On 28-nov-03, at 14:47, Anthony G. Atkielski wrote:
I guess not because I have no idea what you're talking about.
There is a natural tendency to think that by dividing a 128-bit address
field into two 64-bit fields, the address space is cut in half (or
perhaps not diminished at all).
Ah, I see what you mean now. However, the devision is a done deal as
RFC 3513 mandates that all unicast IPv6 addresses except the ones
starting with the bits 000 must have a 64-bit interface identifier in
the lower 64 bits. This has some important advantages, most notably it
allows stateless autoconfiguration. (However, this could have been done
with 48 bits too.) But it does have the downside you mention by only
leaving 64 bits for numbering subnets. The practice of giving all sites
a /48 further deminishes the available bits. The situation is most
notable in the case of a home user, who would get a single IPv4 address
but gets a /48 in IPv6. So we've quadrupled our address space (in bits)
for a 50% gain... (Obviously the situation is much better when looking
at a university that has a /16 now and also gets a /48 as well.)
Putting a 64-bit crypto-based host identifier in the bottom 64 bits of
IPv6 addresses shouldn't get in the way of regular IPv6 addressing
mechanisms and/or operation. There is even a trick to make sure there
is no overlap with either MAC addresses/EUI-64s on the one hand and
most manually configured addresses and RFC 3041 on the other hand by
only using EUI-64 compatible values with the universal/local bit set to
globally unique, but with the group bit set.
It's unlikely you'll have 2^64 countries
to accommodate; and it's equally unlikely that each of these countries
will have exactly 2^64 hosts (no more, no less) to address, so you are
wasting many bits of the address field.
The plan isn't to encode a country in the first 64 bits. However,
together with someone else I came up with an unrelated proposal a while
ago that does encode a country in the IPv6 address. (You can find it at
http://www.muada.com/drafts/ under the name "gapi".) In this proposal
we use 16 bits to allocate a /32 to regions with 250 - 500 thousand
inhabitants, so there is no fixed boundary for the country number.