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    Networks Networks Presentation Transcript

    • Communications Networks
    • What is a Network?
      • An arrangement of two or more computers interconnected to enable sharing of resource and data.
      • A true network is characterised by having its processing distributed across the various processors which constitute the network itself.
    • Advantages of Networks
      • Sharing of data
      • Sharing of resources
        • hardware and software
      • Communication
      • Easier resource management and security.
    • Servers
      • A server is a computer that is designed to support a computer network.
      • File Server
        • an entire file is sent to the requesting computer and it does the processing.
      • Client Server
        • processing is done on the server before the file is transmitted.
    • Networks
      • LANS - Local Area Networks
      • MANS - Metropolitan Area Networks
      • WANS - Wide Area Networks
      • WINS - Wireless In-building Networks
    • LANS
      • Restricted area - room, building.
      • Privately owned transmission systems - cable based media.
      • Doesn’t cross public roads.
      • High transmission rate.
    • LANs - peer to peer
      • LANs do not have to use a single server but may use a peer to peer network.
      • Peer to peer networks allow any computer to share the resources with any other computer on the network.
        • Microsoft's Home Networking and Apple’s AppleTalk are examples of this.
    • MANS
      • Network spans a municipality.
      • Transmission is left to Public Access Utility Carriers (Telstra)
      • Area covers a town, city or bigger.
    • WINS
      • High speed communications among PC’s and other equipment within one site.
      • Use radio frequency that can carry a large amount of data at high speed.
      • Possible security problems.
    • The Internet
      • The internet is a worldwide network of computer networks.
      • The Internet has millions of users and can be used for:
        • email, file transfer, research, discussion groups and entertainment
    • Network Topologies
      • STAR
      • RING
      • BUS
    • STAR
      • Each node is connected to the network controller (or host) by a separate transmission medium.
      • All communication between nodes must first be directed to the controller where it is re-addressed.
        • e.g. PABX, Time sharing Main Frame
    • STAR NETWORK Server Nodes
    • Star network
      • Expensive
        • due to amount of cabling
      • Other nodes can continue if one link is broken.
      • No contention for access to lines.
      • Capacity of network determined by the speed of the controller.
    • BUS Network
      • A single link (the bus) traversing the area of the network. Each node is tapped into the passing bus line forming a multidropped configuration.
      • All nodes share a common transmission medium.
      • Messages and destination address are broadcast to all nodes, but only the addressee accepts it.
      • ETHERNET is the most common example of the bus.
    • Bus network
      • Usually uses twisted pair or coaxial cable.
      • Easy to add extra nodes.
      • Easy installation.
      • Performance degrades if network gets busy.
      • Requires medium access control.
      • Usual transmission speed 10Mbps.
      • A number of point-to-point links between nodes with the first and last being joined to form a loop.
      • Each node shares the transmission line.
      • Each message must be addressed.
    • Ring Network
    • Ring Network
      • A common type of ring network is the TOKEN ring network.
      • Nodes that want send data must first get the token (an electronic signal) to gain access to the communication channel.
    • Ring Network
      • The token is attached to the message and when received correctly an acknowledgement signal is sent back.
      • The token is then released back onto the network.
      • Only one token is available at any one time.
    • Ring Network
      • Data only travels in one direction.
      • Requires medium access control.
      • Typical speed 1-10Mbps