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Floods reveal weaknesses in the resilience of UK broadband

December’s floods exposed a major flaw in the UK’s fibre to the cabinet networks, which are almost impossible to waterproof

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Mobile networking

The history of telecoms networks is littered with great tales of heroism – often featuring armies of technicians pulling together in the face of horrendous crisis conditions, such as power failures, high winds, falling trees, freezing snow and floods.

So was the wet end to 2015 the same old story?  No – it was worse. At least, it was worse for digital network designs that were exposed to flooding.

However, it also demonstrated, for the first time ever, that the conditions were no problem for those enjoying fully fibred services.

The floods of 2015 exposed a mighty flaw in fibre to the cabinet (FTTC) networks – those hybrid fibre and copper networks that pretend to be ‘superfast’. Outsourcing part of your hub exchange to a street cabinet is not a good idea when it’s underwater. 

The recent floods were the first time that parts of the UK began to understand what they’ve known in Sweden for some considerable time – that wet and harsh winters demand network resilience, and that means making sure you keep the electronics dry.

As a young telecoms technician in the 1960s, I witnessed the first gas pressurisation schemes – pumping gas into cables to stop water ingress whenever damage occurred and, at the same time, raising an alarm when such incidents occurred.

But that was back in the day when local distribution networks were almost entirely passive. Now that phone and cable companies are trying to re-purpose their legacy analogue networks to deliver digital services, the temptation to leverage those assets was obvious – until swollen rivers reminded designers about network resilience.

Most of the media has focused on water management, flood prevention, bridge maintenance and the consequences of austerity on investment. A typical comment would be “prevention costs less than a fraction of repair”, but that applies equally well to the design of the nation’s critical infrastructure.

Street cabinets impossible to waterproof

Cabinets with electronics are almost impossible to make waterproof – they need ventilation to stay cool. If, instead of floods, we’d had icy blizzards and deep snowdrifts, we would now be marvelling at how the cabinets were keeping pavements warm.

But it’s not just about water – it’s also about power. Most cabinets have batteries stowed in the base – and that at least provides a few inches of freeboard. Once the power is overwhelmed, the service is sunk – and any loss of power has an even wider impact regardless of flooding.

In recent mild conditions, the National Grid had less than 100MW generating margin and requested plant shut-down.   

A tale of broadband in two cities

In the recent floods, 60,000 homes lost power in the Lancaster area, and the FTTC cabs did not keep the service once their batteries died because they lack generator sockets.

But in the adjacent rural area served by B4RN’s FTTH network, they kept their hubs working, first with the UPS and then with generators. This enabled people outside the power cut area to keep their connections. Those with their own UPS also stayed online within the power cut area.

None of B4RN’s customers lost connectivity. But in Lancaster, if you had power at your house but were connected to a cabinet that didn’t, you were offline.

Even mobile doesn’t react well to rain

One could ask, in these times of damp despair, who exactly needs their broadband service? After all, there’s always mobile, isn’t there? Alas, not so.

Mobile broadband masts need backhaul and, for the most part, they also depend on fixed connectivity. Looking forward, the trend is for millions of ever-smaller cells (picocells) at higher frequencies with a broadcast coverage of up to a 200-metre radius – a sort of next-generation public Wi-Fi on steroids. That must surely give network designers pause for thought.

Meanwhile, and especially in places where mobile coverage is already patchy, the lifeline is hardly up to the job.

York was hard hit in the recent floods but, as John Franklin, engineering director at City Fibre, said: “All our pure fibre networks are designed and built to ensure they are at minimal risk of failure due to flooding.

“By ensuring no active components are located outside the customer premises and our exchanges, the remaining fibre components are unaffected by water ingress and continue to provide critical services when submerged in flood waters.

“As we continue to roll out the UK’s alternative national infrastructure, our networks are not only delivering a new generation of internet speeds, but also demonstrate their increased resilience when compared with traditional copper networks.”

Why fibre is better in wet weather

To achieve network reliability and resilience, the obvious design principles are to minimise electronics, reduce the amount of material needed, and consume less energy. The old copper network needed more than 6,000 switch sites in the UK. With optical fibre nationwide, this number drops to below 70. Instead of 20,000 technicians, network management might need only 1,000 – and all water ingress faults would go away.

Judith Rodin, president of the Rockefeller Institute, points out that, in times of increasingly chaotic climates, resilience is an “urgent social and economic issue”. There are big lessons here – and we should not waste the design experience only to be surprised when the next crisis arrives.


David Brunnen is editor of Groupe Intellex, director of the UK’s Foundation for Information Society Policy and an RSA fellow.

This was first published in January 2016

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