NBN Co has revealed that one-third of all active fibre-to-the-node (FTTN) services are currently incapable of achieving a downlink in excess of 50 Mbps.

The network builder this afternoon released a set of figures showing Layer 2 attainable bitrates for the FTTN portion of its network, as of June 18.

The figures – for the first time – reveal just how many FTTN lines are incapable of achieving higher speeds in the part of the network that NBN Co controls.

The company repeatedly quotes a topline number of “approximately 65 percent of FTTN services [that] can achieve between 50 and 100 Mbps” down.

In a further breakdown, it has been shown that 32 percent of FTTN connections can achieve a maximum wholesale bitrate of between 75 and 100 Mbps, and 33 percent can attain 50-75 Mbps.

A further 29 percent of lines have maximum attainable bitrates of between 25 and 50 Mbps, while the remaining 6 percent of connections top out at 25 Mbps.

ACCC figures released today show there were 906,662 FTTN services in operation as at June 30 this year.

On that basis, 262,932 active FTTN connections have a maximum attainable bitrate of 50 Mbps – and 54,400 of those cannot get beyond 25 Mbps.

One possible limiting factor on these figures is that an unspecified number are subject to “co-existence profile settings”.

That is, in the 18-month window allowed for customers to migrate from ADSL to FTTN, the FTTN connections are subject to performance settings designed to prevent interference with the legacy copper services.

Once the 18-month window expires and those restrictions are lifted, “Layer 2 attainable bitrate [speeds] will increase”, NBN Co said.

It is important to note that attainable speeds represent the maximum an end user could get if their end-to-end connection to the NBN operated in perfect conditions.

In reality, users only see some of this speed due to a variety of factors, such as the condition of in-home wiring, and the amount of bandwidth that their ISP has provisioned to take internet traffic to and from the NBN.

NBN Co is presently campaigning hard to solve one of those factors – getting ISPs to purchase more bandwidth, which would allow end users to get closer to the maximum attainable rates than they are able to get now.

The network builder said the average – not maximum - attainable download rate over FTTN is 67.7 Mbps and the average attainable uplink is 30.63 Mbps.