The nam trace queue states is given by:
q -t time -s src -d dst -a attr
Queues are visualized in nam as a straight line along which packets
(small squares) are packed.
In queue trace events, the flag -a specifies the orientation of the
line of the queue (angle between the queue line and the horizontal
line, counter-clockwise).
For example, the following line specifies a queue that grows
vertically upwards with respect to the screen (here 0.5 means
the angle of the queue line is pi/2):
q -t * -s 0 -d 1 -a 0.5