prioritization based on DSCP markings.

Hi,

I have been testing the Mikrotik for usage in my company.
I have completed the testing for all our standard features and so far so good. The only bit I have left is QOS so far it seemed fairly complex and to be honest I have not yet to got to the bottom on how it all works. Before I delve any deeper into the on line documentation, I was hoping someone could tell me, if our set-up is at least possible.

I would like to have 3 queues.
The traffic would arrive on the LAN interface DSCP marked. I would like the traffic prioritized based on these markings. So an EF priority queue, AF priority queue and best-effort queue for unmarked traffic.
The traffic would have to keep its markings on the egress (WAN interface).
This is for VOIP handsets so delay is especially important for the EF queue. So even when the WAN egress is slightly congested it would still have to maintain low latency for the prioritized EF traffic.
We currently use Cisco/juniper routers for this and I am looking to mimic their behaviour.
It seems like fairly standard stuff but my first tests (again probably me not quite understanding the behaviour of the Mikrotik) with the IXIA testers did not show the expected behaviour.