Architecture and Design
What this domain tests
Architecture and Design asks whether a candidate can translate requirements into a resilient, scalable voice topology. Core concepts include high availability and redundancy models, geographic distribution, capacity planning headroom, and separation of concerns between call control, media handling, and integration layers. Understand active-active versus active-passive designs and the failure behavior each produces. Know how session border controllers, gateways, and registrars fit together, and why placing media handling close to users reduces latency. Design questions reward candidates who identify single points of failure and state assumptions explicitly.
Traps to watch
The most common trap is a design that meets functional requirements but ignores failure modes. If a stem describes a single data center with no redundancy, the "best" answer usually addresses resilience, not features. Another trap is over-engineering: a small deployment may not justify active-active across regions, and the exam may reward proportionate design. Watch for confusion between redundancy (surviving failure) and scalability (handling growth); they are different goals. Also beware answers that add components without explaining what failure they mitigate.
Worked example
Suppose a requirement states 99.99 percent availability for 500 users across two offices. A single-site design cannot meet that target because any site outage removes all service. A proportionate answer places call control redundantly across both sites, keeps media local to each office, and defines failover behavior for registrations. That satisfies the availability target without unnecessary global complexity. When evaluating options, ask what specific failure each component survives.
Study focus
Prioritize availability models, capacity headroom, latency-aware media placement, and proportionality.