Describe how QoS is implemented in Cisco SD-WAN and how it differs from traditional WAN QoS.

• A. QoS static per interface
• B. QoS not supported
• C. QoS in Cisco SD-WAN is policy-driven at the edge with data policies that mark, shape, and route traffic across multiple transports
• D. QoS only applies to VPN links

Answer: (C)

In Cisco SD-WAN, QoS is implemented as policy-driven control at the edge. Data policies at the edge devices define how traffic is marked, shaped, and routed across multiple transports (like MPLS, Internet, and cellular). This means QoS isn’t tied to a single link; it follows the application through the dynamic path selections the SD-WAN fabric makes, ensuring consistent treatment of traffic across all available paths. The edge applies markings (for example, DSCP), enforces shaping and bandwidth guarantees, and uses the policy to influence routing decisions based on service requirements and link conditions.

This differs from traditional WAN QoS, which is typically configured per interface on a single transport and often lacks centralized, cross-transport coordination. It’s more static and tied to the specifics of one path rather than being applied consistently across multiple simultaneous paths. QoS in SD-WAN, therefore, reflects a flexible, application-aware, multi-transport approach rather than per-link, isolated QoS.

So the best description is that QoS in Cisco SD-WAN is policy-driven at the edge with data policies that mark, shape, and route traffic across multiple transports.