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Transcript of MELJUN CORTES internet and www
The Internet and the World Wide Web
MELJUN CORTESMELJUN CORTES
Electronic Commerce, Sixth Edition 2
The Internet and the World Wide Web
• Computer network– Any technology that allows people to connect
computers to each other
• The Internet – A large system of interconnected computer
networks spanning the globe
• World Wide Web– A subset of computers on the Internet
Electronic Commerce, Sixth Edition 3
Origins of the Internet• Early 1960s
– U.S. Department of Defense funded research to explore creating a worldwide network
• In1969, Defense Department researchers connected four computers into a network called ARPANET
• Throughout the 1970s and 1980s– Academic researchers connected to ARPANET
and contributed to its technological developments
Electronic Commerce, Sixth Edition 4
New Uses for the Internet• 1972
– E-mail was born • Mailing list
– E-mail address that forwards any message received to any user who has subscribed to the list
• Usenet– Started by a group of students and programmers
at Duke University and the University of North Carolina
Electronic Commerce, Sixth Edition 5
Growth of the Internet• In 1991, the NSF
– Eased restrictions on commercial Internet activity – Began implementing plans to privatize the Internet
• Network access points (NAPs)– Basis of the new structure of the Internet
• Network access providers– Sell Internet access rights directly to larger
customers and indirectly to smaller firms and individuals through ISPs
Electronic Commerce, Sixth Edition 6
Growth of the Internet
Electronic Commerce, Sixth Edition 7
Emergence of the World Wide Web (continued)
• Tim Berners-Lee developed code for a hypertext server program
• Hypertext server– Stores files written in the hypertext markup
language– Lets other computers connect to it and read files
• Hypertext Markup Language (HTML)– Includes a set of codes (or tags) attached to text
Electronic Commerce, Sixth Edition 8
Packet-Switched Networks• Local area network (LAN)
– Network of computers located close together
• Wide area networks (WANs)– Networks of computers connected over greater
distances
Electronic Commerce, Sixth Edition 9
Packet-Switched Networks (continued)
• Packets– Files and e-mail messages on a packet-switched
network that are broken down into small pieces
– Travel from computer to computer along the interconnected networks until they reach their destinations
Electronic Commerce, Sixth Edition 10
Routing Packets• Routing computers
– Computers that decide how best to forward packets
• Routing algorithms– Rules contained in programs on router computers
that determine the best path on which to send packets
– Programs apply their routing algorithms to information they have stored in routing tables
Electronic Commerce, Sixth Edition 11
Router-based Architecture of the Internet
Electronic Commerce, Sixth Edition 12
Internet Protocols• Protocol
– Collection of rules for formatting, ordering, and error-checking data sent across a network
• Rules for message handling– Independent networks should not require any internal
changes to be connected to the network– Packets that do not arrive at their destinations must
be retransmitted from their source network– Router computers act as receive-and-forward devices– No global control exists over the network
Electronic Commerce, Sixth Edition 13
TCP/IP• TCP
– Controls disassembly of a message or a file into packets before transmission over the Internet
– Controls reassembly of packets into their original formats when they reach their destinations
• IP
– Specifies addressing details for each packet
Electronic Commerce, Sixth Edition 14
IP Addressing• Internet Protocol version 4 (IPv4)
– Uses a 32-bit number to identify computers connected to the Internet
• Base 2 (binary) number system– Used by computers to perform internal
calculations• Subnetting
– Use of reserved private IP addresses within LANs and WANs to provide additional address space
Electronic Commerce, Sixth Edition 15
IP Addressing (continued)• Private IP addresses
– Series of IP numbers not permitted on packets that travel on the Internet
• Network Address Translation (NAT) device– Used in subnetting to convert private IP addresses
into normal IP addresses• Internet Protocol version 6 (IPv6)
– Protocol that will replace IPv4– Uses a 128-bit number for addresses
Electronic Commerce, Sixth Edition 16
Domain Names• Sets of words assigned to specific IP
addresses
• Top-level domain (or TLD)– Rightmost part of a domain name
• Internet Corporation for Assigned Names and Numbers (ICANN)– Responsible for managing domain names and
coordinating them with IP address registrars
Electronic Commerce, Sixth Edition 17
Top-Level Domain Names
Electronic Commerce, Sixth Edition 18
Web Page Request and Delivery Protocols
• Web client computers– Run software called Web client software or Web
browser software • Web server computers
– Run software called Web server software• Client/server architecture
– Combination of client computers running Web client software and server computers running Web server software
Electronic Commerce, Sixth Edition 19
Web Page Request and Delivery Protocols (continued)
• Hypertext Transfer Protocol (HTTP)– Set of rules for delivering Web page files over the
Internet
• Uniform Resource Locator (URL) – Combination of the protocol name and domain
name
– Allows user to locate a resource (the Web page) on another computer (the Web server)
Electronic Commerce, Sixth Edition 20
Electronic Mail Protocols• Electronic mail (e-mail)
– Must be formatted according to a common set of rules
• E-mail server– Computer devoted to handling e-mail
• E-mail client software– Used to read and send e-mail– Examples include Microsoft Outlook and Netscape
Messenger
Electronic Commerce, Sixth Edition 21
Electronic Mail Protocols (continued)
• Simple Mail Transfer Protocol (SMTP) – Specifies format of a mail message
• Post Office Protocol (POP)– POP message can tell the e-mail server to
• Send mail to a user’s computer and delete it from the e-mail server
• Send mail to a user’s computer and not delete it• Simply ask whether new mail has arrived
– Provides support for Multipurpose Internet Mail Extensions (MIME)
Electronic Commerce, Sixth Edition 22
Intranets and Extranets• Intranet
– Interconnected network that does not extend beyond the organization that created it
• Extranet
– Intranet extended to include entities outside the boundaries of an organization
– Connects companies with suppliers, business partners, or other authorized users
Electronic Commerce, Sixth Edition 23
Public and Private Networks
• Public network– Any computer network or telecommunications
network available to the public• Private network
– A private, leased-line connection between two companies that physically connects their intranets
• Leased line – Permanent telephone connection between two
points
Electronic Commerce, Sixth Edition 24
Internet Connection Options• Bandwidth
– Amount of data that can travel through a communication line per unit of time
• Net bandwidth– Actual speed that information travels
• Symmetric connections – Provide the same bandwidth in both directions
• Asymmetric connections – Provide different bandwidths for each direction
Electronic Commerce, Sixth Edition 25
Voice-Grade Telephone Connections
• POTS, or plain old telephone service– Uses existing telephone lines and an analog
modem – Provides bandwidth between 28 and 56 Kbps
• Digital Subscriber Line (DSL)– Connection methods do not use a modem
• Integrated Services Digital Network (ISDN)– Bandwidths between 128 Kbps and 256 Kbps
Electronic Commerce, Sixth Edition 26
Broadband Connections• Operate at speeds of greater than 200 Kbps
• Asymmetric digital subscriber (ADSL)– Transmission bandwidth is from 100 to 640 Kbps
upstream and from 1.5 to 9 Mbps downstream
• Cable modems– Provide transmission speeds between 300 Kbps and
1 Mbps
• DSL– Private line with no competing traffic
Electronic Commerce, Sixth Edition 27
Leased-Line Connections• DS0 (digital signal zero)
– Telephone line designed to carry one digital signal
• T1 line (also called a DS1)– Carries 24 DS0 lines and operates at 1.544 Mbps
• Fractional T1– Provides service speeds of 128 Kbps and upward in
128-Kbps increments
• T3 service (also called DS3)– Offers 44.736 Mbps
Electronic Commerce, Sixth Edition 28
Wireless Connections• Bluetooth
– Designed for personal use over short distances– Low-bandwidth technology, with speeds of up to
722 Kbps– Networks are called personal area networks
(PANs) or piconets– Consumes very little power– Devices can discover each other and exchange
information automatically
Electronic Commerce, Sixth Edition 29
Wireless Ethernet (Wi-Fi or 802.11b)
• Most common wireless connection technology for use on LANs
• Wireless access point (WAP) – Device that transmits network packets between
Wi-Fi-equipped computers and other devices • Has potential bandwidth of 11 Mbps and a
range of about 300 feet• Devices are capable of roaming
Electronic Commerce, Sixth Edition 30
Wireless Ethernet (Wi-Fi or 802.11b) (continued)
• 802.11a protocol – Capable of transmitting data at speeds up to 54
Mbps
• 802.11g protocol– Has 54 Mbps speed of 802.11a – Compatible with 802.11b devices
• 802.11n– Expected to offer speeds up to 320 Mbps
Electronic Commerce, Sixth Edition 31
Cellular Telephone Networks
• Third-generation (3G) cell phones– Combine latest technologies available today
• Short message service (SMS)– Protocol used to send and receive short text
messages
• Mobile commerce (m-commerce)– Describes the kinds of resources people might
want to access using wireless devices
Electronic Commerce, Sixth Edition 32
Internet2 and the Semantic Web• Internet2
– Experimental test bed for new networking technologies
– Has achieved bandwidths of 10 Gbps and more on parts of its network
– Used by universities to conduct large collaborative research projects
Electronic Commerce, Sixth Edition 33
Internet2 and the Semantic Web (continued)
• Semantic Web– Project by Tim Berners-Lee – If successful, it would result in words on Web
pages being tagged (using XML) with their meanings
• Resource description framework (RDF) – Set of standards for XML syntax
• Ontology– Set of standards that defines relationships among
RDF standards and specific XML tags