#Omega network with 8 terminal nodes and 12 switches
20 4

 0 T  8
 1 B  9
 2 B 10
 3 B 11
 4 B  8
 5 B  9
 6 B 10
 7 B 11
 8 N 12 13
 9 N 14 15
10 N 12 13
11 N 14 15
12 N 16 17
13 N 18 19
14 N 16 17
15 N 18 19
16 N  0  1
17 N  2  3
18 N  4  5
19 N  6  7