[IPv6]Re: Analysis of Ungleich ULA Registry

[Ole Troan <[e-mail]>]

Mark,

draft-ietf-v6ops-dhcp-pd-per-device:

" Assigning a prefix of sufficient size to support SLAAC is possible on
large networks. In general, any network that numbers clients from an
IPv4 prefix of length X (e.g., X=/18, X=/24), would require an IPv6
prefix of length X+32 (e.g., X=/40, X=/56) to provide a /64 prefix to
every device. As an example, Section 9.2 of [RFC7934] suggests that
even a very large network that assigns every single one of the 16
million IPv4 addresses in 10.0.0.0/8 would only need an IPv6 /40. A
/40 prefix is a small amount of address space: there are 32 times
more /40s in the current IPv6 unicast range 2000::/3 than there are
IPv4 addresses. Existing sites that currently use a /48 prefix
cannot support more than 64k clients in this model without
renumbering, though many networks of such size have LIR status and
can justify bigger address blocks.
“

Is proposing to essentially change IPv6 addressing to 64-bits.

“...would only need a /40”.

I think it is good operational practice that the ULA prefix, ULA routing and subnet assignments are aligned with the GUA usage.
Meaning that if this proposal is common we will also see /40 in ULA.

I don’t think we can publish PD per device without also accepting that ULA site prefixes will be shorter than /48.
Prior to this draft a /48 meant 64K links and an infinite number of hosts. With this draft a /48 means 64K hosts.

Best regards,
Ole