11-ACL and QoS Configuration Guide

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03-MPLS QoS configuration
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03-MPLS QoS configuration 58.73 KB

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:

·     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 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 CAR

About this task

A CAR policy for traffic entering an MPLS network performs the following operations:

·     Limits the transmission rate to avoid network congestion.

·     Marks priority for the traffic.

For more information about configuring traffic policing, see "Configuring traffic policing, GTS, and rate limit."

Procedure

1.     Enter system view.

system-view

2.     Enter interface view.

interface interface-type interface-number

3.     Configure an MPLS CAR policy for the interface.

qos car { inbound | outbound } { any | acl [ ipv6 ] acl-number | carl carl-index } cir committed-information-rate [ cbs committed-burst-size [ ebs excess-burst-size ] ] [ green action | red action | yellow action ] *

qos car { inbound | outbound } { any | acl [ ipv6 ] acl-number | carl carl-index } cir committed-information-rate [ cbs committed-burst-size ] pir peak-information-rate [ ebs excess-burst-size ] [ green action | red action | yellow action ] *

By default, no CAR policy is configured for an interface.

The action argument for MPLS can be either of the following options:

¡     remark-mpls-exp-continue new-exp: Sets the EXP value to new-exp and continues to process the packet using the next CAR policy. The new-exp is in the range of 0 to 7.

¡     remark-mpls-exp-pass new-exp: Sets the EXP value to new-exp and permits the packet to pass through. The new-exp is in the range of 0 to 7.

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."

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.

-     if-match [ not ] mpls-exp exp-value&<1-8>

-     if-match [ not ] second-mpls-exp exp-value&<1-8>

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

-     remark second-mpls-exp exp-value

By default, no 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."