Which use case matches the description of finding the reason traffic is straining total capacity?

The use case that directly addresses the concern of finding the reason traffic is straining total capacity is related to network saturations and slowdowns. This scenario involves analyzing network performance issues, where an influx of traffic can lead to congestion, thereby affecting the overall capacity and efficiency of the system.

By focusing on network saturations and slowdowns, you can investigate traffic patterns, identify bottlenecks, and determine whether the infrastructure can handle the current load. This understanding is crucial for maintaining performance and ensuring that resources are allocated effectively to prevent overloads.

Other options, while relevant to network health and performance, do not specifically hone in on the issue of traffic capacity constraints caused by network overloads. For instance, measuring the health of physical devices involves assessing the status of hardware rather than traffic analysis. Checking connections primarily focuses on the verification of links and endpoints, which is a different aspect of network management. Managing third-party plugins and services deals with external integrations and their impact on systems, not directly with internal traffic capacity issues.