Network Topologies

• A topology is essentially the layout of the network. Networks can be arranged in lots of different topologies, but Star and Mesh are the two important ones
• In a star topology all devices are connected to the centre

  
• In a star topology, all the devices are connected to a central switch or server that controls the network. The central switch allows many devices to access the server simultaneously

  
• Star networks may be wired or wireless

  
• Pros of a Star network

  • If a device fails or a cable is disconnected, the rest of the network is unaffected
  • It's simple to add more devices to the network
  • Better performance - data goes straight to the central device so all devices can transmit data at once (unlike ring network) and there are very few data collisions (unlike bus network)
• Cons of a Star network

  • In wired networks, every device needs a cable to connect to the central switch or server. This can be expensive, e.g. for an office building with 50 terminals
  • If there is a problem with the switch or server then the whole network is affected
• In a bus topology, all the devices are arranged in a line, connected to a single backbone cable. Devices send data in both directions. This causes data collisions, which slow the network

  
• In a ring topology, data moves in one direction around the ring, preventing collisions. But only one device can send data at a time and data passes through many devices before reaching its destination

  
• In a mesh topology all devices are connected to each other

  
• A mesh topology is another popular network layout. It's decentralised - networking devices are either directly or indirectly connected to every other one without the need for one central switch or server

  
• Mesh networks work by sending data along the fastest route from one device to another

  
• The main advantage of a mesh topology is that there is no single point where the network can fail. If the central switch or server of a star network fails then the whole network fails - in a mesh network, if one device fails then the data is sent along a different route to get to its destination

  
• The traditional problem with mesh networks has been that they were very expensive - you need a lot of wire to connect so many devices together. But now more people are using wireless technology, mesh networks are a more practical option
• A full mesh topology is where every device is connected to every other device. In a partical mesh topology, not all devices are fully connected