Queues, qdiscs, classes and filters

Very familiar with linux tc, new to mikrotik queues.

Under what conditions is it necessary to specify the size of the incoming pipe so that the queuing system ‘grabs’ the queue from
the upstream? I understand that certain qdiscs only kick in when the pipe is full otherwise there is no need for the shaping. Thus one has to specify the pipe size at something less than the actual pipe size to help create that artificial queue.

Seems to me that simple queues do not require this, these seem to create queues of their own regardless of full pipe.

Seems to be that any form of traffic max limiting does not require grabbing the queue as max limiting is made of simple queues anyhow

But perhaps any form of guaranteeing minimum bandwidth does require grabbing the queue, as one needs to take bandwidth away from some queues to give it to others. This is only necessary when the pipe is full.

I got this right?

Homer

What happens to unallocated bandwidth when using PCQ to fairshare bandwidth associated with various subnets?

Say router has two sets of cusomers on two different subnets, 10.0.0.0/24 and 10.0.1.0/24

Those on 10.0.1.0/24 you want to PCQ to a limit of 5x1 each. No guaranteed bandwidth, but yes a guaranteed max.

Those on 10.0.0.0/24 you want to have access to all other bandwidth by default and let them fight over it.

Homer