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Example: Configuring Queue Scheduling Priority
You can configure the bandwidth scheduling priority of individual queues by specifying the priority in a scheduler, and then using a scheduler map to associate the scheduler with a queue.
Configuring Queue Scheduling Priority
CLI Quick Configuration
To quickly configure queue scheduling priority, 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 fcoe-sched priority low set schedulers nl-sched priority low set scheduler-maps schedmap1 forwarding-class fcoe scheduler fcoe-sched set scheduler-maps schedmap1 forwarding-class no-loss scheduler nl-sched
Step-by-Step Procedure
To configure queue priority using the CLI:
Create the FCoE scheduler with
lowpriority:[edit class-of-service] user@switch# set schedulers fcoe-sched priority low
Create the no-loss scheduler with
lowpriority:[edit class-of-service] user@switch# set schedulers nl-sched priority low
Associate the schedulers with the desired queues in the scheduler map:
[edit class-of-service] user@switch# set scheduler-maps schedmap1 forwarding-class fcoe scheduler fcoe-sched user@switch# set scheduler-maps schedmap1 forwarding-class no-loss scheduler nl-sched
Requirements
This example uses the following hardware and software components:
One QFX switch
Any supported Junos release
Overview
Queues can have one of several bandwidth priorities:
-
strict-high—Strict-high priority allocates bandwidth to the queue before any other queue receives bandwidth. Other queues receive the bandwidth that remains after the strict-high queue has been serviced.Note:If you configure strict-high priority queues on a port, we strongly recommend that you configure a transmit rate (for QFX10000 Series switches) or a shaping rate (non-QFX10000 Series switches) on those queues. The transmit rate or shaping rate sets the amount of traffic that the switch forwards as strict-high priority; traffic in excess of the transmit rate or shaping rate is treated as best-effort traffic that receives the queue excess rate. Even if you configure only one strict-high priority queue, we strongly recommend that you configure a transmit rate or shaping rate on the queue to prevent it from starving other queues. If you do not configure a transmit rate or shaping rate to limit the amount of bandwidth a strict-high priority queue can use, then the strict-high priority queue can use all of the available port bandwidth and starve other queues on the port.
Note:On switches that support enhanced transmission selection (ETS) hierarchical scheduling, if you use ETS and you configure a
strict-highpriority queue, you must create a forwarding class set that is dedicated only tostrict-highpriority traffic. Only one forwarding class set can contain a strict-high priority queue. Queues that are not strict-high priority cannot belong to the same forwarding class set as strict-high priority queues.On switches that use different output queues for unicast and multidestination traffic, the multidestination forwarding class set cannot contain strict-high priority queues.
high—High priority. Traffic with high priority is serviced after any queue that has astrict-highpriority, and before queues with low priority.low—Low priority. Traffic with low priority is serviced after any queue that has astrict-highpriority.
By default, all queues are low priority queues.
Table 1 shows the configuration components for this example.
This example describes how to set the queue priority for two forwarding classes (queues) named fcoe and no-loss. Both queues have a priority of low. The scheduler for the fcoe queue is named fcoe-sched and the scheduler for the no-loss queue is named nl-sched. One scheduler map, schedmap1, associates the schedulers to the queues.
Component |
Settings |
|---|---|
Hardware |
One switch |
Schedulers |
|
Priority |
|
Scheduler map |
FCoE mapping: scheduler No-loss mapping: scheduler |
Verification
To verify that you configured the queue scheduling priority for bandwidth and mapped the schedulers to the correct forwarding classes, perform these tasks:
- Verifying the Queue Scheduling Priority
- Verifying the Scheduler-to-Forwarding-Class Mapping
- Platform-Specific Behavior
Verifying the Queue Scheduling Priority
Purpose
Verify that you configured the queue schedulers fcoe-sched and nl-sched with low queue scheduling priority.
Action
Display the fcoe-sched scheduler priority configuration using the operational mode command show configuration class-of-service schedulers fcoe-sched priority:
user@switch> show configuration class-of-service schedulers fcoe-sched priority priority low;
Display the nl-sched scheduler priority configuration using the operational mode command show configuration class-of-service schedulers nl-sched priority:
user@switch> show configuration class-of-service schedulers nl-sched priority priority low;
Verifying the Scheduler-to-Forwarding-Class Mapping
Purpose
Verify that you configured the scheduler map schedmap1 to map scheduler fcoe-sched to forwarding class fcoe and schedule nl-sched to forwarding class no-loss.
Action
Display the scheduler map schedmap1 using the operational mode command show configuration class-of-service scheduler-maps schedmap1:
user@switch> show configuration class-of-service scheduler-maps schedmap1 forwarding-class fcoe scheduler fcoe-sched; forwarding-class no-loss scheduler nl-sched;
Platform-Specific Behavior
Use the following table to review platform-specific behaviors for your platforms.
|
Platform |
Difference |
|---|---|
|
QFX5000 Series and EX4600 |
|
|
QFX10000 Series |
|