QoS - DSCP

[Brad_199]

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?

[rpopa]

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.

[Brad_199]

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?