[ppml] IPv6 flawed?

Christopher Morrow christopher.morrow at gmail.com
Wed Sep 12 00:18:29 EDT 2007

On 9/10/07, David Conrad <drc at virtualized.org> wrote:

> Interestingly, if you look at the ratio of ASes that are announcing a
> single prefix to all ASes, it has consistently gone up (from 27% in
> 1999 to 42% today).
> I suspect both of these are causes for worry.  The first is likely
> driven primarily by people breaking up aggregates for good or bad
> reasons.  The second is likely due to multihoming.  Fortunately, the
> growth isn't that great right now.  The big question is how these
> trends will change in the future.

I think, as a few presentations vaf or jason or I have given, that
this trend of more multihoming by customers (many with a single
prefix) is increasing ,  and will continue for the next while to
increase. The drivers we see are regulatory in nature (SOX, GLB, etc).

> >> Since IPv6 uses the same
> >> routing and traffic engineering technology as IPv4, I am curious what
> >> constraints could be put in place to keep PI space down to about 1
> >> per ASN.
> >
> > Prefixes per AS aren't limited by routing technology (if only it
> > could...) so this is irrelevant.
> Yet you go ahead and address this irrelevancy:
> > in IPv6, you'll be either getting a /32 or a /48 as a PI block. So
> > unless you manage to get multiple PI blocks, any efforts to inject
> > more than a single prefix will easily be thwarted by prefix length
> > filters.
> Of course, this assumes people will implement and maintain prefix
> length filters.  I'm told by some in the ISP business that the
> economic pressure to remove such filters is sufficiently high that
> they don't believe prefix length filters are viable in the long term
> (I'm paraphrasing a bit).

There will be competing pressures inside each SP, to be sure. Some
will 'lose', some will 'win'. It will likely get very ugly for a time.

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