Wired Intelligent Edge

I read that by default a switch does not need to have specific QoS settings to support 802.1p priorities on tagged ports but is the same true about DSCP?

 

For example, if a phone marks an IP packet with a DSCP priority will the connected switch (if L3) honor the marked priority and assign the packet to the correct traffic class/queue or does the command "# qos type-of-service diff-services" need to enabled first?

In an environment with only VoIP prioritization needs, normally you would define the vlan carrying the VoIP traffic as Voice VLAN and it's automatically setting it to a higher priority value.

Doesn't that prioritise at L2?
What if VoIP traffic is routed, if its marked by the handset would the DSCP priority automatically be honoured or does diff-services need to set as the ToS?