I'm reading Stallings' Data and Computer Communications. In its chapter about routing, it uses the following convention when talking about distance vector routing:
Then it shows the following example:
I don't know if I'm reading the tables wrong, but I don't think the vectors D describe the costs of going from one router to another. For example, according to D2, it would take a cost of 3 to go from N2 to N1, even though the cost is clearly 2. According to D3, it would take a cost of 4 to go from N3 to N2, but the graph shows a cost of 3. If you look thoroughly, there are many entries that appear to be wrong, at least from my point of view.
Is there something that I'm missing or is the example actually incorrect?