Dell OS10 QoS: Trust Maps and Queue Scheduling

OS10 QoS is a three-stage pipeline - classify on ingress, act on ingress, then schedule on egress - and each stage has its own object type. Getting the objects right is the difference between a policy that does what the diagram says and one that silently does nothing because the service policy was applied in the wrong direction. This guide covers trust modes and trust maps, ingress class-maps and policy-maps, egress queuing with weighted deficit round robin or strict priority, and the verification commands that confirm classification is actually happening.

Trust first: decide what to believe

OS10(config)# trust-map dscp MY-DSCP-MAP
OS10(config-tmap-dscp)# dscp 46 qos-group 5
OS10(config-tmap-dscp)# dscp 34 qos-group 4
OS10(config-tmap-dscp)# exit

OS10(config)# interface ethernet1/1/1
OS10(conf-if-eth1/1/1)# trust-map dscp MY-DSCP-MAP
OS10(conf-if-eth1/1/1)# exit

A trust map translates an incoming DSCP or CoS value into an internal traffic class (traffic class ID). Trusting on an access port lets an endpoint's markings influence scheduling, which is only safe if you control the endpoints - otherwise a workstation can mark all of its traffic as voice. The conservative pattern for user-facing ports is to trust nothing, classify by policy, and mark explicitly.

Classify on ingress

OS10(config)# class-map type qos match-any CM-VOICE
OS10(config-cmap-qos)# match dscp 46
OS10(config-cmap-qos)# exit

OS10(config)# policy-map type qos PM-INGRESS
OS10(config-pmap-qos)# class CM-VOICE
OS10(config-pmap-c-qos)# set qos-group 5
OS10(config-pmap-c-qos)# exit
OS10(config-pmap-qos)# exit

OS10(config)# interface ethernet1/1/10
OS10(conf-if-eth1/1/10)# service-policy input type qos PM-INGRESS

Ingress QoS policies are applied in the input direction on physical interfaces or through system-qos. A qos-group value set here follows the packet through the switch and becomes the basis for egress queue selection.

Schedule on egress

OS10(config)# class-map type queuing CM-QUEUE-5
OS10(config-cmap-queuing)# match queue 5
OS10(config-cmap-queuing)# exit

OS10(config)# policy-map type queuing PM-EGRESS
OS10(config-pmap-queuing)# class CM-QUEUE-5
OS10(config-pmap-c-que)# priority
OS10(config-pmap-c-que)# exit
OS10(config-pmap-queuing)# class class-default
OS10(config-pmap-c-que)# bandwidth percent 20
OS10(config-pmap-c-que)# exit
OS10(config)# interface ethernet1/1/49
OS10(conf-if-eth1/1/49)# service-policy output type queuing PM-EGRESS

Queuing policies are applied in the output direction. Two constraints matter: bandwidth percent and priority are mutually exclusive on the same queue, and the scheduler is WDRR by default (a deficit counter allocates bandwidth between non-priority queues). Use strict priority sparingly - a high-volume priority queue can starve everything else - and cap it with a policer or explicit shape where the platform supports it.

Congestion avoidance

OS10(config)# wred WRED-ECN
OS10(config-wred)# random-detect ecn
OS10(config-wred)# random-detect min-threshold 200 max-threshold 1200
OS10(config-wred)# exit

OS10(config-pmap-c-que)# random-detect WRED-ECN

WRED drops or marks packets before a queue is full, and with ECN enabled it signals congestion to TCP instead of dropping. This is essential for lossless RoCE fabrics and useful for any congestion-sensitive workload.

Verify the whole chain

OS10# show class-map
OS10# show policy-map
OS10# show qos system
OS10# show qos system buffers
OS10# show queuing statistics interface ethernet1/1/49

Confirm four things: the class-map matches what you intended, the policy-map is bound to the right interface and direction, the queuing statistics show non-zero counters in the expected queue, and the trust map is present on the ingress port. A policy bound in the wrong direction produces no error at configuration time and no effect at runtime - which is why the statistics check is mandatory rather than optional.

Related: Dell OS10 VRRP configuration, OS10 VLT troubleshooting, and the cross-vendor view in H3C Comware priority trust and mapping.

原文链接：https://www.dell.com/support/manuals/en-gt/dell-emc-smartfabric-os10/smartfabric-os-user-guide-10-5-0/configure-quality-of-service