Mpls Qos Overview; Configuring Mpls Qos - 3Com MSR 50 Series Configuration Manual

89

MPLS QoS Overview

Configuring MPLS QoS

MPLS Q
n
To understand the contents in this chapter, you should have some background
knowledge related to MPLS. Refer to
for the description of MPLS basic concepts and related configurations.
The QoS solution for MPLS mainly completes the following functions:
Classify the service traffic on CE or PE according to specific needs. For example,
■
classify into three types: voice, video and data.
When PE adds a Label to the packet, it will map the IP precedence flag carried
■
by the IP packet to the EXP domain of the flag, and thus the class information
carried by IP is carried by the flag now.
Among the PEs, the differentiated dispatching (such as PQ, WFQ, and CBQ) is
■
performed, that is, transmit the service traffic with flag on a LSP in the mode of
differentiated QoS.
n
The EXP field in an MPLS label is processed in the following ways
The TOS field in an IP packet is directly changed into the EXP field in an MPLS
■
label when an MPLS label is encapsulated into an IP packet.
Any forwarding device can re-assign a value to the EXP field of a top label.
■
The EXP field remains unchanged when label switch is performed.
■
In a push operation, the EXP field of a newly pushed outer label inherits the
■
EXP field of an inner label.
After a pop operation, if the packet is still an MPLS packet, the popped EXP
■
field is duplicated to an inner label (meaning the EXP field remains unchanged
if the packet is still an MPLS packet); if the packet is an IP packet after the pop
operation, the EXP field will not be duplicated to the TOS field of the IP packet.
To configure MPLS QoS, you should first perform the related configuration of
MPLS and specify to display the route forwarding mode. For detailed
configurations of MPLS, refer to
chapter only describes MPLS QoS configuration.
MPLS QoS configuration includes:
MPLS PQ. Refer to
■
details.
S C
O ONFIGURATION
"MPLS Basics Configuration" on page 1311
"MPLS Basics Configuration" on page
"Configuring MPLS PQ" on page 1690
1311. This
for configuration