← Back to the activity

Year 9 Computing — The shapes a network is built in

Work out how much cable a bus, star, ring or mesh needs, and what a single break costs each of them.

Name: ________________________

  1. 1.A bus network joins nine computers along one long cable. The cable is cut, leaving four computers on one side of the break. How many pairs of computers, one taken from each side, have lost contact with each other?

  2. 2.Six computers are joined in a star. Each one has a single cable running to the switch in the middle, and no other cables at all. How many cables does the network use?

  3. 3.Five computers are joined in a mesh, so every computer has its own cable to every other computer. How many cables is that altogether?

  4. 4.A full mesh is almost never used for a large office. What is the reason?

    • a) A mesh stops working the moment a single cable is cut
    • b) A mesh can only carry a message in one direction round the office
    • c) The number of cables climbs far faster than the number of computers does
    • d) No more than four computers can ever be joined in a mesh

  5. 5.In a mesh every computer has a cable to every other one. Match each mesh to the number of cables it needs.

    • 3 computers
    • 8 computers
    • 9 computers
    • 10 computers
    • 12 computers
    • 36
    • 3
    • 66
    • 28
    • 45

  6. 6.In a mesh, every computer has a cable to every other one. How many cables run from one single computer in a mesh of seven?

  7. 7.A star has eight computers around one switch. The switch itself stops working. How many of the eight can still reach another computer?

  8. 8.In a star network each computer has one cable of its own to the switch in the middle. One of those outer cables is cut. What happens?

    • a) Nothing changes at all, because messages take a different route
    • b) Every computer on the network is cut off from every other one
    • c) The switch is cut off but the computers can still reach each other
    • d) The computer on the far end of that cable is cut off, and the rest carry on as before

Answer key — Year 9 Computing — The shapes a network is built in

  1. 1. 20
  2. 2. 6
  3. 3. 10
  4. 4. c) The number of cables climbs far faster than the number of computers does
  5. 5. 3 computers → 3; 8 computers → 28; 9 computers → 36; 10 computers → 45; 12 computers → 66
  6. 6. 6
  7. 7.
    • 0
    • none
  8. 8. d) The computer on the far end of that cable is cut off, and the rest carry on as before