1. Jiangsu Engineering Centre of Network Monitoring; Nanjing University of Information Science & Technology; Jiangsu, Nanjing 210-044 China
2. School of Computer & Software; Nanjing University of Information Science & Technology; Jiangsu, Nanjing 210-044 China
3. Huafeng Meteorological Media Group; Beijing 100-086 China
4. Department of Computer Engineering; Kyung Hee University; Suwon 446701 Korea