QoS Model for Voice and Video Priority

Quality of Service (QoS)

What is used to create a QoS solution that delivers priority to voice and video traffic across a network?

  1. CBWFQ
  2. traffic shaping
  3. DiffServ Source Reference Answer
  4. traffic policing

Community Votes

C
100%

100% of anonymous learners picked answer C. Votes are pick records left by other test-takers — they are not the verified answer.

Community Insight

The question tests the distinction between QoS models (DiffServ) and QoS mechanisms (CBWFQ, Shaping, Policing). The common trap is selecting a specific queueing method instead of the overarching architecture.

DiffServ is the architectural model used to classify and prioritize traffic classes like voice and video across a network. Community consensus confirms DiffServ as the correct answer because it defines the service levels, whereas other options are specific mechanisms.

Community Discussion (3 comments)

G0y0 👍 1 Selected: C
You are right. CBWFQ is a congestion management method to guarantee bandwidth to each class of traffic, but it does not deliver priority to voice and video as LLQ method do. Traffic Policy and Shaping are congestion avoidance methods, they just support QoS in saturated links. And DiffServ is a QoS model that offer special treatment to the different class of traffic using marking, classification, congestion avoidance, congestion management (LLQ in this case for voice and video priority). So let us choose C. Reference: CCNP and CCIE Collaboration Core CLCOR 350-801 Official Cert Guide 2nd Edition Chapter 13: Layer 2 and Layer 3 QoS Parameters
b3532e4 👍 2
C. DiffServ
R4m0nECPC 👍 1 Selected: C
DiffServ is a model for specifying and enforcing QoS (Quality of Service) across a network. It prioritizes network traffic by classifying and managing network packets based on the type of service they need. This is especially important for voice and video traffic, which require low latency and minimal packet loss.

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Expert Analysis

Why the Answer Is Correct

DiffServ (Differentiated Services) is a scalable QoS architecture that classifies and manages network traffic by marking packets with DSCP values. It provides differentiated treatment (priority) to different classes of traffic, which is essential for real-time applications like voice and video that require low latency and jitter.

Why the Other Options Are Wrong

CBWFQ is a congestion management mechanism within Cisco's MQC, not the overall model; specifically, Low Latency Queuing (LLQ) built on CBWFQ handles priority queuing. Traffic shaping and policing are congestion avoidance techniques that regulate bandwidth usage rather than defining the end-to-end priority model.

Community Comment Notes

Comment [1] correctly distinguishes that while CBWFQ guarantees bandwidth, LLQ is needed for priority, and notes that DiffServ is the broader model offering special treatment via marking. Comment [2] reinforces that DiffServ is the model for specifying and enforcing QoS based on packet type. All comments agree on C.

Official Reference

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9300/software/release/17_6/configuration_guide/qos/b-qos-9300-cg.pdf

Exam Strategy

Always distinguish between 'models' (DiffServ, IntServ) and 'mechanisms/tools' (Policing, Shaping, Queueing). If the question asks for the solution or model that delivers priority/classification, look for DiffServ; if it asks for the configuration command or specific queueing technique, look for LLQ or CBWFQ.

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