- A
End-to-end path computation via PCEP
Why wrong: PCEP is for SR-TE, not part of DiffServ basics.
- B
Classification and marking at the edge using DSCP
Edge devices classify and mark packets with DSCP.
- C
IntServ resource reservation via RSVP
Why wrong: IntServ is a different model; DiffServ does not use per-flow reservation.
- D
Per-hop behaviors (PHB) including EF, AF, and CS
PHBs define how traffic is treated at each hop.
- E
Traffic conditioning through policing and shaping
Policing and shaping enforce traffic contracts.
Question 253 of 1,000
350-501 Automation and Quality of Services Practice Question
This 350-501 practice question tests your understanding of automation and quality of services. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which three mechanisms are used within the DiffServ model to provide QoS in an SP network? (Choose three.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Classification and marking at the edge using DSCP
In the DiffServ model, QoS is implemented by classifying and marking packets at the network edge using the DSCP field in the IP header. This marking determines how each packet is treated within the core network, enabling scalable, class-based service differentiation without per-flow state.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
End-to-end path computation via PCEP
Why it's wrong here
PCEP is for SR-TE, not part of DiffServ basics.
- ✓
Classification and marking at the edge using DSCP
Why this is correct
Edge devices classify and mark packets with DSCP.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
IntServ resource reservation via RSVP
Why it's wrong here
IntServ is a different model; DiffServ does not use per-flow reservation.
- ✓
Per-hop behaviors (PHB) including EF, AF, and CS
Why this is correct
PHBs define how traffic is treated at each hop.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Traffic conditioning through policing and shaping
Why this is correct
Policing and shaping enforce traffic contracts.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between the DiffServ and IntServ models, so the trap here is that candidates may confuse RSVP (IntServ) as a DiffServ mechanism, or incorrectly associate PCEP with QoS instead of its actual role in traffic engineering path computation.
Detailed technical explanation
How to think about this question
DiffServ relies on the DS field (RFC 2474) where DSCP values (e.g., EF for low-loss/latency, AF classes for assured forwarding, CS for backward compatibility) are set at the edge. Each router along the path applies a Per-Hop Behavior (PHB) based on the DSCP, using queuing disciplines like LLQ or CBWFQ. Traffic conditioning (policing, shaping, and remarking) at the edge ensures that traffic conforms to the agreed service profile, preventing congestion in the core.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 350-501 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Automation and Quality of Services — study guide chapter
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FAQ
Questions learners often ask
What does this 350-501 question test?
Automation and Quality of Services — This question tests Automation and Quality of Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Classification and marking at the edge using DSCP — In the DiffServ model, QoS is implemented by classifying and marking packets at the network edge using the DSCP field in the IP header. This marking determines how each packet is treated within the core network, enabling scalable, class-based service differentiation without per-flow state.
What should I do if I get this 350-501 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jul 4, 2026
This 350-501 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-501 exam.
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