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CHAPTER 3 INTERNET TECHNOLOGY 3.1 (3.1.4 Classifications of Network…

- - - - • Transmission media refers to the materials or
        substances capable of carrying one or more
        signals.
        • Examples:
        – cable, radio signal, satellite signal
        • Two types of transmission media:
        – Physical transmission media (wired)
        – Wireless transmission media
        
        • Physical transmission media use wire, cable,
        and other tangible materials to send
        communications signals.
        • Examples:
        – Twisted-pair cable
        – Coaxial cable
        – Fiber-optic cable
        
        Wireless transmission media send
        communications signals through the air or
        space using radio, micro wave, and infrared
        signals.
        • Examples of wireless signals:
        – infrared
        – radio waves
        – microwaves
        
        Advantages of Network
        • Facilitates communications
        – People may communicate efficiently and easily via
        email, instant messaging, chat, and online social
        network.
        • Share data and information
        – Users can share and access data and information
        stored on the network faster and easier.
        
        Disadvantages of Network
        • Theft of personal information
        – Theft of personal information such as name,
        address, and credit card number can easily occur
        when users give information on unsecured
        websites.
        • Virus threat
        – Users are easily exposed to virus attacks on their
        systems when they connect to the Internet.
- - - - • A network in which each computer (called peer)
        have equal capabilities and responsibilities to
        share hardware, data or information with other
        computers on the network.
        • Each computer stores files on its own storage
        devices.
        • Suitable for small network where high level
        security is not necessary.
        • Some OS, such as Windows, include a peer-topeer
        networking utility that allows users to set up
        a peer-to-peer network.
        
        Advantages of Peer-to-Peer
        • Easy and inexpensive to set up the network.
        • More reliable because failure of one peer will
        not affect other peers.
        • All the peers can share their resources to
        others.
        
        Disadvantages of Peer-to-Peer
        • Lack of security control or other management
        functions.
        • Data recovery or backup is very difficult. Each
        computer have to maintain its own backup
        system.
    - - • A network in which one or more computers act as
        a server, and the other computers, called client,
        request services from the server.
        • Consists of two types of computers called server
        and client.
        – A server, or host, is a computer that controls access to
        hardware, software and other resources on the
        network and provides a centralized storage for
        programs, data and information.
        – Clients are other computers or devices on the network
        that rely on the server for its resources.• Efficient for large network which handle sensitive
        and confidential data.
        • Require a network administrator to manage the
        network.
        • Examples of client/server systems are:
        – automated teller machine (ATM) network
        – email service (ex: gmail)
        – network printing
        – World Wide Web (www)
        – Online social network (ex: Facebook)
        
        Advantages of Client/Server
        • Centralized control by the server promotes
        better security and management of the
        network.
        • Data backup and recovery is easier since all
        data is stored in the server.
        
        Disadvantages of Client/Server
        • High cost to set up and maintain the network.
        • Less reliable because too dependent on the
        server; failure of server will affect the
        network.
        • Network congestion may occur if too many
        clients request services from server at the
        same time.
- - - - Layout:
        • All computers and devices are arranged along
        a cable that forms a closed loop.
        
        Data Transfer:
        • Data transmitted on a ring network travels
        from one device to another around the entire
        ring in one direction.
        • When a device sends data, the data travels to
        each computer on the ring until it reaches its
        destination.
        
        Advantages:
        • Can span a larger network than a bus network.
        • Cable faults are easily located, making
        troubleshooting easier.
        • The transmission of data is relatively simple as
        data travels in one direction only.
        
        Disadvantages:
        • More difficult to install compared to bus
        network.
        • Failure of any cable or node will affect the
        operation of the entire network.
        • Slower data transmission as the data sent will
        go through all the nodes.
    - - Layout:
        • All computers and devices are connected to a
        central device (hub or switch).
        • Hub or switch are devices that provide a
        common central connection point for nodes
        on the network.
        
        Data Transfer:
        • All data that transfers from one node to
        another passes through the hub or switch.
        • The hub takes a signal that comes from any
        device and passes it to other devices in the
        network
        
        Disadvantages:
        • Failure of hub or switch will shut down the
        entire network.
        • Requires more cable than the other
        topologies.
        • More expensive due to the cost of the
        hub/switch.
        
        Advantages:
        • Failure of one node will not affect the entire
        network.
        • Devices can be added to or removed from the
        network with little or no disruption to the
        network.
        • Easy to identify problems, making
        troubleshooting easier
    - - Layout:
        • All computers and devices are connected to a
        single central cable (called bus).
        • The bus is a physical cable that connects the
        computers and other devices.
        • Terminators are required at both ends of the
        backbone cable.
        
        Data Transfer:
        • Data transmitted on a bus network travels
        along the bus in both directions.
        • When a sending device transmits data, the
        address of the receiving device is included
        with the transmission so that the data is sent
        to the appropriate receiving device.
        • If the device address does not match the
        intended address for the data, the device
        ignores the data.
        • If the data address match the device address,
        the data is accepted.
        
        Disadvantages:
        • Failure of the central cable will shut down the
        entire network.
        • Only suitable for small size network.
        • Data collision may occur because data
        transmitted will travel in both directions.
        
        Advantages:
        • Easy and inexpensive to set up.
        • Adding and removing nodes can be done
        without disturbing the rest of the network.
        • Failure of one node does not affect the rest of
        the network.
- - - - Wireless LAN
        • A wireless LAN (WLAN) is LAN that uses radio
        signals to connect computers and other
        devices.
        • Computers and devices that access wireless
        LAN must have built-in wireless capabilities.
        • All communications pass through the
        network’s centrally located Wireless Access
        Point (or WAP) • Computers and mobile devices on a wireless
        LAN often communicate with a wired LAN to
        access its software, printer, the Internet, and
        other resources.