What Defines Cisco's Core System Sizing Methodology?
Short answer
AD Performance testing measures resource usage (CPU, memory) accurately for each function. Busy hour call attempts, where the busy hour call attempts system is the user busy hour call attempts multiplied by the number of users.
Question
Key Takeaways
The exam tests your familiarity with Cisco’s official sizing calculations, where candidates frequently mistake infrastructure scaling outcomes for foundational methodological steps.
This question evaluates knowledge of Cisco’s standardized system sizing framework, emphasizing empirical performance testing and traffic modeling. Community consensus confirms that accurate resource measurement and proper Busy Hour Call Attempts calculation are the definitive pillars of the methodology.
Common mistake: Option E is commonly selected because administrators often add UCM nodes during expansion, but this reflects a deployment adjustment rather than a core sizing methodology component.
Expert Analysis
Why the Answer Is Correct
Cisco’s system sizing methodology relies on empirical performance testing to measure CPU, memory, and network usage for each function accurately, making option A essential. Additionally, the methodology uses Busy Hour Call Attempts (BHCA) as a primary traffic metric, calculated correctly in option D based on user concurrency during peak periods. These two elements provide the quantitative baseline required for reliable capacity planning across Cisco collaboration platforms.
Why the Other Options Are Wrong
Option B incorrectly suggests regional sizing considerations, which are deployment strategies rather than core methodological components. Option C misrepresents the BHCA formula by implying a simple multiplication without accounting for actual concurrent call patterns and traffic distribution. Option E describes a potential scaling outcome or troubleshooting step, not a prescribed element of the official sizing framework itself.
Community Comment Notes
Candidates like comment [1] note that while BHCA is central, the exact wording in some options can be misleading regarding how Cisco calculates peak loads. Comment [2] reinforces that option E represents post-sizing adjustments rather than methodology pillars. Comment [3] highlights that test-takers often overcomplicate sizing questions by including infrastructure scaling tactics instead of sticking to Cisco’s documented calculation models.
Official Reference
https://www.cisco.com/c/en/us/td/docs/solutions/PA/size/SRND_sizing14/sizing14.html#46067
This link opens the official vendor documentation in a new tab.
Exam Strategy
Prioritize memorizing Cisco’s official sizing formulas and performance benchmarking criteria over real-world troubleshooting habits. Eliminate options describing hardware additions or geographic deployments, as they rarely represent the core mathematical or testing frameworks evaluated on the exam.
Community Votes
100% of anonymous learners picked answer AD. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 3 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 3
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c6176b5 👍 2AE seems to be correct, BHCA is also part of it, but not like the answers are suggerating https://www.cisco.com/c/en/us/td/docs/solutions/PA/size/SRND_sizing14/sizing14.html#46067
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OSJAY 👍 1Agree with AD - E is not part of the main components of the methodology
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decdca7 👍 1I don't see the E is a methodology for sizing!?
Reader comments & corrections
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