Scalable path provision in software defined networks

The OpenFlow-based SDN is widely studied to better network performance through providing flexible routing paths. However, being designed to configure path hop-by-hop, it faces the scalability issue — both the flow table overhead and path setup delay are unacceptable for large-scale networks. In this paper, we propose PACO, a framework based on Source Routing (SR) to address that problem through quickly pushing path information into packet header at network edges. The straightforward implementation of SR is inefficient as it would incur heavy header overhead (e.g., Sourcey); other approaches would sacrifice path flexibility for efficiency (e.g., DEFO). To leverage SR efficiently while maintaining path flexibility, PACO preloads a small group of pathlets in network and uses them to concatenate each desired path. Efficient algorithms are proposed to preprogram suitable pathlets and encode on-demand paths with minimum header overhead. Our extensive simulations confirm the scalability of PACO as it saves the flow table overhead up to 94% compared with OpenFlow-SDN solutions, and show that PACO outperforms the state-of-art SR-SDN solution by supporting more than 40% paths with negligible header overhead.