To correctly model traffic in packet switched networks for single link
s with FC-FS discipline at each node, we introduce the influence of th
e phenomenon of short packets agglutinating behind long packets. It is
then necessary to abandon the usual notions of local traffic sources
and local G/G/1 queues in favor of the more realistic notion of traffi
c sources at the network input with local queues appearing as the cons
equence of a tandem queue whose parameters we define. The influence of
the upstream transfer delay and the upstream network topology then ap
pear. We compare theoretical results with those derived by traffic sim
ulations.