Download Technology Infrastructure: The Internet and the World Wide Web

Internet
technologies
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
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Growth of the Internet
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Packet-Switched Networks
• Local area network (LAN)
– Network of computers located close together
• Wide area networks (WANs)
– Networks of computers connected over
greater distances
• Circuit
– Combination of telephone lines and closed
switches that connect them to each other
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LAN (Local Area Network)
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MAN (Metropolitan Area Network)
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WAN (Wide Area Network)
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Packet-Switched Networks (Continued)
• Circuit switching
– Centrally controlled, single-connection model
• Packets
– Files and e-mail messages on a packetswitched network that are broken down into
small pieces
– Travel from computer to computer along the
interconnected networks until they reach their
destinations
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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 packet
– Programs apply their routing algorithms to
information they have stored in routing tables
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Router-based Architecture of the
Internet
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Internet Protocols
• Protocol
– Collection of rules for formatting, ordering, and
error-checking data sent across a network
• Rules contributing to success of Internet
– 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
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TCP/IP
• TCP
– Controls disassembly of a message or a file
into packets before transmission over Internet
– Controls reassembly of packets into their
original formats when they reach their
destinations
• IP
– Specifies addressing details for each packet
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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
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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
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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
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Top-level Domain Names
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Domain Names
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Web Page Request and Delivery
Protocols
• Web client computers
– Run software called Web client software or
Web browser software
• Web server computer
– Runs software called Web server software
• Client/server architecture
– Combination of client computers running Web
client software and server computers running
Web server software
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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)
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Electronic Mail Protocols
• Electronic mail (e-mail)
– Must also be formatted according to common
set of rules
• E-mail server
– Computer devoted to handling e-mail
• E-mail client software
– Used to read and send e-mail
– Example: Microsoft Outlook, Netscape
Messenger
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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 user’s computer and delete it from
e-mail server
• Send mail to user’s computer and not delete it
• Simply ask whether new mail has arrived
– Provides support for Multipurpose Internet
Mail Extensions (MIME)
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Markup Languages and the Web
• Text markup language
– Specifies set of tags that are inserted into text
• Standard Generalized Markup Language
(SGML)
– Older and complex text markup language
– A meta language
• World Wide Web Consortium (W3C)
– Not-for-profit group that maintains standards
for the Web
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Development of Markup Languages
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Hypertext Markup Language (HTML)
• Prevalent markup language used to create
documents on the Web today
• HTML tags
– Interpreted by Web browser and used by it to
format the display of the text
• HTML Links
– Linear hyperlink structure
– Hierarchical hyperlink structure
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Hypertext Markup Language (HTML)
(Continued)
• Scripting languages and style sheets
– Most common scripting languages
• JavaScript, JScript, Perl, and VBScript
– Cascading Style Sheets (CSS)
• Sets of instructions that give Web developers
more control over the format of displayed
pages
• Style sheet
– Usually stored in a separate file
– Referenced using the HTML style tag
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Extensible Markup Language (XML)
• Uses paired start and stop tags
• Includes data management capabilities that
HTML cannot provide
• Differences between XML and HTML
– XML is not a markup language with defined
tags
– XML tags do not specify how text appears on
a Web page
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Processing a Request for an XML Page
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Intranets and Extranets
• Intranet
– Interconnected network that does not extend
beyond organization that created it
• Extranet
– Intranet extended to include entities outside
boundaries of organization
– Connects companies with suppliers, business
partners, or other authorized users
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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
– A permanent telephone connection between
two points
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Virtual Private Network (VPN)
• Extranet that uses public networks and their
protocols
• IP tunneling
– Effectively creates a private passageway
through the public Internet
• Encapsulation
– Process used by VPN software
• VPN software
– Must be installed on the computers at both
ends of the transmission
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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 same bandwidth in both directions
• Asymmetric connections
– Provide different bandwidths for each direction
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Voice-Grade Telephone Connections
• POTS, or plain old telephone service
– Uses existing telephone lines and analog
modem
– Provide bandwidth between 28 and 56 Kbps
• Digital Subscriber Line (DSL)
– Connection methods do not use modem
• Integrated Services Digital Network (ISDN)
– Offers bandwidths between 128 Kbps and 256
Kbps
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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
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Leased-Line Connections
• DS0 (digital signal zero)
– Telephone line designed to carry 1 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
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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
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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
range of about 300 feet
• Devices are capable of roaming
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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
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Fixed-Point Wireless
• One version uses system of repeaters to
forward radio signal from ISP to customers
• Repeaters
– Transmitter-receiver devices (transceivers)
• Mesh Routing
– Directly transmits Wi-Fi packets through
hundreds, or even thousands, of short-range
transceivers
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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
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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
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Summary
• TCP/IP
– Protocol suite used to create and transport
information packets across the Internet
• POP, SMTP, and IMAP
– Protocols that help manage e-mail
• Languages derived from SGML
– Hypertext Markup Language (HTML)
– Extensible Markup Language (XML)
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Summary
• Intranets
– Private internal networks
• Extranet
– Used when companies want to collaborate
with suppliers, partners, or customers
• Internet2
– Experimental network built by a consortium of
research universities and businesses
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