Reply to post: Re: Analogy Units

Stern Vint Cerf blasts techies for lackluster worldwide IPv6 adoption

Alan Brown Silver badge

Re: Analogy Units

" it means that IPV6 can handle 2^53 routable networks."

The Keyword in all this discussion is "networks"

When IPv4 was first created, the first octet was routing information, similar to an international dialling code. The idea that the first octet gave some indication of the network's position on the planet went out the window when the address space was broken up into Class A/B/C

Whilst IPv4 can only handle 65536 BGP4 networks one of the more important problems is the amount of routing update traffic that's flowing around and the number of updates that need to be made to memory tables in core routers. Calculating best paths is a big CPU hog.

IPv6 space is so big BECAUSE it makes provision for hierarchical routing, which in turn means that the number of routing updates flying around can be kept relatively low, which makes things more efficient at machine level (not numerically).

Sparseness in network addressing tables is a good thing. Imagine if your phone number was +441234567890 whilst your neighbours were +423210457895 and +622136 and that kind of chaos was repeated all the way up and down your street as well as across town.

Just because it can theoretically hold trillions of addresses, doesn't mean it is ever intended to. Once it sinks in that the first few bytes of IPv6 is supposed to be geographical/network routing information the size of the space makes sense - and the other reason it's "so big" is so that we don't have to go through this entire exercise again in a few years.

IPv4 was a hacky kludge only intended to remain in service for 5-6 years. That it's lasted as long as it has is a testament to ingenuity in the face of adversity more than Vint's original design.

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