1. State Key Laboratory of Networking and Switching Technology, Beijing University of Posts and Telecommunications, Beijing, China
2. Guangdong Network Technology Research Institute, China Telecom, Guangzhou, China
3. School of Electronic and Information Engineering, Beijing Jiaotong University, Beijing, China
4. School of Computer, Qinghai University, Xining, China
5. Information Engineering College, Capital Normal University, Beijing, China
6. Performance Engineering Laboratory, School of Electronic Engineering, Dublin City University, Dublin 9, Ireland