A cost-benefit framework for judicious enterprise network redesign

Recent works, have shown the benefits of a systematic approach to designing enterprise networks. However, these works are limited to the design of greenfield (newly deployed) networks, or to incremental evolution of existing networks without altering prior design decisions. In this paper, we focus on redesigning existing networks, allowing for changes to existing decisions. Such redesign (migration) may be desirable from the perspective of improved network performance or lower complexity. However, the key challenge is that the costs of redesign may be high due to the presence of complex dependencies between network configurations. We consider these issues in the context of virtual local area networks (VLANs), an important area of enterprise network design. We make three contributions. First, we present a model to capture VLAN redesign costs. Such costs may arise from the need to reconfigure policies (e.g., security policies) to reflect the changes in VLAN design and ensure the continued correctness of the network. Second, we present a framework that enables operators to systematically determine the best strategies to redesign VLANs so the desired performance goals may be achieved while the costs of redesign are minimized. Finally, we demonstrate the effectiveness of our approach using data obtained from a large-scale campus network.