Cisco WS-SUP32-GE-3B - Supervisor Engine 32 Software Configuration Manual page 648

Understanding MPLS QoS
If the ingress port receives both IP-to-IP and IP-to-MPLS traffic, classification should be used to
separate the two types of traffic. For example, if the IP-to-IP and IP-to-MPLS traffic have different
destination address ranges, you can classify traffic on the destination address, and then apply IP ToS
policies to the IP-to-IP traffic and apply a policy (that marks or sets the EXP value in the imposed MPLS
header) to the IP-to-MPLS traffic. See the following two examples:
•
•
Classification for IP-to-MPLS MPLS QoS
MPLS QoS at the ingress to PE1supports:
•
•
MPLS QoS at the egress of PE1 supports the mpls experimental topmost command.
Classification at IP-to-MPLS Ingress Port
Classification for IP- to- MPLS is the same as for IP-to-IP. LAN port classification is based on the
received Layer 2 802.1Q CoS value. OSM and FlexWAN interfaces classify based on information in the
received Layer 3 IP header.
Classification at IP-to-MPLS Egress Port
LAN port classification is based on the received EXP value and the egress CoS values is mapped from
that value.
OSM and FlexWAN interfaces classify traffic when you use the match mpls experimental command to
match on the egress CoS as a proxy for the EXP value. The match mpls experimental command does
not match on the EXP value in the topmost label.
If the egress port is a trunk,the LAN ports and the OSM GE-WAN ports copy the egress CoS into the
egress 802.1Q field.
MPLS to IP
PFC3B mode MPLS QoS supports these capabilities at the MPLS-to-IP edge:
•
•
This section provides information about the MPLS-to-IP MPLS QoS classification. Additionally, this
section provides information about the capabilities provided by the ingress and egress modules.
Catalyst Supervisor Engine 32 PISA Cisco IOS Software Configuration Guide, Release 12.2ZY
39-10
A PFC3B policy to mark IP ToS sets the internal DSCP—If it is applied to all traffic, then for
IP-to-IP traffic, the egress port will rewrite the CoS (derived from the internal DSCP) to the IP ToS
byte in the egress packet. For IP-to-MPLS traffic, the PFC3B maps the internal DSCP to the imposed
EXP value.
A PFC3B policy to mark MPLS EXP sets the internal DSCP—If it is applied to all traffic, then for
IP-to-IP traffic, the egress port rewrites the IP ToS according to the ingress IP policy (or trust). The
CoS is mapped from the ToS. For IP-to-MPLS traffic, the PFC3B maps the internal DSCP to the
imposed EXP value.
Matching on IP precedence or DSCP values or filtering with an access group
The set mpls experimental imposition and police commands
Option to propagate EXP value into IP DSCP on exit from an MPLS domain per egress interface
Option to use IP service policy on the MPLS-to-IP egress interface
Chapter 39 Configuring MPLS QoS
OL-11439-03