A 10/7 + ε approximation for minimizing the number of ADMs in SONET rings

SONET ADMs are dominant cost factors in WDM/SONET rings. Whereas most previous papers on the topic concentrated on the number of wavelengths assigned to a given set of lightpaths, more recent papers argue that the number of ADMs is a more realistic cost measure. Some of these works discuss various heuristic algorithms for this problem, and the best known result is a 3/2 approximation in G. Calinescu and P.J. Wan (2001). Through the study of the relation between this problem and the problem of finding maximum disjoint rings in a given set of lightpaths we manage to shed more light onto this problem and to develop a 10/7 + ε approximation for it.