“…Take 4-Tree topology shown in Fig. 1(a) as an example and assume that there are 12 flows traversing the net: (1,2), (1,3), (1,4), (2,1), (2,3, (2,4), (3,1), (3,2), (3,4), (4,1), (4,2), (4,3). Note the rate of commodity k as k R , k = 1, 2, ..., 12.…”