R0106-HP MSR Router Series ACL and QoS Configuration Guide(V7)

Configuring MPLS QoS

Overview

MPLS uses 3 bits, called EXP bits, to carry class-of-service information to provide support for DiffServ.

MPLS QoS identifies different traffic flows with different EXP bits and implements differentiated services.

MPLS QoS can guarantee low delay and low packet loss ratio for critical service traffic, such as voice

and video traffic. For more information about MPLS, see MPLS Configuration Guide.

MPLS QoS supports CAR and priority marking. MPLS QoS provides the following functions:

• Classify traffic on the PE to apply differentiated QoS strategies for different traffic classes. For

example, MPLS QoS can organize packets with EXP value 1 into a class and packets with EXP value

2 into another class. Then it performs traffic policing and priority marking for each class of packets.

• When a PE labels a packet, it maps the IP precedence to the EXP field of the label. In this way, the

class information carried in the IP header is carried in the label.

The EXP field in an MPLS label is processed following these rules:

• The device re-sets the EXP field of only the topmost label.

• During label encapsulation, the ToS field of the IP packet is directly changed into the EXP field of the

MPLS label.

• The EXP field remains unchanged when label swapping is performed.

• During a label push operation, the EXP field of the newly pushed outer label inherits the EXP field

of the inner label.

• After a label pop operation, if the packet is still an MPLS packet, the EXP field of the popped label

is not copied to the inner label. If the packet is an IP packet, the EXP field of the popped label is not

copied to the ToS field of the IP packet.

Configuration prerequisites

Before configuring MPLS QoS, complete basic MPLS configuration. For more information about basic

MPLS configurations, see MPLS Configuration Guide.

Configuring MPLS CAR

By configuring a CAR policy for traffic entering an MPLS network, you can limit the transmission rate to

avoid network congestion, and mark priority for the traffic. For more information about traffic policing,

see "Configuring traffic policing, GTS, and rate limit."

To configure MPLS CAR:

Ste

Command

Remarks

1. Enter system view.

system-view N/A

2. Enter interface view.

interface interface-type

interface-number

N/A