My personal opinion that ISPs should /ideally/ not remark DSCP. However, I do not feel strongly about this. If an ISP flattens all the DSCP to 0, it probably doesn't matter in practice. If I understood correctly, one major international network recently told me they flatten everything to DSCP 0. I have implemented prioritization at layer 2. So we do /ignore/ DSCP when determining the incoming traffic class of traffic. All Internet traffic gets CoS 0 (e.g. by "qos cos 0"). In my gear, I believe CoS 0 is actually traffic-class 1 under the hood, such that CoS 1 can be traffic-class 0 for below best effort. We do not use below best effort, though. We have non-Internet traffic that gets prioritized. For example, SLAed point-to-point Ethernet circuits get a higher CoS value (again fixed, regardless of the customer's incoming p-bit or DSCP). Prioritization is maintained through the network using VLAN p-bit values. That means I do MPLS-in-VLAN, which feels a bit odd and requires extra configuration (i.e. a separate "interface Vlan123"). I would like to use MPLS EXP bits, but my vendor does not seem to support explicit null labels. Without the VLAN p-bit, penultimate hop popping would thus lose the priority value to the last /router/. Priority still matters at the last router because there are switches and PON access gear behind the router. So we /should/ be transparent to DSCP. I think we have been when I've looked, but I can't remember for certain. Again, take this all with a grain of salt. I'm just one guy at a little ISP. As always, if I'm doing something dumb, I welcome education from others. -- Richard