Optical grooming with grooming ratio nine

Grooming uniform all-to-all traffic in optical ring networks with grooming ratio CC requires the determination of graph decompositions of the complete graph into subgraphs each having at most CC edges. The drop cost of such a grooming is the total number of vertices of nonzero degree in these subgraphs, and the grooming is optimal when the drop cost is minimum. The minimum drop cost is determined for grooming ratio 9. Previously this bound was shown to be met when n≡0(mod9) with two exceptions and eleven additional possible exceptions for nn, and also when n≡1(mod9) with one exception and one possible exception for nn. In this paper it is shown that the bound is met for all n≡2,5,8(mod9) with four exceptions for n∈{8,11,14,17}n∈{8,11,14,17} and one possible exception for n=20n=20. Using this result, it is further shown that when n≡3,4,6,7(mod9) and nn is sufficiently large, the bound is also met.