A Case for Complexity Models in Network Design and Management

Abstract

Anecdotal evidence and intuition suggest that an operator?s ability to manage a network decreases as the network becomes more complex. However, there is currently no way to systematically quantify how complex a network?s design is nor how complexity may impact network management activities. In this paper, we develop a suite of complexity models that describe the routing design and con?guration of a network in a succinct fashion, abstracting away details of the underlying con?guration languages. Our models, and the complexity metrics arising from them, capture the dif?culty of con?guring speci?c control and data plane behaviors in various routers. They also enable measurement of the inherent complexity of reachability constraints that a network implements via its routing design. Our models simplify network design and management by facil- itating comparison between alternative designs for a network. To demonstrate their value, we use the metrics to perform a comparative study of the complexity of ?ve different networks, including three university networks and two enterprise networks.