What the NDT7 test measures
M-Lab describes NDT as a single-stream test of a connection's bulk-transport capacity. Xpeed runs download and then upload through the official NDT7 client.
A selected server, protocol and the conditions during the test all form part of the result. A different test can use a different path or measurement method.
Mbps and MB/s
Mbps means megabits per second; MB/s means megabytes per second. Divide Mbps by eight to express the same rate in MB/s. The unit control changes the display, not the measured data.
A file-transfer estimate assumes a constant rate. Actual downloads can be affected by protocol overhead and a changing connection, so an arithmetic estimate is not a completion-time promise.
Why the upload source matters
While upload runs, the client reports a provisional rate. For the final value, Xpeed prefers the bytes received by the server divided by the server measurement interval. If that information is unavailable, a valid client rate can be used and its source is retained.
An incomplete or missing upload is not changed into a successful zero. Canceling a run does not create a completed history entry.
TCP RTT and RTT variation
The Ping card uses TCPInfo.MinRTT, converted from microseconds to milliseconds. It is the minimum TCP round-trip time for the M-Lab path during the measurement.
RTT variation uses TCPInfo.RTTVar. It is not a UDP packet-jitter measurement. Neither number establishes latency to your game server, video-call service or every internet destination.
Before you repeat a test
A new run transfers data again. Review the consent notice, especially on a metered connection. Other traffic, Wi-Fi conditions, VPN routing and the selected server can change the path's performance.
M-Lab receives and publishes test data under its policy, including IP information. Optional local history is a separate Xpeed setting and starts off.