A Computational Perspective on Network Coding

Figure 4

(a) One subnetwork of a feasible acyclic multicast network, in which if we blot out the red color, two encoding nodes $v_5$ and $v_6$ disappear. Here, at least one color path passes through the bold black links; (b) The other subnetwork in which if we blot out red color, two encoding nodes $v_1$ and $v_3$ disappear.

(a)

(b)