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Class of Service

  • Queue-depth monitoring support for virtual output queues (PTX10001-36MR, PTX10004, PTX10008, and PTX10016)—Virtual output queue (VOQ) queue-depth monitoring, or latency monitoring, measures peak queue occupancy of a VOQ. Starting with Junos OS Evolved Release 22.2R1, PTX Series routers running Junos OS Evolved support VOQ queue-depth monitoring to report peak queue length for a given physical interface for each individual Packet Forwarding Engine.

    [See VOQ Queue-depth Monitoring.]

  • CoS support for EVPN-VXLAN (PTX10001-36MR, PTX10004, PTX10008, and PTX10016)—Starting in Junos Evolved OS Release 22.2R1, you can configure CoS features to prioritize traffic on an Ethernet VPN-Virtual Extensible LAN (EVPN-VXLAN) fabric.

    [See Implementing CoS on VXLAN Interfaces (Junos OS Evolved).]

  • Support for CoS within MPLS networks (QFX5220)—Starting in Junos OS Evolved Release 22.2R1, you can use CoS within MPLS networks to prioritize certain types of traffic during periods of congestion by applying packet classifiers and rewrite rules to the MPLS traffic. We have also added MPLS EXP rewrite support.

    • Default CoS on the provider (P) and provider edge (PE) routers for MPLS interfaces–The MPLS traffic uses the default EXP classifier. MPLS traffic is treated as best-effort traffic using the 802.1 default untrusted classifier. The default EXP classifier applies to all MPLS traffic on interfaces configured as family mpls. Differentiated Services code point (DSCP) classifiers are not applied to MPLS traffic.

    • Default CoS on PE routers for Layer 3 interfaces–By default, all Layer 3 VPN logical interfaces are bound to default DSCP classifiers.

    If you apply an EXP classifier on a penultimate-hop popping (PHP) node, then by default, the MPLS header TLL value overwrites the IP header time-to-live (TTL) value. In this case, a zero (0) overwrites the IP header DSCP bits, which signifies uniform mode. To use pipe mode, where nothing overwrites IP header TTL values or IP header DSCP bits, you should configure the following command:

    set protocols mpls no-propagate-ttl


    The DSCP of IP in MPLS packets can’t be remarked either at PE or P routers.

    [See Understanding CoS MPLS EXP Classifiers and Rewrite Rules.]

  • Support for BGP flowspec DSCP action (PTX Series)—Starting in Junos OS Evolved Release 22.2R1, you can configure mapping rules to translate a Differentiated Services code point (DSCP) value in the BGP flowspec (set DSCP action) into forwarding classes. With the mapping option enabled, you can change forwarding behavior, CoS treatment, and control EXP or DSCP rewrite of the packets. You can control rewrite of the packets using rewrite rules on a platform that does not support direct DSCP rewrite capability in a filter.