1. College of Computer Science and Electronic Engineering, Hunan University, Changsha, China
2. College of Information Science and Technology, Donghua University, Shanghai, China
3. Department of School of Computer and Information Engineering, Central South University of Forestry and Technology, Changsha, China
4. School of Computing Science, Simon Fraser University, Burnaby, BC, Canada
5. College of Engineering, Mathematics and Physical Sciences, University of Exeter, U.K.
6. Distributed Systems Group, TU Wien, Vienna, Austria