Quality of Service (QoS) is different from throttling in several ways. First, it is not automatically triggered by reaching a certain data level. With throttling, speeds will automatically be dramatically reduced to 128-256 Kbps as soon as a certain data allotment is reached, regardless of network capacity. QoS is the act of prioritization of network data where reduced speeds only occur during periods of network congestion.
If a Mobile Beacon customer reaches their Fair Use Threshold (currently 100 GB/month), it is only after that point that they would experience any deprioritization only at times in and in areas where the T-Mobile network is constrained. If this occurs, customers may experience a temporary slowdown for a few seconds, a few minutes, a few hours, or not at all. This slowdown will cease as soon as network resources are freed up (which is re-evaluated every nanosecond).
QoS is a network management technique that is used by all telecommunication operators, including T-Mobile.