Distance

Space and time are intimately linked by the fact that all communication of information from one position in space to another takes time, in fact time is the preferred dimension in which to talk about distance! This is true in every day life too; when we're talking about travelling from A to B, it's how long it will take that we're really concerned with, not how far.

In both real life and in the network, the time-oriented distance between points is determined not only by the actual distance, but also by the transport methods, schedules and traffic conditions amongst other things. In the network, the actual physical distance between nodes is not very relevant at all and propagation time is the fundamental distance measurement.