300-420 Question 253
Single answerA network engineer is designing a QoS policy for a branch office that experiences occasional bandwidth congestion. The goal is to ensure traffic remains within the allocated bandwidth on a WAN link while avoiding packet drops caused by congestion. Which traffic shaping mechanism would best achieve this objective?
- A
Traffic shaping with a committed burst size (Bc) and excess burst size (Be) configured for the link
- B
Traffic policing to enforce strict bandwidth limits on the WAN link
- C
Weighted Random Early Detection (WRED) to manage congestion proactively
- D
Priority queuing to ensure high-priority traffic is always transmitted first
Show answer and explanation
Correct answer: A
Explanation
Traffic shaping is the best mechanism for regulating traffic to stay within the allocated bandwidth on a WAN link while avoiding packet drops. By configuring a committed burst size (Bc) and an optional excess burst size (Be), traffic shaping buffers packets during congestion instead of dropping them. This ensures smoother traffic flow and prevents excessive packet loss, which aligns with the design goal in the scenario.
- A. Correct.
Traffic shaping with a committed burst size (Bc) and excess burst size (Be) allows the network to regulate traffic rates by buffering packets during congestion, which prevents packet drops and keeps traffic within bandwidth limits. This is the most appropriate solution for the scenario.
- B. Incorrect.
Traffic policing enforces strict bandwidth limits by dropping packets that exceed the configured rate. This can lead to packet loss during congestion and is not ideal for ensuring smooth traffic flow.
- C. Incorrect.
Weighted Random Early Detection (WRED) proactively drops packets to manage congestion before queues fill up. However, it is primarily used for congestion avoidance and does not regulate traffic rates like shaping does.
- D. Incorrect.
Priority queuing ensures that high-priority traffic is transmitted first, but it does not address the need to regulate overall traffic rates or prevent packet drops during congestion.