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Carrier Grade NAT – A Look at the Tradeoffs

Owen DeLong is Director of Professional Services at Hurricane Electric, the world’s largest IPv6-native Internet backbone and leading colocation provider. Owen, who is also an IPv6 Evangelist, has more than 25 years of industry experience.

magine a restaurant parking lot where each space is permanently assigned to a single patron’s car. This would be very counter-productive because you could never have a big enough parking lot and the vast majority of the lot would go unused the majority of the time. Since there’s only so much space and no way to make more, it’s a terrible waste of that space. Given limited space, it’s important to come up with a better solution. If things aren’t too crowded, we simply let customers park where there’s a space and the space is only tied up for that customer so long as they are at the restaurant. When someone leaves, another customer can use the space.

However, what happens if the restaurant grows or the parking lot shrinks?  Remember, we can’t create more space.  Usually a combination of clever ways to park more vehicles in the same space is developed, and valets manage the insertion and removal of vehicles from those tighter spaces. Sometimes the valet may have to park in an alternate lot off-site. The valet maintains a translation table of keys to a cars’ locations.

Clearly, the ideal scenario would be if we could make more space. That’s what IPv6 does for us. In fact, if IPv6 addresses were parking spaces, IPv6 would literally allow us to park every car ever built in each parking lot and still have 4 billion more spaces for each and every car ever built in each parking lot.  Further, we have enough room for every single restaurant, building, house, apartment, condo, shack, shed, office, and any other structure, building, or tenant to have 65,536 such parking lots and still leave more than half of the space unpaved and unused.

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