ORP: An Online Rule Placement Scheme to Optimize the Traffic Overhead for Data Center Networks

In cloud data centers, the requirement for fine-grained policy leads to a large number of server rules. However, the servers cannot efficiently handle all of these rules due to limitations of the central processing unit (CPU) and memory resources. Thus, a rule partition and placement algorithms have been proposed to divide the original ruleset into several rule subsets and migrate some rule subsets to other devices. Correspondingly, the traffic, which is meant to be blocked by the original server's migratory rules, will also be redirected to the new device. The rule partition and placement algorithms should minimize this extra traffic overhead. The state-of-the-art algorithm, vCRIB, is offline, as its solution is calculated based on a static traffic matrix. In reality, when facing dynamic traffic, the vCRIB solution may actually be suboptimal in terms of traffic overhead. To reduce the traffic overhead, we propose the online rule replacement (ORP) algorithm. Specifically, ORP utilizes the difference between the old and new traffic matrices to discover the rule subsets matching the notably changed traffic overhead or blocked traffic. These rule subsets are then preferentially adjusted to their proper placement. In this manner, ORP can promptly make rule subset adjustments according to the newly updated traffic matrix. Additionally, ORP effectively avoids the invalid migrations existing in vCRIB. The simulation results confirm that ORP is capable of reducing traffic overhead by 26.67%–56.9% compared to vCRIB.