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

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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