$D_v(u)=2,D_w(u)=3$graph: $G=(N,E)$

$c_{a,b}$: cost of direct link connecting a and

$e.g.,c_{w,z}=5,c_{u,z}=$

cost defined by network operator: could be inversely related to bandwidth, or inversely related to congestion

$]\}$

$[\{(x,y),(w,y),(w,z),(y,z)$