NBN Co has reached the halfway mark of its network roll-out early, thanks to a reduction in the total number of premises that will be connected by 2020. 

The government-owned company is celebrating the halfway milestone on Monday after rolling its infrastructure past 5.7 million premises, with about 2.2 million of those premises actively using the network. 

By 2020 NBN Co expects to connect a total of 11.2 million premises, down from an earlier estimate of 11.9 million premises. Both these estimates are down from a 2011 expectation that NBN Co would connect 13 million premises. 

It aims to have 8 million active customers using its network by 2020, generating $4 billion of revenue. 

​"It is a pivotal milestone, I think, in Australia's connectivity history," NBN Co's chief network engineering officer, Peter Ryan, told Fairfax Media. 

"The mandate we have is to connect every single premise in Australia no matter where it is. No premise gets left behind." 

A spokesman said NBN revises forecasts all the time and the smaller number was calculated by "staff walking street to street across the entire country".

Nearly one million of the 5.7 million premises already on the network have been reached through two satellites and hundreds of fixed wireless towers. NBN Co recently announced speed upgrades for the fixed wireless customers and increased data allowances on satellite connections. 

So far the $49 billion project has focused on rural and outer urban areas, but is now entering its metropolitan phase.  

The next five million premises will be connected with fixed infrastructure that was initially going to be all fibre-to-the-premises (FTTP), but was changed by the incoming Coalition government in 2013 to include a mix of fixed technologies. 

Mr Ryan said mixing different technologies in the network is "going extremely well", although NBN Co has had to update equipment inside the 1500 Telstra exchanges it uses to ensure all the different technologies can connect to the transit network.

By the end of the roll-out up to 21 per cent of premises will have FTTP connections, up to 27 per cent upgraded cable connections, and up to 54 per cent of Australia premises will have either fibre-to-the-node (FTTN), fibre-to-the-basement (FTTB) of apartment buildings, or fibre-to-the-curb (FTTC). 

FTTN requires less construction and is quicker and cheaper to roll out because it uses the existing copper telephone network. This avoids laying underground fibre-optic cables to every house and installing equipment inside the home or office. Instead, up to 200 premises are connected at a time by installing a single 'node' at the end of the street. This faster method has seen NBN Co covering thousands of premises daily. 

A spokeswoman for Communications Minister Mitch Fifield said "Labor's gold-plated NBN would have cost an additional $30 billion, and taken six to eight years longer to complete, leaving millions of Australians without access to high-speed broadband well into the next decade".

Mr Ryan says NBN Co is now trying to find a way to avoid house visits for the one million premises to be connected through FTTC to avoid the additional labour. 

"The biggest challenges we face are primarily around the scale of what we have to achieve. We are essentially moving the entire country onto a new network," he said. 

Meanwhile a Choice survey of 1910 people recently found 62 per cent had internet problems in the last six months with speed and reliability accounting for 81 per cent of all problems. NBN users said they experienced slow speeds and drop-outs 76 per cent of the time.