what does parent do in simple queue

I am having hard time grasping what is the function of a parent in a simple queue

Winbox, queues/simple queues/Advanced/parent

Right now I have 13m/700k mbs inet feed,

3 simple queues with target by by vlan interface

t=vlan1 cir=8m/300k mir=12m/600k prio=1
t=vlan2 cir=3m/200k mir=12m/600k prio=2
t=vlan3 cir=1m/100k mir=12m/600k prio=3

above queues dont have any parent, should they have one ? what would be the function of such parent ?

Hi,
it is not necessary to use a parent Queue for your setup.
but let’s say you want to limit all the three queues to 30Mbps/1.8Mbps, then you can create a new Queue name=master limit=30M/1800k, and assign it as a parent for the queues. with this setup, the max traffic used by 3 queues won’t exceed 30Mbps/1.8Mbps.

Could you please come up with an example

Ok, I can set parent bps limits to D/U, and leave limits in children to unlimited and the sum of the children D/U will be limited by the parent,

What impact do have other parent params like priority, queue type on its children ?