Protocol organs: modularity should reflect function, not timing

The paper proposes a functional architecture for protocol systems, as opposed to the conventional temporally layered one. Each block of information to be communicated is operated on by several organs, e.g. for routing, integrity and flow control. The architecture retains a skeleton protocol stack to determine the sequence of these operations. However, unlike conventional stacks, the operators themselves are separate from the layers of the stack. This functional architecture eliminates several shortcomings that plague layered systems. The architecture provides a path along which current systems can evolve to provide the performance and economy that will be required in the future