The evolution of layered protocol stacks leads to an hourglass-shaped architecture

Abstract

In the fourth chapter, a study of protocol stacks (and layered architectures, more generally) and their evolution has been done in a rigorous and quantitative manner. Instead of only considering a specific protocol stack, an abstract evolutionary model, referred to as EvoArch, in which protocols are represented by nodes and services are represented by directed links, is considered. In this layered directed acyclic graph representation of protocol stack, this chapter concentrates on the topology of the graph which changes with time as new nodes are created at different layers, and existing nodes are removed as a result of competition with other nodes at the same layer. A robustness study shows that the model produces hourglass structures for a wide range of parameter values.