Layering of protocols offers several well-known advantages, but typically leads to performance inefficiencies. We present a model for layering, and point out where the performance problems occur in stacks of layers using this model. We then investigate the common execution paths in these stacks and how to identify them. These paths are optimized using three techniques: optimizing the computation, compressing protocol headers, and delaying processing. All of the optimizations can be automated in a compiler with the help of minor annotations by the protocol designer. We describe the performance that we obtain after implementing the optimizations by hand on a full-scale system.