For the first time, the January 2019 Netflix ISP speed index separates Telstra's NBN and non-NBN services.
The top ranked ISP is Telstra NBN, with prime-time Netflix speeds of 4.38Mbps.
Telstra's non-NBN (cable and DSL) services came in fourth place at 3.83Mbps.
Second place Optus went from 4.05Mbps to 4.04Mbps, followed by Exetel (3.99Mbps, down from 4/02).
The remaining three majors all move down one place, below Telstra non-NBN.
TPG managed 3.81Mbps (down from 3.83Mbps), iiNet achieved 3.76Mbps (was 3.78Mbps), and Dodo/iPrimus slid from 3.70Mbps to 3.64Mbps.
No explanation was given for the changes, but there does seem to be some seasonal variation as three of the previous six leading ISPs also showed a decline between the December 2017 and January 2018 reports.
How are these numbers obtained? According to Netflix, "For 'Prime Time', we calculate the average bitrate of Netflix content in megabits per second (Mbps) streamed by Netflix members per ISP. We measure the speed via all available end user devices. For a small number of devices, we cannot calculate the exact bitrates and streaming via cellular networks is exempted from our measurements."
According to a Telstra spokesperson, "The Netflix results is due to Telstra customers enjoying the fastest Internet speeds available in Australia, combined with access to Australia's most extensive and sophisticated caching capacity in the region."