Protocol based architectures.

Doyle and Csete offer an interesting essay on "Rules of Engagement" in the recent issue of Nature Magazine. (PDF here). Their summary:

Complex engineered and biological systems share protocol-based architectures that make them robust and evolvable, but with hidden fragilities to rare perturbations.

They draw an analogy between the protocol based architecture (TCP/IP) of the internet and transcription and translation protocols that regulate the horizontal transfer of genes between organisms.