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Class of Service

  • Hierarchical Class of Service (CoS) support (ACX7024, ACX7100-32C, ACX7100-48L, and ACX7509)—Starting with Junos OS Evolved 22.3R1, ACX routers that run Junos OS Evolved support hierarchical CoS. By enabling hierarchical scheduling, an ACX interface running Junos OS Evolved can support three levels of scheduling (physical interfaces, logical interfaces, and queues). ACX routers running Junos OS Evolved do not support hierarchical CoS on integrated bridging and routing (IRB) or aggregated Ethernet interfaces. Also, hierarchical CoS schedulers should not include buffer or drop profile configurations.

    To enable hierarchical scheduling, set hierarchical-scheduler at the [edit interfaces interface-name hierarchy level.

    [See Hierarchical Class of Service in ACX Series Routers.]

  • Priority-based flow control X-ON Threshold and per-queue alpha support (QFX5220)—The priority-based flow control (PFC) X-ON threshold is the ingress port's priority group (PG) shared buffer limit. At this limit, the ingress port's peer resumes transmission of packets after a brief PAUSE because of the PFC message sent by this ingress port. You can tune globally the limit of buffers that each queue can consume from the shared pool based on the dynamic threshold setting called the alpha value. Starting with Junos OS Evolved 22.3R1 on QFX5220 devices, you can fine tune the X-ON threshold through the congestion notification profile (CNP) and fine tune the alpha value on a per-queue basis through a scheduler.

    [See xon (Input Congestion Notification) and buffer-dynamic-threshold .]