Research On Openflow-based Cross-layer Control Of Intra Data Center Optical Networks

With respect to modern cloud data centers (DC), the development of new applicationsresults in massive growth in data traffic, which also leads to higher requirements for latency, bandwidth, and scalability for the intra-DC networks. Traditional electrical switching suffers from difficultiesindealing with these challenges. The optical switching technologies, however, may provide intrinsic advantages in lower latency and higher bandwidth and have been widely regarded as promising enablers for future high performance intra-DC networks.On the other hand,centralized resource scheduling in the DC networks has also been broadly applied in reality due to flexibility and efficiency considerations. OpenFlow, which is simple and flexible in operation, is one of the mostly discussed approaches for cross-layer control in the DC network, yet there are still lots to do by integratingOpenFlow with the Optical Switching intra-DC networks. As a daunting problem in the DC network caused by lack of cross-layer coordination, TCP incast may occur when there are much traffic following certain many-to-one communication pattern, and throughput would crash sharply.In this thesis, we mainly focus on this issue and explore the cross-layer optimization abilities of OpenFlow-based centralized control in the intra-DC optical network. We propose detailed networkcontrolschemes and corresponding OpenFlow protocol extensions to alleviateTCP incast effectively.Firstly,we investigated an optical burst transport network (OBTN) architecturefor intra-DC interconnection, and we found TCP incast problem occurs mainly at the access OBTN node connected with multiple serversor withinthe OBTN ring network. To resolve the contention at access node, we designed an OpenFlow-based cross-layer control mechanism, in whichanetwork controller is able to monitor the status of buffer in the access node via OpenFlow interface, and then interwork with an application controllerto dynamically adjust the number of active source severs. Such a coordination mechanism betweenapplication and optical switching layer is validated with OpenFlow protocol extensions as well as Matlab simulation. Secondly, in the OBTN ring network, we also developed an enhanceddynamic bandwidth allocation (DBA) algorithm to further mitigate TCP incast effects.Inthe proposed DBA, all traffic that is more likely to suffer TCP incast ishandled as a whole and prioritized with guaranteed bandwidth. Numericalsimulations and network simulationsare conducted to evaluate the performance of the proposed algorithm, and simulation results show that network resource utilization and service performance were improved as expected.