  Vector boson scattering is (together with the production of multiple
electroweak gauge bosons) the key process in the current run 2 of LHC to probe
the microscopic nature of electroweak symmetry breaking. Deviations from the
Standard Model are generically parameterized by higher-dimensional operators,
however, there is a subtle issue of perturbative unitarity for such approaches
for the process above. We discuss a parameter-free unitarization prescription
to get physically meaningful predictions. In the second part, we construct
simplified models for generic new resonances that can appear in vector boson
scattering, with a special focus on the technicalities of tensor resonances.
