Experts say UFB fibre is the best way to guarantee the Rugby World Cup will be smoothly streamed to your home via Spark Sport - which will be the only way to watch all 48 games live.
But there's a problem: there are around 650,000 households within reach of UFB who have yet to connect - but Chorus said this morning it only has capacity to hook up around 50,000 before kick off on September 20.
A Spark spokeswoman said that the smaller UFB companies - Ultrafast Fibre, Northpower and Enable Networks will be able to chip in to help Chorus.
But a spokesman for Enable emphasised Chorus's get-in-quick, slots-are-limited message, telling the Herald, "We only have about 10,000 fibre broadband connection appointments available between now and the tournament. There's a real risk rugby fans will miss out on getting fibre broadband in time if they don't order."
"Fibre is definitely the answer if you're a rugby fan and want to see all the games on your giant-screen TV without missing a beat," tech commentator Paul Brislen said.
"There's no issue with contention rates as you have on copper lines."
"Contention" is industry jargon for the peak-time overloading that happens to copper lines at peak-time internet usage times, such as when school's out, prime time (which these days means Netflix time after dinner) or a big sports event that everyone wants to watch at once.
"It's incredibly frustrating having all your neighbours sit down to watch the game at the same time and everyone's connection slows to a crawl as a result," Brislen says.
A copper line can also slow - which can freeze streaming video - if multiple people in a household are all trying to use the internet at once.
Here is the maths - which, for Spark, just doesn't add up.
According to the Government's latest Broadband Update, for the December quarter, fibre has been laid past 1.43 million premises. (The ultimate goal is to have 1.75m premises within reach of Ultrafast Broadband by 2022 Chorus is still on track for that schedule. It's just that it doesn't match Spark's World Cup timetable.)
But of those 1.43 million, only half - or 714,258 - have got around to phoning their retail ISP (such as Spark, Vodafone or Orcon) and arranged to have fibre connected from the street to their home.
In March, Chorus said it could install fibre at about 3400 homes a week, which meant more than 600,000 of those within reach of UFB fibre right now will be fibre-less come World Cup kick-off.
In an update today, Chorus said it had connected around 40,000 since then, and confirmed it would be limited to around 50,000 further connections by RWC kick-off on September 20.
And the network company has limited ability to put its foot down, given the tight labour market and that many of its subcontractors are already in hot water with the Labour Inspectorate for cutting corners. And even if it didn't have those constraints, the publicly listed Chorus - which won't directly benefit financially from the World Cup - still needs to keep a leash on costs.
The UFB project was awarded to four companies, but Chorus won the lion's share and is responsible for almost all outstanding work now that Enable in Canterbury and NorthPower Fibre in Northland have finished their rollouts and Ultrafast Fibre in the central North Island is coming up the home straight.
There is a separate Rural Broadband Initiative to cover those outside towns and cities.
But on that front, there's potential trouble, too.
Like the UFB, the rural project is proceeding at pace, but was never timelined for the Rugby World Cup.
In March, Crown Infrastructure Partners told MPs that around 40,000 rural households won't have good enough broadband to stream the World Cup.
The message from Chorus chief customer officer Ed Hyde is that rugby fans should book a UFB fibre installation, via their ISP, as soon as possible before those 50,000 spots run out.
It's free for most homes, and fibre plans are comparable in price to copper.
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Chorus said it is expecting huge data spikes during the Cup, and that its network will be able to accommodate the anticipated surge in traffic.
A Spark Sport spokeswoman said, "In general, we've seen very pleasing industry engagement off the back of our Industry Network Working Group to prepare for the Rugby World Cup.
"We'd join Chorus in encouraging customers to check now that their broadband is ready to stream the Rugby World Cup.
"Spark has also brought forward a significant amount of investment in fixed and mobile networks in preparation for RWC 2019.
"We have upgraded hundreds of mobile sites and built new sites to accommodate the expected demand and made significant upgrades to the core network to support content delivery up and down the country."
She added, "you do need a decent broadband connection to watch streaming services like Spark Sport – but this can be any kind of broadband technology - fibre, copper or wireless broadband.
"The general rule of thumb is that if you can watch streamed content, such as a YouTube video or Lightbox, on the device that you want to watch Spark Sport on during peak hours - 8-9pm in the evening - and are happy with the viewing experience, you should be okay to watch the Rugby World Cup."
If you want to watch Spark Sport on a Smart TV, Spark recommends a minimum download speed of 15 megabits per second (Mbps).
If you want to watch Spark Sport directly on a mobile or tablet, Spark recommends a minimum download speed of 6Mbps (sites like speedtest.net can be used to measure your bandwidth).
"You might be able to stream with a slower connection than this, but the quality of the image will be diminished," the spokeswoman said.
That is true - families in areas with poor broadband will still be able to watch the stream. But gathering around a cellphone to watch grainy footage won't have quite the same feel as watching a game on Sky or TVNZ.
Brislen said that if you're in an urban neighbourhood that still lacks UFB fibre, check if your ISP offers fixed wireless (which Spark has been pushing hard and is faster than copper). If you're in a rural or provincial area, a wireless ISP can be a workable alternative. See www.wispa.nz for a list.
If you're a rugby fan, the message from all-comers is: get in early.
Sort out a fibre connection and, while you're at it, get Chorus or your ISP to check that your home's Wi-Fi network is up to snuff. Many aren't - and you don't want to be stuck in a monster call centre queue come September.