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Class of Service

  • Support for ToS/DSCP rewrite option protocol (PTX and QFX)—Starting in Junos OS Release 21.4R1, you can mark IP ToS bits when IP packets enter MPLS tunnel during MPLS push events, by enabling the CoS rewrite feature 'protocol mpls' in your PTX Series and QFX Series devices. By enabling this configuration, you ensure that dedicated Internet access (DIA) traffic is not treated with QoS across the core of the network.
  • [See Routing Policies, Firewall Filters, and Traffic Policers]
  • Support for CoS in EVPN-VXLAN topology (QFX5210)—Starting in Junos OS Release 21.4R1, you can configure CoS on a QFX5210 L3 VXLAN gateway in an EVPN-VXLAN fabric. However, this configuration presents a few limitations:
    • For uniform packet classification within the system, both the access port and the loopback port must have the same behavior aggregate (BA) or fixed classifier.
    • If traffic from multiple access port converges on the same loopback port and if some of the access-port traffic needs a different classification, then you must apply a multifield classifier on the loopback port for the traffic of interest.
    • PFC (both IEEE and DSCP based) is not supported as PFC backpressure will not reach the access port from network port due to the loopback port design.
    • If you need a classifier on the network port (DSCP), you must have the same classifier on the network, loopback, and access ports, as network-to-access traffic also goes through the same loopback port.
    • Other general VxLAN CoS limitations applicable for all QFX5000 switches apply to the QFX5210.
    [See Understanding CoS on OVSDB-Managed VXLAN Interfaces and CoS Support on EVPN VXLANs]