Networks

Networks

1. Types Of Network

   • Bus
     • Disadvantages
       • High chance of catastrophic failure
       • Lots of collisions
       • Slows down as more computers are added
     • Advantages
       • Cheap to install
   • Ring
     • Disadvantages
       • High chance of catastrophic failure
       • Difficult to expand
     • Advantages
       • Cheap to install
       • No collisions
   • Star
     • Advantages
       • Low chance of catastophic failure
       • No collisions
     • Disadvantages
       • Expensive
       • Depends of a switch

2. Advantages

   • Computers can communicate easily
   • Can share usernames and passwords
   • Can share programmes

3. Disadvantages

   • Viruses can spread very easily
   • If one computer gets a virus, all others can get it as well.
   • Very expensive to keep up, because of the amount of hardware needed

4. IP Adresses

   • An IP address is a unique number that helps computers know who they are
     • There are 4 billion different IP addresses that can be used

5. Internet

   • Packets
     • All data on the Internet is split up into small chunks called packets. Each packet is numbered and sent independently. This means that each packet may end up taking a completely different route through the mesh. The packets are re-assembled on the other side.
   • Routing
     • Before we can transmit, we need to decide what route the data is going to take In order to do this, each node continually tests its connections and assigns them a “cost” – a lower cost means faster connection. Route-finding algorithms are used to determine which route through the mesh will have the lowest cost, and therefore take least time As the costs change because nodes become more or less busy, new routes are needed
   • Mesh Topology
     • Rather than using a star, bus or ring topology, each node is connected to one or more other nodes in an ad-hoc manner The layout of these nodes is called a Mesh Topology In a mesh topology, there is excellent resilience to outages as messages can take many different routes to reach a destination If any node or connection becomes unavailable, the message can simply take a different route