How must the queue sizes be designed to ensure that an application functions correctly?

Application performance depends on the end-to-end delay experienced by the traffic, which includes:

Queuing delay at each device.

Serialization delay based on link speed and packet size.

Propagation delay.

For the application to meet its performance SLA, the total of all delays (queuing + serialization + propagation) must remain within the application's maximum tolerable delay budget. This is critical for delay-sensitive applications such as voice or real-time video.

This directly aligns with CCDE v3.1 business-driven design, where application requirements dictate network performance guarantees.

Why other options are incorrect:

A: Focusing on individual devices ignores cumulative delay.

B: Uniform queuing delay isn’t practical or necessary.

C: Default queue sizes are not always suitable for real-time applications.

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