On Jul 10, 2007, at 15:33, Scott Leibrand wrote:
[...]
As stated previously, the rules for getting PI space are based on
the expectation that PI blocks can be announced into the DFZ. The
proposed rules for ULA-G space are based on the expectation that
ULA-G blocks will not be announced into the DFZ, and that they will
be allocated out of a single global netblock, identified in an RFC,
that everyone knows can and should be filtered. As stated quite
clearly by Joe Abley in the "Why ULA-* will not harm the DFZ"
thread, that difference in expectation, and ease in filtering when
desired or necessary, makes it possible to give out ULA-G space in
a non-discriminatory manner (which is simply not prudent for PI
space today).
Look, if we want to enable the operation of "very large local DFZ"
routing realms (in the hundreds of thousands or millions of networks)
and we're really, really concerned about accidental leakage of local
prefixes into the DFZ with PI addressing, then I can understand the
motivation for ULA-G/C. Is that really what this is all about? If
so, then I'd like to see the Introduction revised accordingly.
Here is some proposed text, which I think improves the draft and
makes it clear what we are intending to do:
This document defines the characteristics and technical allocation
requirements for centrally-assigned Unique Local IPv6 addresses,
as defined in [ULA]. They are not expected to be routed in the
default-free zone of the public Internet. They are intended for
use in pre-arranged interconnection between organizations and
sites in very large local routing realms.
All Unique Local IPv6 addresses, as defined in [ULA], have the
following characteristics:
- Globally unique prefix.
- Well known prefix to allow for easy filtering at site
boundaries.
- Internet Service Provider independent and can be used for
communications inside of a site without having any permanent or
intermittent Internet connectivity.
- In practice, applications may treat these addresses like global
scoped addresses.
The most important property of ULAs is that they are unique, as
ULA uniqueness allows routing realms to be merged or privately
interconnected with minimal risk of prefix collisions. The
statistical uniqueness of locally-assigned ULAs is deemed adequate
when routing realms contain a small number of local prefixes, but
insufficient in the case where routing realms routinely comprise
hundreds of thousands or even millions of networks. A single,
global federated registry for assigning unique local prefixes is
required to address these concerns. Using ULAs for this purpose
instead of Provider Independent [RIR-PI] addresses has the
attraction of making it easy to prevent leakage of local prefixes
into the default-free zone of the public Internet, thereby
enforcing the requirement to pre-arrange interconnections.
--
james woodyatt <[EMAIL PROTECTED]>
member of technical staff, communications engineering
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