Basic Network Concepts



  • A simple point-to-point network.

    Not commonly used, not practical, used for a lab environment, sometimes used to transfer files between computers. The main purpose here is to demonstrate a simple network can be created with just two computers and a cable.

    Components

    .
    Network interface card, NIC for short (not shown on diagram). This is built into some computers motherboards, for instance on laptops.
    Ethernet port on the computer the port which a network cable is connected, One end goes on one computer port and other end goes on the other computer port.
    Computer device In the picture this is a laptop, but can be a server or any device with ethernet ports

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    A simple point-to-point network with no network hardware in between, just a net work cable. This cable has to be something called a crossover cable the wires that receives & transmits data are switched on one end of the cable, alternatively an adapter which does the crossover is used.

    Now we decide that we in our small team we want to share & access other network devices. We do this by installing a network switch. Each device connected to the switch has an IP address (not explained here), a form of unique identification for each network device. Via the switch, this allows our team to share the printer and access data on the network storage device. The company has only one floor in an office block, The ethernet cables allow up to 100m, for potential degradation of speed consistency.

    The picture below shows the cables going directly into the switch, it can be done with tidy cable trunking, cable ties, offices have each desk ports for voice & data, the designs varies based on the number of ports and the types of ports required, some integrate USB ports. The Figure 1.3 below roughly shows how cabling is done in offices. The main purpose is to explain the use of the switch to start sharing devices, in doing this you have create a Local Area Network (LAN).

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    Figure 1.3
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    Modern switches operate on the Layer 2 OSI & Layer 3 OSI layer, but the switch is usually just called a Layer 3 switch, this is usually shortened to L3. A Layer 3 switch is mainly used for LANS & VLANS.

    At Layer 2 - Each device effectively has its own ethernet segment, by using MAC address (hardware address) it stores this in a table, so next time it know which port is being used by that particular device. At Layer 3 it uses IP routing tables to determine where to forward packets on to (referred to as switching). You send a document to the printer, the switch know which port the printer is on and what IP address it has, all your packets go there.



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