Hii Samuel,
Descriptive characteristic and CDP Planning are two different things.
Descriptive chacteristic: in DM we are using descriptive characteristics for the release of planned independent requirements; you can release the planned independent requirements with reference to a particular customer.
With descriptive characteristics, certain product allocations can be retained for individual customers in planning, even if large sales order quantities are received from other sold-to parties.
Descriptive characteristics are not transferred to the procurement elements (planned orders). However, they can be read using the pegging relationships. So no need to mix up two things.
Find the same in sap help
http://help.sap.com/saphelp_scm41/helpdata/en/d0/61603b5a13c401e10000000a114084/content.htm.
For CDP find the help
http://help.sap.com/saphelp_scm41/helpdata/EN/19/187a375f0dbc7fe10000009b38f8cf/content.htm