[ppml] Re: [address-policy-wg] Is the time for conservation over?

Leo Bicknell bicknell at ufp.org
Mon Oct 27 14:58:41 EST 2003

In a message written on Mon, Oct 27, 2003 at 11:42:34AM -0800, Michel Py wrote:
> This topic has been extensively discussed on ipv6mh in the past, and
> it's half-true and half-false. The issue is that "If every ASN had a
> single IPv6 /32" does not register. Large multihomers need either
> multiple /32s or to announce subsets (such as /36) of their own /32,
> which for all practical purposes does not change much in terms of number
> of entries. There is potential for much more than 12%.

Clearly 12% is best case.  However, I think worst case is about the
same as what we have today in IPv4.  There are people today who
announce multiple swap prefixes and the like not because they need
to, but because they won't take the effort to renumber into one
block.  Getting IPv6 "right enough" to prevent that will take out
a good chunk.  There will still be people who multihome with cut-outs
and multiple blocks and all that stuff, so the answer should be in
the middle.

> Note that in terms of what is being announced in the global IPv6 routing
> table today, look at the bottom of this email, a snapshot I capture from
> my own IPv6 BGP4+ feeds. Not only I see /48s but also /64s and anything
> else you can imagine. Call it swamp, soup or anything you like it's here
> already.

Using the existing table as a reference is an extremely bad idea.
Most of the people I know of who are playing with IPv6 right now
are doing just that, playing.  Many IPv6 networks are in research
and test mode.  That means the filtering practices are different
from an operational network.  It means people put up a /64 just to
see where it ends up.  I remember talking to Team Cymru about a "secure
IPv6 BGP template" with bogon lists and the like....no one seems to
have developed one yet.  So to take the current state of the IPv6
routing table and extrapolate that to the future of IPv6 is very

Note also, much of the junk you listed is 6bone space, which was done
as the rules were developed, so many things were put in place when
there were no rules.  It's all going away.

> > I am going to strongly disagree on this point at this time. We
> > don't know that there will /ever/ be a strong migration of users
> > to IPv6. IPv6 may yet flop completely, be replaced by IPv8
> I'm sure Jim Fleming will be pleased :-D

This was pointed out to me off list.  I had no idea Jim Flemming had
introduced an IPv8 proposal.  I wanted to pick a hypothetical future
version.  Ah well.

       Leo Bicknell - bicknell at ufp.org - CCIE 3440
        PGP keys at http://www.ufp.org/~bicknell/
Read TMBG List - tmbg-list-request at tmbg.org, www.tmbg.org
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