1. Suppose that a data packet is to be sent through the computer network of 4 nodes, from A to G. It is possible that some nodes are down at the time. The data packet must be sent through as few nodes as possible, but must not be sent through a node that is down.

a. What is the shortest route for the data packet?

1. when no nodes are down;
2. when nodes B and D are down;
3. when nodes B, D, and F are down?