Nokia QoS cheat sheet

QoS distinguishes traffic by forwarding class (FC), which maps to per-hop behavior (PHB); Nokia supports eight FCs: NC, EF, AF1-AF4, L1, L2, BE.

The Nokia QoS architecture is hierarchical: ingress classification and marking, then queuing/scheduling at egress; policies can be applied at SAP, subscriber, or network interface level.

Scheduler hierarchy: port scheduler > subscriber/interface scheduler > queue; each level enforces CIR/PIR and priority.

Eight queues per egress port (one per FC); queues can be shaped with CIR and PIR; excess bandwidth distribution is controlled by scheduler weights.

Admission control: policers at ingress limit traffic to contracted rates; shapers at egress shape to line rate or contracted PIR.

QoS policy types: SAP ingress/egress, network ingress/egress, subscriber profile, and slope policies for WRED.

Nokia SR OS uses QoS policies (ingress, egress, slope, scheduler) referenced by service SAPs or network interfaces; policies are applied in a consistent order: classification > policing > queuing > scheduling > shaping.

Forwarding class mapping: dot1p, DSCP, EXP, or IP precedence bits map to FC and profile (in/out); default mappings exist but are configurable.

Ingress classification uses match criteria: dot1p, DSCP, IP precedence, MPLS EXP, or combinations; match lists are applied in order with a default action.

Marking at ingress sets FC and profile (in/out) for internal queuing and may re-mark DSCP/EXP for downstream devices.

Queuing: each FC has a dedicated queue; queue type can be best-effort, expedited (EF), or assured (AF) with WRED thresholds per profile.

WRED slope policy defines min/max average queue depth and drop probability for in-profile and out-of-profile traffic; out-of-profile typically has lower thresholds.

Scheduling: strict priority (SP) or weighted round robin (WRR) per queue; SP queues are served first up to a configured rate.

Egress port scheduler distributes bandwidth among child schedulers using CIR/PIR and priority levels; unused bandwidth is redistributed based on weights.

Policing: ingress policers use srTCM (committed/in excess) or trTCM (peak) to mark or drop out-of-profile packets; Nokia supports color-aware policing.

Queue monitoring: queue statistics (forwarded, dropped, in/out profiles) are available via CLI show commands and telemetry.

QoS policies are defined globally then applied to SAPs (ingress/egress) or network interfaces; a SAP can have separate ingress and egress policies.

SAP ingress policy: classification, policing, marking; SAP egress policy: queue selection, WRED, scheduling.

Subscriber-level QoS: subscriber profiles define aggregate rates and scheduler hierarchy; applied via RADIUS or local configuration.

Service-level enforcement: SLA parameters (CIR, PIR, delay, jitter, loss) are mapped to policers, shapers, and queue thresholds; monitoring verifies compliance.

Policy overrides: per-SAP overrides can adjust queue rates or policer rates without changing the global policy.

Hierarchical scheduling: subscriber scheduler parent to queue group scheduler; ensures aggregate subscriber rate is enforced before per-queue scheduling.

Configuration validation: use 'admin display-config' and 'show qos' commands to verify policy application; commit fails if referenced policies are missing.

Nokia recommends applying egress policies to both SAP and network interfaces to maintain consistent PHB across the network.

Mobile transport: 5G QoS flows are mapped to DSCP/EXP at the gNB and transported over backhaul/midhaul; Nokia routers map QoS Flow Identifier (QFI) to FC.

Fixed transport: GPON/NG-PON uses VLAN priority (802.1p) or DSCP for classification; Nokia ISAM and 7750 SR support hierarchical QoS for residential and business services.

Mobile backhaul: MPLS EXP bits are used for classification; Nokia supports mapping of DSCP to EXP at network ingress.

Network slicing: each slice can have dedicated QoS policies and scheduler resources; Nokia supports slice-aware QoS via SR OS.

Timing-sensitive traffic (e.g., sync) uses high-priority queues (NC or EF) to minimize delay and jitter.

Fixed wireless access (FWA) uses QoS to prioritize latency-sensitive traffic over best-effort; policers enforce per-subscriber rates.

End-to-end QoS requires consistent marking across mobile core, transport, and fixed access; Nokia provides mapping tools for DSCP/EXP/802.1p.

Monitoring tools: queue statistics, policer statistics, and scheduler statistics via CLI (show qos stats) and telemetry (gNMI).

Assurance: Nokia NSP or third-party tools collect QoS metrics (delay, jitter, loss) via TWAMP or Y.1731 to verify SLA.

Troubleshooting steps: verify classification (show qos match), check policer drops (show qos policer stats), inspect queue depths and WRED drops.

Common issues: misconfigured DSCP mapping, policer rate too low, queue starvation due to strict priority, WRED thresholds too aggressive.

Use 'show qos sap ingress/egress' to display applied policies and counters; 'show qos scheduler' to check bandwidth distribution.

Logging and alarms: configure QoS threshold alarms (e.g., queue drop rate) to trigger notifications.

Performance testing: use RFC 2544 or Y.1564 to validate throughput, delay, and loss per QoS class.

Telemetry: stream queue and policer statistics to a collector for real-time monitoring and historical analysis.