[c-nsp] 7600 MPLS PFC QoS - mls qos rewrite ip dscp

[Jerome Durand]

Hi all,

I'm trying to put QoS in our IP/MPLS backbone with 7600's and LAN 
cards... All the 7600's are P and PE's and therefore can receive on a 
backbone interface either MPLS or IP traffic. Customers are marking 
packets (I use their marcking for my policy) and I want to do DSCP 
transparency.

I read the following reference:
http://www.cisco.com/en/US/docs/routers/7600/ios/12.2SR/configuration/guide/mplsqos.html
and found the following that I don't understand:
"The *no mls qos rewrite ip dscp* command is incompatible with MPLS. The 
default *mls qos rewrite ip dscp* command must remain enabled in order 
for the PFC to assign the correct EXP value for the labels that it imposes."

This seems to cause a problem for me when IP traffic flows over our 
network. A router being both P and PE (depending of weither traffic is 
just transiting or not), it can receive a pure IP packet when it is 
egress PE (due to PHP). But that router can also receive MPLS packets 
for transiting traffic.

Therefore for this router I would need to leave *mls qos rewrite ip 
dscp* for P behaviour and *no mls qos rewrite ip dscp* for PE behaviour 
(to keep DSCP transparency) ???

I'm a bit lost here as I doubt router will keep both configuration 
statements ;) What do I misunderstand?

Any hint?

Thanks,

Jerome