Dave Cridland writes:
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.
Not as long as I still see people claiming that 128
bits will provided
2^128 addresses _and_ that it can still be divided
into multiple bit
fields.
You state, loosely, that 128 bits will not
realistically yield
2**128 addresses, which is entirely true.
Yes.
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.
I don't think many people appreciate just how
quickly such policies
can exhaust an address space--mainly because they
keep emphasizing
that 2^n addresses are available in n bits,
apparently oblivious to
the multiple factors that will waste most of the
addresses.
Your conclusion, however, is that we should be
switching to a
zero-wastage allocation mechanism preferably based
on variable
bitlength addresses.
That is one option. Another is to stop trying to
plan the entire
future of IP addressing today. As I've said, just
adding one more bit
to 32-bit addresses would hold the Internet together
for years to
come. Immediately blowing 2^125 addresses is
absurd.
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.
I'll accept the opinion, but as long as it remains
opinion, I can
continue to assert the contrary. I don't see any
insurmountable
obstacle that would prevent this type of
implementation. Indeed, I
should think it would greatly simplify routing.
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?
In this respect I'm going by past history. As I've
said, engineers
routinely underestimate capacity and overestimate
their own ability to
foresee the future, often with expensive and
defect-ridden results.
The Internet gets bigger all the time, and the cost
of these mistakes
will be astronomically high in the future--more than
high enough to
justify changing this mindset. I'm just trying to
limit the damage by
suggesting changes as early as possible.
Has anyone else noticed that the simplest standards
tend to last the
longest, and that complex, committee-designed
standards are often
obsolete even before the 6000-page specifications
are printed and
bound? I see that SMTP is still around, but I don't
see too many
people using X.400. I see people writing code in C,
but not in Ada.
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