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Example: Configuring Minimum Guaranteed Output Bandwidth
Scheduling the minimum guaranteed output bandwidth for a queue (forwarding class) requires configuring both tiers of the two-tier hierarchical scheduler. One tier is scheduling the resources for the individual queue. The other tier is scheduling the resources for the priority group (forwarding class set) to which the queue belongs. You set a minimum guaranteed bandwidth to ensure than priority groups and queues receive the bandwidth required to support the expected traffic.
Configuring Guaranteed Minimum Bandwidth
CLI Quick Configuration
To quickly configure the minimum guaranteed bandwidth for a priority group and a queue, copy the following commands, paste them in a text file, remove line breaks, change variables and details to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level:
[edit class-of-service] set schedulers be-sched transmit-rate 2g set traffic-control-profiles be-tcp guaranteed-rate 4g set scheduler-maps be-map forwarding-class best-effort scheduler be-sched set traffic-control-profiles be-tcp scheduler-map be-map set forwarding-class-sets be-pg class best-effort set interfaces xe-0/0/7 forwarding-class-set be-pg output-traffic-control-profile be-tcp
Step-by-Step Procedure
To configure the minimum guaranteed bandwidth hierarchical scheduling for a queue and a priority group:
Configure the minimum guaranteed queue bandwidth of 2 Gbps for scheduler
be-sched:[edit class-of-service schedulers] user@switch# set be-sched transmit-rate 2g
Configure the minimum guaranteed priority group bandwidth of 4 Gbps for traffic control profile
be-tcp:[edit class-of-service traffic-control-profiles] user@switch# set be-tcp guaranteed-rate 4g
Associate the scheduler
be-schedwith thebest-effortqueue in the scheduler mapbe-map:[edit class-of-service scheduler-maps] user@switch# set be-map forwarding-class best-effort scheduler be-sched
Associate the scheduler map with the traffic control profile:
[edit class-of-service traffic-control-profiles] user@switch# set be-tcp scheduler-map be-map
Assign the
best-effortqueue to the priority groupbe-pg:[edit class-of-service forwarding-class-sets] user@switch# set be-pg class best-effort
Apply the configuration to interface
xe-0/0/7:[edit class-of-service interfaces] user@switch# set xe-0/0/7 forwarding-class-set be-pg output-traffic-control-profile be-tcp
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 or Junos OS Release 14.1X53-D20 or later for the OCX Series
Overview
The priority group minimum guaranteed bandwidth defines the minimum total amount of bandwidth available for all of the queues in the priority group to meet their minimum bandwidth requirements.
The transmit-rate setting in the scheduler configuration determines the minimum guaranteed bandwidth for an individual queue. The transmit rate also determines the amount of excess (extra) priority group bandwidth that the queue can share. Extra priority group bandwidth is allocated among the queues in the priority group in proportion to the transmit rate of each queue.
The guaranteed-rate setting in the traffic control profile configuration determines the minimum guaranteed bandwidth for a priority group. 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.
You must configure both the transmit-rate value for the queue and the guaranteed-rate value for the priority group to set a valid minimum bandwidth guarantee for a queue. (If the priority group does not have a guaranteed minimum bandwidth, there is no guaranteed bandwidth pool from which the queue can take its guaranteed minimum bandwidth.)
The sum of the queue transmit rates in a priority group should not exceed the guaranteed rate for the priority group. (You cannot guarantee a minimum bandwidth for the queues that is greater than the minimum bandwidth guaranteed for the entire set of queues.)
When you configure bandwidth for a queue or a priority group, the switch considers only the data as the configured bandwidth. The switch does not account for the bandwidth consumed by the preamble and the interframe gap (IFG). Therefore, when you calculate and configure the bandwidth requirements for a queue or for a priority group, consider the preamble and the IFG as well as the data in the calculations.
You cannot configure minimum guaranteed bandwidth on strict-high priority queues or on a priority group that contains strict-high priority queues.
This example describes how to:
Configure a transmit rate (minimum guaranteed queue bandwidth) of 2 Gbps for queues in a scheduler named
be-sched.Configure a guaranteed rate (minimum guaranteed priority group bandwidth) of 4 Gbps for a priority group in a traffic control profile named
be-tcp.Assign the scheduler to a queue named
best-effortby using a scheduler map namedbe-map.Associate the scheduler map
be-mapwith the traffic control profilebe-tcp.Assign the queue
best-effortto a priority group namedbe-pg.Assign the priority group and the minimum guaranteed bandwidth scheduling to the egress interface
xe-0/0/7.
Table 1 shows the configuration components for this example:
Component |
Settings |
|---|---|
Hardware |
QFX3500 switch |
Minimum guaranteed queue bandwidth |
Transmit rate: |
Minimum guaranteed priority group bandwidth |
Guaranteed rate: |
Scheduler |
|
Scheduler map |
|
Traffic control profile |
|
Forwarding class set (priority group) |
|
Queue (forwarding class) |
|
Egress interface |
|
Verification
To verify the minimum guaranteed output bandwidth configuration, perform these tasks:
- Verifying the Minimum Guaranteed Queue Bandwidth
- Verifying the Priority Group Minimum Guaranteed Bandwidth and Scheduler Map Association
- Verifying the Scheduler Map Configuration
- Verifying Queue (Forwarding Class) Membership in the Priority Group
- Verifying the Egress Interface Configuration
Verifying the Minimum Guaranteed Queue Bandwidth
Purpose
Verify that you configured the minimum guaranteed queue bandwidth as 2g in the scheduler be-sched.
Action
Display the minimum guaranteed bandwidth in the be-sched scheduler configuration using the operational mode command show configuration class-of-service schedulers be-sched transmit-rate:
user@switch> show configuration class-of-service schedulers be-sched transmit-rate 2g;
Verifying the Priority Group Minimum Guaranteed Bandwidth and Scheduler Map Association
Purpose
Verify that the minimum guaranteed priority group bandwidth is 4g and the attached scheduler map is be-map in the traffic control profile be-tcp.
Action
Display the minimum guaranteed bandwidth in the be-tcp traffic control profile configuration using the operational mode command show configuration class-of-service traffic-control-profiles be-tcp guaranteed-rate:
user@switch> show configuration class-of-service traffic-control-profiles be-tcp guaranteed-rate 4g;
Display the scheduler map in the be-tcp traffic control profile configuration using the operational mode command show configuration class-of-service traffic-control-profiles be-tcp scheduler-map:
user@switch> show configuration class-of-service traffic-control-profiles be-tcp scheduler-map scheduler-map be-map;
Verifying the Scheduler Map Configuration
Purpose
Verify that the scheduler map be-map maps the forwarding class best-effort to the scheduler be-sched.
Action
Display the be-map scheduler map configuration using the operational mode command show configuration class-of-service schedulers maps be-map:
user@switch> show configuration class-of-service scheduler-maps be-map forwarding-class best-effort scheduler be-sched;
Verifying Queue (Forwarding Class) Membership in the Priority Group
Purpose
Verify that the forwarding class set be-pg includes the forwarding class best-effort.
Action
Display the be-pg forwarding class set configuration using the operational mode command show configuration class-of-service forwarding-class-sets be-pg:
user@switch> show configuration class-of-service forwarding-class-sets be-pg class best-effort;
Verifying the Egress Interface Configuration
Purpose
Verify that the forwarding class set be-pg and the traffic control profile be-tcp are attached to egress interface xe-0/0/7.
Action
Display the egress interface using the operational mode command show configuration class-of-service interfaces xe-0/0/7:
user@switch> show configuration class-of-service interfaces xe-0/0/7
forwarding-class-set {
be-pg {
output-traffic-control-profile be-tcp;
}
}