RSS 2009
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John Doyle

Rules of Engagement: The Architecture of Robust, Evolvable Networks
John C. Doyle

Abstract

Biological systems are robust and evolvable in the face of even large changes in environment and system components, yet can simultaneously be extremely fragile to small perturbations. Such universally robust yet fragile (RYF) complexity is found wherever we look. The amazing evolution of microbes into humans (robustness of lineages on long timescales) is punctuated by mass extinctions (extreme fragility). Diabetes, obesity, cancer, and autoimmune diseases are side-effects of biological control and compensatory mechanisms so robust as to normally go unnoticed. RYF complexity is not confined to biology. The complexity of technology is exploding around us, but in ways that remain largely hidden. Modern institutions and technologies facilitate robustness and accelerate evolution, but enable catastrophes on a scale unimaginable without them (from network and market crashes to war, epidemics, and global warming). Understanding RYF means understanding architecture — the most universal, high-level, persistent elements of organization — and protocols. Protocols define how diverse modules interact, and architecture defines how sets of protocols are organized.

Insights into the architectural and organizational principles of networked systems can be drawn from three converging research themes. 1) With molecular biology's description of components and growing attention to systems biology, the organizational principles of biological networks are becoming increasingly apparent. Biologists are articulating richly detailed explanations of biological complexity, robustness, and evolvability that point to universal principles. 2) Advanced technology's complexity is now approaching biology's. While the components differ, there is striking convergence at the network level of architecture and the role of layering, protocols, and feedback control in structuring complex multiscale modularity. New theories of the Internet and related networking technologies have led to test and deployment of new protocols for high performance networking. 3) A new mathematical framework for the study of complex networks suggests that this apparent network-level evolutionary convergence within/between biology/technology is not accidental, but follows necessarily from the universal system requirements to be efficient, adaptive, evolvable, and robust to perturbations in their environment and component parts.

Selected references:

[1] Csete M.E. and J.C. Doyle, (2004), Bow ties, metabolism, and disease, Trends in Biotechnology, Vol 22, Issue 9, pg. 446-450
[2] H. El-Samad, H. Kurata, J.C. Doyle , C.A. Gross, and M. Khammash, (2005), Surviving Heat Shock: Control Strategies for Robustness and Performance, PNAS 102(8): FEB 22, 2005
[3] Jin C, Wei D, Low SH, Bunn J, Choe HD, Doyle JC, et al (2005), FAST TCP: From theory to experiments IEEE NETWORK 19 (1): 4-11 JAN-FEB 2005
[4] J. Doyle and M. Csete (2005). Motifs, stability, and control. PLOS Biology, 3, 2005.
[5] Doyle et al, (2005), The "Robust Yet Fragile" Nature of the Internet, PNAS 102 (41), October 11, 2005
[6] MA Moritz, ME Morais, LA Summerell, JM Carlson, J Doyle (2005) Wildfires, complexity, and highly optimized tolerance, PNAS, 102 (50) December 13, 2005;.
[7] L Li, D Alderson, JC Doyle, W Willinger (2006) Towards a Theory of Scale-Free Graphs: Definition, Properties, and Implications, Internet Math, Vol. 2, No. 4, 2006
[8] H El-Samad , A Papachristodoulou, S Prajna, J Doyle, and M Khammash (2006), Advanced Methods and Algorithms for Biological Networks Analysis, PROCEEDINGS OF THE IEEE, 94 (4): 832-853 APR 2006
[9] Kurata, H El-Samad, R Iwasaki, H Ohtake, JC Doyle, et al. (2006) Module-based analysis of robustness tradeoffs in the heat shock response system. PLoS Comput Biol 2(7): July 2006
[10] M Chiang, SH Low, AR Calderbank, JC. Doyle (2006) Layering As Optimization Decomposition, PROCEEDINGS OF THE IEEE, Volume: 95 Issue: 1 Jan 2007
[11] Martins NC, Dahleh MA, Doyle JC (2007) Fundamental Limitations of Disturbance Attenuation in the Presence of Side Information, IEEE Trans Auto Control, Feb 2007
[12] Doyle J, and Csete M, Rules of engagement. NATURE 446 (7138): 860-860 APR 19 2007 (PMID: 17443168)