On 15-aug-2007, at 16:00, <[EMAIL PROTECTED]>
<[EMAIL PROTECTED]> wrote:
Nobody from the IETF was available to explain why the designers of
IPv6
intended for /48 to be the fixed length network size when ARIN
passed a
policy to allow ISPs to allocate /56s to consumer customers. Even
though
the ARIN decision was not a bad one,
I'm still somewhat blue in the face from explaining exactly why this
was a bad decision.
- extremely few people need more than a /48
- /48 everywhere means that you don't have to renumber bits 48 - 63
when you change ISPs
- a decent number of people need more than a /56
- of that number, many won't know it in advance
- with 256 subnets deployed you're already big enough that
renumbering is painful
The right choice is to give a /48 to people who want one and a /60 to
everyone else. If you discover that you need more than a /60 and you
only have upto 16 subnets deployed renumbering is much easier than
with /56 and 256. With /56 you need to think about it in advance,
which we want to avoid because thinking hurts and usually, the
results are wrong.
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