Routing optimization with path cardinality constraints in a hybrid SDN

Abstract

The emergence of Software Defined Networking (SDN) increases the flexibility of routing and provides an efficient approach to balance network flows. Due to the economical and technical challenges in transiting to a full SDN-enabled network, a hybrid SDN, with a partial deployment of SDN switches in a traditional network, has been a prevailing network architecture. For a hybrid SDN, the routing flexibility is influenced by the expensive and limited Ternary Content Addressable Memory (TCAM) resource, where SDN switches store the flow entries dispatched from SDN controllers. Considering the limited TCAM resource, to reduce the abundant flow entries in TCAM, we propose to impose the constraints on the number of routing paths (i.e., path cardinality constraints) when optimize flows routing. To solve this problem, in this paper, we first formulate the routing optimization problem with the path cardinality constraints in a hybrid SDN as a Mixed Integer Non-Linear Programming (MINLP) problem. Then, we propose an incremental deployment method for obtaining a hybrid SDN and an H-permissible Paths Routing Scheme (HPRS) to effectively route traffic flows under the path cardinality constraints. After that, the theoretic analysis is given to prove that the approximation ratio of HPRS is O(logL). Finally, through extensive experiments, we demonstrate that our proposed algorithm HPRS can efficiently reduce flow entries and approximates optimal routing under different network topologies.