If routing is put in place, what are our possibilities? the maximum number of possible routes? that you can offer Mr. A to join Mr.B?

The total number of possibilities, without any selection, is roughly equal to the possibilites at every routing node…

Are all the possibilities logical, make sense? what do you think of A going through router R1 and then looping back to R_A? in cases where routing is done based on the packet destination address, source address, or both?

In the case of destination-based routing, a minimum criterion is that any possibility should help lead person A to B. We wont accept routes that loops back, leads to the same departure, “cycles”…