Local area network

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A local area network (LAN) is a group of computers (network) in a small area like a home, office, or school. Many computers can be connected to share information and Internet connections. Most LANs use Ethernet to connect together.

LAN topologies tell you how network devices are organized. Five common LAN topologies exist: bus, ring, star, tree, and mesh. These topologies are logical architectures. This means that they tell you the directions that signals go between devices, but that the actual cables that connect the devices might not be connected the same way. For example, logical bus and ring topologies are commonly organized physically as a star.

  • A bus topology means that the signal is put onto the medium and every device on the bus receives the signal. If more than one device tries to send a signal at the same time, they can interfere with each other. A long copper wire with other wires tapped into it is an example of a bus topology.
  • A ring topology means that each device talks to two other devices in the network and the devices all talk in a circle. If a computer sends data out one of its interfaces, it could get an answer back on the other one. Some rings send traffic in only one direction, other ring networks send traffic in both directions. Token Ring and FDDI are examples of ring topologies.
  • A star topology means that one device (the middle of the star) connects to several other devices. The only way devices on the points of the star can talk to each other is through the device in the middle. A network switch is an example of a star topology. Computers on the LAN need to go through the switch to talk to each other.
  • A tree (or hybrid) topology is named because when you draw a picture of how the devices in this topology are connected, it starts off narrow with few devices at the bottom, then branches out at the top. Large networks are an example of a tree topology. There are switches and servers near the bottom of the tree, then all the user's computers "branch out" at the top of the tree.
  • A mesh topology means that every device can talk to every other device, and they will not interfere with each other. You can also have a partial mesh, where some devices do not talk to all of the others. There are not many simple examples of a mesh network. A wireless data network where all of the devices use multiplexing or different frequencies to avoid interfering with each other would be one example.