NBN speeds are determined by NBN Co,
They have 5 speed tiers, 4 common and one I have never actually seen offered:
Tier 1 - which is the standard that most RSP use, is a mere 12Mbps download and 1Mbps upload.
Tier 2 - Which is what Telstra used as their standard speed is 25Mbps download and 5Mbps upload
Tier 3 - Which is one I haven't seen much which is 25Mbps download and 10Mbps upload
Tier 4 - Which is what Telstra call their Very Fast Speed Boost, is 50Mbps download and 20Mbps upload
and Tier 5 - Which is what Telstra call their Super Fast Speed Boost, which is 100Mbps download and 40Mbps upload
The government decided when they first developed the NBN that 12Mbps was a right perfect speed to offer as the standard, Telstra had always set their cable and velocity internet to 30Mbps, so they had decided that they will offer Tier 2 at 25/5Mbps, my assumption is that it was to keep their speeds as inline as possible to current customers expectations.
They have 5 speed tiers, 4 common and one I have never actually seen offered:
Tier 1 - which is the standard that most RSP use, is a mere 12Mbps download and 1Mbps upload.
Tier 2 - Which is what Telstra used as their standard speed is 25Mbps download and 5Mbps upload
Tier 3 - Which is one I haven't seen much which is 25Mbps download and 10Mbps upload
Tier 4 - Which is what Telstra call their Very Fast Speed Boost, is 50Mbps download and 20Mbps upload
and Tier 5 - Which is what Telstra call their Super Fast Speed Boost, which is 100Mbps download and 40Mbps upload
The government decided when they first developed the NBN that 12Mbps was a right perfect speed to offer as the standard, Telstra had always set their cable and velocity internet to 30Mbps, so they had decided that they will offer Tier 2 at 25/5Mbps, my assumption is that it was to keep their speeds as inline as possible to current customers expectations.