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Configuring CoS on an MPLS Provider Edge Switch Using IP Over MPLS (CLI Procedure)

 

You can use class of service (CoS) within MPLS networks to prioritize certain types of traffic during periods of congestion. This topic describes configuring CoS components on a provider edge (PE) switch that is using IP Over MPLS.

This task describes how to create a custom DSCP classifier and a custom EXP rewrite rule on the ingress PE switch. It includes configuring a policer firewall filter and applying it to the customer-edge interface of the ingress PE switch. The policer firewall filter ensures that the amount of traffic forwarded through the MPLS tunnel never exceeds the requested bandwidth allocation.

Before you begin, configure the basic components for an MPLS network:

This topic includes:

Configuring CoS

To configure CoS on a provider edge switch:

  1. Import the default DSCP classifier classes to the custom DSCP classifier that you are creating:
    [edit class-of-service]

    user@switch# set classifiers dscp classifier-name import default
  2. Add a forwarding class to this custom DSCP classifier and specify a loss priority and code point:
    [edit class-of-service]

    user@switch# set classifiers dscp classifier-name forwarding-class forwarding-class loss-priority loss-priority code-points code-point
  3. Specify the values for the custom EXP rewrite rule, e1:
    [edit class-of-service]

    user@switch# set rewrite-rules exp e1 forwarding-class forwarding-class loss-priority loss-priority code-points code-point
  4. On EX8200 switches only, bind the custom EXP rewrite rule to the interface:
    [edit class-of-service]

    user@switch# set class-of-service interfaces interface unit unit rewrite-rules exp e1

Configuring an LSP Policer

To configure an LSP policer:

Note

You cannot configure LSP policers on EX8200 switches. EX8200 switches do not support LSP policers.

  1. Specify the number of bits per second permitted, on average, for the firewall policer, which will later be applied to the customer-edge-interface:
    [edit firewall]

    user@switch# set policer mypolicer if-exceeding bandwidth-limit 500m
  2. Specify the maximum size permitted for bursts of data that exceed the given bandwidth limit for this policer:
    [edit firewall policer]

    user@switch# set mypolicer if-exceeding burst-size-limit 33553920
  3. Discard traffic that exceeds the rate limits for this policer:
    [edit firewall policer]

    user@switch# set mypolicer then discard
  4. To reference the policer, configure a filter term that includes the policer action:
    [edit firewall]

    user@switch# set family inet filter myfilter term t1 then policer mypolicer
  5. Apply the filter to the customer-edge interface:
    [edit interfaces]

    user@switch# set ge-2/0/3 unit 0 family inet address 192.168.121.1/16 policing filter myfilter
Note

You can also configure schedulers and shapers as needed. See Defining CoS Schedulers and Scheduler Maps (CLI Procedure).