N customers move about among r servers The service times at server i are exponential at rate , and when a customer leaves server i it joins the queue (if there are any waiting-or else it enters service) at server j,ji, with probability 1/(r 1) Let the state be (n,, ..., n,) when there are n, customers at server i, i = 1,.,r Show the corresponding continuous-time Markov chain is time reversible and find the limiting probabilities