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					A Brief History of the Internet
          Internet: The early years …

The Proliferation of LANs

    Engineers have devised many LAN technologies

    LAN performance determines cost; high
     performance LANs are more expensive

    A particular LAN technology may only work with
     specific computers
         Internet: The early years …

The Proliferation of LANs




                Star topology
         Internet: The early years …

The Proliferation of LANs




              Ring topology
         Internet: The early years …

The Proliferation of LANs




                 Bus topology
         Internet: The early years …

The Proliferation of LANs




              Ethernet sharing
         Internet: The early years …

The Proliferation of LANs

    A LAN technology is chosen for its speed,
     ease of use, and the availability of
     interfaces for specific computers. Most
     large organization use many LAN
     technologies
         Internet: The early years …

LANs are incompatible

   Various LAN technologies are completely
    incompatible.
       Accounting Dept.




                          Shipping Dept.
        Internet: The early years …

LANs are incompatible
                            Simply
                        connecting the
   Various LAN technologies are completely
    incompatible.        cables cannot
                          make them
      Accounting Dept.  work together




                         Shipping Dept.
          Internet: The early years …

Wide Area Technologies Exist
A wide area network
technology (WAN) differs
from a set of disjoint
transmission lines because
the WAN includes an
additional special purpose
computer at each side that
connects to the
transmission lines and
keeps communication
independent of the
computers that use the
WAN
        Internet: The early years …

Wide Area Technologies Exist
        Internet: The early years …

 Few WANs, Many LANs

 WANs and LANs are Incompatible

   Many LAN and WAN technologies exist, and most
    are incompatible with each other. One cannot
    produce a usable, large network merely by
    interconnecting the wires from two different
    networks.
         Internet: The early years …

 The Desirability of A Single Network …
        Internet: The early years …

 The Internet Emerges …

   ARPANET …

      Advanced Research Project Agency (ARPA)
       funded research projects to research new
       approaches to connecting LANs and WANs.

      A prototype system that researchers built
       became known as an internetwork – Internet.
        Internet: The early years …

 The Internet Emerges …




                      Diagrams of two nodes on the ARPANET
                      IMP - Interface Message Processors
        Internet: The early years …

 The Internet Emerges …
        Internet: The early years …

 The Internet Emerges …
        Internet: The early years …

 Internet Software

   Computer software forms an important part
    of the technology that makes it possible to
    interconnect networks
        Internet: The early years …

 The Name is TCP/IP

   Two pieces of Internet software stand out
    as particularly important and innovative

     Internet Protocol – software provide basic
      communication

     Transmission Control Protocol – Provide reliable
      communication
        Internet: The early years …

 An Open System

   The Internet project aspired to produce an
    open system that permitted computers
    from all vendors to communicate.
         Internet: The early years …

 Summary …

  The Internet began as a research project funded by ARPA.
   Researchers studied ways to connect computers that used
   various kinds of networks. The name Internet refers to
   both the project and the prototype network system that
   researchers built.

  TCP/IP is the software necessary to make the Internet
   works. The software hides the detail of the underlying
   hardware and provides the illusion of a seamless system.

  The Internet is an open system.
        Internet: Incredible Growth

 1981 – The Internet connects about 100
  computers at research sites and universities

 20 years later – 60,000,000

     Year   #computers   Year   #computers
     1983   562          1991   500,000
     1984   1,024        1992   727,000
     1985   1,961        1993   1,200,000
     1986   2,308        1994   2,217,000
     1987   5,089        1995   4,852,000
     1988   28,174       1996   9,472,000
     1989   80,000
     1990   290,000
Internet: Incredible Growth
Internet: Incredible Growth



             By 1999; a
           computer was
            added to the
           Internet every
              second.
      Internet: Incredible Growth


  By 2006; more
than 10 computers
were added to the
  Internet every
     second.
         Internet: Incredible Growth

 Factors contribute to its growth …

   Advances in computer science research – the
    introduction of UNIX operating system

   UNIX meets TCP/IP – enables connection of LANs to
    the Internet

   US Military Chose the Internet – The military funded
    and adopted the Internet, technologies were
    developed at civilian sites
        Internet: Incredible Growth

 Factors contribute to its growth …

   National Science Foundation (NSF) Takes a Leading
    Role – connect universities to the Internet

   NSF decided that to keep the US competitive, it
    needed to extend network access to every science
    and engineering researcher.

   The NSFNET
        Internet: Incredible Growth

 Factors contribute to its growth …

   The NSFNET Backbone
         Internet: Incredible Growth

 Factors contribute to its growth …

   The ANS Backbone – IBM, MERIT, and MCI formed a
    nonprofit company, Advanced Networks and
    Services (ANS)

   ANS owned the transmission lines and computers
    that comprised the network – ARPANET and NSFNET
    were funded by government

   First step toward commercialization and
    privatization of the Internet
              The Global Internet

 Internet starts from the USA …expanded to
  the globe

   Electronic mail connection – use existing voice
    telephone network – require a modem and a piece of
    communication software
             The Global Internet

 Internet starts from the USA …expanded to
  the globe

   In the UK … JANET
             The Global Internet

 Internet starts from the USA …expanded to
  the globe

   In Europe … Ebone
             The Global Internet

 Internet starts from the USA …expanded to
  the globe

   In Hong Kong … HARNET
The Global Internet
   1998, every populated
   country in the world is
         connected
   Internet: A Global Information Infrastructure

 Infrastructure – basic foundations on which
  society depends on – electricity power
  stations and supply facilities, railways, roads
  …

 New infrastructure makes new industries
  possible
   Internet: A Global Information Infrastructure

 Communication Infrastructure

    Postal mail services adopted the nation of universal
     access and delivery; and individual and send a letter to
     any other individual.

    The telegraph changed the basic communication
     infrastructure because it introduced high speed delivery

    Telephone changed the communication infrastructure by
     extending communication services to individual homes
     and offices, and by providing the instantaneous
     communication needed for interactive conversation
    Internet: A Global Information Infrastructure

 The Internet Infrastructure

    The basic Internet communication facilities are both
     general and efficient, almost any network applications can
     use the Internet

    The Internet offers a wide variety of services. Most of the
     services currently available had not been invented when
     the Internet was first designed.

    The Internet is a global infrastructure. Although it offers
     many services, the Internet’s chief advantage lies in the
     design of TCP/IP software that has accommodated
     changes in computers, networks, and services
                      Summary

 Many different LAN technologies that are completely
  incompatible.

 WANs exist

 Few WANs, Many LANs

 WAN and LAN are incompatible

 Desirable to have a single seamless network
                       Summary

 ARPANET

 ICP/IP

 Open Systems

 Computer science research, UNIX, NSFNET, TCP/IP …
  contributed to the rapid growth of the Internet.

 Internet is a global information infrastructure.
Sharing transmission path




   Communication Path
Sharing transmission path

    Sharing saves
         cost



   Communication Path
Sharing transmission path

          Sharing
     introduces delay



   Communication Path
Sharing transmission path

          Sharing
     introduces delay



   Communication Path
Sharing using Selectable Channels

              Carrier 1




      Communication Path




                   Carrier 2
     Sharing using Selectable Channels
                    Each channel is assigned
Carrier 1            a unique carrier which
                    encodes the information
                     of that communication
                             channel



            Communication Path




                       Carrier 2
        Sharing by Taking Turns

                                      C
A
             Divide data to be
             transmitted into
            small trunks, call a
                packet; and
               transmit one
             packet at a time             D
    B

             Data to be transmitted
         Sharing by Taking Turns

                            1st packet          C
A                          from B to D




              B|C     A|C B|D A|C

                                                    D
    B
                                   1st packet
 1st packet         2nd packet    from A to C
from B to C         from A to C
     Packet
      Sharing by Taking Turns
    Switching
                            1st packet          C
A                          from B to D




              B|C     A|C B|D A|C

                                                    D
    B
                                   1st packet
 1st packet         2nd packet    from A to C
from B to C         from A to C
Packet Switching Avoids Delay
Packet Switching Avoids Delay

                    A customer
                     ordered a
                    single item




                        Another
                       ordered 50
                          items
        Each packet must be labeled

                            1st packet          C
A                          from B to D




              B|C     A|C B|D A|C

                                                    D
    B
                                   1st packet
 1st packet         2nd packet    from A to C
from B to C         from A to C
        Computers Have Addresses

                                      C
A                          10.0.0.1



            B|C   A|C B|D A|C

                                          D
            Each computer attached
    B          to the network is
               assigned a unique
             number called address
        Computers Have Addresses

                                          C
A                              10.0.0.1



             B|C   A|C B|D A|C

                                              D
            Each packet contains the
    B       address of the computer
          that send it and the address
           of the computer to which it
                     is sent
    Packets are Not All the Same Size

                                         C
A                             10.0.0.1



            B|C        B|D      A|C

                                             D
    B

          Packets can have different
                    sizes
Packets Transmission Seems Instantaneous

                                                   C
  A


              B|C       B|D         A|C

                                                       D
          A packet switching system permits
      B   multiple computers to communicate
          across a shared network with minimal
          delay because it divides each
          conversation into small packets and
          arranges for the computer that sharing
          a network takes turns sending packets
        Sharing is Automatic

                                             C
A


          B|C       B|D        A|C

                                                 D
    B   From a computer’s point of view,
        obtaining fair access to a shared
        network is automatic – the network
        hardware handles the details.
Many Devices Can Use Packet Switching

                                            C
 A


            B|C     B|D        A|C

                                                D
     B   Many type of devices can connect
         directly to a computer network,
         each such device must contain a
         small computer that handles
         communication
     Relevance to the Internet



All data is transferred across
the Internet in packets
     Relevance to the Internet



A sender divides a message or
document into packets and
transfer the packets across the
Internet
    Relevance to the Internet



A receiver re-assembles the
original message from the
packets that arrive.
    Relevance to the Internet



Packets from many machines
traverse the Internet at the
same time.
                      Summary

 Packet switching – a fundamental technique used to
  ensure faire access to shared network resources.

 Before data can be transferred across a network, it
  must be divided into small trunks – packets

 Each computer connected to a network has a unique
  address

 Each packet contains a header – records the sending
  and receiving computers’ addresses

 Each computer takes turns to send its packet. One
  each turn, a computer sends one packet.
       Internet: A Network of Networks

How multiple packet switching networks can be
interconnected to form an Internet that function like a
single, large network.
Use A Computer to Interconnect Networks




               Interconnecting
                  Computer
            Computers that interconnect networks are
              dedicated to the interconnection task.
Use A Computer to Interconnect Networks
             They can use conventional hardware and
            run on special-purpose software that starts
            automatically when the system is powered
              on and remains operating all the time.




                Interconnecting
                   Computer
Interconnection Computers Pass Packets




              Interconnecting
                 Computer
Interconnection Computers Pass Packets




              Interconnecting
                 Computer
Interconnection Computers Pass Packets




              Interconnecting
                 Computer
Interconnection Computers Pass Packets




              Interconnecting
                 Computer
Interconnection Computers Pass Packets




               Interconnecting
                  Computer

      An
interconnect
      ing
 computer is
 call router
Routers are Building Blocks of the Internet

 The Internet is not a single computer network

 It consists of thousands of computer networks
  interconnected by dedicated, special purpose
  computers called routers
Routers are Building Blocks of the Internet

 The Internet is not a single computer network

 It consists of thousands of computer networks
  interconnected by dedicated, special purpose
  computers called routers
The Hierarchical Structure of the Internet



                                                Major ISP
          Major ISP


  Regional                          Regional        Regional
    ISP                               ISP             ISP




  Local           Local                 Local
   ISP             ISP                   ISP



  subscribers             subscribers      subscribers
             Where Packets Travel



                                      Major ISP
        Major ISP


Regional                   Regional       Regional
  ISP                        ISP            ISP




Local           Local        Local
 ISP             ISP          ISP
             Where Packets Travel



                                      Major ISP
        Major ISP


Regional                   Regional       Regional
  ISP                        ISP            ISP




Local           Local        Local
 ISP             ISP          ISP
             Where Packets Travel



                                      Major ISP
        Major ISP


Regional                   Regional       Regional
  ISP                        ISP            ISP




Local           Local        Local
 ISP             ISP          ISP
             Where Packets Travel



                                      Major ISP
        Major ISP


Regional                   Regional       Regional
  ISP                        ISP            ISP




Local           Local        Local
 ISP             ISP          ISP
             Where Packets Travel



                                      Major ISP
        Major ISP


Regional                   Regional       Regional
  ISP                        ISP            ISP




Local           Local        Local
 ISP             ISP          ISP
             Where Packets Travel



                                      Major ISP
        Major ISP


Regional                   Regional       Regional
  ISP                        ISP            ISP




Local           Local        Local
 ISP             ISP          ISP
             Where Packets Travel



                                      Major ISP
        Major ISP


Regional                   Regional       Regional
  ISP                        ISP            ISP




Local           Local        Local
 ISP             ISP          ISP
Interconnecting Networks was Revolutionary




               Interconnecting
                  Computer
                  (Router)
                      Summary

 To the user the Internet seems to be a single network

 It in fact consists of thousands of networks
  interconnected by a dedicated device known as routers.

 A router can connect LAN/LAN, LAN/WAN, WAN/WAN

 Networks in the Internet are arranged into a conceptual
  hierarchy of ISPs.

 Using routers to interconnect networks produced a
  revolution.
   ISPs: Broadband and Wireless Access


 How your compute can connect to and use the
  Internet
   ISPs: Broadband and Wireless Access


 How your compute can connect to and use the
  Internet
    Internet Service Providers and Fees

 A company that provides Internet access is
  known as an Internet Service Provider (IPS)

 ISP levy two types of fees

     A charge for using the Internet
     A charge for a physical connection to the Internet
                  Leased Line

 Dedicated connection, available all the time
  (24/7)

 Expensive

 Large business users
                    Dial-Up Access

                                           ISP’s
                                           Computer
                                           Attached
User’s Computer                            To the Internet


                         Voice
                       Telephone
                        system     Modem
            Modem
                                            ISP’s
                                            Permanent
                                            Connection to
                                            The Internet
 Modern Technologies Offer Inexpensive Dedicated
                     Access

 Cable Modem – From cable TV …

 DSL (ADSL) – Digital subscriber line
  (Asynchronous digital subscriber line)

 Wireless Access
 Modern Technologies Offer Inexpensive Dedicated
                     Access

 DSL (ADSL) for residential users

    A separate pair of copper wires connects each
     residence to the telephone office

    The technology sends digital data over the same
     wires that are used for conversational telephone
     service, there is no interference. Telephone calls
     do not interfere with Internet use, and Internet
     use does not interfere with telephone calls.
               Wi-Fi and 3G …

 Most laptop has Wi-Fi …

 3G …Mobile phone access to the Internet …

				
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