Indicates whether the particular virtual cir-
cuit is operational. In the absence of a Data
Link Connection Management Interface, virtual
circuit entries (rows) may be created by set-
ting virtual circuit state to 'active', or
deleted by changing Circuit state to 'invalid'.
Whether or not the row actually disappears is
left to the implementation, so this object may
actually read as 'invalid' for some arbitrary
length of time. It is also legal to set the
state of a virtual circuit to 'inactive' to
temporarily disable a given circuit.