I'm reading TE with MPLS book. The chapter about QoS explains the following rules in unifomrm QoS mode:
- when push label, copy the IPP in the EXP imposed label
- when imposed label, copy the received EXP into the imposed EXP
And after, there is this exemple:
==> DSCP 40 -- EXP3|DSCP 40 -- EXP0|EXP3|DSCP40 -- EXP0|EXP3|DSCP40 -- EXP0|DSCP40 -- DSCP0 ==>
For me in this example, there is only downward propagation.
They said that the propagation is upward and downward. For me, this will be like that:
==> DSCP 40 -- EXP5|DSCP 40 -- EXP5|EXP5|DSCP40 -- EXP5|EXP5|DSCP40 -- EXP5|DSCP40 -- DSCP40 ==>
Can you explain me why I'm wrong?
This behavior is regardless of your entry point (PE router) so I agree with the book.
In book example, they associate DSCP 40 to EXP 3 instead of 5 (default behavior) and they remark in the middle which results of a remarking of the DSCP field at the egress PE.
In your example, you keep default configuration and because there is no remarking in the middle, you keep your original DSCP field.