  A summary of recent results on filamentary transport, mostly obtained in the
ASDEX-Upgrade tokamak (AUG), is presented and discussed in an attempt to
produce a coherent picture of SOL filamentary transport: A clear correlation is
found between L-mode density shoulder formation in the outer midplane and a
transition between the sheath limited and the inertial filamentary regimes.
Divertor collisionality is found to be the parameter triggering the transition.
A clear reduction of the ion temperature takes place in the far SOL after the
transition, both for the background and the filaments. This coincides with a
strong variation of the ion temperature distribution, which deviates from
Gaussianity and becomes dominated by a strong peak below $5$ eV. The filament
transition mechanism triggered by a critical value of collisionality seems to
be generally applicable to inter-ELM H-mode plasmas, although a secondary
threshold related to deuterium fueling is observed. EMC3-EIRENE simulations of
neutral dynamics show that an ionization front near the main chamber wall is
formed after the shoulder formation. Finally, a clear increase of SOL opacity
to neutrals is observed associated to the shoulder formation. A common SOL
transport framework is proposed account for all these results, and their
potential implications for future generation devices are discussed.
