Prof. Michael Elkin

This paper studies the client-server version of the 2-spanner problem. This is a natural generalization of the sparse 2-spanner problem that turns out to be useful for certain network design problems. The paper presents a logarithmic ratio approximation algorithm for this problem. The algorithm and the analysis are extended to the directed client-server 2-spanner problem and to the client-server augmentation 2-spanner problem, establishing a
logarithmic approximation ratio for these problems too.