MPLS DiffServ QoS Modes

Recap:

DiffServ Tunnelling Uniform Mode:
The MPLS DiffServe domain and non-MPLS DiffServe domain share the same DiffServ priorities, e.g. an enterprise running its own MPLS WAN. The ingress PE copies ingress DSCP/802.1P value to the MPLS EXP value on label imposition and queues towards the MPLS core based on this copied value. Any EXP re-marking along the away is reflected in the MPLS VPN payload 802.1P/DSCP field. The egress PE pop's final label(s) and performs egress queueing based on MPLS VPN payload DSCP/802.1P marking.

DiffServ Tunnelling Pipe Mode:
The MPLS core uses separate QoS priorities to MPLS VPNs making MPLS VPN priority markings completely transparent, e.g. traditional multi-customer Service Provider network. An ingress PE sets the MPLS EXP value at label imposition independent of the ingress DSCP/802.1P value. Egress queueing towards MPLS core is based on the EXP value. The EXP value may be remarked across the core but the MPLS VPN payload DSCP/802.1P value is not updated/remarked. At the egress PE, the final label(s) are popped, egress queueing occurs based on final EXP value, not the revealed MPLS VPN payload DSCP/802.1P priority marking.

DiffServ Tunnelling Short-Pipe Mode:
In Short-Pipe mode the only difference to Pipe mode is that at the egress PE, egress queuing after MPLS label disposition is performed based on the revealed MPLS VPN payload DSCP/802.1P priority marking. Through the core all queueing will have been based on the MPLS EXP value which wasn’t copied from the ingress DSCP/802.1P marking and any EXP remarking along the core won’t have been reflected in the MPLS VPN payload markings.

---