Which capability is accurately attributed to QoS?

• A. QoS can control bandwidth.
• B. QoS can assign IPv6 addresses automatically.
• C. QoS can perform DNS resolution.
• D. QoS can mirror traffic to a SPAN port.

Answer: (A)

Quality of Service is all about managing how traffic gets space on the network so critical applications perform reliably. The key capability is controlling bandwidth: QoS can allocate, limit, or shape the amount of bandwidth different traffic flows receive, ensuring that important services—like voice or video—get enough room even when the network is busy. This might involve prioritizing certain packets, reserving a minimum amount of bandwidth, or enforcing rate limits to prevent any one user from overwhelming the network.

Other options describe functions outside QoS. Automatically assigning IPv6 addresses is a job for DHCPv6 or SLAAC, not QoS. DNS resolution is handled by DNS servers and resolvers. Mirroring traffic to a SPAN port is a monitoring/traffic inspection function, not a bandwidth-management capability.