Sprint has said it will begin slowing the data speeds of its heaviest users, which amounts to a massive policy change for the carrier. Sprint has long sought to differentiate itself from competitors by maintaining an unlimited plan with no throttling or overage charges. Beginning today, however, customers who exceed 23GB of data in a single billing period will see their data speeds reduced when cell sites are congested or constrained. "This QoS practice is intended to protect against a small minority of unlimited customers who use high volumes of data and unreasonably take up network resources during times when the network is constrained," explained Sprint. "It's important to note that this QoS technique operates in real-time and only applies if a cell site is constrained. Prioritization is applied or removed every 20 milliseconds. And performance for the affected customer returns to normal as soon as traffic on the cell site also returns to normal, or the customer moves to a non-constrained site." Sprint says the new policy will protect the network for the 97% of customers who don't use excessive amounts of data. Sprint claims the 23GB threshold is far more than most customers ever use, and can be used to load 600 photos, stream 60 hours of music, or stream 50 hours of video. T-Mobile has a similar QoS policy in place.