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Configuring CoS on 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 now 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.

For this procedure, we assume that the switch has already been configured for MPLS. See Configuring MPLS on Provider Edge Switches Using IP Over MPLS (CLI Procedure).

  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 dscp1 import default
  2. Add the expedited-forwarding class to this custom DSCP classifier, specifying a loss priority and code point:

    [edit class-of-service]
    user@switch#set classifiers dscp dscp1 forwarding-class expedited-forwarding loss-priority low code-points 000111
  3. Specify the values for the custom EXP rewrite rule, e1:

    [edit class-of-service]
    user@switch# set rewrite-rules exp e1 forwarding-class expedited-forwarding loss-priority low code-point 111
  4. 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]
    set policer mypolicer if-exceeding bandwidth-limit 500m
  5. Specify the maximum size permitted for bursts of data that exceed the given bandwidth limit for this policer:

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

    [edit firewall policer]
    set mypolicer then discard
  7. 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
  8. Apply the filter to the customer-edge interface:

    [edit interfaces]
    user@switch# set ge-2/0/3 unit 0 family inet address 121.121.121.1/16 policing filter myfilter

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


Published: 2010-01-13

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