QoS in mobile and fixed transport networks
Scope
This domain tests QoS across Nokia mobile backhaul and fixed broadband access, where the transport must honour radio/access-layer priorities and timing.
Core rules
- Mobile backhaul maps QCI/5QI to DSCP or MPLS EXP at the cell site. Typical: conversational voice QCI 1 to EF/EXP 5; signalling QCI 5 to AF41/EXP 3; best-effort QCI 9 to BE. The mapping must be consistent end to end.
- 5G QoS flows carry a 5QI and may use reflective QoS; the transport classifies on the outer DSCP/EXP because it cannot see the 5QI.
- Mobile transport also carries synchronization: 1588v2 PTP and SyncE are sensitive to queuing delay and asymmetry; keep them in a high-priority, low-jitter class.
- Fixed GPON (Nokia ISAM) uses traffic containers (TCs) and GEM ports. Upstream bandwidth is granted by DBA; downstream is shaped per TC. Queue groups combine queues across TCs.
- GPON priority queues map 802.1p to P-bit queues; a shaper per TC enforces the committed rate, and DBA assigns upstream grants.
- Both environments need a clear trust boundary: cell site/ONT marks, aggregation network trusts and preserves.
Worked example
A 5G gNB marks voice 5QI 1 as DSCP EF and EXP 5, and eMBB as AF11. The Nokia backhaul router classifies EXP 5 to FC ef with strict priority, and AF11 to af with WRED. At the fixed side, the ONT maps 802.1p 5 to a high-priority GEM/TC queue; the OLT DBA gives that TC a fixed grant so voice is not starved. The mapping is verified with queue statistics at both ends.
Traps
- Marking the inner IP header only when the transport reads EXP.
- Treating PTP as best effort, causing sync loss under load.
- Assuming DBA alone guarantees downstream QoS; downstream needs shaping/scheduling.
- Mismatched QCI-to-DSCP maps at cell site and aggregation.