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Example: Configuring Traffic Control Profiles (Priority Group Scheduling)

Requirements

• 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 priority group 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 priority group can share. Extra port bandwidth is allocated among the priority groups on a port in proportion to the guaranteed rate of each priority group.

  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 priority group. If a priority group does not have a guaranteed minimum bandwidth, the queues (forwarding classes) that belong to the priority group 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 priority group 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 priority group bandwidth, not the amounts or percentages of total link bandwidth.)

Note: Because a port can have more than one priority group, when you assign resources to a priority group, keep in mind that the total port bandwidth must serve all of the queues associated with that port. For example, if you map three priority groups to a 10-Gigabit Ethernet port, the queues associated with all three of the priority groups share the 10-Gbps bandwidth as defined by the traffic control profiles. Therefore, the total combined guaranteed-rate value of the three priority groups 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 queue (forwarding class) transmit rates cannot exceed the total guaranteed-rate of the priority group to which the queues belong. If you configure transmit rates whose sum exceeds the priority group guaranteed rate, the commit check fails and the system rejects the configuration. If you configure the guaranteed-rate of a priority group as a percentage, configure all of the transmit rates associated with that priority group 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

1. Create the traffic control profile and set the guaranteed-rate (minimum guaranteed bandwidth) to 4g:
   [edit class-of-service]
user@switch# set traffic-control-profiles san-tcp guaranteed-rate 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 the traffic control profile san-tcp has been created 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:

scheduler-map san-map1;
shaping-rate percent 8g;
guaranteed-rate 4g;