Hi to all:
Maybe I’ve not understood the basis of the problem. Are we talking about circuit switched or packet switched networks?
From my own expererience, I’ve never mixed Erlang circuit) with Poisson (packet).
Even when a switched circuit is being used, the transfer of packetized data within it is far better modelled by Poisson and Markov models of “packet store and forward links”.
Poisson-Markov allows to contemplate the queuing of packets in a given node, related to the capability of the node to “tose out” the packets of the incoming link and is highly sensitive to the packet lenght.
I’d use Poisson to model one circuit seizure, and then I’d use erlang.