For telephony, I've always trusted TRUNK uplinks with the "trust cos" command, and access-port uplinks with the auto qos dscp command. This has never been am issue because the switchport DSCP<-> COS mappings would map COS 5 to EF and COS 3 to AF24 or, AF24 to COS3, and EF to COS5 when traversing access port, to trunk, to access port.

However, we're rolling out pervasive video and want to use mark at the ingress for Immersive Video to have CS4 for media, and multi-purpose video to have AF41. The problem is with trusting COS, and traversing from access port to trunk port, back to access port, AF41 and CS4 both get mapped to COS4, and then back to CS4, so I lose the value of the drop probability.

So my question: Do I lose anything by configuring my trunk ports with "mls qos trust dscp", so I keep the DSCP value and not follow the COS<-> DSCP mapping? I'm wondering if perhaps how queuing may work for that 802.1p value in the trunk header....... 

auto qos voip trust

mls qos trust cos <E> ! Verses:

mls qos trust dscp <E>

Any input would be appreciated!

Thanks,

Mike.