What is the difference between Policy based QoS and DSCP Marking in Lync 2010?

Hello, 

I'm looking little clarity in the following phrase of the below technet link:

http://technet.microsoft.com/en-us/library/gg405407(v=ocs.14).aspx

"In Lync Server 2010, DSCP marking can be enabled by using Windows policy-based QoS to specify port ranges for each communication type. For operating system s that do not support policy-based QoS, you can use the DSCP marking policy in Lync Server. "

I understand Windows policy-based QoS is Creating GP Object. But how DSCP marking policy can be done in Lync for unsupported OS

Please help.

MUCH THANKS.