According to theDesigning and Implementing Enterprise Network Assurance (300-445 ENNA)framework, application health is not just about reachability, but about the functionality of business-critical paths. For an e-commerce checkout process, which involves multiple interactive steps such as "Add to Cart," "Enter Shipping Info," and "Finalize Payment,"Transaction monitoring(Option B) is the most beneficial functionality.

Transaction tests provide a high-level view of application performance by executing a script that simulates a real user's interaction with the site's various components. UnlikeHTTP server monitoring(Option A), which merely verifies that a single URL returns a specific status code (like 200 OK), Transaction monitoring validates that the underlying application logic and database transactions are working as expected across the entire session. If a user can reach the homepage but the "Checkout" button fails due to a slow backend API call or a JavaScript error, only a Transaction test will identify the failure and provide a granular waterfall chart to show exactly where the process broke down.

WhileDNS monitoring(Option C) andRouting visibility(Option D) are crucial for identifying foundational connectivity issues, they are insufficient for monitoring complex transactional workflows. A DNS failure would prevent access to the site entirely, but a "broken" checkout process often occurs while the network and DNS appear perfectly healthy. Transaction monitoring bridges this gap by providing "layer 7" visibility into the end-to-end user experience, making it the definitive choice for e-commerce performance assurance.