Contents

Configuring MPLS QoS·· 1

About MPLS QoS· 1

Configuring MPLS priority marking· 1

Appendixes· 1

Appendix A Default priority maps· 1

Configuring MPLS QoS

About MPLS QoS

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 supports CAR and priority marking. MPLS QoS classifies traffic on the PE and 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.

The EXP field in an MPLS label is processed according to the following rules:

·     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 for a packet, the following rules apply:

¡     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.

An MPLS label is encapsulated between the Layer 2 header and Layer 3 header of a packet. Multiple MPLS labels are supported, which are referred to as a label stack. If there are m labels between the Layer 2 header and Layer 3 header, the label closest to the Layer 2 header is called the first label (top label). The label closest to the Layer 3 header is called the mth label (bottom label).

Configuring MPLS priority marking

About this task

In an MPLS network, you can adjust the priority of an MPLS traffic flow by marking its EXP value. For more information about priority marking, see "Configuring priority marking."

Restrictions and guidelines

The remark mpls-exp command takes effect only when the QoS policy is applied to the inbound direction and modifies the EXP values in all labels.

Procedure

1.     Enter system view.

system-view

2.     Define a traffic class.

a.     Create a traffic class and enter traffic class view.

traffic classifier classifier-name [ operator { and | or } ]

b.     Configure match criteria for the traffic class. Choose the options to configure as needed:

-     if-match mpls-exp exp-value&<1-8>

-     if-match second-mpls-exp exp-value&<1-8>

-     if-match mpls-label { label-value&<1-8> | label-value1 to label-value2 }

-     if-match second-mpls-label { label-value&<1-8> | label-value1 to label-value2 }

By default, no match criteria are configured.

The match criteria apply only to MPLS packets.

c.     Return to system view.

quit

3.     Define a traffic behavior.

a.     Create a traffic behavior and enter traffic behavior view.

traffic behavior behavior-name

b.     Configure an EXP marking action in the traffic behavior. Choose the options to configure as needed:

-     remark mpls-exp exp-value

By default, no EXP marking action is configured.

c.     Return to system view.

quit

4.     Define a QoS policy.

a.     Create a QoS policy and enter QoS policy view.

qos policy policy-name

b.     Associate the traffic class with the traffic behavior in the QoS policy.

classifier classifier-name behavior behavior-name

By default, no traffic behavior is associated with a traffic class.

c.     Return to system view.

quit

5.     Apply the QoS policy.

For more information, see "Configuring a QoS policy."

Appendixes

Appendix A Default priority maps

Table 1 Default dscp-exp priority map

Table 2 Default exp-dscp map

Table 3 Default ippre-exp priority map

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