Kiwi fibre provider prepares Christchurch resiliency

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Kiwi fibre provider prepares Christchurch resiliency
(Credit: Mat Watkins/Enable Networks)

Building fibre to withstand disaster.

The fibre provider subsidiary of Christchurch City Council in New Zealand is preparing to build earthquake-resilient aggregation nodes as the base for its share of the country's national broadband network.

Enable Networks was one of four telcos chosen by the government's Crown Fibre Holdings earlier this year to connect premises across New Zealand to fibre as part of its $NZ1.5 billion Ultra-Fast Broadband network.

It has been tasked with connecting 180,000 premises in three of the 33 fibre-serving areas designed across the country, serving the areas of Christchurch, Rolleston and Raniora.

Christchurch has become an area of focus for telecommunications after suffering three major earthquakes and thousands of aftershocks during the past 12 months.

According to Mat Watkins, Enable Network's former operations manager, Enable was the only provider to survive the multiple earthquakes without a fibre cut.

The provider's open access fibre network in Christchurch's central business district had received minimal damage and power outages but no other significant issues, despite a significant drop in the city as a whole.

Watkins attributed Enable's survive largely due to "dumb luck", helped by a 40-metre fibre slack left in each manhole and the use of kit-set aluminium chambers rather than concrete.


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"Dumb networks survive," Watkins said of the Layer 2 network at the Australian Network Operators Group 2011 conference in Sydney this month. "Dumb networks do their job, they do their job very, very well and when you have a thing like an earthquake, they survive very, very well."

Both Watkins and Enable chief executive Steve Fuller pointed to the use of central exchanges as another key point of survival during the earthquakes.

Where other telcos had attempted to use public structures and carparks to establish temporary aggregation nodes and fibre terminals, the introduction of civil defence immediately following the natural disasters had meant many providers could not access their own equipment.

Fuller told iTnews that there would likely be few design changes in the construction of the UFB network, set to begin later this year.

They would rely on the same hub-spoke-ring architecture used to build the existing CBD fibre network. Given the diverse nature of the UFB construction, contractors had to comply with a standard fibre optic interface and a mutually agreed Layer 2 service description in building their designated areas.

But unlike the CBD, which relied on two geographically diverse exchanges, the greater Christchurch network would build out to approximately 20 exchanges, each covering about 10,000 connections.

Each exchange, or "cell", would fail over to one another.

"What we are doing is strengthening up the design parameters relative to the central offices we will build," Fuller said.

"We will increase the robustness of the building and also the seismic base of the central offices so that when we do have another earthquake there's a big chance they will survive."

Watkins said the cell design would mean a single point of failure would cut access for only 12,000 customers at any one time.

It differed to the 121-point design planned for the whole of Australia under its National Broadband Network.

NBN Co general manager of design and planning, Peter Ferris, used his keynote at AusNOG earlier this month to criticise the design decided upon by the competition watchdog. The decision effectively created 121 "single points of failure" that could ultimately cut access to 150,000 premises at a time during an outage, he said.

Enable continued to negotiate potential infrastructure access agreements with incumbent Telecom NZ and other carriers in the area, which meant use of aluminium chambers was not guaranteed as part of the construction.

However, where possible, it would continue to install the fibre using compressed air-blown techniques and leaving slack for future natural disasters and other construction.

"It's not just about the cheapest build," Fuller said.

"We knew how to build and operate a network so I hope the fact that we came through the earthquake without any damage just reinforced the fact that we were a safe bet."

The appearance of liquefied mud following the earthquakes had remained as the most significant concern for repairs to the network. One chamber in Enable's existing fibre ring remains due for repair in the near future.

"I'd love to say we planned for it, but we didn't," Watkins said of the network design during the earthquakes. "It was something that happened because there were basically three points of movement within the network - the duct, the fibre within the duct and of course the chambers.

"When everything moved it was flexible enough to move with it."

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