Robustness and the Internet: Theoretical Foundations

This article uses the Internet as a starting point to illustrate universal aspects of complex systems throughout technology and biology. Complexity in most systems is driven by the need for robustness to uncertainty in their environments and component parts far more than by basic functionality. Protocols organize highly structured and complex modular hierarchies to achieve robustness, but also create fragilities to rare or neglected perturbations. We claim these are also the most important and universal features of complex systems. All of this complexity is largely hidden, deliberately creating the illusion of superficially simple systems, which encourages development of specious theories. We also discuss an emerging theoretical foundation for the Internet. The aim is to provide a framework for understanding both the successes and shortcomings of existing Internet technology, offer alternative protocols for identified problems, guide rational design for future evolution of ubiquitous networking, and suggest what new mathematics and technology will be needed for a useful, general theory of complex systems.