  We investigate the proposed ``D-brane alternative'' to the MSSM model (DMSSM)
which is a type II B string orientifold model with N=1 supersymmetry, three
generations and a $SU(3)\times SU(2)_R\times SU(2)_L \times U(1)_{B-L}$ gauge
group. An accurate analysis at two-loop level is performed to show that
unification constraints predict a ``left-right'' symmetry breaking scale in the
TeV region. The exact value of this scale is the result of the competing
effects of the two loop terms against the low energy supersymmetric threshold
effects. The model accommodates logarithmic unification of the gauge couplings
at an intermediate scale of $10^{12}$ GeV and the necessary conditions to
achieve this are addressed.
