A unified control-theoretic model is presented for routing and network management techniques is circuit switched networks. Various traditional and recently proposed schemes are illustrated in terms of this common framework. Properties of the function relating performance to control variables are derived and the issue of user versus system optimization is discussed. Approximate performance models are compared with an exact Markov chain analysis in the context of small networks employing a range of two link alternate routing policies. The exact performances are obtained through a numerical solution to the balance equations in the state probabilities, a procedure which is only feasible for small networks. The most favourable approximate models have been implemented which enable the numerical performance evaluation of the large asymmetric networks found in practice. Performance results for various routing schemes are then obtained using this model for typical networks with non-uniform traffic loads. An analytic solution to the approximate model has been obtained in the case of symmetrical networks with uniform traffic. This model has been found useful in the interpretation of numerical results.