The Need for Fiber Redundancy

I just read a short article that mentioned that 30,000 customers in Corvallis, Oregon lost broadband and cable service when a car struck a utility pole and cut a fiber. It took Comcast 23 hours to restore service. There is nothing unusual about this outage and such outages happen every day across the country. I’m not even sure why this incident made the news other than that the number of customers that lost service from a single incident was larger than normal.

But this incident points to the issue of network redundancy – the ability of a network to keep working after a fiber gets cut. Since broadband is now becoming a necessity and not just a nice-to-have thing we are going to be hearing a lot more about redundancy in the future.

Lack of redundancy can strike anywhere, in big cities or small – but the effects in rural areas can be incredibly devastating. A decade ago I worked with Cook County, Minnesota, which is a county in the far north of the state. The economy of the county is driven by recreation and they were interested in getting better broadband. But what drove them to get serious about finding a solution was an incident that knocked out broadband and telephone to the entire county for several days. They County has now built their own fiber network that now includes redundant route diversity to the rest of the world.

We used to have this same concern about the telephone networks and smaller towns often got isolated from making or receiving calls when there was a cable cut. But as cellphones have become prevalent the cries about losing landline telephone have diminished. But the cries about lack of redundancy are back after communities suffer the kinds of outages just experienced by Corvallis. Local officials and the public want to know why our networks can’t be protected against these kinds of outages.

The simple answer is money. It often means building more fiber, and at a minimum it takes a lot more expensive electronics to create network redundancy. The way that redundancy works is simple – there must be separate fiber or electronic paths to provide service to an area in order to provide two broadband feeds. This can be created in two ways. On larger networks it’s created with fiber rings. In a ring configuration two sets of electronics are used to send every fiber signal in both directions around a fiber. In that configuration, when a fiber is cut the signal is still being received from the opposite direction. The other (and even more expensive) way to create diversity is to lay two separate fiber networks to reach a given location.

Route redundancy tends to diminish as a network gets closer to customers. In the US we have many different types of fiber networks. The long-haul fiber networks that connect the NFL cities are largely on rings. From the major cities there are then regional fiber networks that are built to reach surrounding communities. Some of these networks are also on fiber rings, but a surprising number are not and face the same kind of outages that Cook County had. Finally, there are local networks built of fiber, telephone copper, or coaxial cable that are built to get to customers. It’s rare to see route diversity at the local level.

But redundancy can be added anywhere in the network, at a cost. For example, it is not unusual for large businesses to seek local route diversity. They most often achieve this by buying broadband from more than one provider. But sometimes this doesn’t work if those providers are sharing the same poles to reach the business. I’ve also seen fiber providers create a local ring for large businesses willing to pay the high price for redundancy. But most of the last mile that we all live and work on has no protection. We are always one local disaster away from losing service like happened in Corvallis.

But the Corvallis outage was not an outage where a cut wire knocked out a dozen homes on a street. The fiber that got cut was obviously one that was being used to provide coverage to a wide area. A lot of my clients would not design a network where an outage could affect so many customers. If they served a town the size of Corvallis they would build some local rings to significantly reduce the number of customers that could be knocked out by an outage.

But the big ISPs like Comcast have taken shortcuts over the years and they have not spent the money to build local rings. But I am not singling out Comcast here because I think this is largely true of all of the big ISPs.

The consequences of a fiber cut like the one in Corvallis are huge. That outage had to include numerous businesses that lost their broadband connection for a day – and many businesses today cannot function without broadband. Businesses that are run out of homes lost service. And the cut disrupted homework, training, shopping, medical monitoring, security alarms, banking – you name it – for 30,000 homes and businesses.

There is no easy fix for this, but as broadband continues to become essential in our lives these kinds of outages are going to become less acceptable. We are going to start to hear people, businesses, and local governments shouting for better network redundancy, just as Cook County did a decade ago. And that clamor is going to drive some of these communities to seek their own fiber solution to protect from the economic devastation that can come with even moderate network outages. And to some degree, if this happens the carriers will have brought this upon themselves due to pinching pennies and not making redundancy a higher priority in network design.

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