Example Differentiated Services Application and Configuration

Figure 64 shows an example topology where a service provider offers the following differentiated services to its customers over its MPLS network:

• QoS Internet service—The CE router is managed by the provider and sets the IP precedence to predefined values. IP policy on the PE router sets the traffic-class/color combination according to the incoming well-defined IP precedence value. The policy also sets the UPC value to the incoming well-defined IP precedence value.
• Plain Internet service—IP policy on the PE router leaves the traffic-class/color combination as the default value, best-effort/green. The policy sets the UPC to 0.
• QoS VPN service—For CE-to-PE traffic, the VPN EXP is copied from the IP precedence value when the PE router pushes VPN stacked labels.

  For PE-to-CE traffic, IP policy on the PE router resets the traffic-class/color combination according to the received, well-defined IP precedence value, so that egress queuing is based on the IP precedence value. This action takes place on the egress line module.

• Plain VPN service—For CE-to-PE traffic, the VPN EXP bits are set to 000 when the PE router pushes VPN stacked labels.

  For PE-to-CE traffic, IP policy on the PE router resets the traffic-class/color combination to the default value, best-effort/green, so that packets are queued as best-effort. The IP precedence value is left unchanged.

In this example, the provider also offers an inter-AS VPN service. The provider's own protocol traffic, for example, BGP signaling traffic such as update messages, is also labeled, with the EXP bits set to the same value as the IP precedence.

The egress queuing of traffic as it leaves the provider is always based on either the VPN EXP bits as received on the core side in inter-AS case, or the IP precedence value in all other cases. It is acceptable that fabric queuing is based on the incoming base label's EXP.

Figure 64: Differentiated Services over an MPLS Network

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