300-420 Question 249
Select 3A network engineer is designing a QoS policy for an enterprise network to prioritize voice traffic while ensuring fair treatment for other traffic types. The engineer plans to classify traffic based on DSCP values and apply appropriate marking for traffic types at the edge of the network. Which of the following actions align with proper traffic classification and marking practices?
- A
Classify traffic into voice, video, and best-effort categories using DSCP values.
- B
Mark all traffic with the same DSCP value to simplify QoS policies.
- C
Ensure that marking is done as close to the source as possible.
- D
Rely solely on CoS values from incoming frames without classifying traffic.
- E
Use DSCP values to differentiate application traffic for downstream devices.
Show answer and explanation
Correct answers: A, C, E
Explanation
Proper traffic classification and marking are critical components of a QoS strategy. Classification allows grouping traffic into different categories, while marking ensures that these categories are identifiable across the network. Using DSCP values ensures consistency and accuracy in QoS application across layer 3 devices. Marking traffic as close to the source as possible enhances the effectiveness of QoS policies throughout the network.
- A. Correct.
Correct. Classifying traffic into categories based on DSCP values is a best practice for ensuring that QoS policies can prioritize traffic effectively.
- B. Incorrect.
Incorrect. Marking all traffic with the same DSCP value removes the advantages of QoS and prevents differentiation between traffic types.
- C. Correct.
Correct. Marking traffic as close to the source as possible ensures that QoS policies can be enforced throughout the network.
- D. Incorrect.
Incorrect. Relying solely on CoS values without proper traffic classification can result in suboptimal QoS application, as CoS is layer 2 and not preserved across layer 3 boundaries.
- E. Correct.
Correct. Using DSCP values enables downstream devices to apply QoS policies accurately based on the type of traffic.