The structural and electronic properties of GeSn in the rocksalt structure have been studied using density functional theory within the local density approximation. Results are given for lattice constant, bulk modulus and its pressure derivative. The calculated structural parameters for this model are given good agreement with previous ab-initio calculations and available experimental results. The electronic band structure is also presented for GeSn. Then, a linear-response approach to the density functional theory is used to calculate the phonon spectrum for GeSn.