When troubleshooting an issue at a site that is running on two cellular links from...

In Prisma SD-WAN, the Signal-to-Noise Ratio (SNR) is a critical metric used to monitor the health and performance of cellular WAN interfaces. SNR measures the strength of the desired signal relative to the background noise level; higher values indicate a cleaner signal, while lower values suggest that noise is overwhelming the signal, typically leading to increased packet loss, high latency, and reduced throughput.

Analyzing the provided graph, Carrier-1 (blue line) shows a severe drop in SNR, plummeting from approximately 4.5 dB to nearly 0.3 dB between 15:00 and 23:00. An SNR value this low is indicative of a failing or highly unstable link that cannot reliably sustain data traffic, directly supporting Inference A—that Carrier-1 experienced significant performance degradation. In contrast, Carrier-2 (green line) maintains a much higher and more consistent SNR throughout the same period.

Prisma SD-WAN’s AppFabric uses application-based path selection and SLA monitoring to ensure the best possible user experience. When the system detects that a primary path (like Carrier-1) has degraded below acceptable thresholds—often triggered by high loss or latency resulting from poor signal quality—it will dynamically steer application flows to an alternative healthy path. Therefore, Inference D is correct: because Carrier-1’s quality became untenable while Carrier-2 remained stable, the ION device would have likely initiated a path switchover to move traffic from the degraded Carrier-1 to the healthier Carrier-2.