QoS Design for Voice and Video on the WAN
Voice and video are sensitive to delay, jitter and packet loss; file transfers and backups are not. When a WAN link fills up, Quality of Service (QoS) decides which traffic goes first.
Start with a simple class model
- Real-time — voice (DSCP EF), with a strict-priority queue capped at a share of the link.
- Interactive video — video conferencing (AF41).
- Business critical — ERP, POS, core applications (AF31).
- Default — everything else.
- Scavenger — backups, updates, bulk transfers, given what is left.
Four to six classes cover most organisations; more adds complexity without much benefit.
Mark close to the source
Classify and mark traffic at the access switch or SD-WAN edge, and trust markings only from known devices such as IP phones.
Queue where congestion happens
QoS only matters where traffic exceeds capacity — usually the WAN edge. Shape traffic to the actual circuit speed so queuing happens on your device, where your policy applies.
Align with the provider
MPLS providers offer a set of classes; map your markings to theirs so priority is honoured across their network.
Verify
Monitor queue drops per class and call-quality scores (MOS) to confirm the design works.
QoS design is included in our MPLS / VPLS and SD-WAN services. Talk to us.
