+comment nbn™ , the entity charged with building and operating Australia's National Broadband Network (NBN), has argued it is better to re-configure its fibre-to-the-node network than to build it to handle high levels of traffic.

In a new post by nbn™ chief architect Tony Cross, the network builder explains “getting the balance right in terms of where we invest taxpayer money” means “we need to make sure every dollar is invested wisely.”

“That means that in an environment where broadband usage is always increasing we not only need to make sure we build a network that can handle all the traffic on it – especially all that video content people are now watching – but we also need to be careful not to over invest and have far more capacity than we actually need,” Cross adds.

The post goes on to say that the kind of backhaul provided from a fibre-to-the-node (FTTN) cabinet, wireless base station or fibre-to-the-premise (FTTP) optical terminals is therefore a tricky decision.

Cross says “our largest FTTP Optical Terminal serves around 3,000 premises and has 10Gbps of backhaul available – but the reality is that we are usually only using around 15% of that capacity at the moment.”

“By contrast an FTTN cabinet will serve only around 384 premises so we don’t need anything like the same amount of capacity as we do for an FTTP Optical Terminal.”

And here's the next part of the post, about FTTN and backhaul:

“In areas where the nbn™ Transit Network is available we could provide all the way up to 20Gbps backhaul for an FTTN cabinet if we chose to do so – but it’s highly unlikely that we will need that amount of backhaul capacity for an FTTN cabinet for quite some time. The reality is that we can quite easily upgrade our FTTN cabinet backhaul capacity whenever we need to do so by simply installing a new optical interface – there is no need whatsoever to run any new fibre.

Cross goes on to say “We are building a network that we can upgrade in an efficient manner and we are making investments in the right amount of capacity at the right time.” He also offers this analysis to show why bulkier backhaul isn't needed:

“… it’s also very important to understand exactly how that consumption is going to occur – not everybody is going to be streaming Netflix video content at exactly the same time, the demand will be spread over the day – which is crucial to understand when planning capacity. In addition, it’s worth remembering that when it comes to streaming video like Netflix that end-users are not all synchronised in their viewing – this means that they are not going to be hitting the backhaul link simultaneously so you are unlikely to have capacity issues even at peak usage times.” A further complication Cross mentions is that nbn™ doesn't do all its own backhaul. It leases some, so has to keep an eye on costs.

+Comment Cross' remarks about streaming video users not all hitting backhaul links simultaneously is correct, but also contestable. Streaming video may be changing viewing habits, but the fact remains that lots of people go to school or work and are therefore more likely to stream in concentrated blocks of time, usually in the evenings.

Yes, different households will choose to stream at different moments, but the streams will all require access to backhaul at the same time. Streaming video providers do caching differently, so not all users will place heavy demands on backhaul. But with Australians signing up for 1.7 million new streaming video on demand services since late 2014, it's clear there's plenty of appetite for such services.

Let's also consider the many tens of thousands of FTTN cabinets to be constructed: they'll make for a very substantial upgrade project even if all that is required is “simply installing a new optical interface.” ®