I feel like having them as a single brick is a bit hyperbolic, since undersea cables are pretty redundant in most of the world. Get rid of one and traffic just routes around it. Ships have been routinely destroying cables in the Gulf of Finland and the Baltic Sea in the past couple of years without causing significant disruptions.

Only mildly. There's not huge amounts of dark capacity just sitting around waiting to take over so if a major fiber connection goes down the remainder will get congested with the extra capacity. It won't cascade like a power outage but the remaining lines will slow down.

The whole Internet was designed for precisely this use case. If there is an outage, the distributed system will try to find another path. No actual central point of failure. As you say, the single brick is hyperbolic. But yea, those sharks can certainly be disruptive at times.

Well that depends on how much traffic that cable was supporting, how much free capacity is available on other cables heading to the same area, how much additional latency the rerouting will add and how sensitive to latency the rerouted traffic is doesn't it?

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