  We consider the class of complete discretely valued fields such that the
residue field is of prime characteristic p and the cardinality of a $p$-base is
1. This class includes two-dimensional local and local-global fields. A new
definition of ramification filtration for such fields is given. It appears that
a Hasse-Herbrand type functions can be defined with all the usual properties.
Therefore, a theory of upper ramification groups, as well as the ramification
theory of infinite extensions, can be developed. Next, we consider an equal
characteristic two-dimensional local field $K$. We introduce some filtration on
the second K-group of a given field. This filtration is other than the
filtration induced by the valuation. We prove that the reciprocity map of
two-dimensional local class field theory identifies this filtration with the
ramification filtration.
