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DES-7200 Configuration Guide Chapter 3 MPLS QOS
Configuration
3-1
3 MPLS QOS
Configuration
3.1 Introduction to MPLS
QOS
In MPLS network, we can use the EXP bits in MPLS label to configure the
priority level of MPLS packets, so as to realize service differentiation (similar to
IP differentiation). We can use "class-map" command to divide MPLS packets
into one class or multiple classes, and use "policy-map" command to configure
the QoS policy for the class. Eventually, we can use service-policy command to
apply the QoS policy to the interface.
Note
Since MPLS label switching routers (LSR) won't check the IP
header during the forwarding process of label switching, MPLS
LSRs use the EXP bits in MPLS label to configure the QoS
policy.
3.1.1 MPLS QOS overview
MPLS QoS means to apply QoS over MPLS network. No specific QoS
architecture is defined for MPLS QoS. In an actual MPLS network, MPLS QoS
generally uses the differentiated services architecture, which is specifically
designed for IP QoS. MPLS QoS architecture is the additional support of MPLS
to differentiated services on the basis of differentiated services architecture.
Basic principle of differentiated services: At the network edge, the service is
mapped to a certain class of service as per the QoS requirement for such
service. As for IP packets, we can use 6-bit Differentiated Services Code Point
(DSCP) to configure the priority of packets, so as to mark such service
exclusively. After that, each node in the backbone network will implement the
pre-configured service policy against various services according to this field, so
as to ensure the quality of service. Different from the traditional IP QoS, MPLS
QoS uses the EXP bits in MPLS labels to configure the priority of MPLS packets,
thus achieving differentiated services.
As for IP QoS, we know that QoS comprises of traffic marking, congestion
management, congestion avoidance and traffic shaping, and such scheduling