“…For retrial models with no waiting room and server breakdowns, customers arriving to find the server unavailable (busy or failed) join the orbit. A variety of failure types are considered in the literature, including starting failures [16,20,27], vacations [7,23], active breakdowns [6,24,26], and, like our model, both active and idle breakdowns [2][3][4][5]11,15]. [2,3,7,16,20,23,24,27]) force these customers into the orbit, whereas others [4][5][6]11,15,26] provide the option of joining the orbit or departing the system.…”