Bad News:
Not approximable within 3/2
for any
[325].
Comment:
Approximable within 3.23 also on directed graphs.
Variation in which the objective is to maximize the routable demand
is approximable within 14.
If the objective is to minimize the number of rounds in
which all demands are routed, is approximable within 13.
The generalized problem in which there are two source vertices
is not approximable within 2
[331].