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priority (Schedulers)


Hierarchy Level


Specify the packet-scheduling priority value.



Available options can vary by platform and software release.

priority-level can be one of the following:

  • low—Scheduler has low priority.

  • medium-low—Scheduler has medium-low priority.

  • medium-high—Scheduler has medium-high priority.

  • high—Scheduler has high priority. Assigning high priority to a queue prevents the queue from being underserved.

  • strict-high—Scheduler has strictly high priority. Configure a high priority queue with unlimited transmission bandwidth available to it. As long as it has traffic to send, the strict-high priority queue receives precedence over low, medium-low, and medium-high priority queues, but not high priority queues. You can configure strict-high priority on only one queue per interface.

  • low-latency—Scheduler has low latency queuing (LLQ) priority. LLQ enables delay-sensitive data to have preferential treatment over other traffic. A queue configured as a low latency queue has the highest priority over any other priority queues, including strict-high queues.

Required Privilege Level

interface—To view this statement in the configuration.

interface-control—To add this statement to the configuration.

Platform Information

  • ACX7000 Series routers running Junos OS Evolved support all six levels of priority, including low-latency.

  • On EX4400 switches, applying strict-high priority schedulers to queues 0 through 3 also applies strict-high priority to queues 8 through 11. Therefore, Juniper recommends applying strict-high priority schedulers only to queues 4 through 7.

  • On QFX10000 switches, you can configure as many strict-high priority queues as you want. On QFX10000 switches, we strongly recommend that you apply a transmit rate to strict-high priority queues to prevent them from starving other queues. A transmit rate configured on a strict-high priority queue limits the amount of traffic that receives strict-high priority treatment to the amount or percentage set by the transmit rate.

  • On QFX5100 and EX4600 switches, you can configure only one queue as a strict-high priority queue. We recommend that you always apply a shaping rate to strict-high priority queues to prevent them from starving other queues. A shaping rate (shaper) sets the maximum amount of bandwidth a queue can consume. (Unlike using the transmit rate on a QFX10000 switch to limit traffic that receives strict-high priority treatment, traffic that exceeds the shaping rate is dropped, and is not treated as best-effort traffic that shares in excess bandwidth.) If you do not apply a 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.

Release Information

Statement introduced before Junos OS Release 7.4.

low-latency support introduced for Junos OS Evolved Release 23.4R1.