  The asymptotic behaviour of a closed BCMP network, with $n$ queues and $m_n$
clients, is analyzed when $n$ and $m_n$ become simultaneously large. Our method
relies on Berry-Esseen type approximations coming in the Central Limit Theorem.
We construct critical sequences $m^0_n$, which are necessary and sufficient to
distinguish between saturated and non-saturated regimes for the network.
Several applications of these results are presented. It is shown that some
queues can act as bottlenecks, limiting thus the global efficiency of the
system.
