Re: 128 bits should be enough for everyone, was:

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On Fri Mar 31 06:17:01 2006, Anthony G. Atkielski wrote:
It depends. People with an emotional attachment to a specific notion
will never been convinced otherwise, but people who simply don't
understand something may change their mind once they understand.

I do understand your argument, and you're correct in all its assertions, but not the conclusion. I suspect that's the case for everyone at this point.

You state, loosely, that 128 bits will not realistically yield 2**128 addresses, which is entirely true. It's been pointed out that IPv6 wasn't designed for that, instead, it was designed to yield 2**64 subnets, and even so, it's acknowledged that a considerable amount of that space will be wasted. People have agreed with this, but pointed out that the "subnet" level can be moved down, since we're only using an eighth of the available address space.

You also state that the relatively coarse prefix-based allocation will yield higher wastage of addresses, and increasing the corseness of this allocation reduces available address space exponentially - again, this is at least loosely true. I'm not utterly sure that "exponential" is the correct word to use here, but I'll accept it in lieu of any other term. Many people have agreed with the implications of this, suggesting that a jump from /64 to /48 is too much, and I'm inclined to agree - the cost of renumbering is not high, and given autoconfiguration, is virtually zero.

Your conclusion, however, is that we should be switching to a zero-wastage allocation mechanism preferably based on variable bitlength addresses. In response to this, several people have commented that this is unworkable using both current hardware and any hardware predicted to be available within the next few years. I don't know about that, but I'm prepared to accept that opinion.

There's an additional unanswered question your argument has, which is whether the - very real - issues you're pointing out with prefix based allocations will cause actual operational problems within a timeframe short enough for anyone to worry over for a few decades, and - a related issue - would these problems hit sufficiently quickly that a replacement for IPv6 couldn't be developed in time?

Dave.
--
          You see things; and you say "Why?"
  But I dream things that never were; and I say "Why not?"
   - George Bernard Shaw

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