Cisco WS-SUP32-GE-3B Software Configuration Guide - Page 651

Chapter 39 Configuring MPLS QoS Understanding MPLS QoS LSRs at the MPLS Core This section provides information about MPLS QoS features for LSRs at the core (MPLS-to-MPLS) for MPLS and MPLS VPN networks. Ingress features, egress interface, and PFC3B features for Carrier Supporting Carrier (CsC) QoS features are similar to those used with MPLS to MPLS described in the next section. A difference between CsC and MPLS to MPLS is that with CsC labels can be imposed inside the MPLS domain. MPLS to MPLS MPLS QoS at the MPLS core supports the following: • Per-EXP policing based on a service policy • Copying the input topmost EXP value into the newly imposed EXP value • Optional EXP mutation (changing of EXP values on an interface edge between two neighboring MPLS domains) on the egress boundary between MPLS domains • Microflow policing based on individual label flows for a particular EXP value • Optional propagation of topmost EXP value into the underlying EXP value when popping the topmost label from a multi-label stack. The following section provides information about MPLS-to-MPLS PFC3B mode MPLS QoS classification. Additionally, the section provides information about the capabilities provided by the ingress and egress modules. Classification for MPLS-to-MPLS For received MPLS packets, the PFC3B ignores the port trust state, the ingress CoS, and any policy-map trust commands. Instead, the PFC3B trusts the EXP value in the topmost label. Note The MPLS QoS ingress and egress policies for MPLS traffic classify traffic on the EXP value in the received topmost label when you enter the match mpls experimental command. MPLS QoS maps the EXP value to the internal DSCP using the EXP-to-DSCP global map. What the PFC3B does next depends on whether it is swapping labels, imposing a new label, or popping a label: • Swapping labels-When swapping labels, the PFC3B preserves the EXP value in the received topmost label and copies it to the EXP value in the outgoing topmost label. The PFC3B assigns the egress CoS using the internal DSCP-to-CoS global map. If the DSCP global maps are consistent, then the egress CoS is based on the EXP in the outgoing topmost label. The PFC3B can mark down out-of-profile traffic using the police command's exceed and violate actions. It does not mark in-profile traffic, so the conform action must be transmitted and the set command cannot be used. If the PFC3B is performing a markdown, it uses the internal DSCP as an index into the internal DSCP markdown map. The PFC3B maps the result of the internal DSCP markdown to an EXP value using the internal DSCP-to-EXP global map. The PFC3B rewrites the new EXP value to the topmost outgoing label and does not copy the new EXP value to the other labels in the stack. The PFC3B assigns the egress CoS using the internal DSCP-to-CoS global map. If the DSCP maps are consistent, then the egress CoS is based on the EXP value in the topmost outgoing label. OL-11439-03 Catalyst Supervisor Engine 32 PISA Cisco IOS Software Configuration Guide, Release 12.2ZY 39-13