The modelling of molecular entanglement in polymeric materials is an old problem, and has evolved gradually over the last 60 years, with two key approaches: the network model of Green & Tobolsky, and the tube model of Edwards and de Gennes. We will show that these models can be merged together in a straightforward manner. The resulting model, called the dual slip-link model, can be handled by computer simulation, and it can predict the linear and nonlinear rheological behaviours of linear and star polymers with arbitrary molecular weight distribution.