[c-nsp] MPLS to IP QoS on 7600 platform

[Cydon Satyr]

Hello,


I hope you can make this a bit clearer.


Reading up on Cisco documentation for 7600 router, there are two outcomes
of popping labels and forwarding an IP packet in regards to what value is
trusted for internal DSCP.


a) If a label is aggregate then ultimately IP packet's DSCP value is used
to make internal DSCP which is then used to write customer 802.1q tag (COS).


b) If it is not aggregate, then exp is trusted, in which case exp is used
for internal DSCP, and finally customer COS.


Why different behavior? By default directly connected vrf routes will be
treated with option a) and other customer routes (per prefix vpn label)
will get COS based on EXP?


Also, I think the only way to rewrite DSCP is with (hidden) command mpls
propagate-cos on PE router's CE-facing L3 interface.


BUT what if we want to simply copy value from EXP in MPLS packet to DSCP
packet for non-L3VPN service? In other words a router will get 'explicit
null' label, but the above command will not copy value from EXP->Internal
DSCP-> DSCP. Also, there are no qos-groups on 7600.


But that means that neither Ingress PE nor Egress PE router cannot change
DSCP for GRT routes that go over MPLS - change has to be done before it
enters PE router, correct?

Sorry if a bit too long. Was trying to be as concise as possible.



Best Regards