200-301 Question 385
Select 3A network administrator is configuring QoS on a router to prioritize voice traffic over other types of data. To achieve this, the administrator needs to ensure that packets are properly classified and marked for appropriate forwarding per-hop behavior (PHB). Which of the following steps are essential to implement this QoS policy correctly?
- A
Classify the traffic based on attributes such as source IP, destination IP, or protocol type.
- B
Mark the packets with the appropriate Differentiated Services Code Point (DSCP) value.
- C
Configure the router to drop all packets without a DSCP marking.
- D
Apply a queuing mechanism on the interface to prioritize traffic based on the marking.
Show answer and explanation
Correct answers: A, B, D
Explanation
To implement QoS policies effectively, traffic must first be classified to identify its type. After classification, marking is used to assign a DSCP value that determines the forwarding behavior for the traffic. Finally, queuing ensures that traffic is prioritized based on its marking, enabling better handling of latency-sensitive traffic such as voice. Dropping unmarked packets is not a best practice and is not required for implementing QoS.
- A. Correct.
Classifying traffic is the first step in QoS, allowing the router to identify and distinguish between different types of traffic for appropriate handling.
- B. Correct.
Marking packets with DSCP values is essential for defining the forwarding behavior of the packets across the network.
- C. Incorrect.
Dropping all packets without a DSCP marking is not a standard QoS practice and could result in unexpected traffic loss.
- D. Correct.
Applying a queuing mechanism ensures that traffic is prioritized appropriately based on the markings and guarantees better performance for critical traffic like voice or video.