1. East China University of Science and Technology; Shanghai 200237 China
2. Cisco Systems; U.S.A
3. Department of CEEN; University of Nebraska-Lincoln; Omaha NE 68182 U.S.A
4. High Performance Network Lab, IOA; Chinese Academy of Sciences; Beijing 100190 China
5. Department of Mechanical Engineering; Massachusetts Institute of Technology; Cambridge MA 02139 U.S.A