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computer Networks

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					Computer Networks
Communication    links
Internet / WWW
Computer Networks
   A is a set of independent computer
    systems interconnected by
    telecommunication links.
Telecommunication Links
   The connection links:
     Areused to transmit data between the
      computers on the network.
     The links could be:
        wires (cables, telephone-lines), or even
        wireless (radio transmitters, satellites).

   The transmission or bandwidth of a link:
     Is the amount of data that can be transmitted
      over a connection in a given period of time.
     Is typically measure in bps (bits-per-second).
   In a local network (office, building,
    campus), computers a usually connected
    via dedicated links, such as:
     Twisted pair wire
     Coaxial cable
     Fiber-optic cable

   But what if we want to connect from
     Telephone-lines
     Cable   TV
Connecting via Telephone Lines
     Problem:
        Telephone systems were build to carry
         voice as analog data, but computers use
         digital (binary) data.
     Solution:
        At the sending end the data is converted to
         analog signal (modulate).
        At the receiving end: the analog signal is
         converted back to digital data
     The device that does this is called a modem.
     Bandwidth: up to 56 Kbps
   Telephone companies are now also
    offering ISDN connections (Integrated
    Services Digital Network)
     Communications   links capable of handling
      digital signals.
     Can also be used for normal telephone calls, a
      device called Terminal Adaptor (TA) converts
      the analog telephone signal to/from a digital
   Need:
     ISDN   adapter in your computer
   Bandwidth: 128Kbps
Cable Modem
   A device called a cable modem allows to
    transmit data via a cable TV connection:
     Does  modulate the digital signals so can be
      transmitted (but without interfering with the TV
   Needs
     Cable TV outlet
     A cable modem (rental included in monthly fee)
     A network card in your computer.
   Advantages:
     Dedicated   connection (don't have to dial in).
Cable Modem Setup-example of
Europe system
Computer Networks
   We distinguish between two different type of
   LAN (Local Area Networks)
     Used  to connect computers in close physical
      proximity (office, building, campus)
   WAN (Wide Area Networks)
     Used  to connect computers across cities, countries,
   The two type of networks use totally different:
     Network
     Communication protocols
Local Area Networks (LANs)
   Many different types of LANs, but (by far)
    the most widely used are Ethernets.
     Bandwidth: 10mbps-100mbps
     Each computer on the network has installed
      an Ethernet adapter.
   Ethernet LAN's can be constructed in two
    different ways, either using
    a  shared cable
     a HUB
Ethernet LAN using a Shared Cable
   A shared (coaxial) cable is stretched around the
    area (a home, office, building, campus, ...).
   The computers connect to the cable via sockets
    called transceivers.

    Shared cable
Ethernet LAN using a HUB
 No shared cable.
 All computers connect directly to a central
  device called a HUB (or a device called a

                      HUB: sends message to all the other
                      Switch: sends message only to callee
    Ethernet Communication Protocol
   The rules of how data is transferred over the
    network is called:
    a  communication protocol (same protocol used
      regardless of how the network is constructed.
   Communication technique (no central control):
     Each computer on the network has an unique address.
     A message to address is broadcasted over the network.
      Every computer receives the message, but only the
      computer with a matching address stores the message.
     Contention-based transmission:
            Listens to line and wait until free, then send.
            If collision (two or more computers send at same time), wait a
             random amount of time, then retry.
Wide Area Networks (WANs)
   Used to connect computer systems that are far
    apart, e.g. across a city, country, continent.
   Network topology different from LAN's:
      Point-to-Point communications links (one
       computer connects directly to another
   Communication protocols different from LAN's:
      Send a fixed maximum size packages instead
       of whole messages.
      Use store-and-forward, package-switching
Network Topology WAN
   Point-to-Point communication lines, that is, a
    link directly connects two computers.
   Not all computers directly connected (but there
    exists a path between any two).
Mixing LAN/WAN
   LAN's connect to WAN's via routers.
   Routers:
     Determine the path to take in the WAN
     Reconfigure messages between LAN/WAN
      communication protocols

The Internet
 The first computer-to-computer message
  was sent in 1969.
 Today the Internet consists of estimated
     30 million interconnected computers
     hundred of millions of users
     in over 150 countries.

   The World Wide Web is the most popular
    component of the internet.
Internet - A network of networks



Internet Infrastructure
 The Internet is a network of networks.
 Is based on an internetworking concept:
     each  network can do whatever it wants
      internally, but
     much speak a standard protocol externally,
     use a standard addressing scheme

   A device called a gateway interconnects
    the networks
     basically   same as a router
Standard Addressing/Protocols
   Addressing:
     Each   computer has a unique address
        IP address

     Domain   Name System
        easier to remember names than numbers
        Can refer to address as:

   Protocols:
     TCP/IP (Transmission Control Protocol/Internet
     More or less the “common language” spoken
      by networks
Usage of internet
 Web-browsing (World Wide Web)
 E-mail
 Telnet (log onto and work on another
 FTP (transfer files from one computer to
 Newsgroups / Chat rooms
 E-Commerce
 ...
World Wide Web
   The World Wide Web (WWW) is an
    information sharing system based on
     inter-linkeddocuments (web-pages)
     that can be accessed over the internet and
     viewed graphically (using a web-browser)

   Located via a URL (Uniform Resource
     <protocol>://<internet   address>/page
Web pages
   A web-page is a hypertext document
     can  have links to another web-pages
     written in a language called HTML

   The web-pages
     are stored on a computer running a web-
     can be accessed from any computer on the
      internet via a web-browser (Netscape,
      Internet Explorer).
   The HTTP protocol specifies
     how the Web-browser (client) gets the
      page from the web-server.
   Computer networks
     computers  connected using
      telecommunication links
     Local Area Networks (LAN)
     Wide Area Networks (WAN)

   Internet
     Network  of networks
     Standard addressing scheme/inter network
   WWW
How to create Internet connection
Must ensure the hardware component is installed.
IP number must be given by
system administrator of
corresponding faculty.
Setting Up internet for home-must pay fee
Setting up printer
 Must have the printer driver installer
 Can find the driver from company website
  of the printer
 or CD/floppy supplied together
 Printing through the Network Several
1) If the printer is connected to your computer then just set up the printer as
being shared. The advantage is that no other equipment is needed. The
disadvantage is that in order for your other computers to use that one
shared printer you have to have that computer (that has the printer) turned
2) Get a Print Server. That is a small box that connects to your printer on
one end, and somehow to your network on the other (the ways vary).
Wireless Print Servers are available. The advantage is that only the printer
has to be on at the time, no additional computers. The disadvantage is that
you have to buy the box (the Printer Server).
3) Get a router that has a Print Server built in. That way you have the
advantages of #2, without having to buy any other hardware. The
disadvantage is that routers with a Print Server built in are a little more
expensive. My wireless router has a Print Server built in.
4) Get a printer than already has an Ethernet connection on it. Then, you
only need to plug the printer, via an Ethernet cable, into your router.
This also has the advantages of #2, and the disadvantage is that these
"network ready" printers are generally more expensive than common USB
or LTP connected printers.
Printing through the Network-
Example 1

   It is very productive to have a printer that can be
    connected directly to the Network (as oppose to
    a single computer), and can be used by any
    Networked computer regardless of the status of
    the other computers.
   The computer that connected to the printer must
    be ON condition so that other computer will be
    able to use the printer.
Printing through the Network-
Example 1-main computer part
   Computer must be ON
   Printer must be ON
   Connected to the same workgroup
   Under LAN iconright clickfind
    propertieswhen local area network properties
    open ensure that “File and printer sharing for
    microsoft work” is enablethis is for both
    computers(main computer that has printer
    directly connected to it and other computer that
    want to access the printer.
Network printer setting-main
 Main computer connected directly to the
  printer must be ON
 Printer must be ON
 Printer must be shared on the network
Network printer setting-network
computer(other computer)
   Must know the IP of the main computer
Bila click pop up keluar dan ask
for comfirmation to install a print
driver in your computer. Click yes
to install network printer
Bila click printer, access to the network printer will
be add in the printers and faxes folder
How to view shared file on the
   Search the computer through the
    connected network
Sharing files and folders
   You can share the files and folders stored on your computer, on a
    network, and on the Web. The method you choose depends on
    whom you want to share files with, and what computer they will use
    to access the files.

   When you share files or folders, they are not as protected as they
    are when you do not share them. People with access to your
    computer or your network might be able to read, copy, or change
    files that are in a shared folder. You should always be aware that the
    files and folders that you share are available to other people and be
    sure to monitor your shared files and folders on a regular basis.
Method of sharing files /folders
   Using Shared Folders
   Using Windows Explorer
   Using a command line
Using Shared Folders
    Open Computer Management (Local).
    In the console tree, click Shares.
     Where?
        Computer Management
           System Tools
             Shared Folders
                 Shares
    On the Action menu, click New File Share.
    Follow the steps in Create Shared Folder.
    You will be prompted to select a folder or drive, type a new share
     name and description of the shared resource, and set
     permissions. After you provide this information, click Finish.
     Notes
    To open Computer Management, click Start, and then click
     Control Panel. Double-click Administrative Tools, and then
     double-click Computer Management.
    You must be a member of the Administrators or Power Users
     group to use Shared Folders.
Using Windows Explorer
   Open Windows Explorer, and then locate the shared folder or drive to
    which you want to add a new share name.
   If you are logged on to a domain, do the following:
   Right-click the shared folder or drive, and then click Sharing and Security.
   Click Share this folder.
   Set any other options that you want, and then click OK.
   If you are not logged on to a domain or if you are running Windows XP
    Home Edition, do the following:
   Right-click the shared folder or drive, and then click Properties.
   On the Sharing tab, click Share this folder on the network.
   Set any other options that you want, and then click OK.
     Note
   To open Windows Explorer, click Start, point to All Programs, point to
    Accessories, and then click Windows Explorer.
Using a command line
   Open Command Prompt.
   Type:
   net share sharename=drive:path
   ValueDescriptionnet shareCreates, deletes, or displays shared
    resources.sharename=drive:pathThe network name of the shared resource
    and the absolute path of its location.
    Notes
   To open a command prompt, click Start, point to All Programs, point to
    Accessories, and then click Command Prompt.
   To view the complete syntax for this command, at a command prompt, type:

   net help share
    Notes
   You can use Shared Folders to manage shared resources on both local and
    remote computers. Windows Explorer and the command line allow you to
    manage shared resources on your local computer only.
   You can hide the shared resource from users by typing $ as the last
    character of the shared resource name. Users can map a drive to this
    shared resource, but they cannot see the shared resource when they
    browse to it in Windows Explorer or in My Computer, or when they use the
    net view command on the remote computer. For more information about
    this command, check Net view.
   You must have the appropriate permissions to complete this procedure.
How to share through the network- Using Windows Explorer
       Internet:
           Requirements to connect to the Internet
           Use of Internet/ Kegunaan Internet

    Present in power point
    List the name of group members
    Must be neat, presentable and easy to understand
    Presentation duration: max 10 min
    Marking: Total 10 marks
           3 marks - teamwork
           4 marks - creativity
           3 marks – presentation skills