Modified for 200 5 Chapter 2: Introduction t o the web and internet 1 Introduction to the Web and Internet Questions Answered in this Chapter: – What is the internet ? – What are the characteristics of the internet that make it work? – What are the content types on the web? – How are websites created? – What is behind the growth of the web and Internet?
Transcript
Slide 1
Modified for 2005Chapter 2: Introduction to the web and
internet 1 Introduction to the Web and Internet Questions Answered
in this Chapter: What is the internet ? What are the
characteristics of the internet that make it work? What are the
content types on the web? How are websites created? What is behind
the growth of the web and Internet?
Slide 2
Modified for 2005Chapter 2: Introduction to the web and
internet 2
Slide 3
Modified for 2005Chapter 2: Introduction to the web and
internet 3 The Original WWW Like the internet, radio began as a
communication medium Early market medium known as wireless
telegraphy or telephony; radios point-to-point wireless messaging
Demand for radio broadcasting surged in 1922 when it shifted from a
point-to-point communication tool to a broadcast medium During the
1920s, all 48 states in the US had at least one radio station By
1925, 27 of the original 48 stations were out of business Revenue
sources such as programming subsides from radio-set sales, radio
taxes, generalized goodwill for corporate sponsors and advertising
emerged as new revenue generation models The pay for service
revenue model allowed radio to compete with telegraph and cut the
price of telegraph by 30%
Slide 4
Modified for 2005Chapter 2: Introduction to the web and
internet 4
Slide 5
Modified for 2005Chapter 2: Introduction to the web and
internet 5 Early networks Internets beginnings can be traced back
to memos written in 1962 by MITs Joseph Carl Robnett Licklider
outlining the galactic networking concept Great advances were made
in network technology in 1960s To connect computers and permit
transfer of information locally, many organizations installed Local
Area Networks LAN technology was limited by geographical distance
To allow computer and networks separated by larger geographical
distance to communicate ARPA (Advanced Research Projects Agency)
developed a Wide Area Network (WAN) called the ARPANET
Slide 6
Modified for 2005Chapter 2: Introduction to the web and
internet 6 APPLICATION APPLICATION EXAMPLE EXAMPLE REQUIREMENT
REQUIREMENT ONLINE DATA ENTRY INVENTORY CONTROL DIRECT RESPONSE
REQUIRED ON-LINE TEXT RETRIEVAL HOSPITAL INFO SYSTEM HIGH VOLUME
REAL TIME RESPONSE LIBRARY SYSTEMS INQUIRY / RESPONSE POINT-OF
SALES RESPONSE WITHIN SECONDS AIRLINE RESERVATIONS CREDIT CHECKING
ADMINISTRATIVE MESSAGES ELECTRONIC MAIL SHORT RESPONSE / DELIVERY
TIMES PROCESS CONTROL COMPUTER AIDED MANUFACTURING : NUMERIC
MACHINE CONTROL CONTINUOUS INPUT / ONLINE RESPONSES INTERCOMPUTER
DATA EXCHANGE ELECTRONIC FUNDS TRANSFER BURST TRANSFER OF LARGE
DATA BLOCKS ON-LINE IMMEDIATE RESPONSE 9.5 Business Tasks Requiring
Networks
Slide 7
Modified for 2005Chapter 2: Introduction to the web and
internet 7 CONTINUOUS WAVEFORM PASSES THRU SYSTEM VOICE
COMMUNICATIONS * 9.8 Analog Signal
Slide 8
Modified for 2005Chapter 2: Introduction to the web and
internet 8 DISCRETE WAVEFORM TWO DISCRETE STATES: 1-BIT & 0-BIT
ON / OFF PULSE DATA COMMUNICATION * 9.9 Digital Signal
Slide 9
Modified for 2005Chapter 2: Introduction to the web and
internet 9 MEANS BY WHICH DATA ARE TRANSMITTED: TWISTED PAIR
(Copper Wires) COAXIAL CABLE: (Insulated Copper Wires) FIBER-OPTIC
CABLE WIRELESS (including radio signals) * 9.10 Ways to Transmit
Signals
Slide 10
Modified for 2005Chapter 2: Introduction to the web and
internet 10 10 5 - 10 8 : AM Radio; Short Wave; FM; VHF-TV 10 8 -
10 10 : UHF-TV, Cellular Phones, RAM Mobile, Data, Cordless Phone,
Paging, Narrow Band PCS, Industrial 10 10 - 10 12 : Radar,
Microwave 10 13 - 10 14 : Infra Red, Remote Control, Wireless *
9.12 Wireless Spectrum (in Megahertz)
Slide 11
Modified for 2005Chapter 2: Introduction to the web and
internet 11 10 15 - 10 16 : Visible Light; Fiber Optics 10 18 - 10
22 : X-Ray, Gamma, Cosmic, Personal Communication Services (PCS) *
9.13 Wireless Spectrum (in megahertz)
Slide 12
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internet 12 MEDIUM MEDIUM SPEED SPEED TWISTED PAIR TWISTED PAIR 300
BPS - 10 MBPS 300 BPS - 10 MBPS MICROWAVE MICROWAVE 256 KBPS - 100
MBPS 256 KBPS - 100 MBPS SATELLITE SATELLITE 256 KBPS - 100 MBPS
256 KBPS - 100 MBPS COAXIAL CABLE COAXIAL CABLE 56 KBPS - 200 MBPS
56 KBPS - 200 MBPS FIBER OPTICS FIBER OPTICS 56 KBPS - 10 GBPS 56
KBPS - 10 GBPS BPS: BITS PER SECOND BPS: BITS PER SECOND KBPS:
KILOBITS PER SECOND KBPS: KILOBITS PER SECOND MBPS: MEGABITS PER
SECOND MBPS: MEGABITS PER SECOND GBPS: GIGABITS PER SECOND GBPS:
GIGABITS PER SECOND 9.18 Speed of Media
Slide 13
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internet 13
Slide 14
Modified for 2005Chapter 2: Introduction to the web and
internet 14 LANS: Multiple Access Methods Fixed assignment
Partition channel so each node gets a slice of the bandwidth
Essentially circuit switching thus inefficient Examples: TDMA,
FDMA, CDMA (all used in wireless/cellular environments)
Contention-based Nodes contends equally for bandwidth and recover
from collisions Examples: Aloha, Ethernet Token-based or
reservation-based Take turns using the channel Examples: Token
ring
Slide 15
Modified for 2005Chapter 2: Introduction to the web and
internet 15 Ethernet History Developed by Bob Metcalfe and others
at Xerox PARC in mid-1970s Roots in Aloha packet-radio network
Standardized by Xerox, DEC, and Intel in 1978 LAN standards define
MAC and physical layer connectivity IEEE 802.3 (CSMA/CD - Ethernet)
standard originally 2Mbps IEEE 802.3u standard for 100Mbps Ethernet
IEEE 802.3z standard for 1,000Mbps Ethernet IEEE 802.11..n Wireless
LAN (1999) IEEE 802.15 (wireless personal area net,
~2002,Bluetooth) CSMA/CD: Ethernets Media Access Control (MAC)
policy
Slide 16
Modified for 2005Chapter 2: Introduction to the web and
internet 16 Ethernet Overview (contd.) Ethernet by definition is a
broadcast protocol - Most popular packet-switched LAN technology
Bandwidths: 10Mbps, 100Mbps, 1Gbps signal can be received by all
hosts Switching enables individual hosts to communicate Network
layer packets are transmitted over an Ethernet by encapsulating
Frame Format Dest addr 644832 CRCPreamble Src addr TypeBody
1648
Slide 17
Modified for 2005Chapter 2: Introduction to the web and
internet 17 Internetworking Software is used to go between discrete
networks The two most well-known pieces of internetworking software
are the TCP and IP IP software set rules of data transfer over the
network TCP software ensures the safe and reliable transfer of data
With open system nature of TCP/IP development, software development
and computer companies could more easily build TCP/IP compliant
software and hardware TCP/IP standard network protocol laid the
groundwork that enabled the deep internetworking that made internet
possible
Slide 18
Modified for 2005Chapter 2: Introduction to the web and
internet 18 http://www.ibiblio.org/pioneers/baran.html Paul Baran
-Worked for RAND from 1959. -Must design a network to survive
nuclear attacks. -Vulnerabilities were in the topology -1964 three
topology types -suggests Packet Switching - Military and AT&T
reject the idea. 1
Slide 19
Modified for 2005Chapter 2: Introduction to the web and
internet 19 J.C.R. Licklider -He worked for several years at ARPA
where he set the stage for the creation of the ARPANET. -He also
worked at Bolt Beranek and Newman (BBN) from 1957 to 1968, where he
acquired 2 computers for BBN, that would be developed into the
first computers connected on the ARPANET. -From 1950 at MIT he had
worked on a Cold War project called SAGE designed to create
computer-based air defense systems against Soviet bombers.
Computing was batch processing and took a lot of time. In 1960,
Licklider published his groundbreaking work "Man Computer
Symbiosis.", andMan Computer Symbiosis. much of his work has lead
to the developments in Interactive processing.
Slide 20
Modified for 2005Chapter 2: Introduction to the web and
internet 20 Early History of the ARPANET 1958Eisenhower forms the
ARPA (Advance Research Projects Agency) in response to the USSR's
launch of the Sputnik. 1966 December: ARPA Computer Network
(ARPANET) project begins. 1967 April: Suggested that the ARPANET
utilize a separate computer between the host and the network. This
computer would perform the packet switching/routing. This separate
computer dubbed the Interface Message Processor or IMP. 1968
December: Contract to build the IMPs is won by Bolt Beranek and
Newman Inc. (BBN) 1969 April: First specification for Host to IMP
communication (BBN report 1822) is released. The discussion of the
Host to Host Protocol begins with RFC 1. The Network Working Group
(NWG) forms to deal with the task of Host- Host layer communication
protocols. September: The first IMP is delivered and connected to a
Sigma 7 computer at UCLA. This IMP constitutes the first node of
the ARPANET. October: The second node of the ARPANET is installed
at Stanford Research Institute (SRI). The IMP is connected to an
SDS 940 Computer. The first message is sent across the network and
received. November: The third node of the ARPANET is installed at
UCSB. December: The fourth node of the ARPANET is installed at The
University of Utah.
Slide 21
Modified for 2005Chapter 2: Introduction to the web and
internet 21 What is the Internet? The internet is a collection of
wires, protocols and hardware that allows the electronic
transmission of data over TCP/IP Any data can be transferred over
the net, e.g., email, faxes,video,voice & web pages Technically
www (web) and the net are not the same.The web is an application
for the net
Slide 22
Modified for 2005Chapter 2: Introduction to the web and
internet 22 BBN Bolt, Beranek and Newman (now called BBN
Technologies) is a technology company that provides research and
development services. BBN is based in Cambridge, Massachusetts. It
is also a defense contractor.defense contractor Founded in 1947 by
Leo Beranek and Richard Bolt, both professors at MIT, with Bolt's
former student Robert Newman, Bolt, Beranek and Newman started life
as an acoustical consulting company. Their first contract was
consultation for the design of the acoustics of the United Nations
Assembly Hall in New York.Leo BeranekRichard BoltMITRobert
NewmanacousticalUnited Nations Work in acoustics then required
substantial calculations which led to an interest and later
business opportunities in computing. Although BBN still has a
substantial interest in acoustics, it is now better known for its
activities in computing. Some of BBN's developments of note are the
implementation and operation of the ARPANET, the first
person-to-person network email sent, the invention of the @ sign in
an email address, the first router and the development of the TCP
protocol.ARPANET@emailrouterTCP BBN creates large multi-processor
systems for warfare simulation for the U.S. Navy. U.S. Navy
http://www.bbn.com
Slide 23
Modified for 2005Chapter 2: Introduction to the web and
internet 23 How the internet works Characteristics that allow
shared access of data in a network : 1.Unique identification of
each computer on the network Internet is a network of millions of
computers and thousands of networks intertwined together. Thus it
was important that each computer can be uniquely identified by
assigning a specific Internet Protocol(IP) address. (16 bit in V4.
128 bit in V6.) e.g.,198.108.95.145 2.Human-friendly addressing
Domain Name System(DNS) gave each computer on the network an
address comprising an easily recognizable letters and words instead
of an IP address. e.g., www.philanthropy.com
Slide 24
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internet 24
Slide 25
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internet 25
Slide 26
Modified for 2005Chapter 2: Introduction to the web and
internet 26 How the internet works(contd) 3.Packet Switching To
remedy delays associated with unequally sized data transfers,
instead of transferring files in their entirety, whole files are
broken up into data packets before being transferred over the
network. 4.Routing Routers are dedicated, special-purpose computers
which serve as an intermediary between networks. They route packets
efficiently through networks. Routers are building blocks of the
internet.
Slide 27
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internet 27
Slide 28
Modified for 2005Chapter 2: Introduction to the web and
internet 28 Switching Networks
Slide 29
Modified for 2005Chapter 2: Introduction to the web and
internet 29 Circuit Switching Basics Dedicated communication path
between two stations Three phases Circuit establishment Data
transfer Circuit disconnect Developed for voice traffic (phone)
Once connected, transfer is transparent Inefficient Channel
capacity dedicated for duration of connection If no data, capacity
wasted Set up (connection) takes time
Slide 30
Modified for 2005Chapter 2: Introduction to the web and
internet 30 Circuit Switching Routing Requirements: Efficiency
Resilience Static routing uses the same approach all the time
Dynamic routing allows for changes in routing depending on traffic
Alternate routing allows different sets of routes may be used at
different times
Slide 31
Modified for 2005Chapter 2: Introduction to the web and
internet 31 Circuit Switching Alternate Routing Example
Slide 32
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internet 32
Slide 33
Modified for 2005Chapter 2: Introduction to the web and
internet 33 Packet-Switching Basics Longer messages split into
packets, data transmitted in small packets. In each switching node,
packets are received, stored briefly, and passed on to the next
node. Advantages: Line efficiency, no busy conditions,
priorities,...
Slide 34
Modified for 2005Chapter 2: Introduction to the web and
internet 34 Packet Switching Datagram Each packet treated
independently Packets can take any practical route Packets may
arrive out of order Packets may go missing Up to receiver to
re-order packets and recover from missing packets
Slide 35
Modified for 2005Chapter 2: Introduction to the web and
internet 35 Packet Switching Virtual Circuit Preplanned route
established before any packets sent Call request and call accept
packets establish connection (handshake) Each packet contains a
virtual circuit identifier instead of destination address No
routing decisions required for each packet Clear request to drop
circuit Not a dedicated path
Slide 36
Modified for 2005Chapter 2: Introduction to the web and
internet 36 Packet Switching Virtual Circuit v Datagram Virtual
circuit Network can provide sequencing and error control Packets
are forwarded more quickly No routing decisions to make Less
reliable Loss of a node looses all circuits through that node
Datagram No call setup phase Better if few packets More flexible
Routing can be used to avoid congested parts of the network
Slide 37
Modified for 2005Chapter 2: Introduction to the web and
internet 37 Routing Requirements Correctness Simplicity Robustness
Stability Fairness Optimality Efficiency
Slide 38
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internet 38
Slide 39
Modified for 2005Chapter 2: Introduction to the web and
internet 39 How the internet works (contd) 5.Reliability and
Transmission control Protocol IP software handles packet deliveries
and TCP handles safe delivery of packages. 6.Standardization
Without the TCP/IP standardization, there would have been many
negative tradeoffs, such as inflexibility and increased functional
and switching costs.
Slide 40
Modified for 2005Chapter 2: Introduction to the web and
internet 40 TCP Standardization Networking technologies are not
inherently compatible. Before the development of internetworking
technology an organization with networks had two options: One
Alternative- allow groups to have network technology best suited to
them, which was not flexible Other alternative have a standard
Slide 41
Modified for 2005Chapter 2: Introduction to the web and
internet 41 Functions of TCP/IP Prevents loss of data Checks
packets Eliminates duplicate packets Sends confirmation when the
packet is received If confirmation is not received, then the packet
is retransmitted Enables reliable and error-free communication over
the net
Slide 42
Modified for 2005Chapter 2: Introduction to the web and
internet 42 What Web pages are made of The entire Web is built upon
three concepts: web pages (documents seen on the browser), links
(connecting one web page to another), and servers (storing and
transmitting the information to the browsers for display) No
special software is required to create a web page Majority of pages
are created using Hyper Text MarkUp Language(HTML). There is a
growing use of XHTML and XML.
Slide 43
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internet 43
Slide 44
Modified for 2005Chapter 2: Introduction to the web and
internet 44 Contents of the web Links Internal Anchor Links:
Internal anchors are used to connect with other locations within
the same document. Page Links: Page links allow users to link to
other web pages. Mail-to Links: Mail links are used to let users
send feedback and questions directly to them. Forms Forms are
basically web pages where the user can enter information on the
fields provided on the page.Forms are useful in getting highly
structured feedback.
Slide 45
Modified for 2005Chapter 2: Introduction to the web and
internet 45 Contents of the web(contd) Images The most supported
image formats on the Web are Graphic Image Format (GIF) and Joint
Picture Encoding Group(JPEG). Multimedia Web supports multimedia
file type such as images, audio and video. Capturing contents and
compressing data Printed images can be captured with low cost
scanners and photos can be downloaded with digital video cameras.
Audio Sounds can be captured, compressed and stored for use on the
web. Video (Streaming Technologies) Video capture cards allow users
to capture the analog video output of camcorders, VCRs and DVD
players.
Slide 46
Modified for 2005Chapter 2: Introduction to the web and
internet 46 How are Web Sites Created? 1.A Web page can be made by
adding text-based codes called Hyper Text Markup Language (HTML) to
a text file.Text editor allows to create WebPages and gives more
flexibility and control over design and layout. 2.Document
conversion tools enable existing documents and new documents to be
created and posted with minimal investment in learning markup
language. 3.Several web authoring tools are available; e.g.,
Microsoft FrontPage lets users add multimedia objects such as sound
and animation to their web pages. 4.High-end Web authoring tools
such as Dreamweaver and Adobe GoLive offer more powerful site
creation and management features, and allow expanded features such
as database integration to be built in a web site.
Slide 47
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Slide 48
Modified for 2005Chapter 2: Introduction to the web and
internet 48 Behind the Scenes Browsers make the retrieval process
transparent Uniform Resource Locator tells the browser several
things about how to access the desired content: 1.The transmission
protocol to access the content. e.g., Hyper Text Transfer Protocol
for Web Pages, File Transfer Protocol (FTP) for transmission of
files and the extended S-HTTP for a higher degree of security.
2.The name of the computer where the content can be found 3.The
directory on the computer where content is stored and the name of
the file containing the content.
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Slide 50
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Slide 51
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internet 51 INTERNET ADDRESS [email protected] INDIVIDUAL OR
ORGANIZATION NAME HOST COMPUTER LOCATION DOMAIN 10.11
Slide 52
Modified for 2005Chapter 2: Introduction to the web and
internet 52 WWW ADDRESS http//www.datamation.com GO TO WEB WEB SITE
NAME TYPE OF ORGANIZATION 10.18
Slide 53
Modified for 2005Chapter 2: Introduction to the web and
internet 53 Factors behind the growth of the net Ease of content
consumption Browser versatility and convenience Speed Easy to
download Platform independence Ease of content creation
Standards
Slide 54
Modified for 2005Chapter 2: Introduction to the web and
internet 54