Erlang Fixed Point Approximation(EFPA) decouple a given system into independent trunks o traffic offered to each trunk follows an independent poisson process Overflow Error Path Error Poisson error underestimate overestimate Independence error underestimate overestimate Overflow error--ignore high variance of deflected traffic and dependence Path error--ignore the effect of traffic smoothing, and the positive correlation of trunk occupancy alons the th that increases the probability to admit burstsErlang Fixed Point Approximation (EFPA) 9  Overflow error -- ignore high variance of deflected traffic and dependence  Path error-- ignore the effect of traffic smoothing, and the positive correlation of trunk occupancy along the path that increases the probability to admit bursts  decouple a given system into independent trunks  traffic offered to each trunk follows an independent Poisson process