Networks 1

Networks 1

1. Topology

   • Advantage
     • Cheap to install (only one wire needed)
     • Cheap to install (one cable per computer)
     • No collisions - only one computer is transmitting on each cable
     • Fast (low chance of collisions)
     • Easy to add new computers
     • Low chance of catastrophic failure (a broken cable only takes out one computer, the rest of the network is fine)
   • Disadvantages
     • High chance of catastrophic failure (a break in the central cable takes out the entire network)
     • High chance of collisions (multiple communications on the same cable that corrupt each other, slowing down the network)
     • High chance of catastrophic failure (if any cable breaks or any computer goes down, the entire network fails
     • Difficult to add new computers
     • Expensive (needs a lot of cabling, and a central switch, which is expensive)
     • Failure of the switch will take down the network

2. iP address

   • The IP Address is unique value assigned to each computer on a network
   • Each IP address on a network must be unique
   • When the format of IP Addresses were decided in 1983, 4 billion addresses seemed more than enough
   • We get round this by assigning an “external” IP address to each house or business, then “internal” IP addresses to the computers in that house or business
   • Globally, there are now more devices on the Internet than the 4’228’250’625 devices it’s possible to assign a unique address to
   • Internet Protocol Address

3. the internet

   • The Internet is a huge, global inter-connected network of devices
   • When we join the Internet, we use a broadband router to connect to one of the existing nodes
   • In a mesh topology, there is excellent resilience to outages as messages can take many different routes to reach a destination

4. revise

   • advantages and disadvantages of networks
   • topologies
     • bus
       • The network consists of a single cable that runs through the network
     • star
       • All computers are connected to a central switch
     • ring
       • Computers are connected to each other in a ring
   • IP addresses
   • the internet
     • routing
     • packets