  The routing capacity region of networks with multiple unicast sessions can be
characterized using Farkas' lemma as an infinite set of linear inequalities. In
this paper this result is sharpened by exploiting properties of the solution
satisfied by each rate-tuple on the boundary of the capacity region, and a
finite description of the routing capacity region which depends on network
parameters is offered. For the special case of undirected ring networks
additional results on the complexity of the description are provided.
