As T-Mobile U.S.  (TMUS) - Get Report prepares for a torrent of streaming video when its free Netflix (NFLX) - Get Reportpromotion starts next week, the carrier scored the fastest network rating in the U.S. from Ookla, maker of the popular SpeedTest app, on Thursday. Verizon (VZ) - Get Report  fell to second, and AT&T (T) - Get Report and Sprint (S) - Get Report remained third and fourth.  The network speed rankings serve as tinder as competition between the carriers heats up with the debut of Apple Inc.'s (AAPL) - Get ReportiPhone 8 next week.

T-Mobile's network clocked in at 23.17 megabits per second (Mbps) in Ookla's second annual test, which blends download and upload speeds from across the country. The carrier broke out of a tie for first place with Verizon in last year's test, which only measured download speeds. Ookla clocked both carriers then at just more than 21 Mbps. 

"The combination of a tightly-spaced cell site grid and a smaller subscriber base than Verizon and AT&T could be the keys to T-Mobile's success in the U.S. market and to their ability to support the exponential growth in mobile data consumption," Ookla observed. 

T-Mobile also ranked first in speed, latency and 4g network coverage in OpenSignal's August report. 

Verizon was second with a score of 21.13 Mbps. "Over the past year, Verizon has been doing a lot of work around network densification, installing thousands of small cells [that improve network coverage] in urban and suburban areas, as well as many commercial venues," Ookla noted. 

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Verizon has started to "refarm" its spectrum portfolio in cities such as New York by repurposing spectrum that had been used for its legacy 3G network for its 4G network. 

AT&T, which may see increased video traffic if it closes its planned purchase of Time Warner Inc. (TWX) , scored 20.05 Mbps and remained in third place.

"AT&T was one of the first carriers to adopt LTE in the U.S., but over the past few years the competition has gotten better," Ookla observed. "That said, AT&T's network performance has started to improve in the last few months, likely due to their deployment of LTE in" bands of spectrum that had previously operated on legacy technology.

Sprint  (S) - Get Report  came in last among the major carriers, with a speed of 15.39 Mbps. Ookla cited Sprint's comparatively low network investment and less-dense infrastructure as reasons for its lagging performance. The network data group noted, however, that Sprint had the biggest gain since the end of last year with its download speeds increasing 23.7%.