Section 1: Internet Technologies

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Section 1Internet Technologies
2
Internet Overview
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What is the Internet?

• Collection of computers networked together
• Uses standards based on TCP/IP
• Data broken down into packets
• Allows for differing computer platforms to
  communicate
• Based on globally unique address for each node
• Network is global

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The Internet Network
Computer
Computer
Data
Data
Computer
Internet
Data
Data
Data
Data
Computer
Computer
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Using the Internet
Computer
Data
Internet
Internet Connection
Data
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Computer to Access Internet Three Requirements

• Application - many available
• E-Mail, Web Browser, Server, File Transfer, Video
  Conferencing, Others
• TCP/IP
• Standard in computer operating systems
• Interfaces to Internet
• Internet Connection

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E-Mail Web Browser, Server File Transfer
Protocol Video Conferencing Others
Included with Computer Operating System (usually)
Internet Connection
Data
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Internet Connection

• Plain Phone Line (POTS)
• Higher Speed Phone Line ISDN, DSL
• Cable Modem
• Ethernet etc.

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ExampleWhat is the throughput capacity of this
system?
100
500
150
250
10
300
Throughput in MB/Sec
Note real Internet is very large scale and
dynamic
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What is the World Wide Web?

• Client browser connected to Internet.
• Uses hypertext and graphics to display
  information
• Server server software connected to Internet
• Client-Server based - no platform
  incompatibilities (?)
• Any WWW browser can connect to any WWW server (if
  both follow standards)
• Rapid growth in capabilities of servers and
  clients (browsers).
• Note use of standards.

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The World Wide Web
Server
Data resides on server
Computer
TCP/IP
Request Received Data Sent
Internet
Data
Request Sent Data Received
Client clicks on hyperlink. Data received
Browser
Computer
TCP/IP
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WWW and Hyperlinks

• Use embedded codes to allow for hyperlinks
  (Hypertext Markup Language).
• When viewed in browser, user does not see
  embedded codes.
• Allows for simple point and click navigation.

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Browsers
Increasing Sophistication

• Hyperlinked text
• Graphics
• Plug-ins (e.g. sound, video)
• Active elements (Java, ActiveX)
• Operating Environment

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Web Pages and HTML

• Hypertext Markup Language (HTML)
• Uses tags that allow browser to change the format
  
• Tools to help write HTML (Word, FrontPage etc.)
• See refs on web site

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HTML Element

• An HTML element may include a name, some
  attributes and some text or hypertext
• lttag_namegt text lt/tag_namegt or
• lttag_name attribute_nameargumentgt text
  lt/tag_namegt or
• lttag_namegt

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HTML Text Elements

• lth1gt . . . lt/h1gt Heading 1 to heading 6 lth6gt . .
  . lt/h6gt
• ltbgt . . . lt/bgt Bold ltigt . . . lt/igt Italic ltugt .
  . . lt/ugt Underline
• Unordered List ul
• ltulgt
• ltligt First item in the list
• ltligt Next item in the list
• lt/ulgt

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HTML Hyperlink

• lta href"URL"gt . . . lt/agt
• Links to another file or resource
• Also need lthtmlgt ltheadgt and ltTITLEgt
• Examples
• Other elements are also defined will be using
  HTML Forms later

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• lthtmlgt
• ltheadgt
• ltTITLEgtHTML Examplelt/TITLEgt
• lt/headgt
• ltbodygt
• ltH1gtHTML is Pretty Easy To Learnlt/H1gt
• ltPgtWelcome to HTML. This is a paragraph.lt/Pgt
• ltIMG SRChttp//www.engineering.uiowa.edu/pjograd
  y/Internet/ImagesSounds/JACKSGLOBE.gifgt
• ltPgt ltA HREF "http//www.engineering.uiowa.edu/p
  jogrady/Internet/Default.htm"gt
• This is a hyperlinklt/Agtlt/Pgt
• lt/bodygt
• lt/htmlgt
• Put the above text in a file named .htm or
  .html (use Notepad or similar text editor.)
• Open using browser
• Browser interprets tags to display contents

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Growth in Number of Web Sites

• 1992
• 50 web sites in world.
• Now
• 65,000 web sites added per hour.

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Thoughts on the Issue of Internet Overload.

• The first suggests that the internet capacity is
  a finite resource but that users are not charged
  for each use. Hence Internet will be overused.
• The second school of thought more optimistically
  suggests that the Internet can continue to grow
  and response time can remain reasonable. Seems to
  be the most accurate.

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Internet Traffic

• Routers on the Internet continually collate the
  return time for test packets and this is called
  the ping delay (next slide)
• Used as part of routing for packets

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Technology Change
Technology will develop in response to customer
demand Peter OGrady

• Processor (Moores Law)
• Communications Capacity (Gilder's Law)
  (infrastructure and bandwidth)
• More complex to forecast than processor
• Estimate to be growing by factor of three per
  year (doubtful)

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From http//www.physics.udel.edu/wwwusers/watson/s
cen103/intel.html.
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From The Economist, 2003
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Computer Processing Power Moore's Law
Compaq Microsoft Dell
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Name Date Transistors Microns Clock speed MIPS
8080 1974 6,000 6 2 MHz 0.64
8088 1979 29,000 3 5 MHz 0.33
80286 1982 134,000 1.5 6 MHz 1
80386 1985 275,000 1.5 16 MHz 5
80486 1989 1,200,000 1 25 MHz 20
Pentium 1993 3,100,000 0.8 60 MHz 100
Pentium II 1997 7,500,000 0.35 233 MHz 300
Pentium III 1999 9,500,000 0.25 450 MHz 510
Pentium 4 2000 42,000,000 0.18 1.5 GHz 1,700
Pentium 4 "Prescott" 2004 125,000,000 0.09 3.6 GHz 7,000
From http//computer.howstuffworks.com/microproce
ssor2.htm
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Communications (2002 1)
Investment in new fiber has slumped Estimated 95
of fiber is dark Potential increase in
efficiency of existing fiber.
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From The Economist, 2003
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What are the implications of this growth in
bandwidth?

• Potential for increasing speed of information
  flow and ideas. This could increase
• Productivity
• Economic growth
• World peace?
• Outsourcing (why?)

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Old and New Economies
OLD
A
B
Little Trade
Tariffs, Regulations, Poor Communications
NEW
A
B
Large Trade
Ricardo - Theory of Comparative Advantage
1817 Increased economic growth
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Manufacturing Output per Hour 1995-2000 Average
Annual Change
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World Trade Volumes
From The Economist
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From The Economist
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Impact of E-Commerce

• Impact of Business to Consumer
• 5 reduction in aggregate distribution costs
• 0.5 - 0.7 reduction in costs in overall economy
• 63-88 of annual increase in total factor
  productivity in G-7 countries
• Impact of Business to Business E-Commerce
• orders of magnitude higher

Source OECD The Economic and Social Impacts
of E-Commerce
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Internet Fundamentals
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How do standards happen?

• Standards organizations (e.g. ISO)
• Usually international
• Often slow
• Non-proprietary
• Industry Groups (e.g. bar codes)
• De Facto (e.g. TCP/IP)
• Result of widespread use
• Can be quick to develop
• Can be quick to change, proprietary, no
  international body to maintain standard

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ISO Model

• The International Standards Organization, based
  in Geneva Switzerland
• Composed of groups from various countries that
  set standards working towards the establishment
  of world-wide standards for communication and
  data exchange.

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ISO Model

• Developed a Reference Model that contains
  specifications for a network architecture for
  connecting dissimilar computers.
• A main goal being that of producing an open and
  non-proprietary method of data communication.

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ISO Model

• This reference model, called the Open Systems
  Interconnect Reference Model (OSI RM), was
  developed in 1981 and revised in 1984.

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The OSI RM

• Uses 7 layers, each independent of each other, to
  allow computers to exchange data.
• To transfer a message from user A to user B, the
  data has to pass through the 7 layers on user's A
  machine, before being transmitted through the
  selected medium.

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The OSI RM

• At the receiving computer of user B, the data
  must then pass through the 7 layers again, this
  time in reverse sequence before being received by
  user B.
• For data to be transferred, it must pass through
  all 7 layers on both computers.

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The OSI RM

• Each layer follows a relatively strict
  specification and this allows the differing
  layers to be produced and implemented by
  different concerns.
• Each layer can then interface with its
  neighboring layers even though they may have been
  developed by different groups.

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The OSI RM

• The Layers Are Arranged in Order As Follows
• Layer 7, Application Layer.
• Layer 6, Presentation Layer.
• Layer 5, Session Layer.
• Layer 4, Transport Layer.
• Layer 3, Network Layer.
• Layer 2, Data Link Layer.
• Layer 1, Physical Layer.

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The OSI RM

• In spite of enormous amount of work, little of
  the OSI RM is in use.
• This is probably due to the rise of TCP/IP

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Internet Network Structure

• The Internet grew out of the 1960s Cold War.
• Response to the issue of making sure that
  computer networks could survive a nuclear weapons
  attack.
• Problem Nuclear war could destroy much of the
  military communications networks - military
  control then lost.

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Internet Network Structure

• Approach needed whereby the networks could
  operate even when substantive portions had been
  destroyed.
• One proposal formed the basis of the Internet
• Based on a simple and elegant digital model of a
  very decentralized network.

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Internet Network Structure

• Such a network is digital in nature and was
  therefore dependent on readily available
  computing power.
• Such power was becoming available only in the
  1970s.

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Internet Network Structure

• The University of California at Berkeley received
  a contract from the United States Department of
  Defense to develop a computer network that would
• Operate on a wide variety of computer hardware
  with differing communications media
• Reconfigure itself if portions of the network
  failed.

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The TCP/IP Model, and Hence the Internet

• Based on two structures
• Data being transmitted
• Computer routers that make up the core of the
  network.

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The TCP/IP Model Data

• Data is broken down into smaller packets.
• Each packet includes address of the destination
  computer as well as other information such as the
  transmitting computer.
• The packets are reassembled into the data file at
  the destination computer.

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Packets

• Data broken into packets
• Each packet sent separately with address (note
  need for unique address)
• Passes through routers in network
• Similar to sending letter via multiple postcards
• Packet switching technology required
• Unique address IMPORTANT

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The TCP/IP Model Routing

• The network is essentially composed of a number
  of routing computers (or routers)
• Route the packets towards their destination
  computer by passing them to the next router that
  is available in the general direction of the
  destination computer.

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Analogy Sending Postcards

• Break a message into smaller parts and send each
  on a postcard
• each packet (or postcard) may follow a completely
  different route and each may arrive at different
  times.
• For the digital Internet network we can improve
  performance by e.g. replicating packets.

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The Internet Network Model

• The model is essentially non-hierarchical in
  character with each router being at the same
  level of control.
• The model is highly decentralized with each
  router operating quasi-independently.
• The model is also self-managing to some extent.

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The Internet Network Model

• The model is also scaleable in that we can
  continue to add (or subtract) routers and
  computers to the network without changing its
  essentially characteristics.
• The Internet model is an open standard with the
  specifications being openly and freely available.

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TCP/IP

• TCP/IP consists of a whole series of protocols
  applications and services.
• Can be thought of as containing five layers (cf.
  OSI RM with seven layers).

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TCP/IP

• The application layer containing such protocols
  and applications as Simple Mail Transfer Protocol
  (SMPT), File Transfer Protocol (FTP), Hypertext
  Transfer Protocol (HTTP) and Telnet.
• The transport layer contains such protocols as
  Transmission Control Protocol (TCP) and User
  Datagram Protocol (UDP).

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TCP/IP

• The Internet layer contains such protocols as
  Internet Protocol (IP), Internet Control Message
  Protocol (ICMP), Address Resolution Protocol
  (ARP), and Reverse Address Resolution Protocol
  (RARP)
• The data link layer and
• The physical layer handle the hardware
  connections. A wide variety of hardware network
  connections are possible ranging from token ring
  to Ethernet and from twisted pair cables to fiber
  optic cables.

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TCP/IP

• Upper layer application
• Mid-layers (transport and Internet)
• Core of Internet
• Allows for applications to communicate with other
  computers
• Lower Layer (data link and physical layers)
• Hardware
• Ethernet, token ring, fiber optic

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TCP/IP

• Modular approach
• Allows for wide variety of configurations
• Need to have at least one from each layer. Often
  called the stack

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TCP/IP Protocols

• See course ref chapter 2.
• Note wide variety possible.
• Modular architecture also allows new protocols
  and applications to be developed

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Internet Addressing

• The Internet Protocol (IP) Uses Numbers to
  Identify Host Computers and Uses These Address
  Numbers to Route Data Between Them.
• The IP Addresses Are 32 Bit (or 4 Byte) Binary
  Values, for Example
• 10000000.11111111. 00010111.10111100

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Internet Addressing

• These Are Usually Expressed in Decimal With a
  Period Between the Bytes for Convenience.
• The Above IP Address Would Therefore Be Expressed
  in Decimal As Follows 128.255.23.188
• (server in instructors office)
• Note IP address often allocated dynamically to
  individual computers

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Example IP Specification in Windows
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Note address in xx.xx.xx.xx form
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Internet Addressing

• Each site connected to the Internet has it's own
  IP Address and messages can be addressed using
  this number. The routers on the Internet then
  pass the message through to its address.
• The numbering scheme was thought to be somewhat
  difficult to use and early in the development of
  the Internet a parallel naming scheme was begun.

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Internet Addressing

• Uses descriptive words for the site address, so
  that telegraph.co.uk for example could be used
  instead of it's IP address of 193.130.188.19
• The system that operates this is called the
  Domain Name System (DNS).
• DNS servers scattered around Internet

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Example DNS Specification in Windows
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Internet Addressing

• Lookup tables are incorporated into the Internet
  to convert from the more descriptive form, the
  DNS name, to the IP number address.
• These are used in DNS servers
• In the DNS, domain types are allocated to
  particular categories.

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DNS Categories

• For example, in U.S. then the categories are
  allocated as follows
• .com Commercial (E.G. intel.com)
• .edu Education (E.G. uiowa.edu)
• .org Organization (E.G. ims.org)
• .gov Government (E.G. nsf.gov)
• .mil Military (E.G. navy.mil)

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DNS Categories

• The countries are also identified. For example
• .jp Japan
• .kr Korea
• .uk United Kingdom.
• .de Germany
• .nl Netherlands

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DNS

• The DNS Name Is Usually Cascaded.
• For example,www.eng.cam.ac.uk refers to the WWW
  site in the Engineering Department (eng) at
  Cambridge University (cam) which is an academic
  institution (ac) in the United Kingdom (uk).

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IP Packet or Datagram
From http//www.inetdaemon.com/tutorials/internet/
ip/datagrams.html
See http//www.inetdaemon.com/tutorials/internet/i
p/datagrams.html
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Ports and IPv6
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Ports

• Generally speaking, a computer has a single
  physical connection to the network. All data
  destined for a particular computer arrives
  through that connection. However, the data may be
  intended for different applications running on
  the computer. So how does the computer know to
  which application to forward the data?
• Through the use of ports. Data transmitted over
  the Internet is accompanied by addressing
  information that identifies the computer and the
  port for which it is destined. The computer is
  identified by its 32-bit IP address, which IP
  uses to deliver data to the right computer on the
  network. Ports are identified by a 16-bit number,
  which TCP and UDP use to deliver the data to the
  right application.
• From sun.com

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Ports

• Port numbers range from 0 to 65,535 because ports
  are represented by 16-bit numbers. The port
  numbers ranging from 0 - 1023 are restricted
  they are reserved for use by well-known services
  such as HTTP and FTP and other system services.
  These ports are called well-known ports.
• There are 65,535 port numbers available for
  application processes that use Transmission
  Control Protocol (TCP). The same number of ports
  are available for application processes that use
  User Datagram Protocol (UDP).
• from sun.com see http//www.iana.org/assignmen
  ts/port-numbers

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Ports
From Microsoft.com
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IPv6

• Present IPv4 is used
• This is 32 bits, and has about 4,300,000,000
  address spaces (232 1)
• IPv6 is started to be implemented.
• IPv6 is 128 bits giving 3.4 x 1038 addresses
• Allows for an (almost) inexhaustible supply of
  addresses.

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Internet History

• Started with design of network to survive nuclear
  attack
• Highly distributed design
• Mainly used by researchers and academics up to
  about 1993-1995

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History of WWW

• 1989 CERN started development to allow physicists
  to communicate
• August 1991 first WWW software publicly released
• February 1993 NCSA published Mosaic
• Exponential growth in WWW servers

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The World Wide Web

• While the Internet provided powerful capabilities
  in such utilities as telnet and FTP, it was not
  particularly easy to use.

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The World Wide Web

• This began to change in 1993 when researcher at
  CERN in Switzerland developed a means of sharing
  data using hypertext, where codes in the document
  being examined allowed users to jump to another
  document merely by clicking on a hyperlink.

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The World Wide Web

• ftp and telnet capability were added so that they
  could also be invoked merely by clicking on a
  hyperlink.
• This type of program became known as a browser
• CERN browser was limited to text documents.

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The World Wide Web

• A team at University of Illinois at
  Urbana-Champaign (specifically the National
  Center for Supercomputer Applications - NCSA)
  developed a more powerful browser called Mosaic
  which allowed for the inclusion of graphics.
• Mosaic was freely available and led to a huge
  increase in the use of the Internet and WWW.

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The World Wide Web

• Some of those involved in the development of
  Mosaic helped form Netscape Corporation, which
  has developed commercial versions of both
  browsers and servers.

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WWW Clients and Servers

• The WWW, in it's early form, is a very large
  collection of clients and servers that support
  the Hypertext Transfer Protocol (HTTP) on the
  Internet.
• This is an open standard and is implemented on a
  wide variety of platforms.

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WWW Developments

• The interaction between WWW servers and clients
  can be classified as follows
• The web server sends a static file to the client
  as a result of a Hypertext Transmission Protocol
  (HTTP) request from the client.
• The WWW Server Can Process Data in Response to
  Input From Client Browser. Such process can
  include, for example, extracting the information
  from the corporate databases in response to the
  client browser requests. SERVER SIDE PROGRAMMING
• A program can be downloaded from the WWW server
  to a client which can then carry out the
  programmed actions on the client. CLIENT SIDE
  PROGRAMMING

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Server Side Programming

• Common Gateway Interface (CGI)
• CGI Is a standard for interfacing external
  applications with WWW servers (Common Gateway
  Interface, 1995).
• Application Programming Interface (API)

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Common Gateway Interface (CGI)

• CGI is just a set of commonly-named variables and
  agreed-upon conventions for passing information
  back and forth between the client (the user's WWW
  browser) and the server (the computer that sends
  web pages to the client).

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Use of APIs

• Each time a new CGI program is started a new
  process is begun and this is notoriously
  inefficient.
• For a server with multiple CGIs executing
  simultaneously, the result can be very slow
  response times.

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Use of APIs

• Recently, therefore, much attention has begun to
  be focussed on more efficient methods of
  executing programs on the server.
• Much of the developments has been on Application
  Program Interfaces (API) that, in their pure
  form, is a set of functions in the operating
  system that programmers can use.

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Use of APIs

• However the APIs tend to be proprietary and
  therefore are particular to server/operating
  system combinations.
• An example Is the Internet Services Application
  Programming Interface (ISAPI) that Is proprietary
  to Microsoft.

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Use of APIs

• ISAPI Allows for Programs to Be Dynamic Link
  Libraries (DLLs) for Use on a Windows Server and
  Only One Copy of the DLL Need Be Loaded No Matter
  How Many Programs Use It.
• Active Server Pages (Microsoft) Java Server Pages
  (Sun/Netscape) have program on server.

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Use of APIs

• Results would indicate that servers that use APIs
  have substantially shorter response time than
  those that use CGIs and we can therefore expect
  that CGIs will tend to fall in relative disuse.

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• Server Side Programming
• CGI
• API
• ASP (Microsoft only)
• JSP
• can include executable and/or scripts

• Client Side Programming
• Java applet
• Java Script
• VB Script (Microsoft only)

Important application is interfacing to
databases. Course homework addresses many of
these.