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Networks

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									Networks

• A network is a collection of computers and
  devices connected together via communications
  devices and transmission media
• Advantages of a network include:
        Facilitating         Sharing        Sharing data
      communications        hardware      and information



                  Sharing          Transferring
                 software             funds

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Bandwidth

• Measurement of the capacity of the channel
• Categories
  – Voiceband also known as low bandwidth
  – Medium band
  – Broadband
     • Used for high capacity transmission
     • Used by DSL, cable, and satellite
Protocols

• Set of communication rules
• Standard for Internet: TCP/IP (Transmission
  control protocol/Internet protocol)
  – Identification
  – Reformatting
Network Classifications

• Local area networks (LAN)
• Home networks
   – WLAN (Wireless LAN)
• Metropolitan area networks (MAN)
• Wide area networks (WAN)




                                     5
Network Classifications

 • A local area network
   (LAN) is a network that
   connects computers
   and devices in a limited
   geographical area
 • A wireless LAN (WLAN)
   is a LAN that uses no
   physical wires



                              6
Network Classifications

• A metropolitan area network (MAN) connects
  LANs in a metropolitan area
• A wide area network (WAN)
  is a network that covers a
  large geographical area




                                               7
Network Architecture

• The design of computers, devices, and media on a
  network is sometimes called the network architecture
                       Client/server      Peer-to-peer



        Terminal




                                                         8
  Client/Server Model                       Peer-to-peer
                                            (P2P) Model
  Client
                                 Client
                                             Peer                   Peer
                 Server

                                             Peers communicate as equals
    Client                     Client        on a one-to-one basis.

Server must be prepared to serve multiple
clients at any time.




                                                                           9
The Client/Server Model
• When processes need to communicate:




• Examples:
  – file server
  – mail server
  – web server    =>
                                        10
The Client/Server Model (continued)
• Client & server have strictly defined roles:
  – client sends request – then waits for answer
  – server accepts request – processes & returns answer

• Protocols, defining how to:
  – encode messages
  – address messages
  – handle sending and
    receiving
• Protocols: Example
   • http, ftp                                            11
The Peer-to-peer Model

• P2P describes an Internet network on which users
  access each other’s hard disks and exchange files
  directly over the Internet




                                                  12
Network Topology

• A network topology refers to the layout of the computers
  and devices in a communications network

    Star network          Bus network         Ring network




                                                             13
Network Topology

• Network topology is the layout pattern of
  interconnections of the various elements
  (links, nodes, etc.) of a computer.
• Types of network topology
  – Star
  – Bus
  – Ring
  – Hierarchical
Star Network
• Smaller computers
  linked to a central unit
• Central unit is called the
  network hub
• Control is maintained by
  polling




                               15
Bus Network
• Each device handles its own communication control
• There is no host computer
• Has a common connecting cable called a backbone




                                                16
Ring Network
• Each device is
  connected to two other
  devices
• No central file server or
  computer
• Useful in a
  decentralized
  environment



                              17
      Hierarchical Network
      • Several computers
        linked to a central host
      • Computers are hosts to
        other computers
      • Useful in centralized
        organizations




Page 264                           18
Principal Network Configurations
Network Communications Standards

            Token
Ethernet            TCP/IP    Wi-Fi
             ring

Bluetooth   UWB      IrDA     RFID


            WiMAX   WAP

                                      20
Network Communications Standards


Ethernet is a network standard that specifies no computer
controls when data can be transmitted

The token ring standard specifies that computers and
devices on the network share or pass a special signal (token)

TCP/IP is a network standard that defines how messages are
routed from one end of a network to another


                                                                21
Network Communications Standards




                                   22
Network Communications Standards

 • Wi-Fi identifies any
   network based on the
   802.11 standard that
   facilitates wireless
   communication
 • Sometimes referred to
   as wireless Ethernet




                                   23
Network Communications Standards

• Bluetooth defines how two Bluetooth devices use short-
  range radio waves to transmit data
• UWB (ultra-wideband) specifies how two UWB devices use
  short-range radio waves to communicate at high speeds
• IrDA transmits data wirelessly via infrared (IR) light waves
• RFID uses radio signals to communicate with a tag placed in
  or attached to an object, animal, or person




                                                                 24
Network Communications Standards




                                   25
Network Communications Standards

                                   Wireless Application
      WiMAX (802.16)
                                     Protocol (WAP)
• Developed by IEEE            • Specifies how some mobile
• Towers can cover a 30-mile     devices can display the
  radius                         content of Internet services
• Two types are fixed            • Web
  wireless and mobile            • E-mail
  wireless                       • Chat rooms
• Provides wireless            • Uses a client/server
  broadband Internet access      network

                                                            26
Communications Software

• Communications software consists of programs
  that:
        Help users establish       Manage the
         a connection to         transmission of
        another computer        data, instructions,
            or network           and information

                        Provide an
                    interface for users
                     to communicate
                     with one another

                                                      27
Communications Over
the Telephone Network
• The public switched telephone network (PSTN) is
  the worldwide telephone system




                                                    28
Communications Over
the Telephone Network

    Dial-up    Dedicated
                           ISDN line
     lines       line

                           T-carrier
      DSL         FTTP
                             line

                  ATM
                                       29
Communications Over
the Telephone Network




                        30
Communications Over
the Telephone Network
• ADSL connections transmit data downstream at a
  much faster rate than upstream




                                                   31
Home Networks

• Home networks provide computers with the
  following capabilities:

  Connect to the       Share a single high-     Access files and
  Internet at the        speed Internet        programs on other     Share peripherals
    same time              connection             computers


                                     Connect game
             Play multiplayer                             Subscribe to and
                                     consoles to the
                  games                                      use VoIP
                                        Internet




                                                                                         32
Home Networks




                33
 Organizational Internets
• Intranets
   – Private network within an organization
   – Provides information to employees
• Extranets
   – Private network that connects
     organizations
   – Used to allow suppliers and others
     access
• Firewalls
   – Security system
   – Protects against external threats


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Careers In IT
• Network Administrator
   – Manage a company’s LAN and
     WAN networks
   – Maintain hardware and
     software
   – Diagnose and repair problems
   – Candidates usually have a
     bachelor’s degree in
     computer science and
     practical experience
   – Annual salary is typically
     between $43,000 and
     $68,000




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