The developer of the iOS application NetDiag+ discovered a critical flaw in the bufferbloat measurement logic. The app's download test was failing to saturate the network connection because it ignored HTTP 403 responses from the Cloudflare speed test server, which limited downloads to a single byte.
This error caused the application to report a download speed of 0.0000008 Mbps while still assigning an A+ grade to the connection. Because the download phase was effectively idle, the bufferbloat classification system incorrectly attributed all network latency to the upload phase, rendering the ISP downstream queue detection feature non-functional.
To resolve this, the developer updated the load generator to measure actual throughput and validate HTTP responses. The new implementation uses 50 MB chunks for download tests and 8 MB chunks for upload tests to ensure continuous line saturation throughout the measurement window.
The application now includes a Health Index feature, which provides a weighted score based on latency, jitter, packet loss, and throughput. The index evaluates network performance across three segments: Wi-Fi, the home router, and the ISP, helping users identify the specific source of connectivity issues.
The developer noted that the tool operates as a heuristic-based system and is limited by single-stream testing and device-side hardware constraints on high-speed connections. Users of previous versions (1.4.5–1.4.8) are advised that their recorded download metrics are unreliable due to the identified bug.
