Search for: [Description = "In the paper approximate formulas for the mean waiting times and the buffer dimensioning in the system with vacations fed by the stream of Poissonian type with constant service times is shown. Furthermore, in the considered system the time intervals of the availability\/not\-availability of the service are constant and are run alternately according to the assumed cycle. More precisely, presented approach begin with derivation of the mean waiting times and, on the basis of this, the required buffer size for guaranteeing the losses less than predefined value is estimated. The accuracy of the presented analytical formulas is on a satisfactory level. The formulas were used for the System IIP dimensioning."]