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CoS on ACX Series Routers Features Overview


Unless otherwise noted in the following topics, CoS on ACX Series Universal Metro Routers functions the same as CoS on other routers, and information common CoS functionality can be found in the Configuring Class of Service section of Class of Service User Guide (Routers and EX9200 Switches).

CoS on ACX routers running Junos OS

The following key CoS features are supported on ACX Series Universal Metro Routers:

  • Physical interface-based classifiers at the [edit class-of-service interfaces interfaces-name] hierarchy level

  • Fixed classification for all ingress packets traversing a logical interface to a single forwarding class. Fixed classification is supported on all interface types.

  • EXP bits located in each MPLS label and used to encode the CoS value of a packet as it traverses a label-switched path (LSP). To configure global EXP bits, include the exp statement at the [edit class-of-service system-defaults classifiers] hierarchy level.

  • Rewrite rules at the physical and logical interface levels including the following: IP type-of-service (ToS), DSCP, MPLS EXP bit value, and IEEE 802.1p bit value.

  • Attachment of the following rewrite rules to the physical interface at the [edit class-of-service interfaces interface-name rewrite-rules] hierarchy level: IP ToS, DSCP, and IEEE 802.1p bit value.

  • Rewrite rules for MPLS EXP bits on the logical interface at the [edit class-of-service interfaces interface-name unit unit-number rewrite-rule] hierarchy level.


    Fine-grained rewrite is not possible, even when you use multifield filters, because of the application-specific integrated circuit (ASIC) limitation.

Queuing and scheduling features include:

  • Support for up to eight forwarding classes.

  • Support for up to eight egress queues per port.

  • Internal buffer of 2 MB with per-egress queue buffer management.

  • Three weighted random early detection (WRED) curves for TCP and one WRED curve for non-TCP. There are two fill levels and two drop probabilities per WRED curve; the drop probability corresponding to the first fill must be zero.

  • Strict-priority and weighted deficit round-robin scheduling.

  • Multiple strict-priority queues per port.

  • Per-queue committed information rate (CIR) and peak information rate (PIR).

  • Per-physical-port shaping.

Queue statistics features include:

  • Per-egress-queue enqueue statistics in packets, bytes, packets per second (pps), and bits per second (bps).

  • Per-egress-queue transmit statistics in packets, bytes, pps, and bps.

  • Per-egress-queue drop statistics in packets and pps.

CoS on ACX routers running Junos OS Evolved

ACX7000 Series routers support the following CoS features:

  • Behavior aggregate (BA) classifiers (Inet-Prec/DSCP/DSCP-v6/EXP/IEEE-802.1p/IEEE-802.1ad) at the logical interface level

  • Fixed and multifield classifiers

  • Maximum of eight forwarding classes

  • Eight virtual output queues (VOQ) per port

  • Two scheduling priority levels - strict-high and low

  • Multiple strict-high priority queues with round robin (RR) scheduling

  • Multiple low priority queues with weighted fair queue (WFQ) scheduling

  • CIR and PIR for low priority queues

  • PIR at the port level

  • Rewrite rules (Inet-Prec/DSCP/DSCP-v6/EXP/IEEE-802.1p/IEEE-802.1ad) at the logical interface level


ACX routers running Junos OS Evolved do not support the following CLI show commands:

  • show class-of-service forwarding-table
  • show class-of-service routing-instance
  • show class-of-service system-defaults