Which statement is correct about QoS capabilities?

• A. QoS allows you to control bandwidth.
• B. QoS rewrites application layer payloads.
• C. QoS preserves packet order without any policy.
• D. QoS eliminates latency completely.

Answer: (A)

Quality of Service is about managing how network resources are used to meet performance goals. The core idea is classifying traffic and applying policies that allocate or limit bandwidth, prioritize important data, and shape how packets are queued and transmitted. That’s why the statement that QoS allows you to control bandwidth is the best fit: it directly reflects the ability to reserve, guarantee, or throttle the amount of bandwidth different traffic classes receive, which is the essence of QoS.

QoS does not rewrite or modify the actual data in packets, so it doesn’t alter payloads. It also doesn’t promise perfect in-order delivery under all conditions—reordering can still happen if different traffic classes traverse separate queues or paths. And while QoS can reduce latency experienced by high-priority traffic, it cannot eliminate latency entirely, because propagation and processing delays due to the physical network remain.