Abstract
One-to-many group communication is a performance bottleneck for high-performance data center applications, due to sending massive data from one source to hundreds of receivers. The state-of-the-art solutions utilize either electrical packet switch (EPS) or optical circuit switch (OCS) multicast to accelerate massive data disseminations. However, there exist competitions between multicast and unicast flows at core EPSes in the electrical multicast. Moreover, the optical multicast suffers from a non-negligible reconfiguration delay and exclusive optical links. In this paper we present iCAST, a system for reducing multicast flow completion time (MFCT) on a generic hybrid EPS/OCS network, which has multiple EPSes and OCSes supporting multicast. iCAST constructs multicast trees by integrating the electrical and optical multicast to fully utilize network resources, and seamlessly schedules flows between the static electrical and dynamic optical networks to reduce the configuration overhead. We evaluate the performance by implementing a small-scale hybrid EPS/OCS testbed and extending the high-performance framework MPICH to support iCAST. Experiments show that iCAST outperforms one order of magnitude in reducing MFCT compared with the ring algorithm. We also develop an event-based flow level simulator to evaluate the performance of iCAST at the scale of thousands of servers. Simulation results show that iCAST reduces the average MFCT by 32% and 28% compared to OCS and EPS respectively, and significantly outperforms binomial tree and ring algorithm by up to 64% and 46% respectively.