In this paper, we take a holistic approach to the protocol architecture design in multihop wireless networks. Our goal is to integrate various protocol layers into a rigorous framework, by regarding them as distributed computations over the network to solve some optimization problem. Different layers carry out distributed computation on different subsets of the decision variables using local information to achieve individual optimality. Taken together, these local algorithms (with respect to different layers) achieve a global optimality. Our current theory integrates three functions-congestion control, routing and scheduling-in transport, network and link layers into a coherent framework. These three functions interact through and are regulated by congestion price so as to achieve a global optimality, even in a time-varying environment. Within this context, this model allows us to systematically derive the layering structure of the various mechanisms of different protocol layers, their interfaces, and the control information that must cross these interfaces to achieve a certain performance and robustness.