1. The problem statement, all variables and given/known data If the network layer is sending a message from A to D via B, it can be sure that a message sent by the data link layer from A to B will always arrive at B, and from B to D will always get to D. How is it possible for the network layer not to be able to correctly deliver a message from A to D. Assume this 4-node network: A---B----D |.....|......| |---C ----| ignore the periods!!! Basically A is connected with B and C; B is connected with A, C and D; C is connected with A, B, D; D is connected with B and C 2. Relevant equations 3. The attempt at a solution I am not sure about this one. Could it be if the two nodes arent using the same addressing scheme? Any help would be appreciated.