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{ "lLangCode": "en", "lName": "English", "lCountryCode": "us", "transcode": "en_US" }
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Configuring CoS on an MPLS Provider Edge Switch Using IP Over MPLS

date_range 14-Dec-23

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:

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:
    content_copy zoom_out_map
    [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:
    content_copy zoom_out_map
    [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:
    content_copy zoom_out_map
    [edit class-of-service]
    user@switch# set rewrite-rules exp e1 forwarding-class forwarding-class loss-priority loss-priority code-points code-point

Configuring an LSP Policer

To configure an LSP policer:

  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:
    content_copy zoom_out_map
    [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:
    content_copy zoom_out_map
    [edit firewall policer]
    user@switch# set mypolicer if-exceeding burst-size-limit 33553920
  3. Discard traffic that exceeds the rate limits for this policer:
    content_copy zoom_out_map
    [edit firewall policer]
    user@switch# set mypolicer then discard
  4. To reference the policer, configure a filter term that includes the policer action:
    content_copy zoom_out_map
    [edit firewall]
    user@switch# set family inet filter myfilter term t1 then policer mypolicer
  5. Apply the filter to the customer-edge interface:
    content_copy zoom_out_map
    [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).

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