Minimizing network complexity through integrated top-down design

The network design process today remains ad-hoc and largely complexity agnostic, often resulting in suboptimal networks characterized by excessive amounts of dependencies and commands in device configurations. The unnecessarily high configuration complexity can lead to a huge increase in both the amount of manual intervention required for managing the network and the likelihood of configuration errors, and thus must be avoided. In this paper we present an integrated top-down design approach and show how it can minimize the unnecessary configuration complexity in realizing user reachability control, a key network design objective that involves designing three distinct network elements: VLAN, IP address, and packet filter. Capitalizing on newly-developed abstractions, our approach integrates the design of the three elements into a unified framework by systematically modeling how the design of one element may impact the complexity of other elements. Our approach goes substantially beyond the current "divide-and-conquer" approach that designs each element in complete isolation, and enables minimizing the combined complexity of all elements. Specifically, two new optimization problems are formulated, and novel algorithms and heuristics are developed to solve the formulated problems. Evaluation on a large campus network shows that our approach can effectively reduce the packet filter complexity and VLAN trunking complexity by more than 85% and 70%, respectively, when compared to the ad-hoc approach currently used by the operators.