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Example: Configuring Traffic Control Profiles (Priority Group Scheduling)

 

A traffic control profile defines the output bandwidth and scheduling characteristics of forwarding class sets (priority groups). The forwarding classes (queues) mapped to a forwarding class set share the bandwidth resources that you configure in the traffic control profile. A scheduler map associates forwarding classes with schedulers to define how the individual queues in a forwarding class set share the bandwidth allocated to that forwarding class set.

Requirements

This example uses the following hardware and software components:

  • A Juniper Networks QFX3500 Switch

  • Junos OS Release 11.1 or later for the QFX Series

Overview

The parameters you configure in a traffic control profile define the following characteristics for the priority group:

  • guaranteed-rate—Minimum bandwidth, also known as the committed information rate (CIR). Each fc-set receives a minimum of either the configured amount of absolute bandwidth or the configured percentage of bandwidth. The guaranteed rate also determines the amount of excess (extra) port bandwidth that the fc-set can share. Extra port bandwidth is allocated among the fc-sets on a port in proportion to the guaranteed rate of each fc-set.

    Note

    In order for the transmit-rate option (minimum bandwidth for a queue that you set using scheduler configuration) to work properly, you must configure the guaranteed-rate for the fc-set. If an fc-set does not have a guaranteed minimum bandwidth, the forwarding classes that belong to the fc-set cannot have a guaranteed minimum bandwidth.

    Note

    Include the preamble bytes and interframe gap bytes as well as the data bytes in your bandwidth calculations.

  • shaping-rate—Maximum bandwidth, also known as the peak information rate (PIR). Each fc-set receives a maximum of the configured amount of absolute bandwidth or the configured percentage of bandwidth, even if more bandwidth is available.

    Note

    Include the preamble bytes and interframe gap bytes as well as the data bytes in your bandwidth calculations.

  • scheduler-map—Bandwidth and scheduling characteristics for the queues, defined by mapping forwarding classes to schedulers. (The queue scheduling characteristics represent amounts or percentages of the fc-set bandwidth, not the amounts or percentages of total link bandwidth.)

Note

Because a port can have more than one fc-set, when you assign resources to an fc-set, keep in mind that the total port bandwidth must serve all of the queues associated with that port.

For example, if you map three fc-sets to a 10-Gigabit Ethernet port, the queues associated with all three of the fc-sets share the 10-Gbps bandwidth as defined by the traffic control profiles. Therefore, the total combined guaranteed-rate value of the three fc-sets should not exceed 10 Gbps. If you configure guaranteed rates whose sum exceeds the port bandwidth, the system sends a syslog message to notify you that the configuration is not valid. However, the system does not perform a commit check. If you commit a configuration in which the sum of the guaranteed rates exceeds the port bandwidth, the hierarchical scheduler behaves unpredictably.

The sum of the forwarding class (queue) transmit rates cannot exceed the total guaranteed-rate of the fc-set to which the forwarding classes belong. If you configure transmit rates whose sum exceeds the fc-set guaranteed rate, the commit check fails and the system rejects the configuration.

If you configure the guaranteed-rate of an fc-set as a percentage, configure all of the transmit rates associated with that fc-set as percentages. In this case, if any of the transmit rates are configured as absolute values instead of percentages, the configuration is not valid and the system sends a syslog message.

Configuring a Traffic Control Profile

This example describes how to configure a traffic control profile named san-tcp with a scheduler map named san-map1 and allocate to it a minimum bandwidth of 4 Gbps and a maximum bandwidth of 8 Gbps:

  1. Create the traffic control profile and set the guaranteed-rate (minimum guaranteed bandwidth) to 4g:
  2. Set the shaping-rate (maximum guaranteed bandwidth) to 8g:
    [edit class-of-service]

    user@switch# set traffic-control-profiles san-tcp shaping-rate 8g
  3. Associate the scheduler map san-map1 with the traffic control profile:
    [edit class-of-service]

    user@switch# set traffic-control-profiles san-tcp scheduler-map san-map1

Verification

Verifying the Traffic Control Profile Configuration

Purpose

Verify that you created the traffic control profile san-tcp with a minimum guaranteed bandwidth of 4 Gbps, a maximum bandwidth of 8 Gbps, and the scheduler map san-map1.

Action

List the traffic control profile using the operational mode command show configuration class-of-service traffic-control-profiles san-tcp:

user@switch> show configuration class-of-service traffic-control-profiles san-tcp