  In our previous publication [1-3] it has been proven that the general
iteration solution of the Shwinger-Dyson equation for the full gluon propagator
(i.e., when the skeleton loop integrals, contributing into the gluon
self-energy, have to be iterated, which means that no any
truncations/approximations have been made) can be algebraically (i.e., exactly)
decomposed as the sum of the two principally different terms. The first term is
the Laurent expansion in integer powers of severe (i.e., more singular than
$1/q^2$) infrared singularities accompanied by the corresponding powers of the
mass gap and multiplied by the corresponding residues. The standard second term
is always as much singular as $1/q^2$ and otherwise remaining undetermined.
Here it is explicitly shown that the infrared renormalization of the mass gap
only is needed to render theory free of all severe infrared singularities in
the gluon sector. Moreover, this leads to the gluon confinement criterion in a
gauge-invariant way. As a result of the infrared renormalization of the mass
gap in the initial Laurent expansion, that is dimensionally regularized, the
simplest severe infrared singularity $(q^2)^{-2}$ survives only. It is
multiplied by the mass gap squared, which is the scale responsible for the
large scale structure of the true QCD vacuum. The $\delta$-type regularization
of the simplest severe infrared singularity (and its generalization for the
multi-loop skeleton integrals) is provided by the dimensional regularization
method correctly implemented into the theory of distributions. This makes it
possible to formulate exactly and explicitly the full gluon propagator (up to
its unimportant perturbative part).
