Scalable Fine-grained Path Control in Software Defined Networks

The OpenFlow-based SDN is widely studied to better network performance through planning fine-grained 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 to address that problem through pre-installing few rules at network core and quickly pushing paths into the packet header at network edges. The straightforward implementation of SR is inefficient as it would incur heavy header overhead (e.g., Sourcey); other efficient approaches would sacrifice path flexibility (e.g., DEFO). To leverage SR efficiently and flexibly, PACO presents each path as a concatenation of pathlets and introduces algorithms to program pathlets and concatenate 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 SRSDN solutions by supporting more than 40% paths with negligible header overhead.