Question about IPng addressing

[Thomas Narten]

> I'm researching IPng, and read various documents, rfc's and white
> papers. Today I found something that confused me. The pages from sun's
> playground,
> http://playground.sun.com/pub/ipng/html/INET-IPng-Paper.html#CH7
> indicated that the prefix for Provider-Based Unicast Address is 010 and
> 100 is reserved for Neutral-Interconnect-Based Unicast Addresses.

> However in the internet-draft draft-ietf-ipngwg-addr-arch-v2-05.txt
> these two are not in the reservation specs, although it is a more
> current document.

In the case of 100 (Geographic-Based Unicast Addresses according to
rfc 1884), there was no concrete proposal on how these prefixes would
actually be used, and in the absense of a concrete proposal, the bits
were simply changed to the "reserved" category. Also, I believe the
ideas behind this prefix are not incompatable with the generic unicast
aggregation prefix (001), so it is not clear that a separate prefix
needed to be reserved.  This could of course be changed in the future
if necessary.

In the case of the provider-based prefix 010, it has changed (in a
sense) to 001 (Aggregatable Global Unicast Addresses). The provider
based schemes are compatable with the definitions of the new
prefix. In a sense the 001 prefix is a superset of the other prefixes,
hence they are no longer needed.

Thomas