[c-nsp] MPLS EXP label imposition

[Merlin Gillespie]

Following reading:
http://www.cisco.com/warp/public/cc/pd/iosw/tech/mpotc_qp.htm

The following passage was brought to my attention:

By default, Cisco IOS® Software copies the three most significant bits 
of the DiffServ code point (DSCP) or the IP precedence of the IP packet 
to the EXP field in the MPLS shim header.

There is not much reference to this feature outside of the prior 
mentioned document.
Can someone confirm that this is the default behaviour.
If it is the default behaviour whether there is a global configuration 
to prevent this from happening.
Or, if the only way to prevent this from happening is to manually 
rewrite all precedence bits to 0.

Many thanks in advance.

-merlin