NBN Co has widened its definition of an “up to gigabit” service to between 500Mbps and 990Mbps on the downlink as it continues to progress the product towards launch.

The company has also revealed how it plans to brand the highly asymmetric broadband tiers it agreed to introduce as part of its wholesale pricing review last year.

It will rebrand 100/20Mbps (and the 25-100/5-20Mbps product for copper-based services) as ‘Home Fast’; 250/25Mbps as ‘Home Superfast’; and “up to gigabit” as ‘Home Ultrafast’.

The new gigabit service tier was always described as an “up to” product, and NBN Co has slowly refined what the range of speeds in that tier would be.

One of the challenges for NBN Co is that prospective users in the hybrid fibre coaxial (HFC) portion of the network are likely to struggle to achieve near gigabit speeds.

That led NBN Co to trial two possible flavours of gigabit - 750/50 and 1000/50 - in the early part of this year, with 750/50 targeted at HFC users and 1000/50 at fibre-to-the-premises (FTTP).

At least one retail service provider had suggested, however, that a 500Mbps tier could be more useful than gigabit, given that only full fibre customers will be able to achieve gigabit speeds.

It appears NBN Co has taken that on board, with technical documentation now describing the up to gigabit, 1000/50Mbps service as “500 - ~1000Mbps” on the downlink and 50Mbps on the uplink.

That range is likely to suit a broader range of use cases.

For example, 500Mbps could be positioned as a step up from 250Mbps - where new sign-ups are growing.

Retail service providers may also be more comfortable taking a 500Mbps product to market, given the amount of connectivity virtual circuit (CVC) bandwidth that would be required to ensure even that level of service.

Despite the wider range and flexibility built into the up to gigabit tier, NBN Co said in technical documentation that it still intends to use 750/50Mbps as the default option for HFC users.

“For the HFC Home Ultrafast bandwidth usage profile, the layer 2 wholesale downstream service will be configured at the layer 2 network management to an information rate of 750Mbps with the potential to burst to a maximum of 990Mbps (depending on, but not limited to; the frame size and line speed capability) at potential burst durations between 1 to 50 seconds … at least once a day,” it said.

The nature of these short-period bursts would depend on user behaviour, NBN Co said, adding that “lower usage instances increases burst durations.”

Additional comment was being sought from an NBN Co spokesperson at the time of publication.

Over-provisioned downlinks

NBN Co also revealed it will over-dimension the 100/20 and 250/25 products by 15 percent on the downlink as part of a plan revealed in November last year to allow users on those tiers to see the topline speeds marketed to them.

An additional 15 percent puts 100/20Mbps slightly above where NBN Co previously said it would land - a likely 115/20Mbps compared to previous expectations of provisioning 110/20Mbps services.

The 15 percent overhead allowance for 250/25Mbps has not been announced before.

“For Home Fast and Home Superfast, NBN network management policers will provide an additional 15 percent overhead allowance to the … downstream peak information rate at layer 2,” NBN Co said.

“This will allow end users to potentially achieve a downstream speed on their network approximate to numerical value of the published layer 2 wholesale downstream peak information rate where NBN infrastructure has capacity.”

NBN Co noted that for Home Ultrafast, the range of peak speeds achievable would be 761Mbps to 990Mbps.