🎫 M/M/c Queue

FIFO
LIFO
Stable
Near-saturation
Multi-server bank
Understaffed
Utilisation ρ—
L (in system)—
Lq (in queue)—
W (time in system)—
Wq (time waiting)—
P(wait > 0)—
Servers busy—
Longest wait—
Served / lost—
Customers arrive randomly (Poisson, rate λ) and are served by c servers, each at exponential rate μ. The system is stable only when ρ = λ/(cμ) < 1. As ρ → 1 the waiting line explodes. Yellow = Erlang-C theory, blue = live measurement.