Which Network Device Plane Handles QoS?

200-901 By islever Editorial Last updated

Short answer

B The data plane classifies, marks, queues and schedules traffic as it forwards each packet.

Question

Which network device plane is responsible for handling QoS?
  1. management plane
  2. data plane Correct Answer
  3. configuration plane
  4. control plane

Key Takeaways

Tests the three functional planes: QoS is enforced per packet during forwarding, so it belongs to the data plane, not the control or management plane.

The data plane enforces quality of service by classifying, marking, queuing and scheduling packets as it forwards them, while the control plane only decides how traffic should be treated.

Common mistake: Learners pick the control plane because QoS policy is configured and "decided" there, but the control plane only builds routing and forwarding state — it does not process the QoS of each packet.

Expert Analysis

Why the Answer Is Correct

The data plane — also called the forwarding plane — is the part of a network device that actually moves packets, so every per-packet QoS action executes there. Classification, marking (DSCP/CoS), policing, shaping, queuing, scheduling and congestion avoidance all run as the packet is forwarded through the device's forwarding hardware. QoS is therefore a property of how traffic is forwarded, which is exactly the data plane's job, and it applies to ordinary data traffic rather than to traffic destined for the device itself.

Why the Other Options Are Wrong

The management plane carries administrative traffic such as SSH and SNMP; it configures and monitors the device but never touches forwarded packets. The control plane runs routing and signalling protocols such as OSPF and BGP and builds the forwarding table the data plane consults — it decides where traffic goes, not how each packet is treated in a queue. "Configuration plane" is not one of the three planes at all and is included only as a distractor.

Community Comment Notes

Commenters split on this question. As Erfan put it, the control plane performs "forwarding decisions and other functions, like quality of service (QoS)", and a second learner repeats that reading. Against that, another commenter describes the data plane as "primarily responsible for handling Quality of Service (QoS) in network devices", pointing to forwarding, QoS and ACL enforcement. Weighing the vendor definition — the data plane forwards data through a device — QoS enforcement sits with the data plane, and this page marks that verdict accordingly.

Official Reference

These links open the official vendor documentation in a new tab.

Exam Strategy

Anchor each plane to a verb: management configures and monitors, control decides and routes, data forwards and enforces QoS. Any question about per-packet treatment points to the data plane.

Frequently Asked Questions

Is QoS configured on the data plane?

Configuration is a management-plane task; the resulting behaviour — classification, marking, queuing and scheduling — is enforced by the data plane on every forwarded packet.

Why is the control plane not the answer?

The control plane runs routing and signalling protocols and builds the forwarding table; it decides where traffic goes, not how each packet is treated.

More 200-901 FAQ →

Community Votes

B
40%
D
60%

60% of anonymous learners picked answer D. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 4 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 4

  1. 81c0313 👍 3
    It is B : The data plane (also known as the forwarding plane) is primarily responsible for handling Quality of Service (QoS) in network devices. The data plane manages the actual forwarding of packets through the router or switch, and it includes features like QoS and access control lists (ACLs) to ensure efficient and prioritized packet handling
  2. cecb9b9 👍 2 Answered D
    The control plane performs forwarding decisions and other functions, like quality of service (QoS). In contrast, the data plane is the network that switches or forwards devices handling the data packets and taking inputs from the control plane.
  3. Pierre_Bouvier 👍 2
    B. Data plane The data plane is responsible for forwarding traffic based on the rules set by the control plane. It handles QoS (Quality of Service) by enforcing policies for traffic prioritization, shaping, and scheduling.
  4. Erfan 👍 1 Answered D
    it should be Control plane . Correct Answer : D

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