In order to provide a valid characterization of the traffic of a connection anywhere along the path of the connection, the traffic model must be flexible enough to capture perturbances as the traffic travels along its path. Also, the network must be modeled as to capture the elements that add perturbance to the traffic as it flows through the network. To model the traffic we use pairs of deterministic traffic bounding functions. To capture the active elements within the network we model it as a network of servers and distinguish between constant and variable servers.