[ppml] IPv6>>32

Tony Hain alh-ietf at tndh.net
Mon May 9 19:11:50 EDT 2005

Geoff Huston wrote:
> > >  We should at this point be
> > > striving to instill some broad confidence in the proposition that we
> can
> > > provide a stable and enduring platform for the world's communications
> > > needs.
> >
> >By your own numbers changing the H-D policy would get us to centuries in
> the
> >current /3, then folding in the non-technical business desires to
> >differentiate based on prefix length we are talking about multiple
> millennia
> >still using the 64/64 split.
> Again referring to the presentation at the ARIN VX IPv6 roundtable what
> was
> presented was the theme that a change in the HD ratio and an additional
> setting in the subnet space of 56 bits would appear to gain us all some 10
> bits  (or thereabouts) of address space - which would certainly be an
> adequate margin to dispel many lingering levels of discomfort with the
> total capacity of the address architecture 

I seriously doubt it. Given that people can't do simple math and realize
that 32 bits got is 30 years while including hosts and that there are 2^13
32 bit chunks in the first /3 that will only have to identify customer
demarc's, there is no amount of change that will dispel lingering doubt in
those that simply don't want to believe. 

> without imposing undue levels of
> imposition or cost on the current and potential user population - these
> are
> after all relatively minor adjustments on the supply side rather than
> changes to the address architecture itself.

There are business reasons to consider other than /48, so we should talk
about the appropriate values. Casting a change as 'needed for address
lifetime' is simply going to reopen battles that were fought long ago. 

> The 64/64 split is not quite in the same category here, and there is an
> impact on the current address architecture. Its true that the original
> motivations for this particular aspect of the address architecture have
> largely gone away, or at least have been unable to be realized, and the
> residual reasons for its adoption are based more in legacy conformance
> than
> in true utility. 

This statement stems from a 'routing' perspective of utility. There are
other forms of utility that have not been given the opportunity to flourish
due to the continuous FUD about the need to micro-manage the space. 

> But here its not quite so clear to me that change is
> necessary. As Thomas Narten has said, maybe it would be more practical to
> go after the low hanging fruit here, when referring to a preference to
> look
> at the HD Ratio and the subnet size points over looking at the 64 bit
> split
> point between local identification and routing identifiers.

The H-D ratio policy is clearly in RIR space and therefore is the lowest
hanging fruit. Some productive discussion about the perceived need for
business differentiators in the customer prefix length would deal with the
hard feelings about a fixed value, but there is nothing that will convince
those who simply want to constrain their customers to the 'old world' model
of IPv4 address management. As such I am not sure it is really an RIR policy
so much as a BCP that provides clue about the negative impact of picking
random values.


> regards,
>      Geoff

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