[1] Univ Erlangen Nurnberg, Dept Comp Sci, Networking Grp, Erlangen, Germany
[2] Univ Calif Irvine, Dept Comp Sci Informat & Comp Sci, Irvine, CA USA
[3] Osaka Univ, Dept Informat & Comp Sci, Fac Engn Sci, Suita, Osaka 565, Japan
[4] Univ Cambridge, Comp Lab, Cambridge CB2 1TN, England
[5] Osaka Univ, Computat Ctr, Suita, Osaka 565, Japan
[6] Osaka Univ, Grad Sch Informat Sci & Technol, Suita, Osaka 565, Japan