  A recently proposed generating functional allows the construction of the full
set of n-point Green functions in QCD at high temperature and at distances
larger than 1/gT. One may then learn how the system maintains its thermal
equilibrium in the quantum field theory approach, i.e. which process
compensates for the important dissipation due to collisions. This system may be
characterized by quantities which have a classical limit. One finds that the
fluctuations of the coloured field are not gaussian ones. A comparison is made
with the semi-classical approach where a random noise is the source of
fluctuations.
