300-320 · Question #609
A customer has an exising WAN circult with capacity of 10 Mbps. The circuit has 6 Mpbs of various user traffic and 5 Mpbs of real-time audio traffic on average. Which two measures could be taken…
The correct answer is A. Increase the WAN circuit bandwidth C. Ensure that real time traffic is prionitized over other traffic. The WAN circuit is over-provisioned with 11 Mbps of traffic on a 10 Mbps link. To protect real-time audio, you must either expand capacity or use QoS prioritization.
Question
A customer has an exising WAN circult with capacity of 10 Mbps. The circuit has 6 Mpbs of various user traffic and 5 Mpbs of real-time audio traffic on average. Which two measures could be taken that avoid loss of real time traffic? (Choose two.)
Options
- AIncrease the WAN circuit bandwidth
- BPolice the traffic to 3.3 Mbps and allow excess traffic to be remarked to the default queue
- CEnsure that real time traffic is prionitized over other traffic
- DConfigure congestion avoidance mechanism WRED within the prority queue
- EPolice the traffic to 5 Mbps and allow excess traffic to be remarked toi the default queue
How the community answered
(47 responses)- A81% (38)
- B11% (5)
- D6% (3)
- E2% (1)
Why each option
The WAN circuit is over-provisioned with 11 Mbps of traffic on a 10 Mbps link. To protect real-time audio, you must either expand capacity or use QoS prioritization.
Increasing the WAN circuit bandwidth resolves the over-subscription (11 Mbps demand on 10 Mbps pipe), eliminating congestion entirely and preventing any traffic from being dropped.
Policing all traffic to 3.3 Mbps would severely throttle legitimate traffic and does not selectively protect real-time audio, causing audio loss rather than preventing it.
Configuring priority queuing (LLQ) for real-time traffic ensures that audio packets are serviced first during congestion, preventing jitter and loss even when total traffic exceeds the link rate.
WRED is a congestion-avoidance mechanism applied to best-effort queues and must not be configured inside a priority queue (LLQ), making this technically invalid.
Policing to 5 Mbps only limits the audio stream to its average rate but does nothing to prevent the 6 Mbps of user traffic from competing with and dropping real-time packets.
Concept tested: QoS prioritization and WAN capacity planning
Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_conmgt/configuration/xe-16/qos-conmgt-xe-16-book/qos-conmgt-oview.html
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