“…However, it is not imbedded to some known class of vacation queueing models. Vacation models are usually classified (see, e.g., Doshi, 1986;Takagi, 1991;Tian and Zhang, 2006), by the discipline of switching the server off (exhaustive, gated, limited, etc. ) and switching it on (N -, T -, E-strategies, etc.).…”