree Topology The tree topology is a hybrid where groups of star-configured networks are connected to a linear bus backbone The tree topology is a hybrid where groups of star-configured networks are connected to a linear bus backbone http://www.webopedia.com/quick_ref/topologies.asp

53. 53 Architecture 6 The two main types of architecture are The two main types of architecture are –Peer-to-Peer (P2P) –Client/Server http://www.rebri.org.nz/images/builder-big.jpg

54. 54 Peer-To-Peer (P2P) Networks In a P2P network each node has equivalent capabilities and responsibilities In a P2P network each node has equivalent capabilities and responsibilities These networks are simpler than Client/Server but do not offer the same performance under heavy loads These networks are simpler than Client/Server but do not offer the same performance under heavy loads

55. 55 Client/Server Networks In a Client/Sever network each node is either a client or server In a Client/Sever network each node is either a client or server Client computers run applications, but rely on servers for resources such as files and printing capabilities Client computers run applications, but rely on servers for resources such as files and printing capabilities Servers are powerful computers that manage files, printers or network traffic Servers are powerful computers that manage files, printers or network traffic This architecture is sometimes called the two- tier architecture This architecture is sometimes called the two- tier architecture

56. 56 Protocols Protocols are agreed formats for transmitting data between devices 6 Protocols are agreed formats for transmitting data between devices 6 The protocol determines: The protocol determines: –The error checking required –Data compression method used –The way the end of a message is signaled T –The way the device indicates that it has received the message

57. 57 Internet Protocols There are many protocols used by the Internet and the WWW, including There are many protocols used by the Internet and the WWW, including –TCP/IP –HTTP –FTP –Electronic mail protocols IMAP IMAP POP POP

58. 58 TCP/IP The Internet uses two main protocols (developed by Vicent Cerf and Robert Kahn) The Internet uses two main protocols (developed by Vicent Cerf and Robert Kahn) –Transmission control protocol (TCP) Controls disassembly of message into packets at the origin Controls disassembly of message into packets at the origin Reassembles at the destination Reassembles at the destination –Internet protocol (IP) Specifies the addressing details for each packet Specifies the addressing details for each packet –Each packet is labeled with its origin and destination

59. 59 Internet Protocol version 4 (IPv4) Uses a 32 bit number to identify each computer Uses a 32 bit number to identify each computer –Called the IP address (4 billion addresses) –IP addresses use the dotted decimal notation, e.g. 0.0.0.0 or 255.255.255.255

60. 60 Internet Protocol version 6 (IPv6) Set to replace version 4 Set to replace version 4 Changes the format of the packets Changes the format of the packets –Removes unused fields Uses 128 bit number (2 128 addresses) Uses 128 bit number (2 128 addresses) –Eight groups of 16 bits e.g. CD18:0000:0000:AF23:0000:FF9E:61B2:884D e.g. CD18:0000:0000:AF23:0000:FF9E:61B2:884D To simplify zeroes may be removed To simplify zeroes may be removed –CD18:::AF23::FF9E:61B2:884D

61. 61 Hypertext Transfer Protocol (HTTP) 7 The hypertext transfer protocol (HTTP) was developed by Tim Berners-Lee in 1991 The hypertext transfer protocol (HTTP) was developed by Tim Berners-Lee in 1991 HTTP was designed to transfer pages between machines HTTP was designed to transfer pages between machines The client (or Web browser) makes a request for a given page and the Server is responsible for finding it and returning it to the client The client (or Web browser) makes a request for a given page and the Server is responsible for finding it and returning it to the client

62. 62 Hypertext Transfer Protocol (HTTP) The browser connects and requests a page from the server The browser connects and requests a page from the server The server reads the page from the file system, sends it to the client and terminates the connection The server reads the page from the file system, sends it to the client and terminates the connection Client Web Server Request sent to Web server Response sent with files (one for each Web page, image, sound clip etc.)

63. 63 Activity 1.6 Using your favourite search engine find out more about the HTTP protocol Using your favourite search engine find out more about the HTTP protocol

64. 64 File Transfer Protocol (FTP) 2 FTP is a protocol that allows a user to: FTP is a protocol that allows a user to: –list files at a remote site –Transfer files between local and remote computers Using FTP you can not run applications on a remote site Using FTP you can not run applications on a remote site Also you can only look at the names of the files on the remote computer; rather than being able to read them Also you can only look at the names of the files on the remote computer; rather than being able to read them FTP is still used today; e.g. to transfer large files between computers, or to upload Web sites FTP is still used today; e.g. to transfer large files between computers, or to upload Web sites

65. 65 Activity 1.7 Go to ftp.FreeBSD.org and get the file gzip.exe from the directory /pub/FreeBSD/tools Go to ftp.FreeBSD.org and get the file gzip.exe from the directory /pub/FreeBSD/tools

66. 66 Electronic Mail Protocols Electronic mail uses the client/server model Electronic mail uses the client/server model The organisation has an email server devoted to handling email The organisation has an email server devoted to handling email –Stores and forwards email messages Individuals use email client software to read and send email (e.g. Microsoft Outlook, or Netscape Messenger) Individuals use email client software to read and send email (e.g. Microsoft Outlook, or Netscape Messenger)

67. 67 Electronic Mail Protocols Cont’d Simple Mail Transfer Protocol (SMTP) Simple Mail Transfer Protocol (SMTP) –Specifies format of mail messages Post Office Protocol (POP) Post Office Protocol (POP) –tells the email server to: Send mail to the user’s computer and delete it from the server Send mail to the user’s computer and delete it from the server Send mail to the user’s computer and do not delete it from the server Send mail to the user’s computer and do not delete it from the server Ask whether new mail has arrived Ask whether new mail has arrived

68. 68 Electronic Mail Protocols Cont’d Interactive Mail Access Protocol (IMAP) Interactive Mail Access Protocol (IMAP) –Newer than POP, provides similar functions with additional features e.g. can send specific messages to the client rather than all the messages e.g. can send specific messages to the client rather than all the messages A user can view email message headers and the sender’s name before downloading the entire message A user can view email message headers and the sender’s name before downloading the entire message –Allows users to delete and search mailboxes held on the email server

69. 69 Electronic Mail Protocols Cont’d The disadvantage of POP The disadvantage of POP –You can only access messages from one PC The disadvantage of IMAP The disadvantage of IMAP –Since email is stored on the email server, there is a need for more and more expensive (high speed) storage space

70. 70 Terminal Emulation - Telnet Telnet is a terminal emulation program for TCP/IP networks Telnet is a terminal emulation program for TCP/IP networks The telnet program runs on a local machine and allows connection to a remote machine The telnet program runs on a local machine and allows connection to a remote machine Commands entered through the telnet program will be executed on the Server; this gives the user the ability to control the Server Commands entered through the telnet program will be executed on the Server; this gives the user the ability to control the Server To log into the Server a valid username and password is required To log into the Server a valid username and password is required

71. 71 Activity 1.8 Use Telnet to execute an HTTP GET request to retrieve the index.html file at www.google.com Use Telnet to execute an HTTP GET request to retrieve the index.html file at www.google.com

72. 72 Ping Ping is a utility for system administrators/ webmasters to allow them to check network connections Ping is a utility for system administrators/ webmasters to allow them to check network connections

73. 73 Activity 1.9 Determine the IP address of your neighbour’s machine and ping it Determine the IP address of your neighbour’s machine and ping it

74. 74 Connecting to the Internet 1 What are some of the ways of connecting to the Internet? What are some of the ways of connecting to the Internet? http://www.co.delaware.ny.us/links.htm

75. 75 Internet Connection Options Internet service providers (ISPs) provide several ways to connect to the Internet, including: Internet service providers (ISPs) provide several ways to connect to the Internet, including: –Voice grade telephone lines –Broadband connections –Leased lines –Wireless The major distinguishing factor is bandwidth (the amount of data that can be transferred per unit of time) The major distinguishing factor is bandwidth (the amount of data that can be transferred per unit of time)

76. 76 Bandwidth and Connections Symmetric connection: provides the same bandwidth in both directions Symmetric connection: provides the same bandwidth in both directions Asymmetric connections: provide different bandwidths for either direction Asymmetric connections: provide different bandwidths for either direction –Upstream bandwidth (upload bandwidth): the amount of information that can travel from the user to the Internet in a given amount of time –Downstream bandwidth (download or downlink bandwidth): the amount of information that can be transferred from the Internet to the user in an amount of time

77. 77 Voice-grade Telephone Connections The most common way to connect to an ISP is through a modem (analog) connected to POTS (plain old telephone service) lines The most common way to connect to an ISP is through a modem (analog) connected to POTS (plain old telephone service) lines The speed of this connection is 28 to 56Kbps The speed of this connection is 28 to 56Kbps It was typical for computers to be shipped with built-in modems It was typical for computers to be shipped with built-in modems

78. 78 Broadband Connections Connections that operate at speeds higher than 200Kbps are considered broadband Connections that operate at speeds higher than 200Kbps are considered broadband Two of the major broadband connections for home users and small businesses are: Two of the major broadband connections for home users and small businesses are: –Digital Subscriber Line (DSL) and –Cable modems

79. 79 Broadband Connections Cont’d Digital subscriber line (DSL) Uses telephone lines and a piece of equipment similar to a network switch Uses telephone lines and a piece of equipment similar to a network switch Both voice calls and an Internet connection are provided simultaneously Both voice calls and an Internet connection are provided simultaneously The closer you are to the provider’s central office, the better the service The closer you are to the provider’s central office, the better the service This service is not available everywhere This service is not available everywhere http://computer.howstuffworks.com/dsl.htm

80. 80 Broadband Connections Cont’d One of the latest broadband technologies is asymmetric digital subscriber line (ADSL) One of the latest broadband technologies is asymmetric digital subscriber line (ADSL) –Bandwidths from 100-640Kbps upstream and from 1.5 to 9 Mbps downstream For businesses a high-speed DSL (HDSL) is available For businesses a high-speed DSL (HDSL) is available –768Kbps of symmetric bandwidth

81. 81 Broadband Connections Cont’d Cable Modems Cable modems connect to the same broadband coaxial cable that serves cable television Cable modems connect to the same broadband coaxial cable that serves cable television Upstream bandwidth of 300Kbps to 1 Mbps is provided and downstream bandwidth of 10Mbps Upstream bandwidth of 300Kbps to 1 Mbps is provided and downstream bandwidth of 10Mbps Please note that upstream and downstream bandwidths vary from provider to provider Please note that upstream and downstream bandwidths vary from provider to provider

82. 82 Broadband Connections Cont’d DSL v Cable DSL is a private line with no competing traffic DSL is a private line with no competing traffic Cable connections bandwidth vary with the user load (number of subscribers using the service) Cable connections bandwidth vary with the user load (number of subscribers using the service) Problems Problems –Web users in rural areas often do not have cable access and have limited telephone access (low cost voice-grade lines, rather than data-grade lines) thus bandwidth is limited (<14Kbps)

83. 83 Activity 1.10 Using your favourite search engine, determine the most recent speeds of the following Internet connection options: Using your favourite search engine, determine the most recent speeds of the following Internet connection options: –Cable modem –DSL

84. 84 Leased-Line Connections Large firms with large amounts of Internet traffic can lease lines from telecommunication carriers Large firms with large amounts of Internet traffic can lease lines from telecommunication carriers Various technologies are used; classified by the amount of telephone lines they include: Various technologies are used; classified by the amount of telephone lines they include: –DS0 (digital signal zero) carries one digital signal (64Kbps) –T1 (or DS1) carries 24 DS0 lines (1.544Mbps) –Fractional T1 (128Kbps and upwards) –T3 (or DS3) carries 30 T1 lines (44.736Mbps) These connections more expensive than POTS and DSL These connections more expensive than POTS and DSL

85. 85 Wireless Connections Satellite Satellite Bluetooth Bluetooth Wireless Ethernet (Wi-Fi) Wireless Ethernet (Wi-Fi) Fixed-Point Wireless Fixed-Point Wireless Cellular Telephone Networks Cellular Telephone Networks

86. 86 Wireless Connections Satellite Satellite microwave transmissions Satellite microwave transmissions –Customer places receiving dish in yard –Download bandwidth of around 500 kbps –Maximum upload bandwidth of 150kbps –Self installation makes cost lower http://www.ccpo.odu.edu/~arnoldo/ocean405/satellite.gif

87. 87 Wireless Connections Bluetooth One of the first wireless protocols One of the first wireless protocols Operates reliably over 35 feet and can be part of up to 10 networks of eight devices each (personal area networks, or PANs) Operates reliably over 35 feet and can be part of up to 10 networks of eight devices each (personal area networks, or PANs) Bandwidth of 722kbps Bandwidth of 722kbps Good for wireless printing Good for wireless printing http://www.bakercountyhealth.org/services/dental/blue-tooth.jpg

88. 88 Wireless Connections Bluetooth Advantages Bluetooth technology consumes very little power Bluetooth technology consumes very little power Bluetooth devices can discover each other and exchange information automatically (e.g. a user can print to a printer on a network without logging on) Bluetooth devices can discover each other and exchange information automatically (e.g. a user can print to a printer on a network without logging on)

89. 89 Wireless Connections Wireless Ethernet (Wi- Fi) (802.11b) Most common wireless on LANs Most common wireless on LANs Bandwidth 11Mbps at 300 feet Bandwidth 11Mbps at 300 feet A computer with a Wi-Fi network can communicate with a wireless access point (WAP) to become a part of the network A computer with a Wi-Fi network can communicate with a wireless access point (WAP) to become a part of the network http://www.homenethelp.com/web/diagram/images/shareing-soft-wireless.gif

90. 90 Wireless Connections Wireless Ethernet Advantages Wi-Fi devices can roam, i.e. shift from one WAP to another without user intervention Wi-Fi devices can roam, i.e. shift from one WAP to another without user intervention Increasingly WAPs are becoming available in public places, e.g. airports Increasingly WAPs are becoming available in public places, e.g. airports

91. 91 Wireless Connections Wireless Ethernet Developments In 2002 an improved version of Wi-Fi, called 802.11a was introduced In 2002 an improved version of Wi-Fi, called 802.11a was introduced –The 802.11a protocol can transmit at speeds up to 54Mbps –802.11a is not compatible with 802.11b Later in 2002, the 802.11g protocol was introduced which is compatible with 802.11b devices and has speeds of 54Mbps Later in 2002, the 802.11g protocol was introduced which is compatible with 802.11b devices and has speeds of 54Mbps In 2004-2005, 802.11n was expected (320Mbps) In 2004-2005, 802.11n was expected (320Mbps) –In January 2006 the 802.11n proposal was confirmed and manufacturers began supplying chips with throughput of 300Mbps - 600Mbps for sampling

92. 92 Wireless Connections Fixed Point Wireless Uses a system of repeaters (transmitter- receiver devices) to forward a radio signal from the ISP to customers Uses a system of repeaters (transmitter- receiver devices) to forward a radio signal from the ISP to customers Users’ antennas are connected to a device that converts radio signals to Wi-Fi packets which are sent to their computers Users’ antennas are connected to a device that converts radio signals to Wi-Fi packets which are sent to their computers http://www.erinc.com/apps_wireless/images/fixed_wireless2.gif

93. 93 Wireless Connections Cellular Telephone Networks In 2003, about 500 million mobile (cell) phones existed worldwide In 2003, about 500 million mobile (cell) phones existed worldwide Originally slow data communication (10 kbps – 384kbps) Originally slow data communication (10 kbps – 384kbps) Third generation cell phones Third generation cell phones –Up to 2 Mbps http://www.mtco.com/graphics/cellularpic.jpg

94. 94 Wireless Connections Cellular Telephone Networks Cont’d Cell phones send and receive messages using the short message service (SMS) protocol Cell phones send and receive messages using the short message service (SMS) protocol Some cell phones (e.g. the Blackberry, http://www.blackberry.com) include: Some cell phones (e.g. the Blackberry, http://www.blackberry.com) include: http://www.blackberry.com –a Web browser which provides web access –Email –short message service (sms) –Instant messaging

95. 95 Wireless Connections Cellular Telephone Networks Cont’d Cell phones send and receive messages using the short message service (SMS) protocol Cell phones send and receive messages using the short message service (SMS) protocol Companies also sell Internet access through their cellular networks Companies also sell Internet access through their cellular networks –Fixed fee plus charge for amount of data transferred Business potential of mobile commerce Business potential of mobile commerce –Companies are identifying the kinds of resources individuals might want to access (and pay for) using wireless devices

96. 96 The OSI Model 9 The Open Systems Interconnect Model (OSI): The Open Systems Interconnect Model (OSI): –provides a fundamental understanding of network data transmission through a set of guidelines –Promotes interoperability –Describes the tasks a protocol suite (the set of rules used which allow computers to communicate) perform –Developed in 1977 by the International Organization for Standardization (ISO)

97. 97 The OSI Model (Cont’d) The OSI model consists of seven layers The OSI model consists of seven layers –Each layer performs a particular function and passes the result to the next layer http://static.howstuffworks.com/gif/osi-model.jpg

98. 98 The OSI Model (Cont’d) The Application layer: The Application layer: –Refers to tools that an application can use to complete a task, e.g. spreadsheet software requesting a file transfer –Defines how network services interact with the network These services include file, print and messaging services These services include file, print and messaging services

99. 99 The OSI Model (Cont’d) The Presentation Layer: The Presentation Layer: –Responsible for formatting data that will be exchanged Data encryption Data encryption Converting character sets Converting character sets Data Compression Data Compression

100. 100 The OSI Model (Cont’d) The Session Layer: The Session Layer: –Specifies how two computers establish, synchronise, maintain and end a session Security authentication Security authentication Data transfer Data transfer Acknowledgements Acknowledgements Connection release Connection release

101. 101 The OSI Model (Cont’d) The Transport Layer: The Transport Layer: –Ensures that data is transmitted error free –Breaks long messages into smaller chunks and recompiles them –Combines short messages into longer chunks –Logical name resolution –Acknowledges packet receipt

102. 102 The OSI Model (Cont’d) The Network Layer: The Network Layer: –Defines protocols to ensure that data arrives at the correct destination Relies on logical network addresses (e.g. IP addresses) Relies on logical network addresses (e.g. IP addresses)

103. 103 The OSI Model (Cont’d) The Data Link Layer: The Data Link Layer: –Creates, transmits and receives packets –Is responsible for: the physical address (MAC) the physical address (MAC) Creating logical topologies Creating logical topologies

104. 104 The OSI Model (Cont’d) The Physical Layer: The Physical Layer: –Converts data into electrical signals i.e. converts 1 and 0 bits to voltages to pass allow the medium (e.g. a cable) i.e. converts 1 and 0 bits to voltages to pass allow the medium (e.g. a cable) –Determines the amount of media that will be used –Is responsible for the physical topology

105. 105 Network Devices Several devices are used in networks including: Several devices are used in networks including: –Hubs –Switches –Bridges –Routers

106. 106 Network Devices (Cont’d) Hub A hub is a central connection point for several network devices A hub is a central connection point for several network devices There are two types of hubs: There are two types of hubs: –An active hub is usually powered Amplifies and cleans up the signal it receives Amplifies and cleans up the signal it receives –A passive hub is not powered Uses some of the signal strength in order to operate -- operates over shorter distances Uses some of the signal strength in order to operate -- operates over shorter distances

107. 107 Network Devices (Cont’d) Switch (or Switching Hub) A switch builds a table of the MAC addresses of the devices connected to it A switch builds a table of the MAC addresses of the devices connected to it When the switch receives the data, the actual node that the data needs to be sent to is determined and the data sent to that node When the switch receives the data, the actual node that the data needs to be sent to is determined and the data sent to that node –This is the difference between a switch and a hub, since the hub sends all the messages to all connected nodes

108. 108 Network Devices (Cont’d) Bridge A bridge logically separates a single network into two segments A bridge logically separates a single network into two segments This is useful when you have one or more servers (for example) on the network that are heavily used and others that are not This is useful when you have one or more servers (for example) on the network that are heavily used and others that are not –By separating the network with a bridge, the performance of the part of the network that is less active is not compromised

109. 109 Network Devices (Cont’d) Router Routing is the process of moving data through a network using routers Routing is the process of moving data through a network using routers Routers store information about which routes packets can take to get to their destinations on files called routing tables Routers store information about which routes packets can take to get to their destinations on files called routing tables –Only packets with specified destinations will be routed

110. 110 Electronic Commerce Software What are some of the software requirements for an e-commerce site? What are some of the software requirements for an e-commerce site?

111. 111 Electronic Commerce Software Cont’d The software requirements for e- commerce sites vary tremendously and are dependent on several factors including: The software requirements for e- commerce sites vary tremendously and are dependent on several factors including: –The size of the enterprise and its projected traffic –The budget

112. 112 Electronic Commerce Software Cont’d All e-commerce solutions must provide at least the following: All e-commerce solutions must provide at least the following: –A catalog display –Shopping cart capabilities –Transaction processing

113. 113 Electronic Commerce Software Cont’d Larger e-commerce sites require additional functionality, such as: Larger e-commerce sites require additional functionality, such as: –Middleware that links the company’s existing system (inventory control, order processing and accounting) to the e-commerce system –Databases and Applications –Supply chain management software –Customer relationship management software –Content management software –Knowledge management software

114. 114 Activity 1.11 Using your favourite search engine find examples of: Using your favourite search engine find examples of: –Supply chain management software –Customer relationship management software –Content management software –Knowledge management software

115. 115 Tools Several tools have been created to allow the easy generation of web pages including: Several tools have been created to allow the easy generation of web pages including: –Microsoft FrontPage –Microsoft Office –Macromedia Dreamweaver These tools are useful since they allow people with very little knowledge of HTML to create web pages These tools are useful since they allow people with very little knowledge of HTML to create web pages

116. 116 Tools (Cont’d) It is important to be careful with tools, however since the code that is automatically generated may be difficult to decipher if a problem does occur It is important to be careful with tools, however since the code that is automatically generated may be difficult to decipher if a problem does occur

117. 117 Activity 1.12 Create a simple web page using Microsoft Word and carefully examine the HTML code Create a simple web page using Microsoft Word and carefully examine the HTML code –How does it differ from the HTML code that you would write if you were using a simple text editor?

118. 118 References [1] Schneider, Gary, P., “Electronic Commerce: The second wave”, Thomson Course Technology, Fifth Annual Edition, 2004 [2] Zhao, Jensen J., “Web design and development for e-business”, Prentice Hall, 2003 [3] Federal Networking Council, “FNC Resolution: Definition of the Internet”, 1995. Online document available at http://www.itrd.gov/fnc/Internet_res.html http://www.itrd.gov/fnc/Internet_res.html [4] NetCraft, “April 2004 Web Server Survey”, 2004. Online document available at http://news.netcraft.com/archives/2004/04/01/april_2004_web_server_survey.html http://news.netcraft.com/archives/2004/04/01/april_2004_web_server_survey.html [5] Furdyk, Michael, “Ultimate Guide to Networking: Part One”, 1999. Online document available at http://www.hardwarecentral.com/hardwarecentral/print/158/ http://www.hardwarecentral.com/hardwarecentral/print/158/ [6] Webopedia, “Network”, 2004. Online document available at http://networking.webopedia.com/TERM/N/network.html http://networking.webopedia.com/TERM/N/network.html [7] Berlin, Dan, et al., “CGI Programming Unleased”, Sams.net Publishing, 1996, pp. 101-102 [8] NetCraft, “April 2006 Web Server Survey”, 2006. Online document available at http://news.netcraft.com/archives/web_server_survey.html http://news.netcraft.com/archives/web_server_survey.html [9] Sybex Inc, “Networking Complete”, Sybex, Inc, Third Edition, 2002